,transcriber's note3 ,in this plain text version1 underlined text in the original is surrounded by equals symbols2 italic typeface is surrounded by underscores2 bold typeface and small caps typeface are represented by ,,upper ,,case4 ,the oe-ligature appears as oe4 ,changes to the text 7to correct typographical errors7 are listed at the end of the book4 ,a few cases of missing punctuation have been regularised in the advertisements without comment4 ,all advertising material has been retained in the same position as it appears in the original book4 ,there are extensive advertisements before and after the title page1 following the index and in a sixteen page publisher's catalogue at the end of the book4 ,,the ,,romance ,,of ,,war ,,inventions 99 99 99 99 99 ,,the ,,ian ,,hardy ,,series ,,by ,,commander ,e4 ,,hamilton ,,currey1 ,r4,n4 ,each ,volume with ,illustrations in ,colour4 #es4 each ,ian ,hardy's career in ,h4,m4 ,navy is told in four volumes1 which are described below4 ,each volume is complete in itself1 and no knowledge of the previous volumes is necessary1 but few boys will read one of the series without wishing to peruse the others4 ,,ian ,,hardy1 ,,naval ,,cadet ,a sound and wholesome story giving a lively picture of a naval cadet's life4--,birmingham ,gazette4 ,a very wholesome book for boys1 and the lurking danger of ,ian's ill deeds being imitated may be regarded as negligible in comparison with the good likely to be done by the example of his manly1 honest nature4 ,ian was a boy whom his father might occasionally have reason to whip1 but never feel ashamed of4--,united ,service ,magazine4 ,,ian ,,hardy1 ,,midshipman ,a jolly sequel to his last year's book4--,christian ,world4 ,the 'real thing4' 444 ,certain to enthral boys of almost any age who love stories of ,british pluck4--,observer4 ,commander ,e4 ,hamilton ,currey1 ,r4,n41 is becoming a serious rival to ,kingston as a writer of sea stories4 ,just as a former generation revelled in ,kingston's doings of his three heroes from their middy days until they became admirals all1 so will the present-day boys read with interest the story of ,ian ,hardy4 ,last year we knew him as a cadet2 this year we get ,ian ,hardy1 ,midshipman4 ,the present instalment of his stirring history is breezily written4--,yorkshire ,observer4 ,,ian ,,hardy1 ,,senior ,,midshipman ,of those who are now writing stories of the sea1 ,commander ,currey holds perhaps the leading position4 ,he has a gift of narrative1 a keen sense of humour1 and above all he writes from a full stock of knowledge4--,saturday ,review4 ,it is no exaggeration to say that ,commander ,currey bears worthily the mantle of ,kingston and ,captain ,marryat4--,manchester ,courier4 ,the ,ian ,hardy ,series is just splendid for boys to read1 and the best of it is that each book is complete in itself4 ,but not many boys will read one of the series without being keenly desirous of reading all the others4--,sheffield ,telegraph4 ,,ian ,,hardy ,,fighting ,,the ,,moors ,by writing this series the author is doing national service1 for he writes of the ,navy and the sea with knowledge and sound sense4444 ,what a welcome addition the whole series would make to a boy's library4--,daily ,graphic4 ,the right romantic stuff1 full of fighting and hairbreadth escapes4444 ,commander ,currey has the secret of making the men and ships seem actual4--,times4 ,by this time ,ian ,hardy has become a real friend and we consider him all a hero should be4--,outlook4 ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,the ,,library ,,of ,,romance ,each volume profusely illustrated4 ,ex4 ,crown #hvo4 #es4 ,,the ,,library ,,of ,,romance ,,offers ,a ,,splendid ,,choice4--,globe4 ,,the ,,romance ,,of ,,piracy ,,by ,e4 ,,keble ,,chatterton1 ,b4,a4 ,,author ,,of ,,the ,,romance ,,of ,,the ,,ship ,with many illustrations ,,the ,,romance ,,of ,,aeronautics ,,by ,,charles ,c4 ,,turner ,a ,,valuable ,,contribution ,,to ,,the ,,literature ,,of ,,this ,,most ,,marvellous ,,subject4--,british ,weekly ,with forty illustrations ,,the ,,romance ,,of ,,modern ,,astronomy ,,by ,,hector ,,macpherson1 ,,junr4 ,with thirty-seven illustrations ,,the ,,romance ,,of ,,savage ,,life ,describing the ,habits1 ,customs1 ,everyday ,life1 ,arts1 ,crafts1 ,games1 ,adventures and ,sports of ,primitive ,man ,,by ,,prof4 ,g4 ,f4 ,,scott ,,elliot ,m4,a41 ,b4,,sc41 ,f4,r4,g4,s41 ,f4,l4,s41 c4 ,with forty illustrations ,,the ,,romance ,,of ,,modern ,,sieges ,,by ,,the ,,rev4 ,,edward ,,gilliat ,with sixteen illustrations ,,the ,,romance ,,of ,,animal ,,arts ,,crafts ,h4 ,,coupin1 ,d4,sc41 ,j4 ,,lea1 ,m4,a4 ,with twenty-seven illustrations ,a ,,charming ,,subject ,,well ,,set ,,forth4--,athenum ,,the ,,romance ,,of ,,modern ,,locomotion ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with twenty-five illustrations ,,crisply ,,written1 ,,brimful ,,of ,,incident4 ,,to ,,intelligent ,,lads ,,should ,,be ,,as ,,welcome ,,as ,a ,,ballantyne ,,story4--,glasgow ,herald ,,the ,,romance ,,of ,,polar ,,exploration ,,by ,g4 ,,firth ,,scott ,with twenty-four illustrations ,extra ,crown #hvo4 #es4 ,,thrillingly ,,interesting4 ,liverpool ,courier ,,the ,,romance ,,of ,,scientific ,,discovery ,,by ,c4 ,r4 ,,gibson1 ,f4,r4,s4,e4 ,with many illustrations ,,the ,,romance ,,of ,,submarine ,,engineering ,,by ,,thomas ,w4 ,,corbin ,,author ,,of ,,mechanical ,,inventions ,,of ,,to-,,day ,with many illustrations diagrams ,,the ,,romance ,,of ,,the ,,ship ,,by ,e4 ,,keble ,,chatterton1 ,b4,a4 ,with thirty-four illustrations ,,the ,,romance ,,of ,,the ,,world',s ,,fisheries ,with descriptions of the ,many and ,curious ,methods of ,fishing in all parts of the world ,,by ,,sidney ,,wright ,with twenty-four illustrations ,,the ,,romance ,,of ,,modern ,,photography ,,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,with sixty-three illustrations ,,the ,,romance ,,of ,,modern ,,engineering ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with many illustrations ,,the ,,romance ,,of ,,mining ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with twenty-four illustrations ,,we ,,cannot ,,praise ,,this ,,book ,,too ,,highly4--,british ,weekly ,,the ,,romance ,,of ,,the ,,mighty ,,deep ,,by ,,agnes ,,giberne ,with illustrations ,,most ,,fascinating2 ,,admirably ,,adapted ,,for ,,the ,,young4 ,daily ,news ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,the ,,library ,,of ,,romance ,lavishly ,illustrated4 ,ex4 ,crown #hvo4 #es4 each volume ,,splendid ,,volumes4--,the ,outlook ,,the ,,romance ,,of ,,the ,,spanish ,,main ,,by ,n4 ,j4 ,,davidson1 ,b4,a4 7,oxon47 ,with many illustrations ,,new ,,revised ,,edition ,,the ,,romance ,,of ,,modern ,,electricity ,,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,with forty-five illustrations ,,admirable 444 ,,clear ,,and ,,concise4--,the ,graphic ,,the ,,romance ,,of ,,modern ,,exploration ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with twenty-six illustrations ,a ,,mine ,,of ,,information ,,and ,,stirring ,,incident4--,scotsman ,,the ,,romance ,,of ,,modern ,,mechanism ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with thirty illustrations ,a ,,genuinely ,,fascinating ,,book4 ,liverpool ,courier ,,the ,,romance ,,of ,,insect ,,life ,,by ,,edmund ,,selous ,with twenty illustrations ,,well ,,merits ,,its ,,alluring ,,title4 ,daily ,telegraph ,,the ,,romance ,,of ,,early ,,british ,,life ,,prof4 ,g4 ,f4 ,,scott ,,elliot1 ,m4,a4 ,a ,,masterpiece ,,of ,,scientific ,,knowledge1 ,,brilliant ,,invention1 ,,and ,,genuine ,,humour4 ,liverpool ,courier ,,the ,,romance ,,of ,,bird ,,life ,,by ,,john ,,lea1 ,m4,a4 ,with thirty illustrations ,,most ,,fascinating1 ,,suggestive1 ,,and ,,readable4--,spectator ,,the ,,romance ,,of ,,modern ,,chemistry ,,by ,j4 ,c4 ,,philip1 ,d4,,sc41 ,,ph4,d4 ,with thirty illustrations ,a ,,fascinating ,,exposition ,,in ,,popular ,,language4--,illustrated ,london ,news ,,the ,,romance ,,of ,,the ,,great ,,war ,,by ,n4 ,j4 ,,davidson1 ,b4,a4 7,oxon47 ,with many illustrations ,,new ,,revised ,,edition ,,the ,,romance ,,of ,,modern ,,invention ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with twenty-five illustrations ,,the ,,romance ,,of ,,early ,,exploration ,,by ,,archibald ,,williams ,b4,a41 ,f4,r4,g4,s4 ,with sixteen illustrations ,,vivid ,,and ,,vigorous4 ,glasgow ,herald ,,the ,,romance ,,of ,,missionary ,,heroism ,,by ,j4 ,c4 ,,lambert1 ,b4,a41 ,d4,d4 ,with thirty-nine illustrations ,a ,,most ,,entrancing ,,volume4 ,expository ,times ,,the ,,romance ,,of ,,plant ,,life ,,by ,g4 ,f4 ,,scott ,,elliot1 ,m4,a4 ,with thirty-four illustrations ,,intensely ,,interesting4 ,leeds ,mercury ,,the ,,romance ,,of ,,the ,,animal ,,world ,,by ,,edmund ,,selous ,with sixteen full-page illustrations ,a ,,very ,,fascinating ,,book4 ,graphic ,,the ,,romance ,,of ,,modern ,,geology ,,by ,e4 ,s4 ,,grew1 ,m4,a4 ,with twenty-five illustrations ,,absorbingly ,,interesting4 ,scotsman ,,the ,,romance ,,of ,,modern ,,manufacture ,,by ,c4 ,r4 ,,gibson1 ,f4,r4,s4,e4 ,with forty illustrations ,,well ,,planned1 ,,well ,,written1 ,,and ,,well ,,illustrated4 ,pall ,mall ,gazette ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,popular ,,science ,,for ,,young ,,people ,,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,among writers for boys on science1 easily the most skilful is ,mr4 ,charles ,gibson4 ,he writes so clearly1 simply and charmingly about the most difficult things that his books are quite as entertaining as any ordinary book of adventure4 ,mr4 ,gibson has a first-rate scientific mind and considerable scientific attainments4 ,he is never guilty of an inexact phrase--certainly1 never an obscure one--or a misleading analogy4 ,we could imagine him having a vogue among our young folk comparable with that of ,jules ,verne4--,the ,nation4 ,mr4 ,gibson has fairly made his mark as a populariser of scientific knowledge4--,guardian4 ,,just ,,published ,,the ,,stars ,,their ,,mysteries 7,vol4 ,,iii4 ,,science ,,for ,,children ,,series74 ,with ,coloured ,frontisp4 other ,illustrations4 #cs4 #f;d4 ,,our ,,good ,,slave ,,electricity 7,vol4 ,i4 ,,science ,,for ,,children ,,series74 ,with ,illustrations4 #cs4 #f;d4 ,an exquisitely clear book for childish beginners4--,the ,nation4 ,told in simple and remarkably clear language1 and with such ingenuity that many pages of it read like a fairy tale4--,glasgow ,herald4 ,,the ,,great ,,ball ,,on ,,which ,,we ,,live 7,vol4 ,,ii4 ,,science ,,for ,,children ,,series74 ,with ,coloured ,frontispiece and other ,illustrations4 #cs4 #f;d4 ,capital4--,field4 ,a most fascinating and suggestive story of the earth4 ,mr4 ,gibson not only knows his subject thoroughly1 but has the capacity of conveying the knowledge to young folk4--,church ,family ,newspaper4 ,,the ,,romance ,,of ,,modern ,,electricity4 ,describing in ,non-technical ,language what is known about ,electricity and many of its interesting applications4 ,with #da ,illustrations4 ,extra crown #hvo1 #es4 ,admirable1 clear and concise4--,graphic4 ,very entertaining and instructive4--,queen4 ,a book which the merest tyro1 totally unacquainted with elementary principles1 can understand4--,electricity4 ,,the ,,romance ,,of ,,modern ,,photography4 ,its ,discovery and its ,applications4 ,with ,illustrations4 ,extra crown #hvo1 #es4 ,there is not a dry or uninteresting page throughout4--,country ,life4 ,the narration is everywhere remarkable for its fluency and clear style4--,bystander4 ,,the ,,romance ,,of ,,scientific ,,discovery4 ,a ,popular ,account of the most important ,discoveries in ,science4 ,with #cj ,illus4 #es4 ,the most curious boy of mechanical bent would find such a book satisfying4--,westminster ,gazette4 ,,the ,,romance ,,of ,,modern ,,manufacture4 ,a ,popular ,account of the ,marvels of ,manufacturing4 #es4 ,a popular and practical account of all kinds of manufacture4--,scotsman4 ,just the sort of book to put into the hands of senior boys as a school prize4--,sheffield ,telegraph4 ,,heroes ,,of ,,the ,,scientific ,,world4 ,an ,account of the ,lives1 ,sacrifices1 ,successes1 and ,failures of some of the greatest ,scientists in the ,world's ,history4 ,with #ai ,illustrations4 ,extra crown #hvo1 #es4 ,the whole field of science is well covered4444 ,every one of the #cjj odd pages contains some interesting piece of information4--,athenum4 ,,the ,,autobiography ,,of ,,an ,,electron4 ,with #h ,illustrations4 ,long #hvo1 #cs4 #f;d4 net4 ,a brilliant study4--,daily ,mail4 ,quite a unique book in its way1 at once attractive and illuminating4--,record4 ,,the ,,wonders ,,of ,,modern ,,electricity4 ,with #ag ,illustrations and ,diagrams4 ,extra crown #hvo1 #bs4 ,,the ,,wonders ,,of ,,modern ,,manufacture4 ,with #bb ,illustrations4 ,extra crown #hvo1 #bs4 ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,the ,,romance ,,of ,,war ,,inventions ,illustration3 ,a ,,tank4 ,these weird-looking engines are literally moving forts1 and are the evolution of a peaceful agricultural machine fitted with caterpillar wheels1 that is1 a broad band encircles the driving wheels1 and so the whole construction moves as it were on its own revolving platform and is thus prevented from sinking into the soft ground4 ,the principle itself is not new1 as it was adapted to transport carts during the ,crimean ,war4 ,,the ,,romance ,,of ,,war ,,inventions ,a ,description of ,warships1 ,guns1 ,tanks1 ,rifles1 ,bombs1 and ,other ,instruments and ,munitions of ,warfare1 ,how ,they ,were ,invented ,how ,they ,are ,employed by ,t4 ,w4 ,,corbin ,author of ,the ,romance of ,submarine ,engineering1 ,mechanical ,inventions of ,to-,day1 c41 c41 c4 ,with many ,illustrations ,london ,seeley1 ,service ,co4 ,limited #ch ,great ,russell ,street #aiah 99 99 99 99 99 ,,the ,,library ,,of ,,romance ,extra ,crown #hvo4 ,with many illustrations4 #es4 each4 ,splendid ,volumes4--,the ,outlook4 ,the ,library of ,romance offers a splendid choice4--,globe4 ,gift ,books whose value it would be difficult to over-estimate4 ,the ,standard4 ,this series has now won a considerable well deserved reputation4 ,the ,guardian4 ,each ,volume treats its allotted theme with accuracy1 but at the same time with a charm that will commend itself to readers of all ages4 ,the root idea is excellent1 and it is excellently carried out1 with full illustrations and very prettily designed covers4--,the ,daily ,telegraph4 ,by ,prof4 ,g4 ,f4 ,,scott ,,elliot1 ,m4,a41 ,b4,sc4 ,the ,romance of ,savage ,life ,the ,romance of ,plant ,life ,the ,romance of ,early ,british ,life ,by ,,edward ,,gilliat1 ,m4,a4 ,the ,romance of ,modern ,sieges ,by ,,john ,,lea1 ,m4,a4 ,the ,romance of ,bird ,life ,by ,,john ,,lea4 ,m4,a4 ,h4 ,,coupin1 ,d4,sc4 ,the ,romance of ,animal ,arts and ,crafts ,by ,,sidney ,,wright ,the ,romance of the ,world's ,fisheries ,by the ,rev4 ,j4 ,c4 ,,lambert1 ,m4,a41 ,d4,d4 ,the ,romance of ,missionary ,heroism ,by ,g4 ,,firth ,,scott ,the ,romance of ,polar ,exploration ,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,the ,romance of ,modern ,photography ,the ,romance of ,modern ,electricity ,the ,romance of ,modern ,manufacture ,the ,romance of ,scientific ,discovery ,by ,,charles ,c4 ,,turner ,the ,romance of ,aeronautics ,by ,,hector ,,macpherson1 ,junr4 ,the ,romance of ,modern ,astronomy ,by ,,archibald ,,williams1 ,b4,a4 7,oxon471 ,f4,r4,g4,s4 ,the ,romance of ,early ,exploration ,the ,romance of ,modern ,exploration ,the ,romance of ,modern ,mechanism ,the ,romance of ,modern ,invention ,the ,romance of ,modern ,engineering ,the ,romance of ,modern ,locomotion ,the ,romance of ,modern ,mining ,by ,,edmund ,,selous ,the ,romance of the ,animal ,world ,the ,romance of ,insect ,life ,by ,,agnes ,,giberne ,the ,romance of the ,mighty ,deep ,by ,e4 ,s4 ,,grew1 ,m4,a4 ,the ,romance of ,modern ,geology ,by ,j4 ,c4 ,,philip1 ,d4,sc41 ,ph4,d4 ,the ,romance of ,modern ,chemistry ,by ,e4 ,,keble ,,chatterton1 ,b4,a4 ,the ,romance of the ,ship ,the ,romance of ,piracy ,by ,t4 ,w4 ,,corbin ,the ,romance of ,submarine ,engineering ,the ,romance of ,war ,inventions ,by ,,norman ,j4 ,,davidson1 ,b4,a4 7,oxon47 ,the ,romance of the ,spanish ,main ,,seeley1 ,,service ,,co41 ,,limited4 99 99 99 99 99 ,,contents ,,chapter ,,page ,i4 ,,how ,,peaceful ,,arts ,,help ,,in ,,war #ag ,,ii4 ,,gunpowder ,,and ,,its ,,modern ,,equivalents #bg ,,iii4 ,,radium ,,in ,,war #ci ,,iv4 ,a ,,good ,,servant1 ,,though ,a ,,bad ,,master #di ,v4 ,,mines1 ,,submarine ,,and ,,subterranean #fa ,,vi4 ,,military ,,bridges #ge ,,vii4 ,,what ,,guns ,,are ,,made ,,of #ib ,,viii4 ,,more ,,about ,,guns #ajh ,,ix4 ,,the ,,guns ,,they ,,use ,,in ,,the ,,navy #abj ,x4 ,,shells ,,and ,,how ,,they ,,are ,,made #ace ,,xi4 ,,what ,,shells ,,are ,,made ,,of #adf ,,xii4 ,,measuring ,,the ,,velocity ,,of ,a ,,shell #aei ,,xiii4 ,,some ,,adjuncts ,,in ,,the ,,engine ,,room #afd ,,xiv4 ,,engines ,,of ,,war #afi ,,xv4 ,,destroyers #ahd ,,xvi4 ,,battleships #aia ,,xvii4 ,,how ,a ,,warship ,,is ,,built #bjb ,,xviii4 ,,the ,,torpedo #bae ,,xix4 ,,what ,a ,,submarine ,,is ,,like #bbc ,,xx4 ,,the ,,story ,,of ,,wireless ,,telegraphy #bdj ,,xxi4 ,,wireless ,,telegraphy ,,in ,,war #beb ,,xxii4 ,,military ,,telegraphy #bfd ,,xxiii4 ,,how ,,war ,,inventions ,,grow #bgf ,,xxiv4 ,,aeroplanes #bhd ,,xxv4 ,,the ,,aerial ,,lifeboat #big ,,index #cac ,,list ,,of ,,illustrations ,a ,,tank ,frontispiece ,,page ,,machine-,,gun ,,versus ,,rifle #cb ,,an ,,italian ,,mine-,,layer #fd ,,an ,,incident ,,at ,,loos #hj ,,an #ah-,,pounder ,,in ,,action #if ,a ,,german ,,automatic ,,pistol #aab ,,bomb ,,throwing #acf ,,bomb-,,throwers ,,at ,,work #afj ,,the ,,tripod ,,mast #bjh ,,listening ,,for ,,the ,,enemy #bdh ,,diagram ,,showing ,,the ,,principle ,,by ,,which ,,the ,,aerials ,,are ,,connected ,,to ,,the ,,apparatus #bea ,,the ,,parent ,,of ,,the ,,tank #bhj ,,the ,,guardian ,,angel ,,parachute #cjd ,,the ,,romance ,,of ,,war ,,inventions ,,chapter ,i ,,how ,,peaceful ,,arts ,,help ,,in ,,war ,in the olden times warfare was supported by a single trade1 that of the armourer4 ,nowadays the whole resources of the greatest manufacturing nations scarcely suffice to supply the needs of their armies4 ,so much is this the case that no nation can possibly hope to become powerful in a military or naval sense unless they are either a great manufacturing community or can rely upon the support of some great manufacturing ally or neutral4 ,it is most astonishing to find how closely some of the most innocent and harmless of the commodities of peace are related to the death-dealing devices of war4 ,of these no two examples could be more striking than the common salt with which we season our food and the soap with which we wash4 ,yet the manufacture of soap furnishes the material for the most furious of explosives and the chief agent in its manufacture is the common salt of the table4 ,common salt is a combination of the metal sodium and the gas chlorine4 ,there are many places1 of which ,cheshire is a notable example1 where vast quantities of this salt lie buried in the earth4 ,fortunately it is very easily dissolved in water so that if wells be sunk in a salt district the water pumped from them will have much salt in solution in it4 ,this is how the underground deposits are tapped4 ,it is not necessary for men to go down as they do after coal1 for the water excavates the salt and brings it to the surface4 ,to obtain the solid salt from the salt water1 or brine as it is called1 it is only necessary to heat the liquid1 when the water passes away as steam leaving the salt behind4 ,important though this salt is in connection with our food1 it is perhaps still more important as the source from which is derived chlorine and caustic soda4 ,how this is done can best be explained by means of a simple experiment which my readers can try in imagination with me or1 better still1 perform for themselves4 ,take a tumbler and fill it with water with a little salt dissolved in it4 ,next obtain two short pieces of wire and two pieces of pencil lead1 which with a pocket lamp battery will complete the apparatus4 ,connect one piece of wire to each terminal of the battery and twist the other end of it round a piece of pencil lead4 ,place these so that the ends of the leads dip into the salt water4 ,it is important to keep the wires out of the solution1 the leads alone dipping into the liquid1 and the two leads should be an inch or so apart4 ,in a few moments you will observe that tiny bubbles are collecting upon the leads and these joining together into larger bubbles will soon detach themselves and float up to the surface4 ,those which arise from one of the leads will be formed of the gas chlorine and the others of hydrogen4 ,it will be interesting just to enumerate the names of the different parts of this apparatus4 ,first let me say that the process by which these gases are thus obtained is called electrolysis3 the liquid is the electrolyte3 the two pieces of pencil lead are the electrodes4 ,that electrode by which the current enters the electrolyte is called the an-ode1 while the other is the cath-ode4 ,in other words1 the current traverses them in alphabetical order4 ,now it is familiar to everyone that all matter is supposed to consist of tiny particles called ,molecules4 ,these are far too tiny for anyone to see even with the finest microscope1 so we do not know for certain that they exist3 we assume that they do1 however1 because the idea seems to fit in with a large number of facts which we can observe and it enables us to talk intelligibly about them4 ,we may1 accordingly1 speak as if we knew for a certainty that molecules really exist4 ,now when we dissolve salt in water it seems as if each molecule splits up into two things which we then call ions4 ,salt is not peculiar in this respect1 for many other substances do the same when dissolved in water4 ,all such substances1 since they can be ionized1 are called ionogens4 ,now the peculiarity about ions is that they are always strongly electrified or charged with electricity4 ,at this stage we must make a little excursion into the realm of electricity4 ,you probably know that if a rod of glass be rubbed with a silk handkerchief it becomes able to attract little scraps of paper4 ,that is because the rubbing causes it to become charged with electricity4 ,in like manner a piece of resin if rubbed will become charged and will also attract little pieces of paper4 ,a piece of electrified resin and an electrified glass rod will1 moreover1 attract each other1 but two pieces of resin or two pieces of glass1 if electrified1 will repel each other4 ,this leads us to believe that there are two kinds of electrification or two kinds of electrical charge4 ,at first these two kinds were spoken of as vitreous or glass electricity and resinous electricity1 but after a while the idea arose that there was really one kind of electricity and that everything possessed a certain amount of it1 the electrified glass having a little too much of it and the electrified resin a shade too little of it4 ,from this came the idea of calling the charge on the glass a positive charge and that on the resin a negative charge4 ,recent investigations seem to show that we have got those two terms the wrong way round1 but to avoid confusion we still use them in the old way4 ,it will be sufficient for our purpose1 therefore1 if we assume that every molecule of matter has a certain normal amount of electricity associated with it and that under those conditions the presence of the electricity is not in any way noticeable4 ,when a molecule becomes ionized1 however1 one ion always seems to run off with more than its fair share of the electricity1 the result being that one is electrified positively1 like rubbed glass1 while the other is negatively charged1 like rubbed resin4 ,thus1 when the common salt is dissolved in water1 two lots of ions are formed1 one lot positively charged and the other lot negatively4 ,each molecule of salt consists of two atoms1 one of sodium and one of chlorine3 consequently1 one ion is a chlorine atom and the other is a sodium atom1 the latter being positive and the former negative4 ,now the electrodes are also charged by the action of the battery4 ,that connected to the positive pole of the battery becomes positively charged and the other negatively4 ,the anode1 therefore1 is positive and the cathode negative4 ,it has been pointed out that two similarly charged bodies1 such as two pieces of glass or two pieces of resin1 repel each other1 while either of these attracts one of the other sort4 ,hence we arrive at a rule that similarly charged bodies repel each other1 while dissimilarly charged bodies attract each other4 ,acting upon this rule1 therefore1 the anode starts drawing to itself all the negative ions1 in this case the atoms of chlorine1 while the cathode gathers together the positive ions1 the atoms of sodium4 ,thus the action of the battery maintains a sorting out process by which the sodium is gathered together around one of the electrodes and the chlorine round the other4 ,those ions1 by the way1 which travel towards the an-ode are called an-ions1 while those which go to the cath-ode are termed cat-ions4 ,thus far1 ,i think1 you will have followed me3 the chlorine is gathered to one place and the sodium to the other4 ,the former creates bubbles and floats up to the surface and escapes4 ,but where1 you will ask1 does the hydrogen come from1 which we found1 in the experiment1 was bubbling up round the cathode4 ,moreover1 what becomes of the sodium8 ,both those questions can be answered together4 ,the sodium ions1 having been drawn away from their old partners the chlorine ions1 are unhappy1 and long for fresh partners4 ,they therefore proceed to join up with molecules of water4 ,but water contains too much hydrogen for that4 ,every molecule of water has two atoms of hydrogen linked up with one of oxygen1 but sodium does not like two atoms of hydrogen3 it insists on having one only4 ,accordingly the oxygen atom from the water1 together with one of the hydrogen atoms1 join forces with the sodium atom into a molecule of a new substance1 a most valuable substance in many manufactures1 called ,caustic ,soda1 while the odd atom of hydrogen1 deprived of its partners1 has nothing left to do but to cling for a while to the cathode and finally float up and away4 ,the sum-total of the operation therefore is this3 when we pass an electric current through salt water1 between graphite electrodes1 chlorine goes to the anode and escapes1 while caustic soda is formed round the cathode and hydrogen escapes4 ,let us see now how this is applied commercially4 ,for the production of ,chlorine the apparatus need be little more than our experimental apparatus made large4 ,the anode can be covered in such a way as to catch the gas as it bubbles upwards4 ,in times of peace this gas is chiefly used for making bleaching powder4 ,it is led into chambers where it comes into contact with lime1 with which it combines into chloride of lime1 a powder which is sometimes used as a disinfectant1 but the chief use of which is for bleaching those cotton and woollen fabrics for the manufacture of which this country is famous throughout the world4 ,the ,germans1 however1 have taught the world another use for chlorine4 ,those gallant ,canadians who were the first victims of the attack by poison gas who suddenly found themselves fighting for breath1 and a few of whom1 more fortunate than the rest1 have reached their homes shattered in health with permanent damage to their lungs1 those brave fellows suffered from poisoning by chlorine4 ,we cannot obtain the other product1 the caustic soda1 by the same simple means4 ,in our little experiment we succeeded in manufacturing some of it in the region around the cathode1 and had we drawn off some of the liquid from there we would have been able to detect its presence4 ,but it would have been mixed up with much ordinary salt1 and for commercial purposes we need the caustic soda separate from the salt4 ,the principle is1 however1 just the same1 as you will see4 ,imagine a large oblong vat divided by vertical partitions into three separate chambers4 ,these partitions do not quite reach the bottom of the vessel1 so that there is a means of communication between all three chambers4 ,this is closed1 however1 by filling the lower part of the vat with mercury up to a level a little higher than the lower ends of the partitions4 ,thus we have three separate chambers with communication between them but that communication is sealed up by the mercury4 ,the two end chambers are filled with salt water1 or brine1 while the centre one is filled with a solution of caustic soda4 ,in each end compartment is a stick of graphite1 both being electrically joined together and so connected up that they form anodes1 while in the centre compartment is the cathode4 ,when the current flows from the anodes it carries the sodium ions with it1 just as it did in our little experiment4 ,but its course1 this time1 is not straight1 since in order to travel from anode to cathode it has to pass through the openings in the partitions1 in other words through the mercury4 ,on arrival at or near the cathode the ions of sodium cause the caustic soda to be formed just as in our experiment1 but in this case1 you will notice1 the formation takes place in a chamber from which the salt brine is completely excluded by the mercury4 ,brine is continually fed into the outer chambers and the solution of caustic soda is drawn from the centre one1 while the chlorine is collected over the anodes4 ,and now we can go a step further on our progress from common salt to explosive4 ,in the soap works there are enormous coppers in which are boiled various kinds of fat4 ,the source of the fat may be either animal or vegetable1 many kinds of beans1 nuts and seeds furnishing fats practically identical with that which can be got from the fat flesh of a sheep1 for instance4 ,to this fat is added some caustic soda solution and the whole is kept boiling for some considerable time4 ,this protracted boiling is to enable the soda thoroughly to attack the fat and combine with it1 whereby two entirely new substances are formed4 ,at first the two new substances are not apparent1 for they remain together in one liquid4 ,the addition1 however1 of some brine causes the change to become obvious for something in the liquid turns solid1 so that it can be easily taken away from the rest4 ,that solid is nothing else than soap4 ,it remained dissolved in the water which forms part of the liquid until the salt was put in1 but as it will not dissolve in salt water1 as you will discover if you attempt to wash in sea water1 it separates out as soon as the salt is added4 ,but still a liquid remains3 what can that be8 ,it is mainly salt water and glycerine1 that sticky stuff which in peace times we put on our hands if they get sore in winter1 or take1 in a little water1 to soothe a sore throat4 ,that it has other and very different uses was brought home to me when1 during the war1 ,i tried to buy some at a chemist's1 only to learn that it could not be sold except in cases of extreme need under the orders of a doctor4 ,the mixed liquid is distilled with the result that the water is driven off and the salt deposited1 which with other minor purifying processes gives the pure glycerine4 ,the next step takes us to the explosives factory1 where the glycerine is mixed with sulphuric and nitric acids4 ,now glycerine1 as you will have observed1 comes from the animal or vegetable sources and therefore is one of those substances known as organic1 and1 like many other of the organic compounds1 it consists of carbon1 hydrogen and oxygen4 ,nature has a marvellous way of combining these same three things together in many various ways to form many widely different substances and if1 to such a compound1 we can add a little nitrogen1 we usually get an explosive4 ,thus1 the glycerine1 with some nitrogen from the nitric acid1 becomes nitro-glycerine1 a most ferocious and excitable explosive1 the basis of several of those explosives without which warfare as we know it to-day would be impossible4 ,,chapter ,,ii ,,gunpowder ,,and ,,its ,,modern ,,equivalents ,the origin of gunpowder appears to be lost in antiquity4 ,at all events it has been in use for many centuries and is still made in many countries4 ,most boys have tried to make it at some time or other and with varying degrees of success4 ,such experiments generally lead to a glorious blaze1 a delightfully horrid smell and no harm to anyone1 the experimenter owing his safety to his invariable lack of complete success1 for although other and better explosives have superseded it for many purposes it is capable of doing a lot of harm when it is well made4 ,it consists of a mixture of charcoal1 sulphur and saltpetre ground up very fine and mixed very intimately together4 ,the mixture is wetted and pressed into cakes and dried1 after which it is broken up into small pieces4 ,the precise proportions of the various materials seem to vary a great deal in different countries1 but generally speaking there is about #ge per cent of saltpetre 7or to give it its scientific name1 nitrate of potash71 #ae per cent of charcoal and #aj per cent of sulphur4 ,now gunpowder1 like all explosives1 is simply some thing or mixture of things which is capable of burning very quickly4 ,when we light the fire we set going the process which we call combustion1 or burning1 and1 as we know from our own experience1 that process causes heat to be generated4 ,what takes place in the fire-grate is that the carbon of the coal enters into combination with oxygen from the air1 the two together forming a new compound called carbonic acid gas4 ,there is nothing lost or destroyed in this process1 the carbon and oxygen simply changing into the new substance1 and could we weigh the gas produced we should find that it agreed precisely with the weight of the carbon and oxygen consumed4 ,for the purpose for which we require the fire1 namely1 to heat the room1 the chief feature about this process is not what is formed in the shape of gas1 for that simply goes off up the chimney1 but the heat which is liberated4 ,we believe that in some mysterious way the heat is locked up in the coal4 ,latent is the term we use1 which means hidden3 in other words we believe that the heat is hidden in the coal3 we cannot feel it or perceive it in any way1 but it comes out when we let the carbon combine with the oxygen4 ,why these two things combine at all is one of those mysteries which may never be solved4 ,we have theories on the subject1 but all we really know is that under certain conditions if they be in contact with one another they will combine1 apparently for the simple reason that it is their nature so to do4 ,when we apply the match to the fire all we do is to set up the conditions under which the carbon and oxygen are able to follow their natural instincts1 so to speak4 ,a coal fire1 as we all know1 burns slowly1 for the simple reason that it is only at the surface of the lumps that carbon and oxygen are in contact4 ,if we grind up the coal into a fine powder and then blow it into a cloud1 so that every tiny particle is surrounded with air1 a spark will cause an explosion4 ,that is how these terrible explosions in coal-pits are caused4 ,this is sometimes seen on a small scale when one shakes the empty fire-shovel after putting coal on the fire to get rid of the fine dust adhering to it and to save making a mess in the fender4 ,that little cloud of fine dust will often burst into flame like a mild explosion4 ,we see from this that to make an explosion we require fuel1 just as we do to make a fire3 but we need that it shall be very intimately mixed with oxygen1 so that all of it can burn up in practically a single instant4 ,now in gunpowder we get these conditions fulfilled4 ,we have the carbon in the shape of charcoal1 we also have some sulphur which likewise burns readily1 and we have saltpetre which contains oxygen4 ,thus1 you see1 we do not need to go to the air for the oxygen1 for the gunpowder possesses it already1 locked up in the saltpetre4 ,moreover1 we can see now why it is so important for all the materials to be ground up very fine1 for it is only by so doing that we can ensure that every particle of charcoal or sulphur shall have particles of saltpetre close by ready to furnish oxygen at a moment's notice4 ,another thing to be observed1 for it lets us into the great key to the manufacture of nearly all explosives1 is the scientific name of saltpetre4 ,it is nitrate of potassium1 and all substances whose names begin with nitr- contain nitrogen3 while the termination ate signifies the presence of oxygen4 ,we need the oxygen to make the explosion but we do not need the nitrogen1 yet the latter has to be present for without it the oxygen would be too slow in getting to work4 ,nitrogen is one of the strangest substances on earth4 ,extremely lazy itself1 it has the knack of hustling its companions1 particularly oxygen1 and making them work with tremendous fury4 ,whenever we get the lazy gas nitrogen to enter into a combination with other things we may confidently look for extraordinary activity of some sort4 ,so when we put a light to a quantity of gunpowder we set up those conditions under which the carbon and oxygen can combine1 and at the same moment our lazy friend the nitrogen turns out his partner oxygen from the nitrate in which they were till then combined and a sudden burning is the result4 ,the solid gunpowder is suddenly changed into a volume of hot gas #bejj times as great4 ,that is to say1 one cubic inch of gunpowder changes suddenly into #bejj cubic inches of gas4 ,that sudden expansion to #bejj times its volume is what we term an explosion4 ,if it takes place in an enclosed space so that the gas formed wants to expand but cannot1 the result is a pressure of about forty tons per square inch4 ,if that enclosed space were the interior of a gun1 that force of forty tons per square inch would be available for driving out the projectile4 ,now1 gunpowder is still used for sporting purposes and also for some special purposes in warfare1 but it has the great disadvantage that it makes a lot of smoke1 so that the enemy would be easily able to locate the guns were it to be used in them4 ,as we know so well1 by the messages from ,france1 guns and rifles drop their shells and bullets apparently from nowhere and are extremely difficult to locate4 ,that is owing to the use of improved powders one of the great features of which is their smokelessness4 ,the reason why gunpowder makes a dense smoke1 is because the burning which takes place is very incomplete4 ,therefore1 by some such means as a more intimate mixture of the materials a better and more complete burning must be brought about4 ,one of the best known of the new powders 7they are all spoken of as powders1 whatever their form1 since they have taken the place of the old gunpowder7 is nitro-glycerine1 the basis of which is glycerine4 ,the way in which we obtain this useful material has already been explained4 ,it consists of carbon1 a lot of hydrogen and some oxygen4 ,these are not merely mixed together but are in combination1 just as oxygen and hydrogen are combined in water4 ,carbon and hydrogen will both combine with oxygen and will give off heat in the process1 but in glycerine they are already happily united together and so glycerine itself is no use as an explosive4 ,if1 however1 we bring nitric acid and sulphuric acid into contact with it a pair of new partnerships is set up1 one being water and the other a compound containing carbon and hydrogen1 a lot of oxygen and1 most important of all1 some of that disturbing1 restless though lazy nitrogen4 ,this is nitro-glycerine1 a particularly furious explosive1 for that curious nitrogen seems to be so uncomfortable in his new surroundings that at the smallest provocation he will break up the whole combination and then there will be a mass of free atoms of carbon1 hydrogen and oxygen1 all seeking new partners1 just right for a glorious explosion4 ,so furious and untamed is this stuff that it was almost useless until the famous ,nobel hit upon the idea of taming it down by mixing it with an earth called ,kieselguhr1 which reduces its sensitiveness sufficiently to make it a very safe explosive to use4 ,to this mixture ,nobel gave the name of dynamite4 ,it is interesting at this point to compare the action of this typical modern explosive with that of the older gunpowder4 ,the latter is only a mixture3 the former is a chemical compound4 ,the smallest particle of material in the gunpowder is a little lump containing millions of molecules and still more of atoms3 when the nitrogen has broken up the original nitro-glycerine1 just before the explosion actually takes place1 we have a mixture of single atoms4 ,thus the mixture is far more intimate in the latter case and the burning is therefore quicker and more thorough4 ,illustration3 ,,machine-,,gun versus ,,rifle4 ,this illustrates the rapidity and accuracy with which the modern rifle can be used4 ,sergeant ,o',leary1 ,v4,c41 tackled a gun crew of five and killed them all before they had time to slew their gun round--a striking contrast to the ,brown ,bess of a hundred years ago4 ,another well-known explosive is gun-cotton4 ,surely this must be a fancy name1 for what can harmless1 simple cotton have to do in connection with guns4 ,it is a perfectly genuine descriptive name1 however4 ,it seems very strange at first1 but it is perfectly true that nitrogen1 as it turned glycerine into dynamite1 can also turn cotton into gun-cotton4 ,cotton consists mainly of cellulose1 a compound of carbon1 hydrogen and oxygen1 happily combined together and therefore showing1 as we well know from experience1 no tendency whatever to change into anything else1 least of all to go off bang4 ,but that state of things is very much changed when we have induced nitrogen to take a hand in the game4 ,in actual practice1 cotton waste1 pure and clean1 is dipped into a mixture of sulphuric and nitric acids whereby the cellulose becomes changed into nitro-cellulose1 just as a similar process changes glycerine into nitro-glycerine4 ,the whole process of manufacture is of course far more than that simple dipping1 but that is the fundamental fact of it all4 ,the rest is concerned with getting rid of the superfluous acid1 tearing the stuff into pulp and pressing it into blocks4 ,it is probably the safest of explosives1 since it can be kept wet1 in which case the danger of an accidental explosion is practically nil1 provided reasonable care be taken4 ,even when dry1 it behaves in a very kindly way4 ,if hit with a hammer1 it only burns for a moment just at the point struck4 ,if ignited with a red-hot rod1 it burns but does not explode1 unless it is enclosed4 ,the burning1 that is to say1 is not sufficiently rapid to constitute an explosion4 ,on the other hand1 if it be exploded by a detonator1 by which is meant a small quantity of a very powerful explosive1 such as fulminate of mercury1 fired close to it1 it then goes off with a violence which leaves little to be desired4 ,it would be better still could we persuade a little more oxygen to enter into its composition1 for as it is there is not quite enough to burn up the other matters completely4 ,that1 however1 does not cause smoke1 since the combustion is complete enough to change everything into invisible gases4 ,with more oxygen more heat might be generated and the power of the explosion be made greater4 ,still1 even as it is1 the explosion of gun-cotton has been estimated by a high authority to produce a pressure of #afj tons per square inch1 four times as much as gunpowder4 ,nitro-glycerine has the advantage of a rather larger proportion of oxygen to carbon1 resulting in its being rather more energetic4 ,yet another class of explosive is made from ,coal ,tar4 ,this is a by-product in the manufacture of gas for lighting and also in the manufacture of coke for industrial purposes4 ,it comes from the retorts along with the gas in a gaseous form but condenses into a black liquid in the pipes and more particularly in an arrangement of cooled pipes called a condenser specially placed to intercept it4 ,in the chemist's eyes it is the most interesting of liquids1 for it is full of mysteries and possibilities4 ,the most wonderful achievements of chemistry have it for their raw material and there is still scope for much more in the same direction4 ,if the tar be gently heated in a closed vessel it will evaporate and the vapour can be led to another vessel1 there cooled and converted back into a liquid4 ,this looks rather like doing work for nothing1 but the various liquids1 of which tar is a mixture1 evaporate at different temperatures1 so that this furnishes a means of separating them4 ,the first liquid thus procured is known as coal tar naphtha1 and if it be again distilled it can be subdivided further1 the first liquid separated from it being known as ,benzine4 ,this1 again1 is another of those almost numberless things which consist of carbon and hydrogen4 ,also1 like the other similar substances which we have been discussing1 it can1 if treated with nitric acid1 be made to take into partnership a quantity of oxygen and nitrogen4 ,thus we get nitro-benzene4 ,we can repeat the process1 when it will take more and become di-nitro-benzene4 ,again we can repeat it1 thus producing tri-nitro-benzene4 ,the second liquid separated from coal tar naphtha is called ,toluene1 which again is composed of carbon and hydrogen in slightly different proportions4 ,like its confrre benzene it1 too1 can be treated with nitric acid1 becoming nitro-toluene and then di-nitro-toluene and finally tri-nitro-toluene1 the deadly explosive of which we read in the papers as ,t4,n4,t4 ,after the naphtha has been removed from the tar another substance is obtained called ,phenol1 which in a prepared form is familiar to us all as the disinfectant ,carbolic ,acid4 ,it also can be treated with nitric acid1 to produce tri-nitro-phenol1 otherwise known as ,picric ,acid1 which after a little further treatment becomes the famous ,lyddite4 ,most of the actual explosives used in warfare are prepared from one or more of the above-mentioned compounds4 ,for example1 nitro-glycerine and gun-cotton1 having been dissolved in acetone 7another compound of carbon1 hydrogen and oxygen7 and a little vaseline added1 form a soft gelatinous substance which on being squeezed through a fine hole comes out looking like a cord or string1 and hence is called ,cordite4 ,other explosives are finished in the form of sheets1 the dissolved gun-cotton or whatever it may be being rolled between hot rollers which give it the convenient form of sheets and at the same time evaporate the solvent4 ,by combining these various substances various characteristics can be given to the finished explosive4 ,for instance1 the one which drives the shell from the gun1 known as the propellant1 must not be too sudden in its action4 ,it must push steadily4 ,its purpose is to drive the shell not to burst the gun1 wherefore its action must be comparatively slow and continuous so long as the shell is still in the gun4 ,it must follow through as the golf player would put it4 ,the charge in the shell1 however1 needs to go off with the greatest possible violence so as to blow the shell to pieces and to scatter the fragments so that they do the maximum of damage4 ,those explosives1 whose function is thus to burst with a sudden shock1 are called ,high ,explosives1 as distinguished from the propellants which produce a more or less sustained push4 ,the great fundamental principle which enables large quantities of these powerfully explosive substances to be handled with comparative safety involves the use of two different substances in combination4 ,that which is used in quantity and which actually does the work is made comparatively insensitive1 indeed in some cases it is very insensitive1 so that it can safely travel by train1 by ship and by road and also may be handled by the soldiers and sailors with very little risk4 ,some of these compounds can be struck or set on fire with impunity4 ,they are none the less violent1 however1 when1 by the agency of a suitable detonator they are caused to explode4 ,the detonator1 of course1 has to be very sensitive indeed1 but it need only be used in very small quantities1 so that by itself it1 too1 is comparatively safe4 ,fulminate of mercury is often employed for this purpose--a compound based upon mercury but in which nitrogen of course figures largely4 ,thus1 there are two things necessary for the successful explosion1 one of which is powerful but insensitive1 while the other is highly sensitive but relatively harmless since it is never allowed to exist in large quantities1 and as far as possible these are kept apart until the last moment4 ,one other thing may be mentioned in regard to this matter which is of the greatest importance4 ,that is the necessity for the utmost uniformity in these various compounds1 so that when the gunners put a charge into a gun they can rely upon it to throw the shell exactly as its predecessor did4 ,modern artillery seeks to throw shell after shell within a small area which would clearly be quite impossible if one charge were liable to be stronger or weaker than another1 for we can easily see that the more powerful the impetus given the farther will the shell go4 ,to secure this uniformity the greatest care is taken at all stages of the manufacture1 and various batches of the same stuff are tested and mixed1 and any of them turning out a little too strong are placed with some a little too weak1 so that their faults may neutralize each other4 ,by such methods as these a remarkable degree of uniformity is attained1 the result of which we see when we read in the papers of the wonderfully accurate gunnery of which our soldiers and sailors are capable4 ,in conclusion1 a word of warning may be appropriate4 ,reference has been made above to the safety of modern explosives in the absence of the detonators1 but do not let that lead anyone to take liberties4 ,should any reader come into possession of any of these materials1 even in the smallest quantities1 let him treat it with the utmost respect1 for although what has been said about safety is quite correct1 it only means comparative safety1 there can be no absolute safety where these substances are concerned4 ,,chapter ,,iii ,,radium ,,in ,,war ,when we remember how all forms of scientific knowledge were called upon to help in the great struggle1 it is not surprising to hear that1 although in a comparatively humble way1 ,radium has had to do its share4 ,now radium is one of the most1 if not actually the most1 remarkable substance known4 ,about a generation ago scientific men1 or some of them at all events1 were getting rather cocksure4 ,of course they were quite right when they realized how much was known about things and what great strides had been made during the years through which they had lived4 ,they were proud of the achievements of their scientific friends1 for ,i am not imputing personal vanity to anyone1 and they had reason to be proud4 ,they made the mistake1 however1 of thinking that in one direction at least they had learnt all that there was to be known4 ,the present generation of scientific men seem to be almost too prone to go to the other extreme and to dwell rather much on how little we know now and the wonderful things which are going to be discovered in time4 ,but that is by the way4 ,a generation ago men seem to have pretty well made up their minds that they knew all about atoms4 ,they said that everything was made up of atoms1 that the atoms could not be subdivided nor changed into anything else except temporarily by combination with other atoms1 and that when these combinations were broken up the atoms remained just as before1 quite unchanged4 ,they believed that the atoms were unchangeable and everlasting4 ,professor ,tyndall1 in a famous address1 referred to this in somewhat flowery language1 telling his hearers that the atoms would be still the same when they and he had melted into the infinite azure of the past1 which a wag translated into the slang expression of the time1 till all is blue4 ,now not very long after ,professor ,tyndall made this historic speech ,professor ,henri ,becquerel1 of ,paris1 was trying some experiments with phosphorescent materials1 that is1 materials which glow in the darkness4 ,in the course of these experiments he used some photographic plates upon which1 to his surprise1 he found marks which he thought ought not to have been there4 ,thinking at first that he had accidentally fogged his plates1 as every photographer has done at some time or other1 he tried his experiments again with special care but still he got the mysterious marks4 ,those marks were caused by some of those unchangeable and everlasting atoms deliberately and of their own accord blowing themselves to bits4 ,for the celebrated ,frenchman was not content to let the matter of those mysterious marks rest3 he wanted to know what caused them and he did not desist until he was on the track of the secret4 ,it appeared after careful investigation that they were made by the action of something in some of the ore of the metal uranium which he had been using4 ,moreover1 this something evidently had the power of penetrating through the walls of the dark-slide to the plate within4 ,finally1 it was tracked down to the uranium itself which was unquestionably proved to be giving off something in the nature of invisible light1 or at all events invisible rays1 of strange penetrative power4 ,a little later it was observed that certain ores of uranium seemed to give off these rays more freely than would be accounted for by the amount of uranium present1 from which fact it was inferred that there must be something else present in the ore capable of giving off the rays much more powerfully than uranium can4 ,madame ,curie ultimately found out two such substances1 one of which she called1 after her native land1 ,polonium 7for she is a ,pole71 and the other ,radium4 ,it is the latter which is responsible for by far the greater part of the rays formed4 ,the rays are invisible1 but they affect a photographic plate in the same way that light does4 ,they also make air into a conductor of electricity and if allowed to impinge upon a surface coated with a suitable substance they cause it to glow4 ,this spontaneous giving off of rays is now spoken of by the general term of radio-activity1 and it has grown into an important branch of science4 ,a number of other substances have been found to exhibit the same peculiar ray-forming powers1 notably ,thorium1 one of the components of the incandescent gas mantle by the prolonged application of a fragment of which to a photographic plate an impression can be obtained due to the rays4 ,what1 then1 are these rays8 ,it is found that they are of three kinds1 not that they vary from time to time1 but that they can be sorted out into three different sorts of rays which are given off simultaneously all the time4 ,the first sort are stopped by a sheet of paper1 the second passing easily through a thick metal plate1 while the third appear to be identical with ,x-rays4 ,for convenience the three sorts are termed ,alpha1 ,beta and ,gamma rays1 respectively1 after the first three letters of the ,greek alphabet4 ,further1 the ,alpha rays prove to be a torrent of tiny particles about the size of atoms1 indeed if they be collected the gas ,helium is obtained1 so that evidently they are helium atoms1 and since that is one of those substances whose molecules consist of a single atom each they are also molecules of helium4 ,no doubt the reason why they are so easily stopped by a piece of paper is because being complete atoms they are large1 huge indeed1 compared with the particles which form the ,beta rays1 for they are apparently those same electrons which are found in the ,x-ray tube1 and which are at least #bjjj times smaller than the smallest atom4 ,when the electrons in the vacuum tube are suddenly brought to a standstill ,x-rays are given off and in like manner ,x-rays no doubt would be given off when they start on their journey1 providing that they started suddenly enough4 ,hence it is the starting or sudden explosion-like ejection of the ,beta particles which is believed to give rise to the ,gamma rays4 ,the strength or intensity of the rays can be measured very conveniently by their action in making air conductive to electricity1 for which purpose a very beautiful but simple instrument called an ,electroscope is employed4 ,it consists generally of a glass-sided box or else a bottle with a large stopper1 consisting of sulphur or some other particularly good insulator4 ,through this a wire passes down into the inside of the vessel terminating in a vertical flat strip to the upper end of which is attached a similar strip of gold leaf or aluminium foil4 ,normally the leaf hangs down close to the strip1 but if the wire above the stopper be electrified by touching it with a piece of sealing-wax rubbed lightly against the coat sleeve the charge of electricity passes down into the inside and causes both strip and leaf to become so electrified that they repel each other4 ,owing to the non-conductivity of the air in its normal condition the leaf will1 if the insulation of the stopper be good1 remain projecting almost horizontally for some time until1 as it loses its charge by a slow leakage1 it gradually settles down close to the strip4 ,if1 however1 a piece of radium be brought near while it is sticking out1 the leaf will fall almost instantly4 ,x-rays have a similar effect even from several feet or yards away4 ,the intensity of the radio-activity of different substances can be compared by noting the difference in the rate at which the leaf falls under the influence of each4 ,what is happening1 then1 to the atoms of radium1 which causes them to show these curious effects and to give off these strange rays8 ,to give any intelligent answer to that question we are bound to assume that which the older generation of scientists thought impossible1 namely1 that atoms can be broken up4 ,then we are forced to believe that the atoms of this particular substance radium are of a peculiarly flimsy unstable sort1 so that they cannot permanently hold their parts together but are liable to break up1 as far as we can see through their own inherent weakness and under the influence of disruptive forces at work within themselves4 ,we must remember1 however1 that the tiniest speck of matter which we can see contains a number of atoms of such a size as to be quite beyond the grasp of our minds4 ,to give a rough idea of it in figures is useless as no one can comprehend the real value of a figure or two followed by probably from a dozen to twenty noughts4 ,it is best to content ourselves with the general statement that a speck of matter only just visible to the eye contains an exceedingly vast number of atoms4 ,of course a speck of radium is no exception to this and we must remember1 too1 that all of them do not break up at once4 ,indeed1 the number breaking up at any time are actually countable by means of a very simple contrivance and a sensitive electrometer4 ,consequently1 in view of the enormous number present and the comparatively small number breaking up at any moment1 it is not surprising to hear that1 so it is estimated1 the process can go on for an almost indefinite number of years1 certainly for hundreds4 ,there are1 moreover1 certain facts which we need not go into here from which the above fact can be clearly inferred1 quite apart from what has been said about the vast numbers of the atoms4 ,it seems as if the uranium atoms break up first1 giving off helium atoms and electrons and leaving an intermediate substance called ,ionium which in its turn breaks up giving off the same things again and leaving radium4 ,that in its turn goes through a complicated series of changes still giving off the same alpha particles or atoms of helium and electrons until1 it is suggested1 it finally settles down into the simple commonplace metal lead of which we make bullets and water pipes and such-like ordinary things4 ,we see then that all through its history--its radio-active history at any rate--this stuff is throwing off atoms of helium at a very high velocity 7about #ej1jjj miles a second71 and if it be enclosed in anything this enclosing vessel or substance will be subjected to a continual bombardment by the alpha particles4 ,now just as a piece of iron gets hot if we hammer it1 so the enclosing matter is heated by the continual blows which it is receiving night and day1 year in and year out1 from the alpha particles4 ,consequently the immediate surroundings of a speck of radium are always slightly raised in temperature4 ,moreover1 if a speck of radium be placed against a screen covered with suitable materials each particle which strikes it will make a little splash of light4 ,at least that is what it looks like when seen through a magnifying glass1 but to the naked eye there only appears a beautiful steady glow4 ,suppose1 then1 that instead of putting the speck of radiant matter in front of a screen we mix it up intimately with a fluorescent substance such as sulphide of zinc1 we then get the same conditions in a slightly different form4 ,each particle of the substance serves as a tiny screen which glows every time a particle hits it4 ,thus is produced a luminous paint which glows by night1 suitable for painting the dials of instruments which have to be used in the dark4 ,no doubt some of my readers will have experienced the strangely mingled delight and horror of seeing a ,zeppelin in the night sky intent on dropping murder and death on the sleeping civilians of a peaceful town or city4 ,some too may have witnessed the later acts in that wonderful drama1 when1 beside the silvery monster illuminated by the beams of the searchlight there must have been1 though quite invisible1 a little aeroplane manned by one man or at most two4 ,that aeroplane was1 no doubt1 fitted with instruments at which the pilot glanced now and then and which he was able to see and read because of the tiny speck of radium mixed into the paint4 ,the little alpha particles gave him the light by which to see1 but they gave no help to the ,germans on the ,zeppelin4 ,hence1 in due time he did his work and the gigantic balloon1 the pride of the ,kaiser and his hordes1 fell to the ground1 a blazing wreck4 ,how he did it ,i cannot tell1 but of this ,i am sure1 that most probably radium helped him by making luminous and visible the instruments which guided him4 ,but probably it has rendered and will still render us even greater services in the way of helping to repair the damages to our injured manhood4 ,how many men came back from the war crippled with rheumatism because of the hardships through which they went4 ,that disease is believed to be due to a substance which mingles with the blood and which1 although usually liquid and harmless sometimes changes into a solid and settles in the joints4 ,now it is believed that radium properly administered will act upon that solid and cause it to change back into its liquid form again1 thereby curing the disease4 ,certainly many of the mineral springs at such places as ,bath and ,buxton give forth a water which shows a certain amount of radio-activity and it may be that which gives those waters their healing properties4 ,if so1 we may look forward with confidence to the time when radio-activity will be induced to play a still more successful part in meeting this painful and widespread illness4 ,then1 of the other ills which will inevitably arise in our men through the hardships which they have endured are sure to be some of the cancerous type1 many of which appear to succumb to treatment by radium4 ,if a very small quantity indeed be carried for a few days in a pocket it will imprint itself upon the skin beneath as if it burnt the tissues4 ,it is never advisable1 therefore1 to carry radium in the pocket without special precautions4 ,one cannot help feeling1 however1 that in that little fact is a hint of usefulness when the best modes of application have been discovered1 for as a means of safely and painlessly burning away some undesirable growth it would seem to be without a rival4 ,it is said1 too1 that it has the strange power of discriminating between the normal and the abnormal1 attacking the latter but leaving the former1 so that when applied1 say1 to some abnormal growth like cancer it may be able to remove it without harmful effect upon the surrounding tissues4 ,of this1 however1 it is too soon to write with confidence4 ,it has not been known long enough for our doctors to find out the best modes of use1 but that will come with time3 meanwhile there are indications that in all probability it will render good service to mankind4 ,,chapter ,,iv ,a ,,good ,,servant1 ,,though ,a ,,bad ,,master ,one morning during the war the whole ,british nation was startled to learn that ,mr4 ,lloyd ,george1 then the ,minister of ,munitions1 had taken over a large number of distilleries4 ,could it be that he1 a teetotaller and temperance advocate1 was going to supply all his workers with whiskey8 ,or was he going to close the places so as to stop the supply of that tempting drink8 ,neither of these suggestions was his real reason4 ,what he wanted the distilleries for was to make alcohol for the war1 not for drinking purposes but for the very many uses which only alcohol can fulfil in most important manufactures4 ,probably alcohol is the next important liquid to water4 ,for example1 certain parts of shells have to be varnished and the only satisfactory way to make varnish is to dissolve certain gums in alcohol4 ,the spirit makes the solid gum for the time being into a liquid which we can spread with a brush1 yet1 after being spread1 it evaporates and passes off into the air1 leaving behind a beautiful coating of gum4 ,that is how all varnishing is done1 the alcohol forming the vehicle in which the solid gum is for the moment carried and by which it is applied4 ,it is far and away the most suitable liquid for the purpose1 and without it varnishing would be very difficult and unsatisfactory4 ,hence one need for alcohol1 to carry on the war4 ,then again some of the most important explosives are solid or semi-solid1 and yet they require to be mixed in order to form the various powders in use by our gunners4 ,the best way to bring about this mixture is to dissolve the two components in alcohol1 thereby forming them both into liquids which can be readily mixed4 ,afterwards the alcohol evaporates2 indeed1 one of its great virtues for this and similar purposes is that it quietly takes itself off when it has done its work like a very well-drilled servant4 ,what then is this precious liquid and how is it produced8 ,in order to answer that question it is necessary first to state that there are a whole family of substances called alcohols1 all of which are composed of carbon1 hydrogen and oxygen in certain proportions4 ,there are also a number of kindred substances also1 not exactly brothers but first cousins1 so to speak1 which because of their resemblance to this important family have names terminating in ol4 ,they owe their existence to the wonderful behaviour of the atoms of carbon4 ,in order to obtain some sort of system whereby the various combinations of carbon can be simply explained chemists picture each carbon atom as being armed with four little links or hooks with which it is able to grapple1 as it were1 and hold on to other atoms4 ,each hydrogen atom1 likewise1 has its hook1 but only one instead of four4 ,now it is easy to picture to ourselves an atom of carbon in the middle with its hooks pointing out north1 south1 east and west with a hydrogen atom linked on to each4 ,that gives us a picture of the molecule of ,methane1 the gas which forms the chief constituent of coal gas such as we burn in our homes4 ,methane is also given off by petroleum and it is the cause of the explosions in coal mines1 being known to the miners as firedamp4 ,it is the first of a long series of substances which the chemist called paraffins4 ,the first1 as you see1 consists of one of carbon and four of hydrogen4 ,add another of carbon and two more of hydrogen and you get the second ,ethane4 ,add the same again and you get the third1 ,propane1 and so on until you can reach a substance consisting of thirty-five parts of carbon and seventy-two parts of hydrogen4 ,all we need trouble about1 however1 is the first two1 ,methane and ,ethane4 ,we have pictured to ourselves the molecule of methane3 let us do the same with ethane4 ,imagine two carbon atoms side by side linked together or hand in hand4 ,each will be using one of its hooks to grasp one hook of its brother atom4 ,hence each will have three hooks to spare on to which we can hook a hydrogen atom4 ,thus we get two of carbon and six of hydrogen neatly and prettily linked up together4 ,the atoms form an interesting little pattern and to build up the various paraffin molecules with a pencil and paper has all the attractions of a puzzle or game4 ,all you have to do is to add a fresh atom of carbon alongside the others and then attach an atom of hydrogen to each available unused hook4 ,if you care to try this you will get the whole series1 each one having one atom of carbon and two of hydrogen more than its predecessor4 ,if you mix together a quantity of methane and an equal quantity of chlorine1 which ,i have shown you in another chapter how to get from common salt1 a change takes place1 for in each molecule of methane one hydrogen atom becomes detached and an atom of chlorine takes its place4 ,how or why this change occurs we do not know4 ,it is a fact that the chlorine has this power to oust the hydrogen and there we must leave it1 for the present at any rate4 ,the substance so formed is called methyl chloride4 ,in another chapter reference has been made to that substance which is made from common salt and which is so important in so many manufactures called caustic soda4 ,if we bring some of it into contact with the methyl chloride the chlorine is punished for its rudeness in displacing the hydrogen2 it is paid back in its own coin1 for it is in turn displaced not this time by a single atom but by a little partnership called hydroxyl one atom of hydrogen and one of oxygen acting together4 ,we can again form a neat little picture of what happens4 ,the oxygen atom has two hooks1 one of which it gives to its friend the hydrogen atom and thus they go about hand-in-hand1 the oxygen having one unused hook with which to hook on to something else4 ,in this case it hooks on to that particular hook from which it pushes the chlorine4 ,we have thus seen two changes take place4 ,first1 the hydrogen is displaced by the chlorine3 then the chlorine is turned out and its place taken by the hydroxyl4 ,and during both these changes the central carbon atom and its three hydrogen partners have remained unaffected4 ,those four atoms are called the methyl group1 and a methyl group combined with a hydroxyl group forms methyl alcohol4 ,similar changes can be brought about with ,ethane as with ,methane1 and in them the two carbon atoms and the five hydrogen remain unchanged1 whence they too are regarded as a group1 the ,ethyl group1 and an ethyl group hooked on to a hydroxyl group gives us a molecule of ethyl alcohol4 ,these groups of which we have been speaking never exist separately except at the moment of change1 but in the wonderful changes which the chemist is able to bring about the atoms forming these groups seem to have a fondness for keeping together and moving together from one substance into another4 ,in a word1 they behave as if they were each a single atom and they are called by the name of ,radicles2 the word simply means a little root4 ,the methyl radicle and the ethyl radicle1 since they form the basis of two of the paraffin series1 are called paraffin radicles1 so that we can describe this useful alcohol as a paraffin radicle with a hydroxyl radicle hooked on to it4 ,if we use the methyl radicle we get methyl alcohol3 if we use the ethyl radicle we get ethyl alcohol4 ,now ethyl alcohol is the spirit which is contained in all strong drink4 ,whiskey has as much as #dj per cent and brandy and rum about the same1 while ale has only about #f per cent4 ,all of them may be regarded as impure forms of ethyl alcohol1 the various impurities giving to each its particular taste4 ,ethyl alcohol1 too1 is what is sold at chemists' shops as spirits of wine1 where also we can purchase that which is familiar as methylated spirits1 whereby there hangs a tale4 ,all ,governments regard alcohol for drinking as a fit subject for taxation4 ,when anyone buys a drink with alcohol in it a part of what he pays goes to the ,government in the form of duty4 ,on the other hand1 when alcohol is used for trade purposes1 for making varnish or something like that1 there is no reason whatever why it should be charged with duty4 ,but if the varnish manufacturer is to have alcohol duty-free what is to prevent him from using some of it for drinking8 ,to get over the difficulty1 that which is supplied to him or to anyone else for trade purposes is deliberately adulterated so as to make it so extremely nasty that no one is likely to want to put it in his mouth4 ,it so happens that methyl alcohol1 while as good as the other for many purposes1 is horrible to the taste and so it forms a very convenient adulterant for this purpose4 ,therefore1 when methylated spirit is sold to you for drying your photographs1 the chemist gives you ethyl alcohol with enough methyl alcohol in it to make sure that neither you nor anyone else will ever want to drink it4 ,that1 then1 is alcohol3 a near relative of paraffin oil and also of coal gas1 yet it is from neither of these that we get it4 ,the changes described above enable you to realize what it is1 but they do not tell how it is made in large quantities4 ,ethyl alcohol is obtained from sugar by the employment of germs or microbes4 ,any sort of sugar will do3 it need not be sugar such as we eat4 ,in practice the sugar is usually obtained from starch1 that very common substance which forms the material of potatoes1 grain of all kinds1 beans and so on4 ,there is a kindly little germ which will quite readily turn starch into sugar for us if we give it the chance4 ,the maltster starts the process4 ,he gets some grain1 and spreading it out in a damp condition upon his floor sets it a-growing4 ,as soon as it has just started to grow1 however1 he transfers it to his kiln1 where by heating it he kills the young plants4 ,as is well known1 every seed contains the food to nourish the little growing plant until it is strong enough to draw its supplies from the soil and the food thus provided for the young wheat plant is starch1 which1 when it is ready for it1 it turns into sugar4 ,the little shoot lives on sugar and the maltster and distiller conspire to steal that sugar intended for the baby plants and turn it into alcohol4 ,so the little plant liberates by some wonderful means a material called diastase1 which has the power of changing starch into sugar4 ,it does it1 of course1 for the purpose of providing its own necessary food1 but the maltster does not want the process to go too far3 he only wants to produce the diastase1 and that is why he kills the plants1 after which he has finished with the matter and hands the malted grain or malt over to the distiller for the next process4 ,the distiller mixes the malt with warm water1 whereupon the diastase commences the conversion of the starch of the grain4 ,at this stage fresh grain may be added and potatoes1 indeed almost anything composed largely of starch for the diastase to work upon4 ,the process goes on until1 in time1 the liquid consists very largely of sugar dissolved in water1 which is strained away from what is left of the grain1 etc4 ,malt sugar is very similar to1 but not quite the same as1 cane sugar4 ,it consists of twelve parts of carbon1 twenty-two of hydrogen and eleven of oxygen4 ,it is an interesting little puzzle to sketch those atoms out on paper1 each with its proper number of hooks1 and see how they can be combined together4 ,malt sugar1 milk sugar and cane sugar all consist of the same three elements in the same proportions and the difference between them is no doubt due to the different ways in which the atoms can be hooked up together4 ,yeast is next added to the liquid1 upon which the process of fermentation is set up1 the tiny living cells of the yeast plant producing a substance which is able to change the sugar into alcohol4 ,the alcohol thus formed is1 of course1 combined with water1 but it can be separated from it by gentle heating since it passes off into vapour at a lower temperature than does water4 ,thus the vapour first arising from the mixture is caught and cooled whereby the liquid alcohol is obtained4 ,this operation1 called fractional distillation1 has to be repeated if alcohol quite free from water is required1 in addition to which the attraction which quicklime has for water is called into play to coax the last remnant of water from the other4 ,and now1 how about the methyl alcohol8 ,that is obtained in quite a different way1 by heating wood and collecting the vapours given off by it4 ,hence it is often called wood spirit4 ,as a matter of fact1 at least two very valuable substances are obtained by this operation1 methyl alcohol and acetone4 ,the vapours given off by the wood are cooled1 whereupon tar is formed while upon it there floats a dark liquid which contains the wood spirit1 acetic acid and acetone4 ,to capture the acetic acid lime is added to the mixture1 and since there is a natural affinity between them1 the acetic acid and lime combine into a solid which remains behind when the whole mass is suitably heated4 ,what comes over in the form of vapour is a mixture of water1 acetone and wood spirit4 ,the former is enticed away by the use of quicklime1 while the other two are separated by the process of fractional distillation already referred to4 ,now let me ask you to form another little picture1 either in your mind or with paper and pencil4 ,imagine two methyl radicles1 each1 let me remind you1 a carbon atom with three hydrogen atoms hooked on and one spare hook4 ,also imagine one atom of oxygen with its two hooks outstretched like two arms1 and just link one radicle on to each4 ,then you have the picture of methyl ether4 ,all the ethers are formed by taking two of the paraffin radicles and linking them together by means of the two hooks of an oxygen atom4 ,the ether which is so largely used in hospitals for wounded soldiers is ethyl ether1 consisting of two ethyl radicles joined by oxygen4 ,how it is made we will come to in a moment1 but as you see already it is a close relative of alcohol4 ,now from methyl ether take away the central oxygen and in its place put carbon4 ,this atom will have two hooks to spare which it can employ to hold on to the two hooks of the oxygen4 ,the result is a molecule of acetone4 ,this is used as a solvent in a similar manner to alcohol for many purposes1 and there was a great demand for it no doubt during the war4 ,one interesting use of acetone is in connection with the gas acetylene4 ,of great use both for lighting and also in conjunction with oxygen for welding and cutting metals1 this gas suffers from the disadvantage that it cannot be compressed into cylinders and carried about as oxygen can4 ,it can1 however1 be dissolved in acetone4 ,the cylinders in which it is carried are therefore filled with coke saturated with acetone and then when the acetylene is pressed in it dissolves1 coming out of solution again as soon as the pressure is released4 ,in this dissolved condition it is quite safe to carry about4 ,for a moment let us turn back to the commencement of the chapter to the subject of methane4 ,when mixed with chlorine1 it will be remembered1 one hydrogen atom gave place to a chlorine atom4 ,if the process be repeated another hydrogen atom will be displaced in the same way1 while a further repetition will result in the removal of a third1 when there will be a carbon atom in the centre with three chlorine and one hydrogen hooked on to it4 ,with that picture in your mind's eye you will be contemplating the molecule of that wonderful and beneficent substance1 chloroform4 ,when we think of the numberless operations which have been carried out by the surgeons in the course of this last war we realize a little how great is the total sum of pain and suffering which has been saved through the agency of this substance1 this simple neat little arrangement of five tiny atoms4 ,now that again is obtained in manufacture from alcohol4 ,alcohol1 bleaching powder and water are mixed and then distilled1 by which of course is meant that the mixture is evaporated by heat and the vapour collected and cooled back into liquid again4 ,the liquid so obtained is chloroform4 ,hardly less important than this1 in our military hospitals1 is ether1 to which reference has already been made4 ,it1 too1 is manufactured from alcohol4 ,the alcohol1 together with sulphuric acid1 is placed in a still and heated1 the vapour given off being led to another vessel and there condensed4 ,the liquid thus obtained is ether and so long as the supply of fresh alcohol is kept up the production of ether goes on continuously4 ,the sulphuric acid does not disappear and so does not need to be replaced1 from which it would appear as if it might just as well not be there1 but that is not the case4 ,it plays the part of what is called a catalyst1 one of the curiosities of chemistry4 ,there are many instances in which two things will combine only in the presence of a third which appears to be itself unaffected4 ,this third substance is a catalyst4 ,it reminds one of the clergyman at a wedding who unites others but remains unchanged himself4 ,in conclusion1 one may mention that many of the medicines with which our injured men were coaxed back to health and strength owe their existence to alcohol1 for many drugs are obtained from vegetable substances by dissolving out a part of the herb with alcohol4 ,thus1 as a drink1 it is unquestionably very harmful4 ,indeed1 in that way it probably kills more people per year than its use in the manufacture of explosives caused in the worst year of the war4 ,yet it also furnishes chloroform1 ether and medicinal drugs and performs a whole host of useful services to mankind4 ,finally1 if oil and coal should ever run short it is quite prepared to run our engines for us4 ,truly it is a wonderful substance4 ,,chapter ,v ,,mines1 ,,submarine ,,and ,,subterranean ,the word mine in its military sense originally meant just the same as it does in the ordinary way1 but like many other words it has got twisted into new uses the connection of which with the original meaning is very obscure4 ,one of the most striking of these verbal puzzles is the submarine mine4 ,there seems at first sight not the remotest connection between the floating barrel of explosives concealed beneath the water and what we ordinarily call a mine4 ,the explanation of this is that the term has acquired this meaning after passing through a series of stages4 ,when soldiers mine for the purpose of blowing up their enemies they dig a hole in the ground1 and conceal therein a quantity of explosives so arranged that they blow up when the enemy pass over or near4 ,the operation of digging the hole in the earth is clearly akin to the work of the miner and so such is quite appropriately called a mine4 ,the hole may be dug from the surface downwards1 the marks of excavation being afterwards covered up and obliterated as much as possible4 ,in other cases the hole may be a tunnel starting from a trench and driving towards the enemy's position4 ,the idea1 of course1 is to burrow until the end of the tunnel is just under some important part of the enemy's works or fortifications4 ,when the end of the tunnel has reached the right spot explosives can be placed there1 the tunnel partly stopped to prevent the explosion from driving back upon those who make it and the whole fired at the desired moment4 ,this tunnelling is also called sapping and the tunnel itself a sap4 ,military engineers are often spoken of as sappers and miners as if the two things were clearly different1 but as a matter of fact both are often used to describe the same thing4 ,roughly1 we may say that a mine which stays still in the hope that the enemy will walk upon it is a mine proper1 while a mine which itself progresses towards the enemy until it ultimately goes off beneath him1 is a sap and the making of such a thing is sapping4 ,or we might say that sapping is under-mining1 in which sense we use it in general conversation when we speak of something sapping a man's strength4 ,soldiers speak of their engineering comrades as sappers just as they term artillerymen gunners1 but the only reason why they call them by that name instead of miners is because the latter is a well-known term applied to those who work in coal mines4 ,a subterranean mine1 then1 is nothing more or less than a hole in the ground1 made in any way that may be convenient1 filled with explosives and fired at a suitable time to do damage to the enemy4 ,in other words1 it is simply some explosive concealed in the ground with means for firing it1 and when the sailor conceals explosives in the sea so that they may blow up the enemy's ships1 he borrows his military comrades' term and calls it a mine too4 ,counter-mining is the enemy's reply to mining4 ,suppose ,i was foolish enough to wish to blow up my neighbour who lives in the house opposite to mine4 ,i might start from my cellar and dig a tunnel under the road until ,i knew that ,i had arrived under his dwelling4 ,but suppose that he got to know of my little scheme3 he could then try counter-mining4 ,in this case it would mean starting a tunnel of his own from his cellar towards my tunnel3 then1 as soon as the two tunnels had come sufficiently near to each other1 he could let off his explosives thereby wrecking my tunnel and putting an end to my operations while yet ,i was only half-way across the road4 ,thus he would stop me before ,i had had time to harm him1 and since he need only tunnel just far enough to render the necessary explosion harmless to his house1 while ,i to succeed would have to tunnel right across the road1 the man who is counter-mining always has a slight natural advantage over the man who is doing the mining4 ,if only he gets to know what is going on in time he can always retaliate4 ,all forms of land mine are improvised on the spot according to circumstances4 ,not so1 however1 with submarine mines on which much ingenuity has been expended1 the mines being made in workshops ashore ready for laying and then laid by ships and sometimes by divers4 ,of these there are two main kinds1 those which are put in place in times of peace for the protection of particular harbours and channels1 and those which are simply dropped overboard from a mine-laying ship during the actual war4 ,they all consist essentially of a case of iron or steel plates riveted together just as a steam boiler is made1 in fact the cases are made in a boiler shop4 ,the charge is gun-cotton fired by a detonator1 the latter being excited by a stroke from a hammer1 as in a rifle1 or else by electricity4 ,in the latter case1 a tiny filament of platinum wire is in contact with the detonator1 and the wire being heated by the current1 just as the filament of a lamp is1 the detonator is fired by the heat4 ,of the permanent mines whereby the entrances to important channels are protected arrangements are often made for firing by observation1 that is to say1 by the action of an observer ashore4 ,being laid by divers and securely anchored to heavy weights laying on the bottom1 wires are carried from the mines to the observation station4 ,the observer watches and fires the mines at the right moment by simply pressing a key thereby making the electrical circuit4 ,more often1 however1 mines are fired by contact4 ,observation mines have the advantage that while they may be exploded under an enemy they will allow a friendly ship to pass in perfect safety4 ,contact mines1 on the other hand1 will afford protection against attacks by night when enemy craft may attempt to creep in under cover of darkness4 ,illustration3 ,,an ,,italian ,,mine-,,layer4 ,this photograph was taken looking down upon the deck of the ship4 ,the mines run upon rails1 and are pushed by the men towards the stern1 whence they are dropped one at a time into the water4 ,the splash indicates that one has just fallen4 ,contact mines are often fired electrically1 sometimes by batteries of their own inside their own cases1 or else by current from the shore through wires1 the circuit being completed by an automatic device of some sort actuated unwittingly by the unfortunate victim4 ,one of these contact devices will illustrate the general character of them all4 ,imagine a little vessel with mercury in it3 it is1 generally speaking1 of some insulating material1 but right at the bottom is a metal stud with which the mercury makes contact4 ,the rim may likewise be of metal or a metal rod may project downwards into it3 it matters not which1 for we can see at once that it is quite easy so to arrange things that whereas1 while upright1 the mercury shall be well clear of the upper contact1 it shall when the vessel is tilted flow on to it1 thereby bridging from lower contact to upper contact and completing the circuit4 ,of course1 a mine must only go off when actually struck by a ship and not when it is gently swung to and fro by the action of tide or current in the water4 ,that is easily arranged1 for the vessel and contacts can be so shaped that contact is not made until an angle of tilt is reached which no tide or ordinary commotion of the water could bring about4 ,it is clearly possible1 too1 to combine the contact and observation arrangements in such a way that contact mines can be made safe for friendly ships during the daytime4 ,it is only necessary to adopt the shore battery arrangement already mentioned and disconnect the batteries during the day or when no enemy is in sight1 restoring the connection during the darkness or in the event of hostile ships trying to rush the passage4 ,another interesting scheme for keeping mines safe until required is to anchor them in what is termed a dormant condition4 ,this means that a loop is taken in the wire rope by which they are anchored1 the loop being fastened by means of a link4 ,this link1 however1 contains a small quantity of explosive which can be fired from the shore4 ,this has the effect of breaking the link1 releasing the loop and allowing the mine to float upwards to the full length of the rope4 ,thus the mine is down deep1 well below the bottom of the biggest ship until released for action4 ,it is doubtful whether much use is made nowadays of permanent mines of the types just described1 for they have1 no doubt1 been largely displaced by the temporary mine which can be laid in a moment by simply being dropping overboard from a ship1 but it is quite possible that some of the defences of1 say1 the ,dardanelles1 were of the permanent nature4 ,so let us pass on to the temporary mines4 ,these were used by the ,germans from the first few hours of the war4 ,one of the first naval incidents was when our ships discovered a small ,german excursion steamer which had been converted into a mine-layer strewing these deadly things surreptitiously in the ,north ,sea in the hope that some of our vessels would run upon them4 ,needless to say1 that ship went on no more excursions4 ,laid thus1 it is evident that there can be no wires running ashore1 so that all mines of this class must be contact mines4 ,what makes them of extreme interest is the way they are laid4 ,just think for a moment what is involved4 ,from the very nature of things their laying must often be done in secret4 ,it is not the ,british practice to place them in the open seas1 except avowedly1 after due notice1 in certain specified areas1 where they are laid quite openly under the protection of adequate forces to ensure against interruption4 ,there is little doubt1 however1 that they have laid many a mine field secretly in purely ,german waters1 while everyone knows that the ,germans have not hesitated to sow the shipping routes broadcast with these things1 such work of course being done secretly and largely at night4 ,the mine can therefore only be laid by dropping it into the water and leaving it4 ,yet it must not float on the surface or it will be easily seen and picked up2 it must float below1 so that the unsuspecting ship may run upon it4 ,and it is quite impossible to make a thing float in water anywhere except upon the surface4 ,if it does not float upon the surface it sinks to the bottom3 there is no half-way house between4 ,many people are surprised to hear this1 judging1 no doubt1 by the fact that a balloon floats in1 and not on1 the air and expecting an object floating in water to be able to do the same thing4 ,the difference is due to the fact that air is easily compressible1 so that the air close to the earth is denser1 more compressed1 and therefore heavier1 than the air higher up owing to its having the whole weight of the upper air pressing downwards upon it4 ,the density of the air diminishes1 for this reason1 as one ascends1 and a balloon which displaces more than its own weight of air at the surface of the earth rises until it has reached just that height when the air displaced exactly equals in weight the balloon itself3 then it goes no higher4 ,precisely the same conditions exist in the sea except that water being incompressible is no denser at the bottom of the sea than on the surface4 ,therefore1 if a thing sinks at all it sinks right to the bottom4 ,there is one very ingenious device for overcoming this difficulty by means of a motor and propeller4 ,the mine has enclosed in its case a motor driven by a store of compressed air which operates a propeller4 ,in this it is somewhat like a torpedo1 but in this case the propeller is set vertically so that its action lifts the mine up in the water4 ,now the mine is so weighted that it just and only just sinks when dropped in1 but on reaching a certain depth the motor starts and by means of the propeller raises it nearly to the surface again4 ,on nearing the surface the motor stops and the mine sinks once more1 only to be raised again in due course1 so that the thing keeps on rising and falling2 it never rises above a certain depth nor falls below a certain depth1 but oscillates continually between its two limits4 ,the question then arises1 what starts and stops the motor at precisely the right moments to produce this result8 ,it is done by means of a hydrostatic valve4 ,as just pointed out1 the water at the bottom of the sea is supporting the weight of all that water which is above it4 ,the water is not compressed by this1 but the pressure is there all the same4 ,obviously the degree of pressure at any point depends upon the weight of the layer of water above1 and since the weight of that layer will obviously increase and diminish with its thickness it follows that1 starting from the surface1 where the pressure is nil1 we get a perfectly steady and regular increase as we descend1 until we reach the maximum at the bottom4 ,now within the mine is a small watertight diaphragm1 the outer surface of which is in contact with the water and upon which1 therefore1 the water presses4 ,as the mine descends1 therefore1 this diaphragm is bent inwards more and more by the pressure of water and that is made to start the motor4 ,adjustments can easily be made so that a certain degree of bending shall result in starting the motor1 which is the same as saying that the motor shall start automatically at a certain depth4 ,likewise as the mine rises under the influence of the propeller the pressure decreases1 the diaphragm straightens out and at a certain predetermined depth the motor is stopped4 ,when1 finally1 the store of motive power is exhausted the mine sinks to the bottom and is lost1 a very valuable feature from a humanitarian point of view1 since it means that the active life of the mine is short and it cannot go straying about the oceans for weeks or even months1 finally blowing up some quite innocent passenger ship4 ,more often1 however1 this difficulty of depth is overcome by anchoring the mine at the depth most suitable for striking the bottom of a passing ship4 ,but here again there seem to be insuperable difficulties1 for the depth of the sea varies and so the length of the anchor rope must be varied with almost every mine that is laid4 ,it has been found possible1 however1 to make the mines automatically adjust the length of their own anchor ropes so that the desired result is attained without difficulty no matter how deep the sea may be4 ,let me describe how it is done in the ,elia mines used by ,great ,britain4 ,the inventor1 ,captain ,elia1 was an officer in the ,italian ,navy4 ,the mine consists of three parts3 7#a7 the mine proper1 a case containing the explosive1 gun-cotton and the firing mechanism2 7#b7 the anchor2 and 7#c7 the weight1 all of which are connected together by suitable wire ropes4 ,the mine is lighter than water and so floats3 the anchor1 which bears no resemblance to the ordinary anchor but which is an iron case containing mechanism1 only able to act as an anchor by virtue of its weight1 is heavier than water and so sinks1 while the weight of solid cast iron sinks more readily still4 ,the anchor is often fitted with wheels so that it forms a truck upon which the mine and the weight are placed1 the whole running upon rails laid on the deck of the mine-layer4 ,as this ship steams ahead the men push the mines along the rails1 dropping them over the stern at regular intervals4 ,when the thing reaches the water1 the weight sinks the most rapidly1 thereby tugging at the chain whereby it is connected to the anchor4 ,the latter1 being less compact1 sinks more slowly so that the pull upon the rope is maintained until at last the weight rests upon the bottom4 ,then and only then is the pull relaxed4 ,now inside the anchor is a winch1 upon which is wound a length of flexible wire rope1 the other end of which is attached to the mine4 ,the latter1 it will be remembered1 is light enough to float and so1 since it lies upon the surface while the anchor sinks1 the rope is drawn off the winch4 ,but there is a spring catch which is able to hold the winch and to prevent it from paying out rope1 and that catch is only held off by the pull of the weight4 ,consequently1 as soon as the weight touches the bottom and its pull upon the anchor ceases1 the winch is gripped by the catch1 no more rope is paid out1 and from that moment1 as the anchor descends1 it drags the mine down with it4 ,the result1 then1 is that the mine becomes anchored at a depth below the surface roughly equal to the length of the rope connecting weight to anchor4 ,mines of this kind can1 of course1 be fired electrically by the tilting of a cup of mercury or similar device as already described4 ,another arrangement is to fit projecting horns upon the surface of the mine made of soft metal so that they will be bent or crushed by a strong blow such as a passing ship would give4 ,this breaks a glass vessel inside1 liberating chemicals which cause detonation4 ,the method adopted in the ,elia mines is to have a projecting arm pivoted upon the top of the mine4 ,the mine is spherical 7they are nearly all either spherical or cylindrical71 with the rope attached to the ,south ,pole1 so to speak1 and the arm pivoted to the ,north ,pole4 ,as the mine floats in the water the arm projects out horizontally4 ,the effect of this arrangement is that when a ship strikes the mine the latter rolls along its side1 but the arm being too long1 simply trails along4 ,thus the spherical case of the mine turns while the arm remains still and that is made to unscrew and eventually release a hammer which1 striking the detonator1 fires the mine4 ,in other words1 this type of mine is exploded not by the ship giving it a blow1 but by its rubbing itself along in contact with the mine4 ,the great advantage of this is that it is only a ship that can do this4 ,no chance commotion in the water can do it3 no chance blow from floating wreckage can do it3 only the rubbing action of a ship can accomplish it4 ,such a mine1 too1 is less likely to be affected by counter-mining1 of which more presently4 ,apparently the laying of these mines must be very dangerous work1 for since a blow will explode most of them1 what is to prevent their receiving that blow while on the deck of the mine-layer1 or at all events as they are dropped into the water4 ,in all cases1 precautions are taken against such an event4 ,sometimes a hydrostatic valve is employed1 the arrangement being that the firing mechanism is locked until released by the valve1 until1 that is1 the mine is immersed to a predetermined depth in the water4 ,another device for the same purpose is a lump of sugar4 ,the mine is so made that it cannot be fired until this lump has been melted by the action of the water3 sal ammoniac is another substance employed for the same purpose4 ,the technical term for this is a soluble seal4 ,the firing arrangement1 whatever it may be1 is sealed up so that it cannot come into operation until the seal has been dissolved away by the water1 or until the mine has been in the water long enough for the mine-layer to get out of harm's way4 ,another interesting feature of the ,elia mine is connected with the source of the power which drives the hammer which causes the explosion4 ,the anchor1 it will be remembered1 pulls the mine down under water1 the latter being of itself buoyant4 ,there is a continual pull1 therefore1 upon the rope by which the mine is held under4 ,it is that pull which works the hammer4 ,and now observe the beautiful result of that simple arrangement4 ,suppose the mine breaks its rope and gets loose1 so that it can drift about and carry danger far and wide4 ,it can break loose and it can drift about1 but at the very moment of getting loose the danger vanishes1 for the rope ceases to pull and the firing mechanism loses its motive power4 ,in other mines the same result has been sought by means of clockwork1 which throws the firing arrangements out of action after the lapse of a given time4 ,this scheme of ,captain ,elia's1 however1 whereby the very act of breaking adrift produces its own safeguard1 is one of the most delightful instances of a happy invention4 ,in conclusion1 just a word about the measures taken against mines4 ,counter-mining is one4 ,it consists in letting off other mines in the midst of a mine-field with the purpose of giving them such a shaking up that some of them will be exploded by the shock4 ,the simplest and indeed the only effective way1 however1 seems to be the simple primitive method of dragging a rope along between two light draught vessels and thus tearing the mines up by their roots1 so to speak4 ,the very act of thus dragging it along by its anchor rope often causes a mine to explode1 well astern of the mine-sweeping vessels1 but sometimes they are pulled up and fired or sunk by a shot from a gun which the sweeper carries for the purpose4 ,the sweeping up of the mine-fields is a duty often allotted to the steam fishing boats or trawlers1 whose crews seem particularly well fitted for the work4 ,it is a hazardous duty1 and many lives have been lost through it4 ,let us hope that in time to come all submarine mines and the dangers connected with them will be a thing of the past1 for they are mean1 cowardly and contemptible weapons4 ,,chapter ,,vi ,,military ,,bridges ,bridging has always been an important part of actual warfare4 ,in my school days ,i studied ,csar from a textbook which is not much in use nowadays and which had very copious notes1 prominent among which was a description1 with drawings1 of a bridge made by the ,roman ,legions in ,gaul4 ,and a fine bridge it was1 too4 ,how its details came to be known was partly through the description given by ,csar himself and partly by a study of certain old timbers found in the bed of the ,rhone1 which timbers were believed to be relics of the very bridge which the great ,julius himself had had built4 ,this bridge of nearly two thousand years ago appeared to be built of baulks of timber fastened together in very much the same manner as that adopted by the engineering units of the great armies of to-day4 ,every observant person has noticed how tall poles and short sticks tied together with ropes can be fashioned into the firm1 strong scaffolding from which workmen can in safety raise great tall buildings4 ,that mode of construction can always be used to form a bridge4 ,equally well known1 no doubt1 are the gantries built over the footway while a large building is in course of construction4 ,generally of huge square baulks of timber1 they are intended to carry very heavy loads of materials and to save the public passing beneath from any possibility of damage through heavy objects falling from above4 ,those gantries furnish us with an example of another sort of construction in wood which can be and is often used in bridging4 ,when the ,germans retired in ,northern ,france they blew up all bridges behind them1 and before the ,allies could use those bridges they had to repair them4 ,if only for foot-traffic1 a contrivance of poles1 lashed together after the manner of the builder's scaffold1 is ample in most of such cases and by its means a strong and safe bridge can be made upon what is left of the old bridge in the course of a few hours4 ,for light vehicles a similar structure but made stronger by more lashings and of poles closer together will suffice1 but for heavy traffic1 with guns and possibly railway trains1 recourse has to be had to the heavy timberwork exemplified by the builder's gantry4 ,this takes longer to make1 since the timbers are big1 heavy and not easy to move about3 they are1 moreover1 not simply laid beside or across each other and tied1 but are cut the right lengths1 and one is notched where the end of another fits into or against it4 ,the baulks are connected by bolts and nuts for which holes have to be drilled or by rods of iron with a sharply pointed prong on each end stretching across from one baulk to another1 one prong being driven into each4 ,with the long-thought-out military operations of modern warfare it is just possible that steelwork for repairing certain particular bridges might be prepared in advance and simply launched across when the time arrives1 but that is manifestly impossible except in certain cases and under particularly favourable conditions1 such as railway facilities for bringing up the new bridge close to the site where it is to go4 ,nearly every military bridge therefore has to be more or less improvised on the spot4 ,in a highly developed country scaffold poles or baulks may be found or brought up by road or rail1 in less civilised lands their equivalents may be cut and prepared from neighbouring forests1 but all armies have1 as a recognised part of their organisation1 certain engineering field companies1 and bridging trains1 which carry with them large quantities of material carefully schemed out long in advance1 so shaped and so prepared that it can be fashioned into almost anything1 much as the strips of a boy's meccano can be adapted to form a great variety of objects4 ,first1 there are pontoons1 large though light boats or punts1 about #bj feet long1 constructed of thin wood with canvas cemented all over to give additional strength and water-tightness4 ,each pontoon rides upon its own carriage upon which there are also stowed away quantities of timbers of various sorts1 anchors for holding the pontoons in place1 oars for rowing them1 ropes of different kinds1 and so on4 ,each pontoon1 moreover1 is divided about the middle into two pieces called respectively the bow piece and the stern piece4 ,the two are normally coupled together by cunningly devised fastenings but they can be quickly separated1 in which state they form two shorter boats4 ,other carriages carry more timber and material intended for the purpose of forming trestle bridges but which is also usable in connection with the pontoons4 ,of this material the chief sorts are legs1 long straight pieces which form the uprights2 transomes1 heavier beams which can be fitted across horizontally between two legs so that the three form a huge letter ,h or a very robust ,rugby goal2 baulks which are light timbers tapered off towards each end for the sake of lightness and of such size that they fit snugly into notches which are cut in the upper surface of the transomes2 and planks called chesses for forming the floors of a bridge4 ,probably the most dramatic incident of the war was when the ,british1 having been apparently beaten by the ,turks in ,mesopotamia1 driven far back and their ,general and many troops captured1 suddenly turned the tables upon their enemies1 driving them from ,kut and sending them fleeing helter-skelter to ,bagdad and then beyond4 ,now the capture of ,kut and then of ,bagdad were both made possible by the rapid bridging of the ,tigris1 and without doubt this is the sort of material which was used4 ,let us see how it is done4 ,an army arrives at a river across which it is decided to throw a pontoon bridge4 ,the pontoons are unloaded off their wagons and launched into the water4 ,one is rowed out and anchored a little way from the shore1 while upon the bank parallel with the river is laid a transome4 ,on the centre of the pontoon is a centre beam with notches in it like those in the transomes and from the one to the other baulks are passed4 ,meanwhile a second pontoon has been rowed into place and more baulks are passed from the first pontoon to the second1 while chesses are laid upon the baulks to form a platform or floor4 ,thus1 pontoon by pontoon1 the bridge grows until it has reached the further bank4 ,if pontoons are scarce and the loads to be carried by the bridge are light they are divided in two1 and instead of a row of pontoons joined by baulks there is a row of pieces joined by baulks4 ,pieces arranged thus form a light bridge1 pontoons a medium bridge1 while pontoons placed closer together form a heavy bridge4 ,which shall be built depends upon the number of pontoons available in relation to the width of the river and the nature of the traffic which will have to pass over4 ,an alternative arrangement is to make the pontoons up first into groups or rafts and then bridge from raft to raft instead of bridging between pontoons4 ,there is still another way of making the bridge1 and that is to put it together alongside the bank1 afterwards swinging it across the river like the opening or shutting of a door4 ,anyone can see that there must be many advantages in this latter method when it is practicable1 since more men can work at once and with greater safety1 for all will be near the bank4 ,it is evident that such a structure depends for its security entirely upon the anchors4 ,those which are carried for the purpose are like those of a ship but there may not be enough or they may not suit every kind of river-bed4 ,they are often improvised therefore4 ,two wagon wheels lashed together1 with heavy stones clipped between them1 are said to be a very effective anchor4 ,under certain conditions a net filled with stones is surprisingly effective4 ,two pickaxes tied together form a good imitation of the conventional anchor1 as also does a harrow sunk and held down by stones thrown upon it4 ,trestle bridges are made in quite a different way4 ,the trestles are formed of two legs or uprights with a transome between1 a shape which resembles1 as has been already remarked1 a very robust ,rugby goal4 ,the transome is connected to the legs by a special form of band which permits it to be fixed at any height without having to drill any special holes for the connections4 ,the legs are so shaped at their ends that they can be shod with steel shoes provided for the purpose1 enabling them to get a good foothold even on shifty soil4 ,the trestles are put together ashore1 and each is taken out in a boat or on a pontoon to the place where it is to stand4 ,then it is launched feet foremost into the water1 the boat being on the side away from the shore1 so that a rope from the trestle to the shore will enable men on land to pull the trestle into an upright position4 ,illustration3 ,,an ,,incident ,,at ,,loos4 ,this picture gives us some little idea of the devastation caused by modern weapons4 ,it also shows the inventiveness of the soldier who makes his rifle into a battering-ram4 ,incidentally we see a kind-hearted soldier rescuing a little girl from danger4 ,this incident really happened4 ,thus trestle after trestle is added until the bridge has grown right across the water to the further bank4 ,the trestles cannot fall over sideways because of their own width1 they cannot fall forwards or backwards because of the baulks which pass between them and carry the floor1 but as a precaution diagonal ties of rope are always added here and there along the bridge1 that is to say1 two trestles are tied together with two ropes1 each rope passing from the bottom of one trestle to the top of the other1 a form of tying which is very effective and very easy and simple to carry out4 ,one interesting thing to notice is the form of the baulks1 in which connection ,i would like to remark that when ,i use the word without inverted commas ,i mean it in the ordinary sense as implying a big heavy timber1 but when ,i use the commas ,i mean it in its technical sense as it is used in military engineering4 ,in this latter sense it describes the timbers specially provided for the purposes just described4 ,large supplies of the ordinary heavy baulks could not be carried with an army3 but strength is required nevertheless4 ,hence the military engineers have invented a form which combines strength with lightness4 ,if you stand a plank upon its edge1 supported at each end so as to form a beam1 its strength will vary as its width and as the square of its height4 ,if then you double its width you only double its strength1 but if you double its height you multiply its strength four times4 ,if you halve the width of a given beam you halve its strength1 but if you then double its height you quadruple that half1 in other words1 without making the beam any heavier by these two operations you double its strength4 ,moreover1 if you support a beam at each end and pass a load over it or spread a load permanently upon it1 its greatest strength is required in the middle4 ,you can shave away the ends without making the beam as a whole any less strong4 ,so these baulks are made like planks1 very oblong if looked at endwise1 also thinner at the ends than in the middle4 ,but if by chance they tipped over on to their sides they would for that very reason be very weak1 and that is why the notches are provided in the transomes and the centre beams of the pontoons1 in order that the baulks1 having been laid edgewise in them1 cannot tip over4 ,thus a considerable saving is made in the weight of the bridging material to be carried4 ,it sometimes happens that when a trestle is dropped into the water one leg will fall into a depression in the river-bed or will sink more deeply if the bed be soft1 leaving the whole structure lop-sided and useless4 ,that1 however1 is easily overcome1 since it is provided against4 ,a little iron bracket1 which is carried for the purpose1 is clipped on to the leg which has sunk near its top and on to it is hung a pair of pulley blocks--one of those little contrivances which everyone has seen at some time or another by which one man pulling a chain quickly can raise1 although slowly1 a heavy load4 ,by this means the end of the transome is raised until it is horizontal and the legs have assumed an upright posture1 when the transome is refastened to the leg in its new position4 ,thus we see the advantage of clamping the transome to the leg rather than fixing it with any arrangement of holes4 ,the iron band1 which is fastened on to the transome and which grasps the leg1 is so arranged that the greater the load the more tightly does it hold1 so that it is perfectly safe under all conditions4 ,the trestle bridge has a great advantage over the floating bridge if the height of the water varies at all1 as for instance1 with the tide4 ,the former remains still1 while the latter goes up and down1 requiring a special arrangement to be contrived for connecting it to the shore4 ,under some conditions a suspension bridge is the most convenient form of all1 particularly if the banks are high and strong1 or if the current be very rapid or the river-bed very soft4 ,in such cases steel wire ropes are stretched across the water between two trestles4 ,the latter may be made in the way just described1 but more often they have to be stronger and are built specially out of big strong timbers securely fastened together4 ,their form does not matter much so long as they are strong and stiff1 high enough to carry the ends of the suspension ropes and of such a shape as not to block the entrance to the bridge itself4 ,the higher they are the better1 because1 according to the natural laws which govern such things1 the more sag or dip there is in the ropes across the river the less severely will they be strained4 ,they need to be very strong1 as the whole weight of the bridge and its load falls upon their shoulders4 ,the pull of the suspension ropes1 moreover1 tends to pull them forward into the water1 so they must be held back by other strong ropes called guys1 and the action of these two sets of ropes entails the unfortunate trestles bearing really more weight than the actual weight of the bridge and load4 ,the guys1 too1 require very strong anchorage or at the critical moment they may give way1 when the whole contrivance1 with possibly valuable guns or ammunition on board1 will be precipitated into the water4 ,the men may be able to swim but the guns will sink4 ,having1 then1 constructed a trestle upon each bank1 securely guyed it back and connected the suspension ropes to it1 the next operation is to attach smaller vertical ropes to the suspension ropes at intervals1 to support the ends of the transomes4 ,then upon the latter are laid baulks and upon them the flooring as usual4 ,or if ropes be not sufficiently plentiful1 timbers may be lashed on to the suspension ropes instead1 the transomes being fastened to them4 ,that is all that is absolutely essential to a suspension bridge1 but one so formed would be rather flimsy and unstable4 ,it needs to be stiffened by diagonal timbers at suitable places and often it has props placed upon the bank reaching out as far as their length will permit over the water to steady and consolidate what to commence with is rather too much like a spider's web4 ,those little strengthening dodges can be laid down in no books4 ,they need to be left to the judgment of the men in charge to do what is necessary in the best way they can with the materials which happen to be at hand4 ,but very often warfare has to be carried on in the most outlandish places where armies can only travel light1 and where1 hampered by bridging material of the conventional sort1 they would have no chance in catching up with a fleet and agile native enemy4 ,yet bridges are needed even more under those conditions perhaps than under any other4 ,there are many examples of this in the wars just beyond the frontier in ,northern ,india4 ,then ingenuity has to make good the luck of prepared material and the bridges are made of those materials which happen to be procurable4 ,an army in ,india once wanted to cross a river1 where no materials of the ordinary kind were available4 ,the river1 however1 was lined with tall reeds4 ,a reed has for centuries been a favourite example of weakness and untrustworthiness1 so how can reeds be made to form a safe bridge8 ,this is how it was done4 ,great quantities of reeds were cut and were made up into neat round bundles about a foot in diameter4 ,ropes were scarce too1 but these likewise were improvised by twisting long grasses into ropes4 ,it is surprising what good ones can be made in this way1 and they served their purpose well4 ,many bundles having thus been made numbers of them were tied together so as to form rafts4 ,each bundle in fact was a small pontoon1 and the rafts which were thus constituted differed only in size from the regulation rafts made of pontoons4 ,while this work was being done two ropes were got across the river and secured on both banks3 then rafts were floated down in succession1 each one on arrival being tied up under the two ropes4 ,finally a track of boards was laid over the centre and the bridge was strong enough for men in fours to walk over it4 ,had it been necessary1 the floor could have been made of brushwood1 interlaced so as to form a kind of continuous matting or of a layer of branches covered with canvas4 ,floors for bridges can be made in many ways4 ,a dodge which soldiers in the ,british ,army are taught is how to make boats for bridging purposes out of a tarpaulin or piece of canvas1 supported on a framework of light wood poles or twigs4 ,the outline of the boat is first drawn roughly on the ground4 ,then three posts are driven in on the centre line of the boat and to the top of these three a horizontal pole is tied1 thin1 flexible branches stripped of their bark1 being fixed by having their ends stuck in the ground on either side4 ,the ends are driven in on the outline already marked out so that when done the branches form a framework like the ribs of a boat upside down4 ,other branches are intertwined among these so as to bind them together and finally a tarpaulin or canvas sheet is laid over all4 ,a number of boats formed after this fashion can be used as pontoons to support a bridge1 or several can be made into a raft and towed to and fro--a sort of floating bridge4 ,another scheme is to make a number of crates like those in which crockery and other things are often packed4 ,these are of very simple and easy construction1 consisting of sticks slightly pointed at the ends driven into other pieces which are perforated with suitable holes to receive the ends4 ,the only tools necessary are an axe 7or even a pocket-knife will do7 to sharpen the ends and an auger to make the holes4 ,almost any sort of wood can be made to serve4 ,the cover for this1 and indeed for most of these improvised rafts1 is tarpaulin or canvas1 the latter of which1 being the material used for so many purposes1 is almost sure to be available in some form or other4 ,for instance1 every one of those familiar ,general ,service ,wagons has its large canvas cover4 ,in fact1 a general service wagon1 taken off its wheels and wrapped up in its own canvas cover1 makes quite a serviceable boat1 pontoon1 punt1 barge or whatever you like to call it4 ,then there is an ingenious type of little bridge which can be quickly and easily made where bamboos or similar light canes or sticks are available4 ,the only tool required in making this is a couple of poles ten feet or so in length4 ,to commence with1 these poles are laid side by side upon the bank with one end of each pointed out over the water1 overhanging it by about four feet4 ,two men then climb along these1 while others sit upon the inshore ends to keep them from tipping into the water4 ,seated1 then1 on the outer ends of the poles the men drive some bamboos or whatever they are using into the water1 after which they tie a crosspiece to the uprights1 so forming a light trestle4 ,then the poles are pushed forward until they overhang another four feet beyond the trestle just made1 the other men1 of course1 continuing to sit upon the rear ends4 ,and so the bridge grows until it entirely crosses the stream4 ,between the trestles other light poles are laid and tied1 forming the floor upon which men can cross in single file4 ,another type1 known as the hop pole bridge is made of slightly heavier poles which are tied together in threes so as to form isosceles triangles4 ,each triangle forms one trestle4 ,the two poles which form the sides project a little above the apex so that in fact we have an isosceles triangle with a ,v at the apex4 ,to the root of the ,v another pole is tied loosely and the whole trestle is pushed feet first into the water4 ,then1 by pushing the pole1 it is forced into an upright position in which it is secured by the pole being firmly fixed to the shore and strongly lashed to the root of the ,v where1 before1 it was only loosely tied4 ,a second trestle is then in like manner fixed in front of the first one1 connected to it by a pole just as the first is connected to the bank4 ,and so the thing grows4 ,to all the upper ends of the ,v's a light pole is tied to form a handrail4 ,in this case1 of course1 the floor of the bridge is nothing more than a pole1 but with the assistance of a handrail it is quite easy to walk along a single pole4 ,and that reminds me of a simple type of suspension bridge which1 an engineer officer once assured me1 is actually copied from one habitually made by some of the ,indian natives4 ,it consists of three ropes upon one of which you walk1 while the other two form a handrail upon either side4 ,the three ropes are held at intervals in their correct relative positions by little wooden frames formed of three sticks tied together1 one rope being tied to each corner of each triangle4 ,on the banks stakes are driven in and tied back with cords to give additional strength1 and to them the ends of the ropes are secured4 ,one drawback to this form of bridge is that the ropes are naturally far from level and one has to walk down a steep hill to commence with and up again at the other end4 ,i once saw a specimen of this kind of bridge across a wide ditch1 a part of the old defences of ,chatham1 and an elderly gentleman who was with me1 a man of considerable proportions1 insisted upon trying it for himself4 ,he took but a step or two when his foot began to slide downhill along the foot rope faster than he dare move his hands along the hand ropes1 with the result that he was very soon in a very uncomfortable position4 ,thus he remained1 to the amusement of all his friends1 until two stalwart ,royal ,engineers came to his aid and uprighted him4 ,in crossing a swamp something in the nature of a bridge is sometimes required4 ,canvas laid upon branches often makes a good road over what would otherwise be impassable4 ,rapidly moving detachments of cavalry are provided with what is called air-raft equipment1 which enables them to get their light ,horse ,artillery guns across rivers which would be impassable otherwise4 ,it consists of sixty bags like huge cylindrical footballs except that the outer covering is canvas instead of leather4 ,these are blown up partly by the mouth and partly by pumps provided for the purpose until they are just about as tight as a football should be4 ,then they are laid out in rows of twelve1 each row being fastened together by the bags being tied to a pole running lengthwise of the row4 ,cords are attached to the bags for the purpose4 ,the five rows are then placed parallel and connected together by two light planks called wheelways placed across the rows and tied thereto4 ,this arrangement is capable of carrying light guns or ammunition wagons4 ,the men are expected to ride through the water1 but if necessary something can be laid upon the raft1 between the wheelways1 to form a floor upon which men and even horses can ride4 ,as part of the equipment there is a small collapsible boat with oars and by its means men first cross1 carrying with them a line by which1 afterwards1 the raft can be hauled to and fro4 ,rafts can be made1 too1 of hay tightly tied up in waterproof ground-sheets or tarpaulins or canvas4 ,indeed1 given a little ingenuity and the need to use it 7for it is very true that necessity is the mother of invention71 it is surprising what a large variety of things can be pressed into this service4 ,of course1 barrels can be made to form excellent pontoons1 but there is one clever little way of using them which is more than usually interesting1 and with that ,i must conclude this chapter which has already exceeded its appointed limits4 ,imagine two poles perhaps ten feet long1 placed parallel4 ,between them1 at one end1 a barrel is lashed3 at the other end is a plank forming with the poles a ,t4 ,a man can then sit upon the barrel and paddle about1 for the poles and planks will steady the barrel just as the outriggers and floats steady the narrow canoes or catamarans of which we read in books of travel4 ,for that reason a bridge formed of such is called a catamaran bridge4 ,of course1 if there are only a few barrels to be had they can be fitted out like this and then combined into a raft4 ,or if there are enough of them they can be anchored at intervals and poles or planks laid from one to another so as to form a continuous bridge4 ,or a single one may be used as a boat4 ,i can almost fancy ,i see some of my readers who have access to a pond rigging up an old barrel in this way1 just to see how it goes4 ,,chapter ,,vii ,,what ,,guns ,,are ,,made ,,of ,no longer ago than the days of the ,crimea1 the largest guns were made of the cheapest and commonest kind of iron1 that known as cast iron4 ,this material has the advantage of being cheap and easily worked1 but is comparatively weak and liable to crack1 so that the guns of that time were comparatively small compared with those of to-day2 they could only withstand a feeble explosion and their range was therefore limited4 ,had the energetic explosives of the present time been employed in them they would inevitably have burst1 killing their gunners instead of the enemy4 ,attempts were made to strengthen them with bands made of wrought iron1 a form of the metal which is tough and elastic and therefore better able to withstand sudden shocks than the more brittle cast iron1 but it was not a real success4 ,at first sight one naturally wonders why the whole gun was not made of the stronger wrought iron4 ,the reason was that while cast iron can be melted and poured in a liquid form into a mould1 so as to produce the shape of the gun1 wrought iron will not melt4 ,it will soften with heat1 in which condition it can be hammered into shape and1 moreover1 when in a very soft state two pieces can be joined by simply forcing them closely together1 which operation is called welding4 ,with the machinery available now it would be possible to make a gun of wrought iron1 but even a few years ago it would have been quite impossible4 ,there was an obvious need therefore of a metal which could be melted and cast in moulds like cast iron1 yet tough and strong to resist shock like wrought iron4 ,fortunately this problem excited the interest of a certain ,mr4 ,henry ,bessemer1 a gentleman who1 having made a considerable fortune through an ingenious method of manufacturing bronze powder1 had sufficient leisure and money to devote himself to its solution4 ,the vast steel industries of ,great ,britain and the ,united ,states are the direct results of this gentleman's labours1 and in the latter country there are quite a number of towns which1 being the home of steelworks1 are called by his name4 ,iron is one of the most plentiful things in the world4 ,deposits running into millions of tons are to be found in many parts1 but it is practically always in the form of ore1 that is to say1 in combination with something else generally oxygen and sometimes oxygen and carbon4 ,the former sort of ore is called oxide of iron and the latter carbonate of iron1 and both of them bear not the slightest resemblance to the metal4 ,they are just rocks which form part of the earth's crust1 and it is only the metallurgist who can tell what they consist of4 ,in order that the iron may be obtained from the ore it is necessary for the oxygen to be separated from it1 an operation which requires the intervention of heat1 and the heat must be obtained from a fuel which consists mainly of carbon4 ,wood fulfils these requirements1 but there is not enough wood in the whole world to smelt all the iron which we need4 ,it was not until pit-cole displaced char-cole 7to use the spelling of the period7 that the iron industry began to assume its present importance4 ,to produce iron cheaply1 therefore1 ore and coal should for preference lie side by side1 and in some few favoured localities that state of things exists4 ,generally speaking1 however1 the ore and the coal are not found together1 with the result that one has to be taken to the other1 and in practice it is usually the ore which is taken to the coal4 ,hence1 the iron and steelworks are generally to be found on the coalfields1 while the ore comes by rail or ship from1 it may be1 remote parts of the world4 ,the method by which the metal is obtained from the ore is in principle very simple4 ,coal and ore are mixed together in a furnace1 the fire being fanned by a powerful blast of air4 ,the result is that the bonds uniting iron and oxygen are relaxed by the heat1 when the oxygen1 having a preference for union with carbon rather than with iron1 leaves the latter to join up with some of the carbon of the coal4 ,the furnace in which this operation is carried out is a tall1 vertical cylinder of iron1 lined with firebrick4 ,the fire is at the bottom and the fresh fuel and ore are thrown in at the top4 ,as the ore is reduced 7the chemist's term for removing oxygen from anything7 the liquid iron accumulates in the lowest part of the furnace1 whence it is drawn off at intervals1 being allowed to run into grooves or gutters in a bed of sand1 where it solidifies into what is called pig iron4 ,along with the coal and ore1 there is thrown into the furnace from time to time quantities of limestone which combines with the earthy impurities with which the ore is contaminated4 ,together these form what is called slag1 which also exists1 while in the furnace1 as a liquid1 but is so much lighter than the molten iron that it keeps quite separate and can periodically be drawn off through a hole higher up than that through which the iron is obtained4 ,the slag solidifies into a hard stone which is broken up and used for making concrete and tar-paving1 also for road metal4 ,the kind of furnace just described is1 owing to the strong blast of air needed for its operation1 called a blast-furnace4 ,one would be inclined to think that a fire so well supplied with oxygen1 both from the blast and from the ore itself1 would cause the fuel to be completely burnt up1 yet such is not the case4 ,the gases which ascend from the fire consist largely of carbon-monoxide1 a burnable gas with lots of heat still left in it4 ,years ago1 and one may still see instances of it1 this gas was allowed to escape at the top of the furnace1 where it burnt in the form of a huge flame4 ,in most modern furnaces1 however1 there is a kind of plug in the orifice at the top which1 while it can be lowered in order to admit the ore and fuel1 normally prevents the escape of the gases1 which are led away through pipes4 ,in some cases the gases are burnt under boilers to provide the works with steam1 in other cases they heat other furnaces for metallurgical purposes1 while in yet others they are employed to drive large gas-engines to generate electricity4 ,it is sometimes a difficulty to find useful employment for the vast quantities of this blast-furnace gas which are produced at a large works4 ,we see1 then1 how is obtained the pig iron from which the other kinds of iron and steel are made4 ,it is not pure iron by any means2 indeed1 it is not sought to make iron pure1 as is the case with most other metals1 since1 in its pure state1 it is too soft to be of much use4 ,all the familiar forms of iron and steel are really alloys of iron and carbon1 a fact which tends to give iron its unique position among the metals1 since by exceedingly slight variations in the percentage of carbon we can vary the properties of the iron to an amazing extent1 thereby producing in effect a wide range of different substances each particularly suitable for a particular purpose4 ,to make cast iron1 such as the guns of the ,crimea were made of1 it is only necessary to melt up some pig iron and to pour it into a mould4 ,there is scarcely a town in which there is not an iron foundry1 either large or small1 and that is the work carried on there4 ,a smaller form of the blast-furnace1 known as a cupola1 melts the pig iron1 and the moulds are generally made of sand4 ,the process of pouring the melted metal into the moulds is called casting and the things so produced are castings1 and are said to be made of cast iron4 ,illustration3 ,,an #ah-,,pounder ,,in ,,action4 ,the crew consists of six men4 ,no4 #a 7the sergeant7 gives instructions4 ,no4 #b stands at the right of the breech4 ,no4 #c fires the gun4 ,no4 #d holds the shell ready for placing in the bore4 ,no4 #e adjusts the fuse and hands the shell to ,no4 #d4 ,no4 #f prepares the ammunition and hands it to ,no4 #e4 ,in this picture only three of the crew are left4 ,wrought iron is made by working the molten pig iron instead of casting it4 ,the work is done in a different type of furnace altogether from the blast furnace and the cupola4 ,it is more like an oven1 in the floor of which is a depression wherein the molten metal lies4 ,the fire-place is so arranged that the flames pass over the metal1 being deflected downwards upon it by the roof as they pass4 ,it should be understood that in casting pig iron one does little more than form it into some desired shape1 the nature of the metal undergoing little or no change4 ,in working it1 however1 into wrought iron1 we change its nature4 ,the pig iron contains from #b to #e per cent of carbon1 which it obtains from the coal in the blast-furnace1 and it is this particular proportion of carbon which gives it its own peculiar properties4 ,to convert it into wrought iron a workman puts a long iron rod into the furnace and stirs the metal about1 thereby exposing it to the air and permitting the carbon to be burnt out4 ,as it loses carbon the iron becomes less and less fluid until it reaches a sticky stage4 ,thus the workman1 who is known by the name of puddler1 as the process is called puddling1 works up a ball of decarbonized and therefore sticky iron upon the end of his rod4 ,having thus produced a rough ball or lump he draws it out of the furnace and leaves it to cool4 ,thus the result of the puddling process is to produce a number of rough lumps or balls of iron with only about one-tenth per cent of carbon4 ,they are next reheated1 in another furnace1 and a number of them are hammered together under a mechanical hammer into larger lumps called blooms or billets4 ,the hammering process has the effect of driving out impurities and also of improving the texture of the metal4 ,iron sheets1 bars1 rods and so on are formed by heating the billets and rolling them out in powerful rolling mills1 machines which in principle are precisely similar to the domestic mangle1 wherein two iron rollers with properly shaped grooves in them squeeze out the billet into the desired form4 ,wrought iron1 owing to the method by which it is produced1 is not homogeneous1 that is to say1 it is nor quite the same all through1 with the result that when it is rolled it develops a grain somewhat similar to the grain in wood1 so that if bent across the grain it is somewhat liable to crack4 ,on the other hand1 it has the advantage over steel that it rusts much less readily4 ,hence1 for outdoor purposes it is still sometimes preferred to the otherwise more popular steel4 ,now the problem which ,bessemer set before himself was to find out how to make a metal which could be cast like cast iron yet should be as strong and tough as wrought iron4 ,after a little experimenting1 by a happy inspiration1 he hit upon the idea of blowing air through a mass of molten pig iron1 thereby burning out the carbon1 just as is done in the puddling process1 only much quicker and with less labour4 ,by this means he produced a metal with less carbon than cast iron and more than wrought iron1 a sort of intermediate state between the two1 and to his joy he found that this ,bessemer steel could be cast like cast iron yet had strength and toughness equal to if not superior to that of wrought iron4 ,moreover1 it was homogeneous and when rolled did not possess the troublesome grain characteristic of wrought iron4 ,having thus found the way to make this new and desirable metal1 ,bessemer encountered a great disappointment1 so great that it would have entirely beaten many men4 ,he made samples of steel and submitted them to experts in iron manufacture4 ,everyone thought them admirable and many large iron works were induced by them to make arrangements with ,bessemer for the right to use his process4 ,his name was already famous and it seemed as if a new fortune was made1 when1 to his alarm1 he learned that wherever it was tried except in his own works1 the process was a miserable failure4 ,instead of being at the end of his labours he was just at the beginning4 ,it turned out that the particular iron which he happened to buy and use at his own works was particularly free from an impurity which is1 generally speaking1 a great nuisance in iron1 namely1 phosphorus4 ,it was pure accident which had led him to use this iron3 it happened to be the kind he could purchase most easily in the small quantities needed for his experiments but it led him into a great difficulty1 for other people1 after paying him for the right to use his process and after spending large sums on the requisite plant1 found themselves unable to make the steel because of the phosphorus in their iron and finding themselves unable to make a success were inclined to write him down a fraud4 ,as it turned out1 after much labour on ,bessemer's part1 it was due to the presence of tiny percentages of phosphorus in most of the iron that is produced4 ,after much trouble he was able to induce certain owners of blast-furnaces to make1 by special methods1 a kind of pig iron practically free from phosphorus and therefore suitable for his process4 ,this special pig iron was known as ,bessemer ,pig ,iron4 ,a little later a new inventor1 a ,welshman1 ,thomas by name1 overcame the difficulty in another way1 but to explain that ,i must first describe the ,bessemer ,converter1 the special apparatus designed by ,bessemer for making his steel4 ,it can best be likened to a huge iron kettle with a big spout at the top and with two projecting pins1 one on each side4 ,these pins rest in supports1 so that it is easy to tilt the whole thing over on to its side4 ,this is lined with fire-clay or some suitable heat-resisting material4 ,through one of the pins 7trunnions is their proper name7 there runs a hole1 communicating to what we might call a grating in the bottom of the converter4 ,to this hollow trunnion there is connected the pipe from a powerful blowing engine1 so that air can be driven in at will4 ,to load or charge the converter it is tilted over somewhat to one side so that molten pig iron can be poured into it4 ,the blast is then turned on after which it is raised to an upright position with the air bubbling up from below through the iron4 ,thus by being brought into close contact with air1 the carbon is burnt out of the metal until none is left4 ,that1 however1 is not desired1 so1 as soon as the carbon is known to have all gone1 a fresh quantity of molten iron is added of a special kind1 the amount of carbon in which is known very exactly4 ,thus all the carbon is first removed and then exactly the right amount is added1 and so the desired result is attained with certainty4 ,now ,thomas's improvement was this4 ,he discovered that the converter could be lined with certain substances which have a great attraction for phosphorus and under those conditions any phosphorus which may be in the ore goes readily from the iron into the lining1 or forms1 with material from the lining1 a slag which floats upon the surface of the metal4 ,when the process is completed the converter is tipped over once more and the metal1 now steel1 is poured into rectangular moulds from which the steel can be lifted after cooling in the form of ingots4 ,steel produced by ,bessemer's process as improved by ,thomas is called ,basic ,bessemer ,steel4 ,incidentally ,thomas1 by this invention1 laid the foundation of much of the steel industry of ,germany and ,belgium1 for there are enormous deposits of ore in the neighbourhood of ,luxemburg which because of the presence of phosphorus were useless until ,thomas showed how it could be dealt with4 ,and there is another interesting feature of this basic process4 ,phosphorus is a valuable fertilizer1 so that the slag makes a very fine chemical manure4 ,it is ground up into a fine powder and is sold to farmers under the name of ,thomas's ,phosphate ,powder4 ,it owes its fertilizing virtues to the presence of the phosphorus which it has stolen from the molten iron4 ,bessemer derived a huge fortune from his process after he had fought and overcome his difficulties1 in addition to which he received the honour of knighthood and became ,sir ,henry ,bessemer4 ,it will be noticed that one of the virtues of the process is its economy in fuel4 ,during the whole time that the metal is in the converter1 from twenty to thirty minutes1 no fuel is used to keep it hot4 ,the reason for that is that the carbon which is being got rid of is acting as fuel4 ,it is burning with the air which is driven through1 thereby generating heat4 ,in ,bessemer's early days1 it was arranged that he should attend a meeting of ironmasters at ,birmingham to explain his new process4 ,on the morning of his lecture two eminent ironmasters were breakfasting together in a ,birmingham hotel when one exclaimed to the other1 ,what do you think1 there is a fellow coming here to-day to tell us how to make steel without fuel4 ,to this eminent ,south ,wales ironmaster the proposal seemed preposterous but it was true all the same4 ,although vast quantities of steel are made by the ,bessemer process there is another one of equal importance known as the ,siemens-,martin ,open-hearth process4 ,in this the molten metal is kept in a huge bath practically boiling until the carbon has been reduced to the required amount4 ,perhaps the most interesting feature about it is the way in which fuel is saved by what is called the regenerative method due to that versatile genius ,sir ,william ,siemens4 ,the open-hearth1 as it is termed1 is a huge rectangular chamber of firebrick with a firebrick roof1 and doors along one side just under the roof through which the process can be watched and new materials be added from time to time4 ,the fire is some way away and not underneath as one might perhaps expect4 ,now if a deep coke fire is fed with insufficient air it does not give off carbonic acid such as usually arises from a fire1 and which as everyone knows will not burn1 but a gas called carbon monoxide which will burn very well4 ,so the fire-place for these furnaces is constructed in such a manner as to produce carbon monoxide1 which then passes through a huge flue to one end of the open-hearth4 ,here it meets air coming through another flue and the two combining burst into flame over the metal4 ,the hot gases resulting from this burning pass out through a flue at the other end of the hearth to a tall chimney which causes the necessary draught1 but on their way they pass through a chamber loosely filled with bricks4 ,consequently the hot gases only reach the open air after having given up much of their heat to these bricks4 ,after that operation has been going on for a time certain valves are operated and the gas and air then come in at the other end of the hearth1 travelling through it in the opposite direction4 ,and the air comes through the chamber which has the hot bricks in it1 bringing back into the furnace a large quantity of that heat which otherwise would have gone up the chimney but which the bricks intercepted4 ,thus all day long does this reversal take place at intervals1 the fresh air all the time picking up and bringing back some of the heat which just previously had escaped towards but not into the chimney4 ,this arrangement enables the process to compete1 so far as economy is concerned1 with the ,bessemer process4 ,at intervals the steel is tapped off from the furnace and run into ingot-moulds1 the same as with the other process4 ,on the whole it is regarded as producing a slightly better steel1 the operation being under slightly better control4 ,however the steel is made the ingots are reheated and either hammered under a powerful steam hammer or pressed in an enormous hydraulic press4 ,this greatly improves the quality4 ,the steel can then be rolled into plates1 bars or whatever form may be required4 ,the finer qualities of steel such as are used for making sharp tools are made in quite another way4 ,instead of being made from crude iron by taking out the carbon1 the materials are the finest qualities of wrought iron and charcoal which are mixed together in the correct quantities and melted in a crucible4 ,this cast steel is very hard1 so that it will carry a very fine1 sharp edge4 ,it is also capable of being tempered by heating and cooling1 so that the exact degrees of hardness and toughness can be attained4 ,of recent years a special quality of steel for tools called high-speed steel has been produced1 mainly by the addition to ordinary cast steel of a small percentage of tungsten4 ,the advantage of this is that1 within certain limits1 this does not soften with heat1 and it is1 ,i can assure you1 a great invention in war-time1 when a nation is straining every nerve to turn out guns and shells as fast as possible4 ,for all these things need to be turned in lathes and if you have ever watched a metal-turning lathe at work you will have noticed that the tool which actually takes a shaving off the article being turned tends to get hot4 ,for this reason lathes are usually fitted with pumps which pump cold soap-suds on to the tool as it works4 ,what you see there is the energy employed in shaving the metal being turned into heat in the tool4 ,if left uncooled by the water it would soon be red-hot4 ,and the faster the machine works the hotter will the tool get4 ,now with the old steel a very little heat will suffice to make it soft1 when its cutting power is lost4 ,so with the old steel1 no matter how much cooling water you might use1 there was a distinct limit to the speed of the lathe and the speed at which the work was finished1 for if that speed were once exceeded a stop became necessary to regrind the tool or to put in a fresh one4 ,but with high-speed steel that limit is much higher1 for it can get almost red-hot before it loses its hardness and consequently machines can be run and jobs finished at a speed which would have been out of the question only a few years ago4 ,if one belligerent knew how to make high-speed steel while the other did not the former would have an enormous advantage in war-time4 ,speaking generally1 steel such as is used for tools is called hard steel1 while that made by the ,bessemer and ,siemens-,martin processes is called mild steel4 ,leaving out of account for the moment fancy steels such as that just described1 where other metals are added to the mixture1 the essential difference between all the varieties of steel is simply a slight difference in the percentage of carbon4 ,this is so remarkable that it is worth while to tabulate these percentages again4 ,cast iron has from #b to #e per cent4 ,steel from one-fifth to one per cent4 ,wrought iron less than one-fifth per cent4 ,mild steel1 which has least carbon of all the varieties of steel and in this respect is therefore nearest to wrought iron1 is used for the same purposes as wrought iron1 such as shipbuilding1 bridges and roofs1 tanks1 gas-holders1 etc4 ,when the ,admiralty want a specially fast ship such as a torpedo-boat destroyer with a hull as light as possible consistent with strength they have it made of steel with a slightly larger percentage of carbon so that the steel is stronger and the vessel's frame can be made lighter4 ,the steel for shells1 too1 needs to be of a certain strength to give the best results1 so the percentage of carbon is adjusted accordingly4 ,for guns themselves1 again1 special properties are needed1 and so not only is the carbon regulated to a nicety but other things such as nickel and chromium are added4 ,altogether1 steel is one of the most marvellous substances known1 certainly the most marvellous metal4 ,copper is just copper and no more1 zinc is just zinc1 and the same with lead1 but iron 7which really includes steel7 can be adapted to so many purposes1 can be endowed at will with so many different properties1 that without doubt iron1 common1 plentiful iron1 is the king of all the metals4 ,,chapter ,,viii ,,more ,,about ,,guns ,as has been remarked elsewhere1 some of the guns used by the soldiers in land warfare are very different from those used in the navy4 ,the latter1 being carried on the ships to which they belong1 can be of those proportions which best suit their purpose4 ,consequently they are usually very long compared with their diameter4 ,the field guns used by the ,royal ,field ,artillery are shorter in proportion to their calibre than are the big naval guns4 ,otherwise they would be far too long to handle in the field4 ,they are mounted on carriages drawn by horses1 and are so handy that they can go anywhere where infantry can go and can travel just as fast4 ,it takes a very short time to get them ready for action1 too1 so that they can accompany infantry quite freely1 neither arm impeding the movements of the other4 ,the ,horse ,artillery1 again1 whose guns are even lighter still1 can accompany cavalry1 travelling as fast and coming into action almost as quickly as the troopers themselves4 ,the famous ,french seventy-fives 7meaning #ge millimetres calibre7 which played such a great part in the war1 are field guns intended to move rapidly and to operate with infantry4 ,both these types of gun were used by the ,british in ,south ,africa1 as also were some field howitzers1 a type of gun to which further reference will be made later4 ,but the ,boers taught the world something new as to the possibilities of moving heavy guns quickly4 ,perhaps the reason for this was that they1 being something of the nature of amateurs in the art of warfare1 were less under the influence of tradition4 ,anyway1 they surprised the ,british by the quick way in which they moved heavy guns1 sometimes into quite difficult positions1 over rough ground and up steep hills4 ,these heavy guns of theirs were called by the ,british soldiers ,long ,toms4 ,but the ,british were quick to respond1 particularly the ever-resourceful navy4 ,when the war broke out there were1 in the neighbourhood of ,durban1 a number of warships which had as part of their own armament some of those guns which afterwards became famous as #dg's1 that being the diameter of the bore in inches4 ,they were of the long shape usual in naval guns1 and it is easy to see that they were much heavier than the field guns of #c inches or so in diameter4 ,captain ,scott 7now ,admiral ,sir ,percy ,scott7 saw that these would be useful1 so he quickly designed some carriages for them1 got these made in the railway workshops at ,durban1 and in a few hours was rushing them up to ,ladysmith4 ,it was these guns very largely which enabled that town to hold out for so long1 until1 in fact1 it was triumphantly relieved4 ,thus the effect of the ,boer war was to show that much heavier weapons could be manipulated in the field than had been considered possible before4 ,the ,great ,war which followed but a few years later carried on this same lesson1 for one of the great surprises with which the ,allies were confronted in the early days of the conflict was the inexplicable fall of fortresses which till then had been deemed almost impregnable4 ,lige1 ,namur1 ,maubeuge and1 finally1 ,antwerp1 all fell to a wonderful gun of enormous dimensions which the ,austrians had produced from up their sleeve1 so to speak4 ,like conjurers they had kept them secret until the last moment4 ,these weapons which made history so fast were of the kind called howitzers1 a name mentioned just now4 ,it should be explained here that gunners talk of guns and howitzers as if the latter were not guns2 but that is only a convenient habit which has grown up1 for the latter are unquestionably guns4 ,the distinction is1 however1 so convenient that we may well adopt it ourselves for the rest of this chapter4 ,repeated references have been made already to the question of the length of guns1 and it has been pointed out that to get high velocity1 great range and vigorous hitting power a gun needs to be as long as possible4 ,on ships this is only limited by the strength of the steel of which the gun is made1 for beyond a certain length the gun bends of its own weight4 ,ashore1 however1 the difficulties of transport impose a further limitation in most cases1 although the famous #dg1 like many other naval guns1 has a length of #ej calibres1 and the guns of small calibre do approximate somewhat to the proportions of the naval guns1 since even then their length comes within manageable limits4 ,modern warfare1 however1 requires the use of larger shells containing larger charges of explosives1 and to fire these requires guns of greater calibre4 ,we hear of shells of as great a diameter as #af inches being thrown into the ,belgian fortresses and of course nothing smaller than a #af-;inch gun could do that4 ,now a #af-;inch gun1 if made to the naval proportions of #ej calibres or even #de calibres1 would mean a length of at least #fj to #gj feet4 ,it would also mean a weight exceeding #ajj tons1 for the #ab-;inch naval gun of #ej calibres weighs about #gj tons4 ,and it is easy to see that such a gun would be very difficult to move on the field of battle4 ,indeed1 it would be almost useless because of the time it would take to get it into position and to construct the foundations which it would need4 ,if the ,austrians had only had such as those the ,belgians would have had plenty of time to prepare for them at ,antwerp1 whereas it was the quickness with which they brought up their heavy guns that astonished everyone and took their opponents by surprise4 ,the secret of this astonishing performance lies in the fact that they were not guns at all but howitzers1 which instead of being long1 slender tubes are short1 fat ones1 and that involves a different idea in gunnery altogether4 ,the gun fires at an object4 ,the howitzer fires its shell upwards with the purpose of dropping it upon the object4 ,the difference between the two is well illustrated by the methods of practising with them4 ,in learning to work a gun the gunners fire at a vertical target just as those of you who practise shooting at a miniature range fire at a target of paper placed vertically against a wall4 ,the target for howitzer practice1 on the other hand1 is a square marked out on the level ground1 and the object of the gunners is to see how great a proportion of a given number of shots they can drop inside that square4 ,of course1 being so much shorter the howitzers cannot throw a shell so far or at such a high velocity as the naval guns1 but that can to a certain extent be compensated for by using a higher explosive for the propellant4 ,that1 however1 involves greater stresses in the tube when firing takes place and also calls for stronger foundations in order that the aim may be steady4 ,a great part1 too1 of the velocity of a naval shell is required for the penetration of the armour1 whereas against forts or earthworks it is sufficient if the shell gets there4 ,moreover1 generally speaking1 it is possible to get much nearer to a fortress or entrenched position for the purpose of attacking it than it is to an enemy ship on the sea4 ,except for the occasional help of a mist there is no cover to be obtained at sea1 while on land the ground must be very flat indeed if there is no low hill or undulation behind which a gun can be set up unnoticed4 ,the ,austrians cherish a piece of steelwork from one of the forts of ,antwerp which they smashed with a shell from one of their big howitzers at a range of seven miles4 ,they evidently were able to get their big howitzers within that comparatively short distance of the ,antwerp fortifications without being molested4 ,illustration3 ,a ,,german ,,automatic ,,pistol4 ,the action is fully described on the illustration4 ,in this connection one often hears the word mortar used1 and just a reference to that will be appropriate here4 ,many years ago short guns which threw their balls very high were in use1 and because of their resemblance to the mortar which is used for pounding up things with the aid of a pestle these were termed mortars4 ,later a man named ,howitzer introduced a type of gun which was something of a compromise between the long thin gun and the short stubby mortar4 ,as time has gone on1 however1 the mortars have grown in length while the howitzers have shortened1 until to-day the two names are used almost indiscriminately to denote the same thing4 ,hence the giant howitzers of the ,austrians are often spoken of as the ,skoda mortars1 ,skoda being the name of the factory where they were made4 ,at one time many people wondered why the ,germans did not put some of these huge mortars on their battleships3 many thought that they would do so1 and that by that means they would demolish our navy as they had already smashed the ,belgian forts4 ,the reason they did not is1 no doubt1 the very simple one1 that our naval guns would have probably sunk their ships before the howitzers could have reached ours1 because if they had attempted to make up for the shortness of the weapons by using higher explosives1 these mortars would1 there is little doubt1 have knocked to pieces the ships on which they were mounted4 ,the old-fashioned fortress1 suddenly made out-of-date by the ,skoda mortars1 was usually armed with guns of the naval type4 ,sea-coast forts are always so armed4 ,nowadays1 however1 the inland fortress takes the form of a labyrinth of trenches and underground passages1 combined with deeply excavated chambers known as dug-outs1 and these do not fitly accommodate large guns at all4 ,the guns are placed well back behind the trenches sheltered behind hills or woods1 over which they hurl their shells4 ,the chief defenders of the actual trench are the machine gun1 which is little more than an automatic rifle on a stand1 and the trench mortar4 ,we are now in a position to sum up broadly the features of modern artillery4 ,there is first the naval gun1 the ideal gun1 long and of great range1 able to send forth its shells with great velocity4 ,this gun appears again in the sea-coast forts1 where the conditions are very much those which obtain on a ship and where the attacking party is of necessity a ship4 ,in the field we have the field and horse artillery1 which we may regard as the naval gun modified somewhat in order to make it easy to move about1 so that it can accompany troops and support the operations of both infantry and cavalry4 ,these light guns are supported by the field howitzers1 which are also light and easily handled1 and the guns of the #dg type1 originally naval guns but now mounted on wheels and possessing a certain amount of mobility1 not equalling the field guns it is true1 but still very serviceable in a campaign4 ,then we have the howitzers of various sizes which have rendered the old-fashioned steel and concrete forts useless1 and which are the chief weapons used in the modern trench warfare4 ,it is these which blow in the walls of the trenches and dug-outs1 shatter the barbed-wire entanglements and render it possible for the infantry to attack an entrenched position4 ,finally1 we have the machine guns1 each of which is equivalent to a considerable number of riflemen and which1 with the trench mortars1 form the chief defences of the actual trench itself4 ,of course these are only useful against attacks by infantry3 they cannot in any way cope with the heavy artillery4 ,that has to be dealt with by the opposing artillery posted away back behind the trenches4 ,and now let us take a rather more close look at some of these weapons4 ,essentially each one is a steel tube4 ,it may be a single tube or it may be several one outside another4 ,it may even have a layer of wire between two tubes as many naval guns have4 ,it is invariably 7one small exception will be mentioned later7 loaded at the breech or rear end and not through the muzzle as used to be the custom4 ,for this purpose it needs a breech-block or door1 which can be opened to put in the shell and explosive1 and which can then be closed tightly so that it will not be driven out or burst open when the explosion takes place and also shall be gas tight so as not to let any of the force of the explosion escape4 ,then the gun must be mounted upon a carriage so that it can be quickly moved about4 ,the lighter forms of artillery are fired when upon the same carriage upon which they travel4 ,in years gone by the whole thing1 carriage as well as gun1 used to run back when the gun was fired1 which was a great nuisance since it had to be got back into position again after each shot4 ,to obviate this the gun is now mounted upon a slide1 and it is the slide which is fitted to the carriage4 ,thus the gun can slide back without the carriage moving at all4 ,the latter is made very strong1 and shoes are provided at the end of chains which go under the wheels just like the drag which coaches and heavy carts have for use going down hills4 ,there is also a part like a spade which can be driven down into the ground so that1 what with the shoes and the spade1 the carriage is fixed very firmly4 ,the gun is kept at the front part of the slide by means of a powerful spring1 which is compressed when the gun is fired but which1 as the force of the recoil is spent1 pushes the gun back to its original position once more4 ,the spring is often reinforced by a cylinder and a piston with compressed air or water behind it1 acting after the manner of those door checks with which we are all familiar1 its function being to steady the motion of the gun and to let it go gently back to its place without slamming1 just as the door check prevents a door from slamming4 ,by this means the gun is returned automatically after each shot to practically the same position which it occupied before1 so that it does not need re-aiming each time1 but only a slight readjustment if even that4 ,the result of this is that such a gun can be fired very rapidly4 ,in fact1 it can be fired just as fast as the gunners can keep on reloading it4 ,the big ,skoda mortars owed their mobility to the clever way in which they were constructed4 ,the gun tube itself1 the support for it or mounting1 and the steel foundation were each fitted to a special motor-driven trolley4 ,the steel foundation was dumped down on the ground1 which of course was prepared for it in advance1 then the mounting was run right on to it so that it simply needed bolting down and finally the tube was hoisted by specially prepared appliances into its place4 ,it is said that the whole operation occupied less than an hour4 ,for firing1 these mortars of course are pointed at a very high angle1 almost like an astronomical telescope4 ,no doubt the gunners have many jokes about shooting the moon and so on1 for that is just what they seem to be attempting4 ,for loading1 however1 they are lowered into a horizontal position3 the shell comes up on a small hand-truck1 is raised by a specially designed jack until it is level with the breech1 and is then pushed into its place4 ,the breech is then closed1 the tube re-elevated1 and all is ready for firing4 ,between these two forms of gun1 the field gun on its light carriage1 which not only bears it from place to place but forms its support while in action1 and the great mortar carried in parts on specially made trolleys1 there are now an enormous variety of guns and mortars adapted for the various purposes which experience in the ,great ,war revealed4 ,artillery suffered many changes in the light of the ,south ,african campaign and of the ,russo-,japanese war1 but of far more importance have been the lessons learnt in ,northern ,france and on the plains of ,poland4 ,to some extent these lessons have been learnt and profited by during the actual war1 but there is no doubt that as men have time to think over them in the years of peace which are ahead many more developments will take place4 ,unless1 that is1 we are on the threshold of that happy time when guns and fighting material of all sorts will be looked upon as the relics of a bad and ruinous time now happily past4 ,in conclusion1 a passing reference must be made to the trench mortars and similar contrivances which have arisen as the result of the prolonged spell of trench warfare which no one had ever contemplated4 ,these are in effect very short range mortars or howitzers1 specially intended for throwing bombs from trench to trench4 ,some are simply the larger mortars on a small scale1 but one has decidedly original features4 ,this consists of a short light mortar into which the bombs are slipped through the muzzle1 thus reverting to the old method of loading4 ,the propellant is combined with the bomb and there is a percussion cap which fires it as soon as it strikes the bottom of the tube4 ,thus the operation is just about as simple as it can be3 the man merely places the bomb in the upturned muzzle and lets it slide down4 ,an instant later1 up it comes again1 to go sailing through the air into the trench of the enemy a hundred yards away4 ,one must not conclude this chapter1 however1 without a reference to those useful weapons which are known among the soldiers as ,archibalds and officially as anti-aircraft guns4 ,these are perhaps the most familiar guns of all to the general public1 since they were installed in many places in ,britain for the purpose of dealing with the ,zeppelins4 ,no doubt not a few of my readers have had the experience of being awakened from their beauty sleep by the cracking of the anti-aircraft guns and have seen their shells bursting like squibs in the air4 ,they are fairly long guns1 not unlike field guns1 but they are mounted upon special supports which enable them to be pointed at any angle so that they can fire right up into the sky4 ,the sights1 also1 are somewhat different1 being fitted with prisms1 or reflectors1 so that the gunners can look along the sights and align the gun upon an object overhead without lying on their backs4 ,much more could be said on this subject1 but national interests forbid1 so with this general review of modern artillery we must pass to another subject4 ,,chapter ,,ix ,,the ,,guns ,,they ,,use ,,in ,,the ,,navy ,both the great ,english-speaking nations are immensely proud of their navies4 ,they can1 on occasion1 produce soldiers by the million of the very highest and most efficient type1 but they never feel quite that pride and patriotic fervour over their soldiers that they do over their ships of war and their sailors4 ,the guns1 therefore1 with which the ships are armed1 always form a subject of great interest1 especially those large ones which constitute the armament of the ,dreadnought battleships and battle-cruisers4 ,let us first consider what is required in a naval gun1 for it must be remembered that the naval and military weapons are different in some respects4 ,experience at the ,dardanelles showed that even the guns of the ,queen ,elizabeth1 the largest and most powerful then known1 fresh from the finest factories1 were not particularly successful against the ,turkish forts4 ,the ,germans1 too1 set up what was probably a naval gun and occasionally dropped shells into ,dunkirk with it at a range of twenty miles or so1 but without causing much harm1 and the fact that they only did it occasionally and then abandoned it altogether seems to indicate that in their opinion they were not doing much good with it4 ,it must not be assumed from this that naval guns are bad guns or poor guns1 however1 but simply that they are made for a special purpose for which they are highly efficient1 from which it follows almost as a natural consequence that they are somewhat less efficient when used for some other purpose4 ,their purpose is to pierce the hard steel armour with which warships are protected and then to explode in the enemy's interior1 whereas in modern warfare the greatest military guns are chiefly required to blow a big hole in the ground or to shatter a block of concrete4 ,in both cases the ultimate object is to carry a quantity of explosive into the enemy's territory and there explode it1 but whereas the land gun has simply to do that and no more1 the naval gun has to pierce thick armour-plate as well4 ,and just think what that means4 ,many large ships have their vital parts protected by armour-plates twelve inches thick4 ,moreover1 the armour-plates are made of very special steel1 the finest that can be invented for the purpose4 ,vast sums of money have been expended in experimenting to find out just the best sort of steel for resisting penetration by shells4 ,some time ago ,i saw several pieces of armour-plate which had been used in one of these tests4 ,they had been set up under conditions as nearly as possible the same as those obtaining on the side of a ship and then they had been fired at from varying distances1 the effects of the various shots being carefully recorded4 ,and that is only one experiment out of tens of thousands which have been tried again and again1 while the steel manufacturers are always trying to improve and again improve the shell-resisting properties of their steel4 ,thus1 we see1 the presence of the steel armour which has to be perforated before the shell can do its work makes the task set before the naval gun somewhat different from that which confronts its military brother4 ,these considerations result in the naval gun needing to have as flat a trajectory as possible and its projectiles the highest possible speed4 ,now trajectory1 it may be useful to explain1 is the technical term employed to denote the course of a projectile1 which is always more or less curved4 ,let us imagine that we see a gun1 pointed in a perfectly horizontal direction1 and let us also imagine that by some miracle we have got rid of the force of gravity and also that there is no air4 ,under those conditions the shot from the gun would go perfectly straight and with undiminished velocity for ever and ever4 ,then let us imagine that the air comes into being4 ,the effect of that is to act as a brake which gradually slows the shell down until finally it stops it4 ,theoretically1 perhaps1 it would never quite stop it1 but for all practical purposes it would4 ,again1 let us suppose that while the air is absent the force of gravity comes into play1 what effect will that have8 ,it will gradually pull the shell downwards out of its horizontal course1 making it describe a beautiful curve4 ,but1 someone may think1 does not a rapidly-moving body remain to some extent unaffected by gravity8 ,not at all3 it falls just the same and just as quickly as if it were falling straight down4 ,if our imaginary horizontal gun were set at a height of sixteen feet and a shell were just pushed out of it so that it fell straight down the shell would touch the ground in one second4 ,if the ground were perfectly flat and the shell were fired so that it reached a point half a mile away in one second it would strike the ground exactly half a mile away4 ,you see1 the horizontal motion due to the explosion in the gun and the downward motion due to gravity go on simultaneously and the two combined produce the curve4 ,to make this quite clear1 let us imagine two guns precisely alike side by side and both pointed perfectly horizontally4 ,from one the shell is just pushed out3 from the other it is fired at the highest velocity attainable3 both those shells will fall sixteen feet or a shade more in one second1 and if the ground were perfectly level both would strike the ground at the same moment although a great distance apart4 ,clearly1 then1 the faster the shell is travelling the more nearly horizontally will it move1 for it will have less time in which to fall1 and the slower the more curved will be its path1 from which we see that the air by reducing the velocity causes the curve to become steeper and steeper as the shell proceeds4 ,if1 then1 our gun is placed low down1 as it must be on a ship1 to get the longest range we must point it more or less upwards because otherwise the shell will fall into the water before it has reached its target4 ,when we do that we complicate matters somewhat1 for gravity tends to reduce the velocity while the shell is rising and to add to it again while it is falling4 ,we need not go too deeply into that1 however1 so long as we realize that1 whatever the conditions may be1 the shell in actual use has to follow a curved course1 first rising and then falling4 ,the really important part about a shell's journey is the end4 ,so long as it hits it really does not matter what it does on the way1 and if it misses it is equally immaterial4 ,the reason why we need to bother about the first part of the trip is because upon it depends the final result4 ,whatever the trajectory may be we see that the shell must necessarily arrive in a slanting direction4 ,and the more steeply slanting that direction is the less likely is the target to be hit4 ,if the shell went straight it would only be necessary to point the gun in the right direction and the object would be hit no matter how far away it might be4 ,the more curved the course is1 the more likely the shell is to fall either too near or too far1 in the one case dropping into the water1 in the other passing clear over the opposing ship4 ,let us look at it another way4 ,suppose the vital parts of a ship rise #bj feet out of the water and the shell arrives at such an angle that it falls #bj feet in #ajj yards3 then1 if the ship be within a certain zone #ajj yards wide it will be hit in a vital spot4 ,if it be nearer the shell will pass over1 if it be further the shell will fall into the water4 ,that #ajj yards is what is called the danger zone4 ,if the shell is falling less steeply1 say1 #bj feet in #bjj yards1 then the danger zone is increased to #bjj yards and so on1 which gives us the rule that the flatter the trajectory1 or the more nearly straight the course of the shell the greater is the danger zone and the more likely is the enemy ship to be hit4 ,we have established two facts1 therefore1 first1 that the trajectory must be as flat as possible and1 second1 that to make it flat the velocity must be high4 ,we can also see another reason for high velocity1 namely1 to give penetrating power4 ,to obtain a high velocity the gun must be long1 and consequently naval guns are always long1 a fact which is very noticeable in the photographs of warships4 ,the reason for this is quite obvious after a little thought4 ,you could not throw a cricket ball very far if you could only move your hand through a distance of one foot4 ,to get the best result you instinctively reach as far back as ever you can and then reach forward as far as you are able1 so that the ball shall have as long a journey as possible in your hand4 ,perhaps you do not know it but all the time you are moving your hand with the ball in it you are putting energy into that ball1 which energy carries it along after you have let go of it4 ,and it is just the same with the shell in the gun4 ,so long as it is in the gun energy is being added to it but as soon as it leaves the muzzle that ceases4 ,after that it has to pursue its own way under the influence of the energy which has been imparted to it4 ,the powder which is employed as the propellant or driving power is of such a nature and so adjusted as to quantity that as far as possible it shall give a comparatively slow steady push rather than a sudden shock1 so as to make full use of the gun's length1 the expanding gases following up the shell as it goes forward and keeping a constant push upon it4 ,on the other hand1 a gun can be too long1 for no steel is infinitely strong and stiff1 so that beyond a certain limit the muzzle of the gun would be likely to droop slightly of its own weight and so make the shooting inaccurate4 ,the limit seems to be about #ej calibres or1 in other words1 fifty times the diameter of the bore4 ,for a considerable time the standard big gun of the ,british ,navy was the #ab-;inch1 that being the calibre or diameter of the bore4 ,the famous ,dreadnought had guns of that calibre and so had her immediate successors4 ,the #ab-;inch gun of fifty calibres weighs #fi tons and fires a projectile weighing #hej lbs4 which it hurls from its muzzle at a velocity of about #cjjj feet per second4 ,more recently the size has grown to #ac1 #ad and even as great as #ae inches calibre1 but we may for the moment take the #ab-;inch gun as typical of all these large guns and have a look at its construction4 ,it is made of a special kind of steel known as nickel-chrome gun steel1 formed by adding certain proportions of the two rare metals nickel and chromium to the mixture of iron and carbon which we ordinarily call steel4 ,the metal is made after the manner described in another chapter and is cast into the form of suitably-sized ingots which are afterwards squeezed in enormous hydraulic presses into the rough shape required4 ,besides giving the metal the desired form this action has the effect of improving its quality4 ,since a gun is necessarily a tube it may be wondered why the steel is not cast straight away into that shape instead of into a solid block and the reason why that is not done is very interesting4 ,it is found that any impurities in the metal--and it is impossible to make it without some impurities--collect in that part which cools last and obviously that part of a block which cools last is the centre4 ,thus the impurities gather together in the centre of the mass whence they are removed when that centre is cut away1 whereas if the first casting were a tube they would collect in a part which would remain in the finished gun4 ,the ingot1 then1 is cast and pressed roughly to shape4 ,then it is put into a lathe where it is turned on the outside and a hole bored right through the centre4 ,but that is by no means all of the troubles through which this piece of steel has to pass4 ,it undergoes a very stringent heat treatment1 being alternately heated in a furnace to some precise temperature and then plunged into oil1 whereby the exact degree of hardness required is attained4 ,moreover1 this is only one of the tubes which go to make up the gun1 which is a composite structure of four tubes placed one over another with a layer of tightly wound wire as well4 ,first1 there is the innermost tube1 the whole length of the gun1 then a second one outside that1 usually made in two halves4 ,both are carefully made to fit1 and then the outer is expanded by heat to enable it to be slidden over the inner one1 after which on cooling it contracts and fits tightly4 ,outside this second tube is wound the wire1 or more strictly speaking tape1 for it is a quarter of an inch wide and a sixteenth thick4 ,it is so strong that a single strand of it could sustain a ton and a half4 ,it is carefully wound on2 first several layers running the whole length of the gun and then extra layers where the greatest stresses come1 that is to say1 near the breech1 for that has to withstand the initial shock of the explosion4 ,altogether about #acj miles of wire go on a single gun4 ,the advantages of this form of construction are many4 ,for one thing1 a wire or strip can be examined throughout its whole length and any defect is sure to be found1 whereas in a solid piece of steel1 no matter how carefully it may be made1 there may lurk hidden defects4 ,moreover1 if a solid tube develops a crack anywhere it is liable to spread1 whereas a few strands of wire may be broken without in any way affecting the rest4 ,it has been found that even if a shell burst while inside one of these guns no harm is done to the men in the turret where it stands1 a thing which cannot be said for guns composed entirely of tubes1 so that the merit rests with the wire4 ,a third advantage is that the wire can be wound on to the tube beneath it at precisely that tension which is calculated to give the best result1 whereas in shrinking one tube on to another this cannot always be attained4 ,over the wire there come two more tubes not running the whole length but meeting and overlapping somewhat near the middle1 so that at one point there are actually four concentric tubes besides the wire4 ,at the rear end a kind of cap called the breech-piece covers over the ends of all the tubes1 itself having a central hole into which fits the breech-block1 one of the triumphs of modern engineering1 of which more in a moment4 ,while we have in mind the wire-wound form of construction it is interesting to note that something similar but in a crude form was practised sixty years or more ago4 ,the guns of that era were some of them even of cast iron while the more refined consisted of a steel tube strengthened with coils of wrought iron4 ,this iron was first rolled into flat bars1 then it was made hot1 and wound on spirally round an iron bar the same size as the tube4 ,a little hammering converted this spiral into a tube which was then fitted round the steel tube4 ,thus1 although very different there is still a distinct resemblance between this old method and the up-to-date wire-wound weapon4 ,the manufacture of guns1 it may be remarked1 owes more to one man than to any other1 namely1 ,mons4 ,gustave ,canet1 a ,french engineer who1 having fought in the ,franco-,german ,war1 decided to devote his engineering talents to developing the artillery of his native land4 ,he spent many years in ,england but later established works at ,havre for the manufacture of guns upon improved methods1 finally merging his interests into those of the great ,french armament firm of ,schneider of ,creusot4 ,by ,french and ,english artillerists at all events the name of ,canet is regarded with reverence4 ,but to get back to our naval gun4 ,it will be clear that operations such as have been described1 involving the handling of great tubes fifty feet or more in length1 heating them as required1 dipping them in oil while hot and so on1 can only be carried out at works specially designed for the purpose4 ,the furnaces where the tubes are heated are well-like formations in the ground1 deep enough to take the tube vertically4 ,to lift them in and out there have to be tall travelling cranes capable of catching the tube by its upper end and lifting it right out of the furnace so that its lower end clears the ground4 ,to accomplish this with a little to spare the cranes need to be seventy feet or so high4 ,then there are deep pits full of oil so that a tube can be heated in a furnace1 drawn out by a crane and quickly dropped into the adjacent oil bath4 ,likewise there have to be pits of a third kind wherein a cold tube can be set up while a hot one is dropped over it for the purpose of shrinking the latter on4 ,then1 of course1 there have to be lathes of gigantic dimensions capable of taking a length of nearly sixty feet and of swinging an object weighing anything up to fifty tons4 ,but of those machines we can only pause to make mention1 for we must pass on to the breech-block1 in some ways the most interesting part of the gun4 ,when it was first suggested to leave the back end of the gun open so that the powder and projectiles could be put in that way instead of through the muzzle1 people at once foresaw how much would depend upon the arrangements for stopping up the hole while the gun was fired4 ,for1 of course1 the force of the explosion is exerted equally in all directions1 backward just as much as forward1 so that unless very securely fixed the stopper closing the breech would be liable to become a projectile travelling in the wrong direction4 ,to fix such a thing securely enough to avoid accidents would surely take up too much time and so largely neutralize any advantage arising from its use4 ,these fears were1 indeed1 to some extent justified by accidents which actually occurred with the early examples of breech-loading guns1 and for that reason our own authorities for a time looked askance at breech-loaders4 ,now let us take a look at the breech-block of the #ab-;inch naval gun of to-day1 which never blows out1 not even when #cej lbs4 of cordite go off just the other side of it4 ,the explosion hurls an #hej-pound shell at the rate of #cjjj feet per second but it never stirs the breech-block4 ,yet it can be opened and closed so quickly1 including the necessary fastening-up after closing1 that shots can be fired from the gun at the rate of one every fifteen seconds4 ,the breech-block partakes of the nature of a plug and also of a door4 ,it swings upon hinges like the latter but its shape more resembles the former4 ,if we want to make such a thing very secure we usually make it in the form of a screw with many threads1 but that entails turning it round many times and that takes time4 ,given plenty of time to screw the breech-block into its place and there would never have been any anxiety as to the possibility of its blowing out1 but there is not time4 ,the problem1 therefore1 was to get the strength of a screw combined with quickness of action4 ,this dilemma is avoided in the following simple manner4 ,the breech-block is given a screw thread on its exterior surface1 and the hole in the breech-piece is given a similar screw-thread on its inner surface1 just as if the one were to be laboriously screwed into the other after the manner of an ordinary screw in machinery4 ,then four grooves are cut right across the threads on the block and similarly on the breech-piece1 so that at four different places there is no thread left4 ,in other words1 instead of the thread running round and round continuously1 each turn is divided up into four sections with sections of plain unthreaded metal in between4 ,thus in a certain position the block can be pushed into the hole without any threads engaging at all1 for each strip of threaded block passes over an unthreaded strip in the hole and vice versa1 in other words1 the threads on the one part miss those on the other part4 ,yet an eighth of a turn serves to make all the threads engage and the thing is held almost as securely as if it were just an ordinary screw with threads its whole length4 ,the block is carried upon a hinged arm so that although it can be turned in this manner it can also be swung back freely when necessary4 ,combined with the breech-block is a pneumatic contrivance which blows a powerful jet of air through the gun every time the breech is opened1 thereby cleaning away the effects of the last explosion4 ,each of these great guns is mounted upon a slide so that when it is fired it can slide back1 thereby exhausting the effect of the recoil1 yet can be returned instantly to its original position4 ,indeed1 this return is brought about quite automatically by the agency of springs1 compressed air and hydraulic power4 ,thus the gun fires1 slides back1 returns and is at once ready for the next shot4 ,it is trained1 or pointed in a horizontal plane1 by turning the turret in which it stands but the correct elevation is gained by the use of telescopic sights4 ,the principle of these sights is very simple4 ,imagine a graduated circle fixed to the side of the gun4 ,pivoted at the centre of the circle is a small telescope4 ,the telescope can be turned round to any angle upon the circle and it can then be clamped at that particular angle4 ,the range having been given to the officer in command of the gun from the range-finding station on another part of the ship1 the telescope is set to the correct angle4 ,then the gun is elevated or depressed until the ship being aimed at is precisely in the centre of the field of view of the telescope1 in other words1 until the telescope is pointing exactly at the ship4 ,then the gun is fired4 ,the effect1 therefore1 is this4 ,the telescope always points 7while the gun is being fired7 at the object aimed at1 but the gun is pointed upwards at a certain angle1 which angle depends upon how the telescope is set upon the divided circle4 ,thus the setting of the telescope for a given range produces the correct upward tilt of the gun for that range4 ,the breech-block carries a trigger and hammer arrangement whereby the firing can be done and also an electrical arrangement so that an electric spark can be employed4 ,both these firing contrivances are so made that they cannot be operated until the breech-block has been inserted and made secure4 ,thus a premature explosion is guarded against4 ,,chapter ,x ,,shells ,,and ,,how ,,they ,,are ,,made ,modern warfare seems to resolve itself very largely into a question of which side can procure the most shells4 ,during the great war there was a time when the ,british and their allies were hard pressed because they had not sufficient shells4 ,the enemy had in that matter stolen a march upon them and had during the winter1 when military activity is at its minimum1 rapidly produced large supplies of high-explosive shells4 ,discovering their lack the ,british set about remedying it in true ,british fashion4 ,it is quite characteristic of this strange people to let the enemy get ahead at the commencement1 after which they pull themselves together and put on a spurt1 so to speak1 and after that the enemy had better prepare for the worst1 for defeat is only a question of time4 ,so1 finding themselves short of shells1 they set to and dotted the whole country in an incredibly short time with huge factories entirely devoted to making shells4 ,older factories also were adapted to the same purpose4 ,places intended and normally used for the manufacture of the most peaceable things--ploughs1 gramophones and piano parts for example--were soon turning out shells or parts thereof by the thousand4 ,electric-light works1 waterworks1 cotton mills1 technical schools1 all sorts of places where1 for doing their own repairs or for some similar reason1 there happened to be a lathe or two1 all these were organized and in a few weeks they too were working night and day something to do with shells4 ,meanwhile other factories were springing up for the purpose of making explosives while others again were erected for producing the acids and other chemicals necessary for the explosive works2 and yet another kind of works1 the filling factories1 came into being as if by magic and thousands of girls flocked from far and near to these places1 there to fill the shells with the explosives4 ,even the soldiers did not realize a few years ago how important the supply of shells was going to be4 ,the rifle has fallen from its old place of importance while the gun and the shell have risen to the first place4 ,what1 then1 is a shell8 ,it is what its name implies1 a case covering something else1 just as the shell of a fish covers its owner4 ,it is a hollow cylinder of steel with certain things inside it4 ,its chief function is to hold these other things and to be shot out of a gun carrying them with it to their destination4 ,you want to cause an explosion in an enemy's ship4 ,you cannot get near enough to put the explosives there by hand1 for he will not let you1 so you put them into a steel shell and then hurl the whole thing at him out of a gun4 ,illustration3 ,,bomb ,,throwing4 ,one of the most striking things about the war was the re-invention of the bomb thrown by hand4 ,this officer hurled bombs at the enemy for twenty-four hours continuously4 ,in the attempt to prevent your doing him any harm by thus throwing boxes of explosives at him1 the enemy clothes the sides of his most valuable and important ships with thick steel plates1 wherefore you have to make your shell strong and tough so that it shall not splinter against the armour but shall on the contrary bore its way through1 finally exploding in the interior of the ship4 ,if it is not a ship that you are attacking but1 say1 an earthwork or an arrangement of trenches1 then you do not need to penetrate steel armour and your shell can be thinner and of lighter construction4 ,it still needs to be strong1 however1 for it has another function besides simply carrying the explosive4 ,it must hold the force of the explosion in for a moment while it gathers force so that when the hour comes the pent-up energy may strike all round with the utmost violence4 ,even the most powerful explosives are comparatively feeble if they go off in the open4 ,by holding them in check for a moment and then letting their force loose suddenly you get a much more forceful blow4 ,shells which contain only an explosive are called common shells or high-explosive shells4 ,shrapnel shells constitute another type in which the force of the explosion is simply employed to release a number of round bullets1 which strike mainly because of the velocity which they derive from the original motion of the shell4 ,these are above all things man-killing shells1 for their result is akin to a volley of bullets at close range4 ,we can thus sum up the chief types of shell as follows3 the naval shell which has to be capable of penetrating armour3 the high-explosive shell which must be able to break up earthworks and blow down the walls of trenches3 and the shrapnel shell which scatters a shower of bullets and is most useful in attacks upon bodies of men rather than upon material structures4 ,some shells have their propellent explosive combined with them just as the familiar rifle cartridge contains the propellant combined with the bullet4 ,in the larger sizes1 however1 it is much more convenient to have the propellant in a separate cartridge1 which can be handled separately and loaded into the gun separately4 ,as has been already explained1 the propellant is a powder which gives a steady push rather than a destructive blow3 moreover1 it is practically smokeless1 so as not to give away the position of the gun to the enemy4 ,the high explosive1 however1 shatters and usually makes a dense smoke1 so that the observers can see where it fell and report to the gunners whether or not they have got the range4 ,soldiers' letters have told us of the black ,marias and coal boxes used by the ,germans1 those terms being simply soldiers' nick-names arising no doubt from the fact that certain particular shells are filled with tri-nitro-toluene which gives a black smoke4 ,clearly1 smoke1 which is most objectionable in the propellant1 is a positive advantage in the bursting charge4 ,and now let us take a glimpse at the manufacture of one of these terrible missiles4 ,an ingot of shell-steel is first cast as described in an earlier chapter4 ,since impurities are apt to rise1 while the metal is liquid1 the top of the ingot is always cut off and discarded4 ,this waste material is used for many other purposes1 in which a chance flaw would not be a serious matter1 under the title of shell-discard steel4 ,the lower part is then heated and passed through a rolling mill1 a machine very similar in principle to the domestic mangle1 the rollers being of iron with suitable grooves cut in them4 ,a few passages through this machine transforms the ingot into a thick round bar4 ,this is then sawn into short pieces called billets1 each of which is the right size to form a shell4 ,again heated1 a powerful press drives a pointed bar through the softened steel1 thereby converting the short billet into a rough tube4 ,another press then slightly closes in one end1 making it resemble a bottle without a bottom and with the neck broken off4 ,the rough forging is then ready to be machined1 an operation which is performed in a lathe4 ,the outside is made perfectly round and smooth and of precisely the right size4 ,the inside is also bored out to the correct diameter and finished off to an exceeding smoothness so as to avoid the possibility of any rough places irritating the explosive which in due time will be filled into it4 ,for the same reason1 the inside1 when finished1 is varnished in a certain way and with a certain varnish4 ,the formation of this varnish is one of those little thought of but highly important services which alcohol renders to us1 as mentioned elsewhere4 ,the smaller end 7that which has already been partially squeezed in7 is bored out and screwed for the reception of the nose-bush1 while the other end is recessed for the reception of the plate which forms the bottom4 ,most of these operations have to be very accurately carried out and1 to ensure that that is so1 gauges are continually employed to check the work4 ,these gauges are based upon a very simple principle1 known as the limit principle4 ,this is both interesting and important1 sufficiently so to merit a more detailed reference4 ,it must first be realized that no two things are alike and no measurement is perfectly correct4 ,when we lightly speak of two things being alike we really mean that for the purpose contemplated they are nearly enough alike4 ,two things might be alike for one purpose and yet be so unlike as to be useless for another4 ,what the authorities do in the case of shells1 therefore1 and what is done nowadays in many branches of engineering1 is to recognize this fact and at the same time overcome the difficulty by stating what difference is permissible4 ,in other words1 instead of saying that a thing must be a certain size1 it is required to fall between two limits3 it must not be more than one or less than the other4 ,for example1 suppose a hole is required to be nominally an inch in diameter it may be specified that it shall not exceed an inch plus one-thousandth or fall short of an inch minus one-thousandth4 ,in such a case a variation of a thousandth of an inch either way is permitted4 ,the permitted variation may be more than that1 or it may be less and be measured in ten-thousandths1 it all depends upon circumstances4 ,clearly in every case it is desirable to permit as large a variation as is consistent with a good result4 ,now to make measures with the degree of accuracy just mentioned is not easy4 ,one can just about see through a crack a thousandth of an inch wide if held up to a bright light4 ,how then can dimensions such as these be dealt with easily and quickly in the rough conditions of a large workshop8 ,let us again think of that one-inch hole and we shall see how simply and easily it is done4 ,the gauge in such a case would be shaped somewhat like a dumb-bell1 one end being the go end and the other the not-go end4 ,the former is made to agree as nearly as possible with the lower limit1 the other with the higher limit1 and all the inspector has to do is to try first one end in the hole and then the other4 ,one must go in and the other must not-go4 ,so long as that happens he knows that the hole is correct within the prescribed limits4 ,if1 on the other hand1 both go in1 then he knows the hole is too large1 or if neither goes in he knows it is too small4 ,it may be urged by some acute reader that the gauges themselves cannot be correct1 and that is quite true1 but it is possible1 by great care and laborious methods1 to produce gauges which are correct to within far narrower limits than those mentioned4 ,in the case of outside dimensions the gauges take the form of a thumb and finger capable of spanning the object to be measured1 and in that case also two are used1 one of which must go and the other not-go4 ,by methods such as these the shells are measured and examined4 ,one of the most important features of a shell is its driving band4 ,in the old days of round cannon balls it is said that the gunners used to wrap greasy rag round each so as to make it fit the cannon and to prevent the force of the explosion to some extent wasting itself by blowing past the ball4 ,that is one of the functions of the driving band4 ,it is made of copper which is comparatively soft1 and it forms a fairly tight fit in the bore of the gun1 so that while the shell is free enough to slide out of the gun it is tight enough to prevent the loss of any of the driving force of the explosive4 ,its second purpose is to give the necessary spinning action to the shell4 ,the old cannon ball suffered from the fact that it offered a considerable surface to the air in proportion to its weight4 ,the idea arose1 therefore1 of making projectiles cylindrical and with a pointed nose1 so that while the weight might be increased the resistance to the air might be even reduced4 ,but it was clearly no use doing this unless the thing could be made to travel point foremost4 ,now for some rather mysterious reason1 if you shoot a cylindrical object out of a gun1 it will turn head over heels in the air1 unless you give it a spinning motion4 ,this motion1 however1 because of a gyroscopic effect1 keeps the shell point first all the time4 ,it has another effect1 too1 known as air-boring4 ,a spinning shell seems actually to bore its way through the air4 ,probably this is due to a centrifugal action1 the spinning shell throwing the air outwards from itself and so to some extent sucking the air away out of its own path4 ,whether that be the true explanation or not1 the fact remains that the spinning shell makes its way through the air better than a non-spinning one would do4 ,the gun1 therefore1 has formed in its bore a very slow screw-thread called rifling1 from a ,french word meaning a screw4 ,and it is the second function of the copper band to catch this rifling and by it be turned as the shell proceeds along the barrel4 ,the soft copper conforms to the shape of the rifling and so itself becomes in a sense a screw engaging with the rifling4 ,this band is situated near the base of the shell1 lying in a groove turned in the shell for its reception4 ,to prevent the band turning round without turning the shell there is a wavy groove turned in the bottom of the larger groove1 and the band1 being put on hot1 is squeezed into the latter by a powerful press4 ,the nose-bush is a little fitting of brass which screws into the smaller end of the shell and it has a hole in its centre into which another brass fitting1 the nose itself1 is screwed4 ,the base of the shell is closed with a little disc of steel plate4 ,people sometimes wonder why the original forging is not made solid at the bottom so as to save the necessity for this disc1 but the reason is that if that were done defects might very possibly arise in the steel in the centre which1 since it is the very spot whereon the propellant acts1 might let some of the heat or force of the propellant through1 causing a premature explosion of the charge inside the gun itself instead of among the ranks of the enemy4 ,in the case of naval shells1 the nose is not of brass but of a soft kind of steel4 ,one might expect it to be of the very hardest steel1 since it has to pierce the hard armour1 but experience has shown that the soft nose is better than a hard one4 ,the reason probably is that a hard nose splinters1 whereas a soft one spreads out on striking the armour and then acts as a protection to the body of the shell behind it4 ,in these shells1 too1 the fuse which explodes the charge is placed in the base4 ,in the others it is in the nose1 but clearly it could not be so placed in the armour-piercing shell4 ,it is interesting to mention that the propellent powder has combined in it some vaseline or other greasy matter which acts as a lubricant between the gun and the shell when firing takes place4 ,shrapnel is so different from the other types of shell that it merits a short paragraph or two to itself4 ,instead of being filled1 as the others are1 solely with explosive1 the front part of it accommodates a considerable number of small round bullets1 behind which comes a charge of gunpowder4 ,the front half of the shell is separate from the back part1 the two being connected by rivets of soft iron wire1 so that a sudden shock can rend them apart4 ,the shell is fired from the gun and comes flying along3 suddenly1 owing to the action of the fuse1 the gunpowder explodes3 the case then flies in two1 the bullets are liberated and fall in a shower4 ,in the ,south ,african ,war1 where fortifications were few1 these shells were very effective1 but against fortifications1 and particularly against trenches and barbed wire1 big explosive shells are of much greater value4 ,,chapter ,,xi ,,what ,,shells ,,are ,,made ,,of ,the body of a shell is made of steel of a fairly strong variety4 ,that is to say1 it is stronger than that used for shipbuilding and for bridges and such work3 but it is less so than some of the higher grades of steel1 such as that used for making wire ropes4 ,owing to so much of this steel being rolled during the war1 shell quality has come to be as well known to the general engineer as any of the many varieties which he has been accustomed to since his apprentice days4 ,many people wondered1 at one time1 why the cheaper and more easily worked cast iron could not be used for shells4 ,there was a period when the steel works were quite unable to cope with the demands for steel1 yet the iron foundries were crying out for work4 ,this question then arose in many minds1 ,why not make cast iron shells8 ,the answer is that cast iron is too weak3 it would blow into fragments too soon4 ,just think what a shell is and what it has to do4 ,it is a metal case filled with explosive4 ,it is thrown from a gun and is intended to blow itself to pieces on arrival at its destination4 ,it is that self-destruction which carries destruction to all around as well4 ,it is necessary1 in order to obtain the best result1 that an appreciable time should elapse between the ignition of the explosive and the bursting of the case4 ,the force of the most sudden explosion is not really developed at once1 but takes an appreciable time4 ,after ignition1 therefore1 as the explosion gradually becomes complete1 the pressure inside the shell is growing1 and too weak a shell would go to pieces before the maximum pressure had been attained4 ,thus much of the energy of the explosion would simply be liberated into the air instead of being employed in hurling the fragments of shell with enormous force4 ,that is1 of course1 not a complete explanation of the whole action of a high-explosive shell1 but it indicates generally the reason why a special quality of steel is required in order to get the best results4 ,steel having been dealt with in another chapter1 we will pass to the other metals which play important if not essential parts in the production of modern projectiles4 ,so important are several of these that the lack of one or two of them would1 under modern conditions1 mean certain defeat for a nation4 ,let us first of all take copper1 of which is made the driving bands of the shells and which in combination with zinc forms brass of which noses and other important parts are made4 ,its ore is found in many parts of the world1 notably in the ,united ,states1 ,chile and ,spain4 ,the ores are of several kinds1 the simpler ones to deal with being oxides and carbonates of copper1 meaning compounds of copper with oxygen and with oxygen and carbon respectively4 ,it will be remembered that ores of iron are usually of the same nature1 namely1 oxides and carbonates1 and consequently we find that the method of obtaining copper from these ores resembles the methods employed to obtain iron from its ores4 ,the ore is thrown into a large furnace1 like the blast furnaces of the ironworks1 and in the heat of the fire the bonds between copper and oxygen are loosened and the superior attractions of the carbon in the fuel entice the oxygen away1 leaving the metal comparatively pure4 ,unfortunately1 however1 copper is found most plentifully in combination with sulphur with which it forms what is termed sulphide4 ,this copper sulphide is called by miners copper pyrites4 ,another trouble is that mixed with the copper pyrites there is usually more or less of iron pyrites1 or sulphate of iron1 so that to obtain the copper not only has the sulphur to be got rid of but also the iron4 ,this complicates the operations very much1 the ore having to be subjected to repeated roastings and meltings during which the sulphur passes off in the form of sulphur dioxide 7a material from which sulphuric acid can be obtained71 leaving oxygen in its place4 ,thus the copper sulphide becomes copper oxide1 after which the oxygen is carried away by carbon1 leaving the relatively pure metal4 ,moreover1 at each operation various substances are thrown into the furnace called fluxes1 which do not mingle with the metal but float on the top in the form of slag1 and into the slag the iron passes1 so that finally the copper is obtained alone4 ,zinc is another important material for shell-making4 ,its ores used to be found in great plenty in ,silesia1 but the chief source of supply is now ,australia4 ,it is what is called zinc blende1 and consists of zinc sulphide1 or zinc and sulphur in combination4 ,in all these names1 it may be interesting to mention1 at this point1 the termination ide indicates a compound of two substances1 so that we can safely conclude that the ides consist of the two elements named in their titles and no others4 ,thus zinc sulphide is zinc and sulphur and nothing else1 iron sulphide is iron and sulphur1 copper oxide is copper and oxygen1 and so on4 ,the blende is first roasted in huge furnaces specially built for the purpose4 ,to ensure its being thoroughly treated it has to be rabbled or turned over and over1 since otherwise all of it might not be brought into contact with the necessary oxygen4 ,at one time done by men with rakes1 it is now generally accomplished by mechanical means4 ,a description of one such furnace will be of interest4 ,it consists of a long rectangular building of brickwork bound together with steel framework4 ,inside it is divided up into low chambers1 the roof of each forming the floor of the one above4 ,at intervals along its length mighty shafts of iron pass up from underneath right through all the floors1 emerging finally above the topmost1 while along underneath the furnace there runs a shaft the action of which turns the vertical shafts slowly round and round4 ,attached to the vertical shafts are long strong arms of iron1 one arm to each floor1 and upon the arms are placed rabbles1 as they are termed1 pieces of iron shod sometimes with fireclay1 resembling most of any familiar objects a small ploughshare4 ,as the arms slowly revolve1 at the rate of once or twice per minute1 the arms are carried round and round and the rabbles plough up and turn over and over the layer of ore lying upon the floor4 ,there are arms on the top of the furnace1 too1 sometimes1 where the ore is first laid so that it may be dried by the heat escaping from the furnace beneath1 an interesting example of economy effected by utilizing heat which would otherwise be wasted4 ,the whole of the furnace1 from end to end and on every floor1 is thus swept continually by the rotating arms with their dependent rabbles1 and the latter are cunningly shaped so that they not only turn the ore over and over1 but gradually pass it along the different floors or hearths4 ,it is fed automatically by a mechanical feeder which pushes it on1 a small quantity at a time1 to the drying hearth on the top4 ,then the rabbles take charge of it and gradually pass it from the area swept by one shaft to that of the next until it has passed right along the top and has become thoroughly dried4 ,arrived there it falls through a hole on to the topmost hearth or floor1 along which it travels by the same means but in the contrary direction until it again falls through a hole on to the top floor but one4 ,and so it goes on until at last1 fully roasted1 it falls from the bottom floor of the furnace into trucks or other provision for carrying it away4 ,some kinds of ore require to be heated by means of gas which is generated in a gas-producer near by4 ,in others1 however1 the sulphur in the ore acts as the fuel1 and so the furnace1 having been once started1 can be kept up for long periods without the expenditure of any coal at all4 ,very little attention is needed by furnaces such as these1 so that with no fuel to pay for and very little labour1 they are extremely economical4 ,owing to the great heat1 too1 the arms would stand a very good chance of getting melted were they not kept cool by a continual stream of water flowing through the shafts and arms4 ,this furnishes a continual supply of hot water which is sometimes used for other purposes in the works4 ,the process of roasting1 whether carried on in furnaces such as these or not1 results in the formation of oxide instead of sulphide2 in other words1 the sulphur is turned out and oxygen takes its place4 ,the dislodged sulphur then joins up with some more oxygen and forms sulphur dioxide1 which can be led away to the sulphuric acid plant and there1 by union with water1 turned into that extremely valuable substance1 sulphuric acid4 ,we cannot1 however1 treat zinc oxide as we would iron oxide or copper oxide1 for zinc is volatile1 and so1 instead of accumulating in the bottom of a blast furnace as the iron and copper do1 would pass off up the chimney4 ,the oxide is therefore mixed with coal or some other form of carbon and placed in retorts made of fireclay4 ,these retorts are fixed in rows one above the other like the retorts at a gasworks1 and hot gases from a gas-producer down below pass around and among them4 ,to the mouth of each retort is fitted a condenser1 also made of fireclay4 ,now what happens in the retorts is this3 the heat loosens the bonds between the zinc and the oxide1 the latter passing into union with some carbon from the coal4 ,the zinc at the same time becomes vapour and passes into the condenser1 the lower temperature of which turns it into a liquid which the workmen remove at intervals in ladles4 ,on being poured into moulds and allowed to solidify this metal is called by the name of spelter1 which bears to zinc the same relation that pig-iron does to the more highly developed forms of iron4 ,spelter is simply zinc in its crudest form4 ,tin1 although less important in war than copper and zinc1 plays a not unimportant part4 ,it has been found for centuries in ,cornwall4 ,the ,romans used to trade with the natives of ,britain for tin4 ,although considerable quantities of it is still obtained from there1 the greatest tin-producing country of all at present is the ,federated ,malay ,states4 ,australia also furnishes ore1 as does ,bolivia and ,nigeria4 ,in ,cornwall the ore occurs as rock in veins or lodes filling up what must once have been fissures in granite rocks4 ,that near the surface has long been taken1 so that to-day the mines are very deep and costly to work4 ,some can only afford to operate when the market price of tin is above a certain limit4 ,much of the ore from the newer districts--the ,malay ,states1 for example--is in small fragments mixed with gravel in beds near the surface4 ,such is called alluvial or stream tin1 since the deposits were undoubtedly put in their present position by streams or rivers4 ,so long as they last these easily accessible alluvial deposits will always be cheaper to work than the deep mines4 ,on the other hand1 they may give out1 and recent explorations underground seem to indicate that there is still much valuable ore not only of tin but of other metals too1 to be obtained from the old mines of ,cornwall4 ,the ore of tin1 like so many other ores1 is generally oxide4 ,it is first roasted to expel sulphur and arsenic which are often present as impurities1 and then it is melted in a reverberatory furnace such as that described for the manufacture of wrought iron4 ,as usual1 the oxygen combines with carbon1 the impurities form slag which floats on the top1 and the pure metal falls to the bottom of the furnace from whence it can be drawn off4 ,mixed with or in the neighbourhood of tin ore there is sometimes found another mineral called wolfram1 which plays an extremely important part in modern warfare1 so much so that the ,british and other ,governments engaged in the war were at times hard put to it to find enough4 ,its value resides in the fact that it contains tungsten1 an element which has wonderful powers in hardening steel4 ,it consists of tungsten and oxygen1 but is not an oxide since there is also iron in the partnership4 ,this fact is very useful1 however1 since it enables the particles of wolfram to be picked out from the mass of other stuff among which they are found by a magnet4 ,there are some very wonderful machines called magnetic separators1 made for this express purpose4 ,in one1 with which ,i am familiar1 there is an endless band stretched horizontally upon two rollers4 ,one of the rollers being driven round the belt travels along so that the mineral being fed on to it in a stream is carried along under several magnets4 ,these magnets are very different from the ordinary magnet1 inasmuch as they are revolving4 ,we might almost describe them as small magnetized flywheels4 ,as they spin round they pick up slightly the particles of ore which contain iron1 but have no effect at all upon those which do not contain iron4 ,they do not actually lift the particles up on to themselves3 they just exercise a slight pull upon them1 and by virtue of the fact that they are revolving1 pull them off the band and throw them to one side4 ,the wheels can be set closer or farther from the belt at will so as to make them act more or less strongly1 and thus the most magnetic particles can be separated from those less magnetic1 these latter being still kept separate from the wholly non-magnetic particles4 ,thus by simple and purely mechanical means are the precious bits of wolfram obtained from the other less valuable or worthless minerals with which they are mixed4 ,the same method is used with other minerals besides wolfram3 it can be applied to all those which exhibit in some small degree the magnetic properties which we usually associate with iron4 ,this sorting out of one mineral from others continually crops up in connection with nearly all the metals except iron4 ,iron is practically the only one whose ore occurs in vast masses which need simply to be dug up and thrown into the furnace4 ,the others1 where they occur as rock in veins1 have to be crushed to detach what is wanted from what is not wanted1 and then the two have to be sorted in some way4 ,magnetic separation is but one of these ways4 ,another takes advantage of the fact that we seldom find two things together which have precisely the same specific gravity4 ,consequently1 if we throw the mixture on to a shaking table the heavier particles will behave differently from the lighter ones and the two will separate4 ,the same result can be obtained by throwing the mixture into a stream of water1 the water acting differently upon the lighter and upon the heavier particles4 ,another way which may be mentioned is founded upon the fact that some things can be readily wetted with oil while others throw the oil off and refuse to be wetted by it4 ,if a mixture of these two sorts of thing be stirred violently in a suitable oily liquid the former will be found eventually in the froth1 while the latter will sink to the bottom4 ,all these different methods are employed1 as they are found necessary in preparing the ores of the various metals to which we have been referring4 ,except in the case of alluvial ores which have been broken already by the action of ancient streams of water1 nearly all ores 7except iron7 have to be crushed before the ores can be separated out4 ,some of this work is done by the very simplest contrivances1 showing how in some cases invention has almost come to a stop through the machines having been reduced to their simplest form4 ,a notable instance of this is the stamp mill1 in which heavy timbers are lifted up by machinery and then allowed to slide down upon the ore1 just like gigantic pestles4 ,more elaborate grinding machines are sometimes used1 however1 but it is impossible to mention them all here4 ,the action of sorting out the fragments of ore from the miscellaneous assortment of crushed rocks is termed concentrating1 and the sorted ores are called concentrates4 ,another metal which has proved itself of immense importance in war is aluminium1 and it fittingly comes at the close of the list since it is dealt with in a manner peculiar to itself4 ,practically all the others are obtained from their ores by means of heat and heat alone4 ,aluminium is obtained by electricity acting in the process called electrolysis4 ,it is surprising to learn that aluminium is one of the very commonest things on the face of the earth4 ,clay and many common rocks are very largely made of it4 ,clay1 to be precise1 is a silicate of alumina1 a term which is interesting when it is explained4 ,silica is the name given to oxide of silicon4 ,sand is mostly silica4 ,alumina1 too1 is oxide of aluminium4 ,silicate of alumina is a combination of the two4 ,any clay1 therefore1 could be used as an ore from which to obtain aluminium1 but of course there are certain minerals specially suitable for the purpose1 since in them the metal is plentiful and easily extracted4 ,in another chapter reference is made to the production of caustic soda from a solution of common salt by electrolysis4 ,the same principle1 precisely1 is used to obtain the metal aluminium from its ore1 which is generally an oxide4 ,common salt1 let me remind you1 is sodium and chlorine combined4 ,when you dissolve it in water it becomes ionized1 which means that each molecule of salt splits up into two ions one of which is electrically positive and the other electrically negative4 ,then1 when we introduce two electrodes into the solution and connect them to a battery or dynamo1 all the positive ions go to one electrode and all the negative ions to the other4 ,we cannot dissolve aluminium ore in water1 but we can in a bath of molten cryolite1 and for some reason or other1 whether because of the heat or not we cannot say1 the ore becomes ionized1 the aluminium atoms being one sort and the oxygen atoms the other sort4 ,these ions then sort themselves out1 the oxygen ions being taken into combination with the carbon rod which forms the positive electrode1 while the metal ions collect upon the negative electrode4 ,since this latter is a slab of carbon which forms the bottom of the vessel in which the process is carried on1 the result is that pure aluminium gradually accumulates in the bottom of the vessel and can be drawn off from time to time4 ,aluminium is always produced in places where electric power can be obtained cheaply1 such as near waterfalls4 ,,chapter ,,xii ,,measuring ,,the ,,velocity ,,of ,a ,,shell ,in at least two of the preceding chapters of this book reference has been made to the speed at which a shell fired from a gun travels through the air4 ,such velocities as #c1jjj feet per second have been mentioned in this connection1 and some readers are sure to have wondered how such measurements could possibly be made4 ,possibly some sceptics have even supposed that they were not measured at all but simply estimated in some way or other4 ,they are actually measured1 however1 and by very simple and ingenious means4 ,needless to say1 electricity plays a very important part in this wonderful achievement4 ,in fact1 without the aid of electricity it is difficult to see how it could be done at all4 ,people often ask how quickly electricity travels1 as if when we sent a telegraph signal along a wire a little bullet1 so to speak1 of electricity were shot along the wire like the carriers of the pneumatic tubes in the big drapers' shops4 ,that is quite a misconception1 for in reality the circuit of wire is more like a pipe full of electricity1 and when we set a current flowing what we do is to set the whole of that electricity moving at once4 ,if we think of a circular tube full of water with a pump at one spot in the circuit1 we see that as soon as the water begins to move anywhere it moves everywhere4 ,moreover1 if it stops at one point it stops simultaneously at every other point4 ,while practically this is the case it is theoretically not quite so1 for the inertia of the water when it is suddenly started or stopped no doubt causes a slight distortion of the tube itself resulting in a very slight 7quite imperceptible7 retardation of the movement of the water4 ,electricity also has a property comparable to the inertia which we are familiar with in the objects around us1 and there is also a property in every conductor which to a certain extent resembles the elasticity of the water-pipe1 whereby it may for a moment be bulged out4 ,in a short wire1 however 7up to a mile or so71 particularly if the flow and return parts of the circuit be twisted together1 this electrical inertia practically vanishes and consequently we may say that for all practical purposes the current starts or stops1 as the case may be1 at precisely the same moment in every part of the circuit4 ,that fact is of great value when1 as in the case we are now discussing1 we want to compare very exactly two events occurring very near together as to time but far apart as to place4 ,illustration3 ,,bomb-,,throwers ,,at ,,work4 ,many kinds of bombs are used4 ,one has a metal head and a handle about a foot long1 with a streamer to ensure correct flight2 another form resembles a brush when it is flying through the air2 and a third1 known as the egg1 is oval in form4 ,we need to compare the time when the shell leaves the gun with the time when it passes another point1 say1 one hundred yards away1 and then again another point1 say one hundred yards further on still4 ,supposing1 then1 a velocity of #c1jjj feet per second1 the time interval between the first point and the second and between the second and third will be somewhere about a tenth of a second4 ,so we shall need a timepiece of some sort which will not only measure a tenth of a second1 but will measure for us a very small difference between two periods1 each of which is only about a tenth of a second and which will be very nearly alike4 ,that represents a degree of accuracy exceeding even what the astronomers1 those princes of measurers1 are accustomed to4 ,this exceedingly delicate timepiece is found in a falling weight4 ,so long as the thing is so heavy that the air resistance is negligible1 we can calculate with the greatest nicety how long a weight has taken to fall through a given distance4 ,near the muzzle of the gun there is set up a frame upon which are stretched a number of wires so close together that a shell cannot get past without breaking at least one of them4 ,these wires are connected together so as to form one1 and through them there flows a current of electricity the action of which1 through an electro-magnet in the instrument house1 holds up a long lead weight4 ,at some distance away1 say one hundred yards1 there is a similar frame also electrically connected to an electro-magnet in the same instrument house4 ,this second magnet1 when energized by current from the frame1 holds back a sharp point which1 under the action of a spring1 tends to press forward and scratch the lead weight4 ,the third frame is likewise connected to a third magnet controlling a point similar to the other4 ,to commence with1 current flows through all three frames so that all three magnets are energized4 ,the gun is then fired and immediately the shell breaks a wire in the first frame1 cutting off the current from the first magnet and allowing the weight to fall4 ,meanwhile1 the shell reaches the second frame1 breaking a wire there1 with the result that the second magnet loses its power1 lets go the point which it has been holding back and permits it to make a light scratch upon the falling weight4 ,this action is followed almost immediately by a similar action on the part of the third magnet1 resulting in a second scratch on the lead weight4 ,the position of these two scratches on the weight and their distance apart gives a very accurate indication of the time taken by the shell to pass from the first screen to the second and from the second to the third4 ,from those times it is possible to calculate the initial velocity of the shell and the speed at which it will move in any part of its course4 ,indeed1 with those two times as data1 it is possible to work out all that it is necessary to know about the behaviour of the shell4 ,this is rendered practicable by the fact that the moment the wire is cut the magnet lets go1 no matter what the distance of the screen from the instrument may be4 ,but for the instantaneous action of the current1 allowance of some sort would have to be made for the fact that one screen is farther than another and the whole problem would be made much more complicated4 ,even as it is1 someone may urge that the magnets themselves possess inertia and will not let go quite instantaneously1 but that can be overcome by making the magnets all alike so that the inertia will affect all equally4 ,it is only necessary to have a switch which will break all the three circuits at the same moment 7quite an easy thing to arrange7 and then adjust all three magnets so that when this is operated they act simultaneously4 ,after that they can be relied upon to do their duty quite accurately4 ,thus by a method which in its details is quite simple is this seemingly impossible measurement taken4 ,,chapter ,,xiii ,,some ,,adjuncts ,,in ,,the ,,engine ,,room ,before we deal with the subject of the engines employed in warfare1 it may be interesting to mention two beautiful little inventions which have been made in connection with them4 ,let us take first of all a contrivance which tells almost at a glance the amount of work which the engines of a ship are doing4 ,as everyone knows1 there is in every ship 7except those few which are propelled by paddles7 a long steel shaft1 called the tail-shaft1 which runs from the engine situated somewhere near amidships to the propeller at the stern4 ,many ships1 of course1 have several propellers1 and then there are several shafts4 ,now each of these shafts is a thick strong steel rod supported at intervals in bearings4 ,if anyone were told that1 in working1 that shaft became more or less twisted1 he would be tempted to think he was being made fun of4 ,yet such is literally the case4 ,the thick strong massive bar becomes actually twisted by the turning action of the engine at one end and the resistance of the propeller at the other4 ,and the amount of that twisting is a measure of the work which the engine is doing4 ,the puzzle is how to measure it while the engine is running1 for of course the twist comes out of it as soon as the engine stops4 ,a space on the shaft is selected1 between two bearings1 for the fixing of the apparatus4 ,near to each bearing there is fitted on to the shaft a metal disc with a small hole in it4 ,on one of the bearings is fixed a lamp and on the other a telescope4 ,when the engine is at rest and there is no twist in the shaft1 all these four things--the lamp1 the two holes1 and the telescope--are in line4 ,consequently1 on looking through the telescope the light is visible4 ,but when the engine is at work and the shaft is more or less twisted one of the holes gets out of line and it becomes impossible to see the light through the telescope4 ,a slight adjustment of the telescope1 however1 brings all four into line again1 which adjustment can be easily made by a screw motion provided for the purpose4 ,and the amount of adjustment that is found necessary forms a measure of the amount of the twisting which the shaft suffers and that again tells the number of horse-power which the engine is putting into its work4 ,but it is also necessary to know how fast the engine is working4 ,there are many devices which will tell this1 of which the speedometer on a motor-car is a familiar example4 ,most of those work on the centrifugal principle1 the instrument actually measuring not the speed but the centrifugal force resulting from the speed1 which amounts to the same thing4 ,there is one instrument1 however1 which operates on quite a different principle1 because of which it is specially interesting4 ,it consists of a nice-looking wooden box with a glass front4 ,through the glass one sees a row of little white knobs4 ,if this be placed somewhere near the engine while it is at work immediately one of the knobs commences to move rapidly up and down1 so that it looks no longer like a knob but is elongated into a white band4 ,there is no visible connection between the instrument and the engine1 yet the number over that particular knob which becomes thus agitated indicates the speed of the engine4 ,let us in imagination open the case and we shall find that the knobs are attached to the ends of a number of light steel springs set in a row4 ,the springs are all precisely alike except for their length1 in which respect no two are alike4 ,indeed1 as you proceed from one side of the instrument to the other each succeeding one is a little longer than the previous one4 ,now a spring has a certain speed at which it naturally vibrates and other things being equal that speed depends upon its length4 ,you can1 of course1 force any spring to vibrate at any speed if you care to take the trouble1 but each one has its own natural speed at which it will vibrate under very slight provocation4 ,every engine is1 of course1 made to run as smoothly as possible4 ,all revolving or reciprocating parts are for this reason carefully balanced and in turbines the whole moving part1 since it is round and symmetrical1 naturally approaches a condition of perfect balance4 ,hence every engine ought to run perfectly smoothly4 ,as a matter of fact1 however1 no engine ever does4 ,there are certain limitations to man's skill and at the high speed of a fast-running engine1 such as is to be found on a destroyer1 for example1 some little irregularity is sure to make itself felt by a slight vibration in the floor4 ,it may be hardly perceptible to the senses1 but to a spring whose natural frequency happens to be just that same speed or nearly so1 it will be very apparent and in a few seconds that spring will be responding quite vigorously4 ,it is another example of the principle of resonance1 which is employed so finely in making wireless telegraph apparatus selective4 ,every wireless apparatus is made to have a certain natural frequency of its own and it therefore picks up readily those signals which proceed from another station having the same frequency while ignoring those from others4 ,in just the same way a reed or spring in this speed-indicator picks up and responds to impulses derived from the engine only when they are of a frequency corresponding with its own natural frequency4 ,hence1 one spring out of the whole range responds to the vibrations of the engine while the others remain almost if not entirely unaffected4 ,in another form1 the springs are actuated electrically4 ,a magnet1 or a series of magnets1 is arranged so that as the engine turns the magnets pass successively near to a coil of wire1 thereby inducing currents in that wire4 ,they form1 in fact1 a small dynamo or generator1 generating one impulse per revolution or two or three or whatever number may be most convenient4 ,then the current from this is led round the coil of a long electro-magnet placed just under the free ends of all the springs4 ,the magnet therefore gives a series of pulls1 at regular intervals1 and the rapidity of those pulls will depend upon the speed of the engine1 while the frequency of them will be registered by the movement of one or other of the springs4 ,this instrument can also be employed to determine the speed of aeroplane motors and1 in fact1 any kind of engine1 especially those whose speed is very high4 ,,chapter ,,xiv ,,engines ,,of ,,war ,the phrase which ,i have used for the title of this chapter is often given a very wide meaning which includes all kinds and varieties of devices used in warfare4 ,in this case ,i am giving it its narrower sense1 taking it to indicate the steam-engines and oil-engines which are employed to drive our battleships1 cruisers and destroyers1 our submarines and our aircraft4 ,they are inventions of the highest importance1 which have played a large part in shaping modern warfare4 ,the type of engine almost invariably used on ships of war other than submarines is the steam turbine4 ,great ,britain1 for the most part1 uses that particular kind associated with the name of the ,hon4 ,sir ,c4 ,a4 ,parsons1 while the ,united ,states rather favour the ,curtiss machine4 ,other nations have adopted either one of these or else something very similar4 ,all turbines are very simple in their principle1 far more so that the older type of steam-engine1 called1 because the essential parts of it move to and fro1 the reciprocating steam-engine4 ,in these latter machines there are a number of cylinders with closed ends and with very smooth interiors1 in each of which slides a disc-like object called a piston4 ,the steam enters a cylinder first at one end and then at the other1 thus pushing the piston to and fro4 ,the movement of the piston is communicated to the outside by means of a rod which passes through a hole in the cover at one end of the cylinder1 the to and fro motion being converted into a round and round motion by a connecting-rod and crank just as the up and down motion of a cyclist's knees is converted into a round and round motion by the lower leg and the crank4 ,the lower part of a cyclist's leg is1 indeed1 a very accurate illustration of what the connecting-rod of a steam-engine is4 ,as is evident to the hastiest observer1 some arrangement has to be made whereby the steam shall be led first into one end and then into the other end of the cylinder3 also that provision shall be made for letting the steam out again when it has done its work4 ,moreover1 such arrangements must be automatic4 ,hence1 every reciprocating engine has special valves for this purpose and such valves need rods and cranks 7or something equivalent7 to operate them4 ,further1 to get the best results the steam must not simply be passed through one cylinder but through several in succession4 ,engines where the steam goes through only one cylinder are called simple1 where it goes through two they are compound1 where three triple-expansion1 where four quadruple-expansion4 ,generally speaking1 each cylinder has its own connecting-rod and crank1 also its own set of rods1 etc41 for working its valves4 ,hence1 a high-class marine reciprocating engine is of necessity a complicated mass of cylinders1 rods1 cranks and other moving parts continually swinging round or to and fro at considerable speeds1 all needing oiling and attention and all liable at times to give trouble4 ,and now compare that with the turbine1 which has ,,two parts1 only one of which moves4 ,that part1 moreover1 is tightly shut up inside the other one1 being thereby protected from any chance of damage from outside and likewise rendered unable to inflict any damage upon those in attendance upon it4 ,at first sight it seems very strange that the turbine should be the newer of the two1 for it is simply an improved form of the old time-honoured picturesque windmill which used to top every hill and grind the corn for every village and hamlet4 ,the old windmill had four sails against which the wind blew1 driving the whole four round as everyone knows4 ,the new turbine has a great many sails1 only we now call them blades1 and the steam blows them round4 ,the old windmill had to have another smaller set of sails at the back for the purpose of keeping the main sails always in that position in which they would catch the full force of the breeze4 ,in the turbine we need not do that1 for we shut the windmill up in a kind of tunnel and cause the steam to blow in at one end and out at the other4 ,the difference between the various kinds of turbine lies simply in the manner in which the steam is guided in its passage through the machine4 ,after that general description we can take a more detailed view of the ,parsons turbine4 ,the casing or fixed part is a huge iron box suitably shaped for standing firmly and rigidly upon the floor of the engine-room4 ,it is made in two halves1 the upper of which can be easily lifted off when necessary4 ,often1 indeed1 this upper half is hinged to the lower1 so that it can be opened like the lid of a box4 ,inside1 the casing is cylindrical1 comparatively small at one end but increasing by steps till it is very much larger at the other end4 ,at each end is a bearing or support in which the rotor or moving part is held and in which it can turn freely4 ,the rotor or part which rotates is a strong steel forging shaped somewhat to follow the lines of the inside of the casing4 ,it does not entirely fill the casing but leaves a space all round and all the way along1 which space is intended to accommodate the blades4 ,the ends of the rotor are smaller than the body since they are intended to fit into the bearings1 and one of the ends is prolonged so as to be available for coupling to the propeller-shaft of the ship4 ,at one end of the casing1 the smaller one1 is the steam inlet and the steam after emerging from it passes along till it finds its way out at a very large outlet formed at the bigger end4 ,on its way it has to pass thousands of small blades so that the progress of each individual particle of steam is not a straight line but a continual zigzag4 ,there are rings of blades round the rotor1 tightly fixed to its surface4 ,there are likewise rings of blades affixed to the inner surface of the casing1 the rings upon the casing coming in the spaces between the rings on the rotor4 ,let us imagine that we can see through the casing of a turbine at work and that looking down upon it from above we can trace the progress of a particle of steam4 ,it rushes in from the inlet and at once makes straight for the outlet at the further end4 ,suddenly1 however1 it encounters one of the guide blades 7those on the case7 and by it is deflected to one side1 we will suppose the left4 ,that causes it to rush straight at one of the blades upon the rotor against which it strikes violently1 giving that blade a distinct and definite push to the left4 ,rebounding1 it then comes back towards the right but quickly is caught by another guide blade and by it hurled back upon a second rotor blade1 giving it a leftward push just as it did to the first4 ,thus it goes zigzagging from one set of blades to the other until1 tired out1 so to speak1 it finally flows away forceless and feeble through the outlet1 having given up all its energy to the blades of the rotor against which it has struck in its course4 ,that1 then1 is the journey of one single particle4 ,multiply that by an unknown number of millions and you have a description of what takes place in the interior of a steam turbine4 ,the blades are so proportioned1 so arranged and so placed that it is very difficult indeed for a particle of steam to creep past without doing its share of work4 ,practically every one is made use of and while1 of course1 the action of a single particle of steam would have but a negligible effect1 the vast number engaged cause the rotor to be powerfully blown round4 ,the reason why the casing and rotor are made larger and larger as one proceeds from the inlet towards the exhaust or outlet is that the steam must1 if all its energy is to be extracted1 expand as it goes and the enlargement provides room for this expansion4 ,one of the great advantages of the turbine is that the steam is always entering at the same end4 ,in the cylinder of a reciprocating engine the steam enters alternately4 ,it comes in hot but as it does its work and finally goes out it becomes very much cooler3 the next lot of steam which enters1 therefore1 is chilled by the cool walls of the cylinder which have just been cooled by the departure of the previous lot of steam3 so heat is wasted4 ,wasted heat means fuel lost1 and as any given ship can only carry a limited quantity of fuel1 wasted heat means less range and more frequent returns to the base to coal or to oil4 ,also let me remark again upon the simplicity of the turbine as opposed to the other sort4 ,the latter consists of a mass of moving and swaying rods and cranks1 to work among which1 as the engineers have to do1 is a terrifying and nerve-racking experience4 ,the turbine1 on the other hand1 has its only working part enclosed4 ,it is difficult to tell1 by looking at it1 whether a turbine is at work or not1 so silent and still is it1 so self-contained4 ,the reciprocating engine-room is noisy and full of turmoil3 the turbine room is weirdly still by comparison4 ,on the whole1 too1 it makes better use of the steam which it uses1 but it has one decided drawback4 ,it will not reverse1 which the other type of engine does readily4 ,this means that two turbines have to be coupled together1 one with the blades so set that the steam drives it round correctly to produce motion ahead and the other set the opposite way so that it drives the vessel astern4 ,the steam can be sent through either turbine at will and so motion can be obtained in either direction4 ,whichever turbine is in use the other revolves idly4 ,unfortunately it is impossible to make a turbine to go slowly and yet be efficient4 ,consequently1 slow steamers cannot use turbines1 but for warships1 which are nearly all fast boats1 it has almost displaced the older type of engine4 ,the ,curtiss turbine is different from the ,parsons in that the steam encounters periodically1 in its passage through1 a partition perforated with funnel-shaped holes4 ,between the partitions it passes blades upon which it acts just as already described4 ,the chief effect of this is to permit the machine being made of a rather more convenient shape and size4 ,other varieties of turbine are more or less combinations of the two ideas underlying these two4 ,when we look at a locomotive in motion we always see steam coming out of the funnel1 but we never see that in the case of a steamer4 ,that is because all the energy of the steam is taken and used in the latter case1 while in the former much valuable energy goes off up the funnel1 making a puffing noise instead of doing useful work4 ,on the steamship the steam is led not to the open air but to a vessel called a condenser the walls of which are kept cool by a continual circulation of cold water4 ,the steam on entering the condenser at once collapses into water1 leaving a vacuum4 ,a pump called the air-pump removes the water 7which was once steam7 from the condenser and also any air which might get in1 with the result that the engine is always discharging its steam into a vacuum4 ,thus to the pressure of the steam is added the suction of the vacuum4 ,in turbine ships the cooling water for the condensers is circulated by powerful centrifugal pumps driven by subsidiary engines4 ,the steam is obtained from boilers of that special variety known as water-tube4 ,the boilers with which most people are familiar are either ,lancashire or ,cornish1 both sorts being large steel cylinders with two steel flues in the former and one in the latter running from back to front4 ,the fire is made in the front part of the flue and the hot gases from it pass to the back and then along the sides and underneath through flues formed in the brickwork in which the boiler is set4 ,locomotive boilers1 however1 have no flues1 but the hot gases from the fire in the fire-box pass through tubes which run from end to end through the cylindrical shell1 each tube starting from the fire-box behind and terminating in the smoke-box in front4 ,thus we have tubes with fire inside and water outside3 hence such boilers are called fire-tube boilers4 ,on many ships of the merchant type cylindrical boilers are used which combine the features1 to some extent1 of the ,cornish and the fire-tube1 since there is a flue running from front to back in which the fire is made and the hot gases return from back to front through a number of tubes which occupy the space above the fire4 ,arrived at the front the gases pass upwards to the chimney4 ,water-tube boilers are different from all of these1 since in them the water is inside the tubes while the fires play around the outside4 ,this enables steam to be got up very quickly1 a matter of much importance for a warship which may be called upon to undertake some operation at a moment's notice4 ,the boilers are fed with water from the condensers1 so that the same water is used over and over again4 ,when coal is burnt it is put on the fires by hand1 for although mechanical stoking is a great success on land1 there are special difficulties which prevent its use at sea4 ,it is becoming more and more the fashion now to burn oil instead of coal in several types of ships and in those cases the oil is blown in the form of spray into the furnace4 ,this has many advantages1 some of which are exemplified on a small scale by the difference between using a coal fire and a gas stove4 ,like the latter1 the oil spray can be quickly lit when needed and as quickly extinguished4 ,it can be regulated and adjusted with equal facility4 ,oil can be taken on board too through a pipe1 silently and quickly and without the terrible dirt and the exhausting labour involved in coaling a big ship4 ,oil1 too1 can be taken on board at sea1 from a tank steamer1 almost as easily as it can be taken in ashore1 whereas the difficulty of coaling at sea despite many ingenious efforts has never been solved quite satisfactorily4 ,finally1 oil can be stowed anywhere1 for the stokers do not need to dig it out with a shovel4 ,therefore it can be carried in those spaces between the inner and outer bottoms which have to be there in order to give strength to the ship's hull but which would be quite useless for carrying coal4 ,the advantages of oil fuel1 therefore1 are many and no doubt it will be used more and more as time goes on4 ,for ,great ,britain1 oil fuel has the disadvantage that it has to be imported whereas the finest steam coal in the world is found in abundance in ,south ,wales1 but the difficulty may eventually be overcome by distilling from native coal an oil which will serve as well as that which is now imported4 ,so much for the turbine1 the engine of the big ships3 now for the ,diesel oil-engine which drives the submarines4 ,it belongs to that family of engines called internal-combustion since in them the fuel is burnt actually inside the cylinder and not under a separate contrivance such as a boiler4 ,there have been oil-engines1 so called1 for many years1 but they were really gas-engines since the oil was first heated till it turned into vapour and then that vapour was used as a gas4 ,the ,diesel engine1 however1 actually burns oil in its liquid state4 ,to understand how it works let me ask you to conjure up this little picture before your mind's eye4 ,a hollow iron cylinder is fixed in a vertical position3 its upper end is closed but its lower end is open3 inside it is a piston1 free to slide up and down3 by means of a connecting-rod hinged to it and passing downwards through the open lower end the piston is connected to a crank and flywheel4 ,at the upper end of the cylinder are certain openings which can be covered and uncovered in succession by the action of suitable valves4 ,now let us assume that that engine is at work1 the piston going rapidly up and down in the cylinder4 ,as it goes down it draws in a quantity of air through a valve which opens to admit the air at just the right moment4 ,the moment the piston reverses its movement and starts to go up again that valve closes and the air is entrapped4 ,the piston continues to rise1 however1 with the result that the air becomes compressed in the upper part of the cylinder4 ,now it is necessary to remind you at this point that compressing air or indeed any gas1 raises its temperature4 ,this air1 therefore1 which was drawn in at the temperature of the outer atmosphere1 by the time the piston has reached the top of its stroke has attained a temperature well above the ignition point of the oil fuel4 ,the piston1 having arrived at the top of its stroke1 the upper part of the cylinder is filled with hot compressed air3 the next moment the piston commences its descent1 but at precisely that same moment a valve opens and there is projected into the cylinder a spray of oil4 ,instantly it bursts into flame1 heating the air still more1 so that as the piston descends the air1 expanding with the heat1 pushes strongly and steadily upon it4 ,the amount of that push can be varied by varying the duration of the jet4 ,the longer the jet is injected the more heat is generated and the more sustained is the push4 ,on the other hand1 if the jet is cut off very quickly the push is only a gentle one4 ,the power of the engine can thus be adjusted to suit varying circumstances by a slight variation in the valve which controls the jet4 ,the piston having thus been driven down to the limit of its stroke1 it commences another upward movement1 at which moment another valve opens and lets out the hot waste gases which have resulted from the burning of the oil4 ,thus the cylinder is cleaned out ready for a fresh supply of pure air to be drawn in on the next ensuing downstroke4 ,the engine thus works upon a series or cycle of operations which are repeated automatically over and over again4 ,first comes a downstroke1 drawing in air3 then an upstroke1 compressing it3 then a second downstroke1 during which the fuel burns and the power is generated3 and1 finally1 a second upstroke during which the waste products of the burning are ejected4 ,power1 it will be noticed1 is only developed in one out of the four strokes3 the other movements having1 in single cylinder engines1 to be performed by the momentum of the flywheel4 ,in most cases1 however1 the engine has several cylinders in which the cycles are arranged to follow in succession4 ,thus1 if there are four cylinders1 there is always power being developed by one of them4 ,the valves are operated automatically by the engine itself just as is the case with steam-engines4 ,the engine also works a small pump which provides the very highly compressed air necessary to blow the oil jet into the cylinder4 ,arrangements are often provided whereby the engine when working stores up a reserve of compressed air which can be used to start it4 ,from the very nature of its working such an engine cannot develop power until it has accomplished at least four strokes or two revolutions1 so that it cannot possibly start itself4 ,if1 however1 compressed air be admitted to the cylinders to give it a vigorous push or two and so get it going1 it can then take up its own work and go on indefinitely4 ,in some cases this is not necessary and that of an engine in a submarine is one of them4 ,in that instance1 the electric motor1 which drives the boat when submerged1 can be made to give the engine a start4 ,by altering the rotation in which the valves act the direction can be reversed4 ,a very simple mechanism can be made to effect this change1 so that reversing is quite easy4 ,aircraft are mostly1 if not entirely1 driven by petrol engines1 some of which are very little different from those of a motor-car or motor-cycle4 ,these motor-car engines are so well known that little need be said about them4 ,it may be well to explain1 however1 that they1 like the ,diesel engines1 work on a cycle of four strokes1 as follows3-- ,first stroke 7down7 draws in a mixture of air and gas4 ,second stroke 7up7 compresses the mixture4 ,just at the top of this stroke an electric spark fires the mixture1 causing an explosion which drives the piston downwards1 thus making the ,third stroke 7down71 during which the power is developed4 ,fourth stroke 7up7 expels the waste products of the explosion4 ,although all of them work on this same cycle1 in which they resemble the engines of the motor-car1 there are several much-used types of aero-engine in which the mechanical arrangement of the parts is quite different4 ,of these the best known is the famous ,gnome engine which has a considerable number of cylinders arranged around a centre like the spokes of a wheel4 ,the centre is in fact a case which covers the crank1 and the cylinders are placed in relation to it just as the spokes are placed around the hub of a wheel4 ,there is only one crank and all the connecting-rods drive on to it4 ,owing to their position around it they thus act in succession1 giving a nice regular turning effort4 ,further1 these engines differ from all others in that the crank is a fixture while the rest of the engine goes round1 exactly the opposite of what we are accustomed to4 ,the engine1 in fact1 constitutes its own flywheel4 ,rushing thus through the air1 the cylinders tend to keep themselves cool1 doing away with the need for cooling water and radiators4 ,consequently engines of this type are the very lightest known in proportion to their horse-power4 ,a fifty horse-power engine can be easily carried by one man4 ,it would be possible to go on much longer with this most interesting subject of engines1 but having treated the three types which are most used in warfare1 it is now time to pass on to something else4 ,,chapter ,,xv ,,destroyers ,except for the submarine the most prominent craft during the war has undoubtedly been the destroyer4 ,all warships are in one sense destroyers1 since it is their prime duty to destroy other ships1 so why should one particular kind of boat be given this name specially8 ,like many other of the terms which we use it is an abbreviation1 a mere remnant of a fully descriptive title4 ,torpedo ,boat ,destroyer is what these ships are called in the ,navy ,list4 ,even that full title1 however1 only tells us what their original purpose was3 it leaves us very much in the dark as to the many various functions which they perform4 ,the invention of the torpedo called for the construction of small boats whereby the new weapon could be used to best advantage1 and so we got our torpedo boats4 ,they in turn called forth another boat whose duty it was to run down and destroy them1 and in that way we get our destroyers4 ,from that bit of naval history we can almost see for ourselves what the characteristics of the destroyers must be4 ,they have to be bigger than the torpedo boats1 but as the latter were quite small the destroyers1 though larger1 are still comparatively small craft1 latterly of about one thousand tons4 ,then they have to be very fast1 in order to be able to chase the others and1 finally1 they need one or two guns1 comparatively small so as not to overburden the ship and yet large enough to dispose of anything of their own size or smaller4 ,unquestionably1 their greatest feature is their speed4 ,they are the fastest ships afloat1 rivalling even a fairly fast train4 ,some of them can exceed forty miles an hour4 ,they are very active and nimble1 too1 being able to turn in a comparatively small circle4 ,for warships1 too1 they are cheap1 so that a commander can afford to risk losing a destroyer when he would fear to risk another vessel4 ,for all purposes except the actual hard-hitting they are the most useful weapon which the commander of the fleet possesses4 ,when the main fleet puts to sea a whole cloud of these smaller craft hover round looking for submarines or for the surface torpedo boats which might try to attack the large ships under cover of darkness1 while keeping a sharp look-out1 too1 for mines or any other kind of floating danger1 and thus they screen the more valuable ships4 ,likewise do they convoy merchant ships sometimes1 especially through waters believed to be infested with submarines4 ,they also sally forth on little expeditions of their own1 knowing that they can fight any craft equally speedy and show a clean pair of heels to any heavier ships1 while by adroit use of their own torpedoes they may even bag a cruiser or two4 ,they are pre-eminently the enemy of the submarine1 for the under-water boat is necessarily less active even when it is on the surface than they are1 so that a submarine caught by a destroyer stands a very good chance of being rammed by it1 which means that the destroyer deliberately rushes at it1 using its own bow as a ram wherewith to knock a hole in it4 ,or if that be not practicable the destroyer1 while dodging the torpedo of the submarine1 may plant a single well-aimed shot into its opponent and the fight is over4 ,a cleverly-handled destroyer appears to have little difficulty in avoiding the comparatively slow torpedo1 but no ship ever built could avoid a properly aimed shell1 two facts which are clearly indicated by the very few cases in which1 during the war1 a destroyer has succumbed to a submarine4 ,the gun of the latter1 if it has one1 is no match for the guns of the destroyer4 ,naval strategy and tactics1 when one thinks about them carefully1 reveal a very close resemblance to those of the football field4 ,the destroyers are like the forwards1 quick1 light and nimble1 valuable chiefly because of their ability to run swiftly and to dodge cleverly1 while the heavy1 stolid backs represent the battleships in their ability to withstand the heavy shocks of the game4 ,any imaginative boy will be able to carry this simile farther still and a comparison of the description of the battle of ,jutland with his own knowledge of the game will reveal a surprising parallelism4 ,thus the reader will to a very large extent be able to see for himself the manifold uses to which these wonderful little ships lend themselves1 and he will see that above everything else it is their speed which counts1 which fact gives us the key to their peculiar construction4 ,to commence with1 they are made as light as possible4 ,the material used is different from that of ordinary ships1 being high-tensile steel1 a steel into which a little more carbon than usual is introduced1 resulting in about #ej per cent higher tensile strength but also involving1 alas6 rather more brittleness4 ,when made of this material the whole framework of the vessel can be made of lighter beams and the covering can be of thinner plates than would be the case if the mild steel ordinarily employed for shipbuilding were used4 ,the high-tensile steel is lighter for a given strength and therefore a ship built of it is lighter than it would otherwise have to be4 ,besides the use of this particular material every resource in the way of ingenuity and skill on the part of the designers is bent towards saving weight4 ,no unnecessary part is ever put in1 but1 on the other hand1 necessaries are skinned down to the utmost limit consistent with safety in order to produce a light ship4 ,how difficult this problem is is hardly realized until one thinks of the conditions which prevail when a ship floats in the water4 ,the upward support of the water is exerted in a fairly regular way all along the ship while the weights inside which are pressing downward are concentrated in lumps4 ,the engines1 for example1 represent a very heavy weight concentrated in one fairly confined spot4 ,thus the vessel has to have sufficient stiffness to resist the action of these opposing forces which are thus tending to break her in two4 ,that1 moreover1 occurs in the stillest water2 when the sea is rough still worse stresses are brought to bear upon the comparatively fragile hull1 for a wave may lift each end1 leaving the middle more or less unsupported1 or one may lift the middle while the ends to a certain extent are left overhanging4 ,all this1 too1 is in addition to the knocks and buffets caused by huge volumes of water being flung against the ship by cross seas in the height of a tempest4 ,in the case of ordinary ships where speed is not of such great importance1 the problem is simplified by the use of what is termed a high factor of safety1 which means that the designers calculate these forces as nearly as they can and then make the structure amply strong enough4 ,in other words1 care is taken to keep well on the safe side4 ,in a destroyer1 however1 there is no room for such a margin of safety4 ,risks have to be taken1 and it is only the high degree of skill and experience possessed by our ship designers which enable these light ships to be made with1 as experience shows1 a very considerable degree of safety4 ,they have to be continually choosing between strength on the one hand and lightness on the other and the way in which they combine the two is marvellous4 ,the weight thus saved is used for carrying engines1 boilers and fuel4 ,relatively to its size1 the destroyer is about as strong as an egg-shell1 but its engines are of extraordinary power4 ,the destroyers are generally organized and operate in little groups or flotillas of perhaps twenty or so with a small cruiser or a flotilla leader as a flagship1 on which is the officer in command of them all4 ,there is also usually a depot ship for each flotilla4 ,the flotilla leaders are what one might call super-destroyers1 about double the size of the ordinary large destroyer1 which is to say1 about two thousand tons1 and capable of very high speed4 ,the depot ships form a kind of floating headquarters for their respective flotillas4 ,they are usually old cruisers which are specially fitted up for the purpose1 and although they are of comparatively slow speed they can by wireless telegraphy keep in touch with the destroyers1 which can return to them when occasion permits or demands4 ,they carry workshops in which small repairs can be carried out1 spare ammunition and stores of all kinds and spare men for the crews4 ,in fact they can look after the smaller craft much as a mother looks after her children1 and for that reason they are sometimes called mother ships4 ,as has been said1 the destroyer was originally intended to destroy torpedo boats1 but small torpedo boats have almost gone out of existence or rather the class have so grown in size as to have become merged in the destroyers1 which1 it must be remembered1 are well armed with torpedoes which they have at times used with great effect4 ,it is not surprising1 therefore1 to find that a still newer class of ship has arisen which has been described by one authority as destroyer-destroyers4 ,officially known as light armoured cruisers1 not very much is known of their details4 ,they are1 however1 about #cejj tons1 with #aj guns1 large enough that is to dispose of any destroyer which they might encounter4 ,thus1 to review the whole class of ships of which we have been speaking1 we may say that there are the destroyers1 all the more recent of which are about #ajjj tons but diminishing as we go backward in time to about #cej or #djj2 the flotilla leaders about twice the size of the largest destroyers2 and the destroyer-destroyers nearly twice as large as the flotilla leaders3 all are characterised by high speed and by guns just large enough for the work for which they are intended4 ,all are armed1 too1 with the deadly torpedo for attack upon larger ships than themselves4 ,they are essentially night-birds1 much of their time being spent stealing about with all lights out1 in pitch darkness1 seeking for information or for a chance to put a torpedo into some chance victim4 ,these night operations are very hazardous1 but so skilful are the young officers who have charge of these boats that seldom do we hear of mishaps4 ,but although1 as has been said1 the torpedo boat has almost vanished1 its under-water comrade has recently assumed a place in the first rank of importance1 and perhaps to us the most valuable work of all done by the destroyer is that of hunting down and sinking these modern pirates4 ,,chapter ,,xvi ,,battleships ,perhaps the greatest war invention of modern times was the ,british battleship ,dreadnought4 ,of course1 there have been battleships for centuries4 ,in history we read of fleets consisting of so many ships of the line or in other words line-of-battle ships1 meaning ships which were considered capable of taking their place in line of battle1 as distinguished from frigates which correspond to the modern cruiser4 ,the line-of-battle ships were stout and strong with plenty of guns4 ,they went into the thick of the fight1 since they were capable of giving and receiving hard blows1 while the lighter frigates hovered around seeking an opening to use their higher speed to cut off stragglers or to prey upon merchant ships4 ,although so different in form and material that a sailor of the old days1 could he revisit the earth1 would not recognize them1 the battleships of to-day are the real descendants of the line-of-battle ships of those times4 ,they are stout and strong1 with the heaviest guns1 capable of giving and taking the hardest knocks1 and it is they who form the backbone of the fleet4 ,as we saw in the accounts of the battle of ,jutland1 the ,german ,fleet tackled our cruisers and lighter vessels but discreetly withdrew when the battleships came up4 ,looked at in another way1 we may say that a battleship is a floating fortress4 ,its speed is not great1 when compared with other ships1 but it is constructed to carry enormous guns4 ,it is also armoured with steel plates of great thickness and of special hardness placed upon the outside of the hull so as to cover its vital parts and protect them from the shells of the enemy4 ,its chief function1 we may say1 is to carry its guns3 to enable it to do this with safety1 it is armoured3 and to enable it to get to grips with its enemies it has engines and boilers4 ,those are the three features of greatest importance in a battleship1 its guns1 its armour and its engines4 ,all else is of minor importance4 ,it is strange to think how short a time the iron or steel ship has been with us4 ,in the ,american ,civil ,war1 for instance1 only about sixty years ago1 the battleships were made of wood4 ,it was during that war that ,ericcson thought of the idea of putting iron plates to protect the sides of a ship from the hostile shots1 and from that improvised armouring of a wooden ship has arisen the iron-clad or1 more correctly1 steel-clad monsters of to-day4 ,it is just about fifty years ago since the last iron-clad wooden battleship was launched for the ,british ,navy4 ,her name was ,repulse1 and she took the water in #ahfh4 ,with a tonnage of #faij and a horse-power of #ccej1 she had a speed of #ab knots4 ,her armouring of iron was in parts #d inches and in other parts #f inches thick1 while she carried #bj guns of sizes which to-day would seem mere toys4 ,if all her guns were discharged together she would throw a total weight of #bafj lbs4 of projectiles4 ,now1 for comparison1 let us take a modern battleship1 the ,orion1 for example4 ,the tonnage is #bb1fhj1 the horse-power #bg1jjj4 ,she is more than twice the length of the older ship and is armoured with steel #ab inches thick4 ,her #aj large guns1 each #ac inches in diameter1 if fired together 7as ,i once heard them1 like thunder1 though #aj miles away7 throw a weight of #ab1ejj lbs4 ,from this we see the wonderful growth in size1 speed and in hitting power during the comparatively short period of fifty years4 ,but there is a more striking comparison still4 ,the ,repulse's guns threw #bafj lbs4 and the ,orion's throw #ab1ejj4 ,but that takes no account of the energy with which the weight is thrown4 ,a tennis ball hit hard1 might really contain more energy and do more damage to anything it hit than a cricket ball thrown gently1 which illustrates the fact that in comparing the power of guns we need to consider something more than the mere weight of the projectiles4 ,to arrive at a real comparison we take the weight of the projectiles in tons and multiply it by the speed at which they leave the guns in feet per second4 ,and we call the answer so many foot-tons4 ,now the energy of the ,repulse thus reckoned comes to just under #cj1jjj2 that of the ,orion to just under #fij1jjj4 ,the ,orion can hit twenty-three times as hard as could its forerunner of only fifty years ago4 ,since the ,repulse all our battleships have been built of wrought iron or mild steel4 ,speaking generally1 there was a steady development in size and horse-power and in speed until #aijf1 in which year there was launched the world-famous ,h4,m4,s4 ,dreadnought4 ,previously no battleship had been faster than #ai knots3 she was designed for #ba knots4 ,her tonnage was #ag1ijj1 exceeding by more than #ajjj tons anything that had gone before4 ,but the great change was in the guns4 ,pre-,dreadnoughts had1 or one ought to say have for there are still many in existence1 four of the biggest guns1 a number of medium-sized guns and a still larger number of smallish guns intended for the purpose of keeping off torpedo craft and such small fry4 ,at one stroke ,lord ,fisher1 who was then the ,first ,sea ,lord of the ,british ,admiralty1 changed all this4 ,he swept all the medium-sized guns away and gave this new ship ,,ten of the largest guns then in use4 ,the advent of this ship startled the whole naval world1 for it was seen at once by all those able to judge that there was a vessel which might be expected to sink with ease any other ship afloat4 ,the onslaught from those ten guns would be more than any other ship could stand4 ,so other powers set to work to copy more or less exactly1 while ,great ,britain quickly built more like her4 ,so important was this new invention that very soon the strength of the naval powers began to be reckoned entirely on the number of ,dreadnoughts they possessed1 the older ships being left out of account as though they did not make any difference one way or the other4 ,but ,great ,britain was not content with the ,dreadnought1 for each succeeding ship or set of ships was improved until1 only four years later1 there was launched the ,orion already referred to1 nearly #ejjj tons bigger1 with #bejj more horse-power1 and with #ac-;inch guns instead of #ab-;inch4 ,the ,orion and her sisters are often spoken of as super-,dreadnoughts4 ,the ,dreadnoughts as a class are often referred to as all-big-gun ships1 since that is the feature which most distinguishes them from those which went before4 ,these large guns are mounted in turrets as they are called4 ,we might describe these as turn-tables with a cover over something like a small gas-holder4 ,there are usually two guns in each turret1 although there are a few ships whose turrets have three in each4 ,the turrets seem to be standing on the deck of the ship and it is by turning them round that the guns are trained or pointed at their target4 ,the original ,dreadnought had one turret in front and two behind1 all on the centre-line of the ship1 and two more1 one each side1 amidships4 ,in late vessels all five turrets are on the centre-line4 ,thus the ,dreadnought can fire six guns ahead1 eight astern and eight to either side1 while the newer ships can fire four ahead1 four astern and all ten on either side4 ,there are other battleships with even more guns than these1 such as the ,u4,s4,a4 ship ,wyoming1 with twelve #ab-;inch guns1 but the ,british ,navy seems to prefer to stick to the original number of ten4 ,the reason for this is that every such ship is a compromise between three alternatives4 ,the three great features have already been pointed out1 namely1 the guns1 the armour and the propelling machinery4 ,either of these can be increased at the cost of one or both of the others1 but all cannot be increased without sinking the ship1 unless indeed1 the ship be made larger and then other considerations crop up4 ,and that brings us to another class of ship often ranked among the battleships4 ,these remarkable vessels are also termed cruisers and the fashion seems to have established itself of combining the two names and calling them battle-cruisers4 ,they gave a fine account of themselves during the war4 ,the first three of these1 of which the ,invincible is usually taken as the type1 made its appearance the year after the ,dreadnought1 and like the latter were the offspring of the fertile brain of ,lord ,fisher4 ,the ,invincible was about the same size as the ,dreadnought1 but had nearly twice the horse-power 7#da1jjj71 which enabled it to attain an actual speed of nearly six knots more1 namely1 #bhf4 ,for guns it had eight of the same large weapons1 and it was armoured with #g-;inch steel armour-plates instead of #aa-;inch4 ,thus we see illustrated what has just been said1 less guns and thinner armour1 to allow for more engine power and higher speed4 ,or1 to put it the other way1 we observe how higher speed was attained at the expense of the guns and the armour4 ,but just as the ,dreadnought was followed by other still greater improvements in the same direction we get1 in #aiaj1 the famous ship ,lion1 a vessel not unknown to the ,germans1 a super-,invincible4 ,this ship has a tonnage of over #bf1jjj and #gj1jjj horse-power4 ,it was designed to do #bh knots4 ,we saw the use of these ships in the ,jutland battle1 when1 using their high speed1 they attacked the ,german battleships and kept them engaged while the slower battleships came up4 ,though they suffered severe losses1 which probably the more heavily armoured battleships would have escaped1 they held the ,germans so that it was only the failing light which saved them from utter destruction4 ,another example was the way in which they hunted down ,von ,spee and his squadron off the ,falklands1 when they caught the ,germans because of their higher speed and then sank them by means of their heavier guns with practically no loss to themselves4 ,we saw them again in the ,heligoland battle1 coming up to the assistance of the lighter vessels just in the nick of time and scattering the enemy like so much chaff4 ,a fact little known to most people and productive of much surprise is that these battleships and cruisers are not such very large vessels1 when compared with those of the merchant service4 ,the ,lion is #ffj feet long and #hf feet wide1 the ,aquitania is #icj feet long and #ih feet wide1 and the ,olympic is #hhb feet long and #ib feet wide4 ,the mighty ,orion makes a poorer showing still in point of size1 since she is only #ede feet long and #hh feet wide--little over half the length of the ,aquitania4 ,it is difficult to compare the tonnage of a warship with that of a merchant ship1 since they are not measured in the same way4 ,the former is the displacement or actual weight of water displaced3 in other words the precise weight of the vessel in tons of #bbdj lbs4 ,the tonnage of a merchant ship1 however1 has nothing to do with weight but is based upon capacity and is arrived at by a purely arbitrary rule1 thus3 all the enclosed space in the ship is measured in cubic feet and the total is divided by one hundred4 ,that gives the gross tonnage4 ,to arrive at the net tonnage the space occupied by the engines and all other space necessary for the working of the ship is excluded4 ,originally the tonnage of a merchant ship was the number of tuns of wine which it could carry4 ,thus1 you see1 comparing the tonnage of a warship with that of a merchant ship is somewhat like comparing a pound with a bushel4 ,net registered tonnage is generally considerably less than the displacement tonnage of the same ship1 so that a warship is usually less than a merchant ship of the same nominal number of tons4 ,and now let us turn to some of the internal arrangements of these wonderful ships1 more particularly to the means for working the guns4 ,each turret is placed over the top of what we might call a well1 running right down deep into the inside of the ship4 ,at the bottom of this well is the magazine1 where the shells are stored and also the cartridges containing the explosive which drives the shell from the gun4 ,underneath the turret1 forming a kind of basement to it1 is a chamber called the working chamber1 and up to it the shells and cartridges pass by means of lifts4 ,for safety's sake only a small quantity of explosives is kept here at any one time1 but it is from here that the guns overhead are fed4 ,shells and cartridges alike pass up as required by means of hoists right to the guns4 ,indeed1 the hoists are ingeniously contrived so that in whatever position a gun may be the hoist stops exactly opposite the breech1 or opening at the back of the gun through which it is loaded4 ,then a mechanical rammer drives the shell or cartridge into its place in the gun4 ,the hoists are worked by hydraulic power or electricity1 and in most cases by both1 arrangements being made so that either can be used at will1 thus serving as alternatives in case either should get out of order4 ,the turrets themselves are also turned by power4 ,indeed1 so heavy are the weights involved that only by the use of carefully designed machinery is the operation of such great weapons made possible4 ,a single shell of the #ace-;inch gun weighs #abej lbs4 ,around each turret there is placed a wall of thick armour plate as high as it is possible to make it without interfering with the movement of the guns4 ,this is called the barbette armour and the space enclosed by it1 in which the turret stands1 is called a barbette1 an old fortification term meaning a place behind a rampart4 ,the turret is covered over1 as has already been remarked1 by a steel hood1 so that altogether the guns and their crews are about as well protected as it is possible to be4 ,that all this means a considerable burden upon the ship is shown by the fact that a pair of #ab-;inch guns with their turret and barbette armour will weigh something like #fjj tons1 and if there be five of them that means #cjjj tons in all4 ,down below in the magazine there are lifting appliances whereby the shells can be readily picked up and run to the hoist4 ,moreover1 there is elaborate machinery for keeping them cool4 ,our allies the ,french had1 years ago1 several bad accidents through the explosives going off spontaneously in their ships1 and this is quite likely to happen if the magazines become too hot4 ,so refrigerating apparatus is installed similar to that employed in meat-carrying ships1 which provides a constant flow of cool air into the magazines4 ,the ships also are subdivided to the greatest possible extent consistent with efficient working1 so that in the event of a collision or a torpedo making a hole below water the ship may not sink4 ,as far as possible the divisions or bulkheads are made to run right from top to bottom without any openings1 but that obviously is a very inconvenient arrangement1 so in many places there have to be doorways through them1 leading from one part of the ship to another4 ,in such cases these are closed by water-tight doors1 which can be shut before the ship goes into action or into any dangerous region4 ,the engines of these vessels are now always turbines4 ,this type of engine has many advantages over the older type1 in which certain parts move to and fro1 that motion being changed by cranks into a round and round action4 ,for one thing1 they are lighter for a given power1 so that more power can be put into a ship without adding to the weight4 ,that means higher speed4 ,then there is less to get out of order4 ,anyone who has been into a ship's engine room where to and fro or reciprocating engines are at work will realize this1 for there is a maze of rods and cranks all moving together1 and many parts which need to be oiled while in motion and which would get hot and tight if they were not carefully looked after4 ,all this in an enclosed space with possibly an uncomfortable motion of the whole ship used to make the engineer's life at sea a very hazardous and unhappy one4 ,but the turbine is entirely enclosed4 ,there is nothing to be seen moving at all4 ,indeed1 there is only one moving part1 and that is coupled directly to the propeller-shaft1 so that nothing could possibly be simpler4 ,,chapter ,,xvii ,,how ,a ,,warship ,,is ,,built ,when it is decided to build a certain ship1 the first thing to be done is to draw it on paper4 ,the ,admiralties of the world1 and also the great shipbuilders1 have each their own chief designer installed in a big1 light1 quiet office fitted with large strong1 flat tables at which work a number of draughtsmen4 ,the naval authorities tell the chief in general terms what they want the ship to be capable of1 and he determines its size and form4 ,then the draughtsmen work out his ideas on paper1 themselves deciding upon the minor details1 until they have produced exact representations of the ship which is to be4 ,some draughtsmen deal with the actual hull of the ship1 while others design the various fittings and minor details1 all working1 of course1 under the constant supervision of the chief4 ,in this connection one may perhaps allude to a matter which the general public often seems to misunderstand--the work and functions of a draughtsman4 ,i have heard people say of a boy that he is good at drawing so they think of making a draughtsman of him4 ,now the point is that the actual drawing is perhaps the least important part of a draughtsman's work4 ,he has to know what to draw4 ,he is given just a rough idea of something and from that he has to produce a perfect design1 bearing in mind that the thing to be made must well fulfil its purpose1 must be easy and cheap to construct1 must be strong enough yet not too heavy1 must be made of the most suitable material and so on4 ,he has to possess a good deal of the knowledge of the skilled workman1 he has to be something of a scientist and a good mathematician in addition to his ability to make neat and accurate drawings4 ,so1 you see1 these men whose minds conceive the details of our great ships are men of long training and experience1 with far greater knowledge and skill than we sometimes give them credit for4 ,anyway1 there they stand1 each at his own table1 bending over his own drawing-board1 each doing his own particular share towards producing the perfect ship4 ,but when all is said and done1 there are limitations to the cleverness of the cleverest among us1 so the next step1 after the draughtsmen have done their best1 is to test what they have done by experiment4 ,years ago a certain ,mr4 ,william ,froude interested himself in the question of the best shapes for ships1 and he found that by making an exact model of a ship and then drawing that model through water it was possible to foretell just how that ship would behave4 ,he built himself a tank for the purpose of these experiments at ,torquay1 where he lived1 and by its aid he added a very important chapter to the science of shipbuilding4 ,nowadays the ,admiralty have a large and well-fitted tank at ,portsmouth1 the ,united ,states ,navy have one at ,washington1 private shipbuilders have the use of a national tank at ,bushey1 near ,london1 while several of the large firms have tanks of their own4 ,the national tank at ,bushey1 by the way1 was given to the nation by ,mr4 ,yarrow1 a famous shipbuilder1 in memory of ,mr4 ,froude1 it being called the ,william ,froude ,tank in recognition of the great work done by him4 ,now these tanks may be described as rather elongated swimming-baths4 ,such a structure is generally a little narrower than the average bath1 but it is longer and much deeper4 ,at one end there are miniature docks in which the models float when not in use1 while at the other there is a sloping beach upon which the waves caused by the models expend their energy harmlessly4 ,along each side there runs a rail upon which are supported the ends of a travelling bridge4 ,driven by electric motors1 this bridge can run to and fro from end to end of the tank1 and its purpose is to drag the models through the water4 ,carried upon the bridge is a platform which bears a number of instruments1 chief among which is a self-recording dynamometer4 ,now a dynamometer is an instrument for measuring the force of a pull1 and when we call it self-recording we mean that it automatically takes a record of a series of pulls or of a varying pull4 ,in this case there projects below the bridge a lever1 to the end of which the model under test is attached4 ,as the bridge rushes along it pulls the model through the water by means of this lever1 and the force which is expended in doing so is recorded in the form of a wavy line upon a sheet of ruled paper4 ,if the model slips through the water very easily there is little pull upon the lever and the line drawn by the pen of the instrument remains low down upon the chart4 ,if1 however1 much power is needed and the pull is a strong one the pen moves and the line rises towards the top of the paper4 ,any change1 whether increase or decrease1 is thus shown by the rise or fall of the ink line4 ,one model can be thus tried at various speeds and its behaviour noted under different conditions4 ,other matters can be investigated too1 such as whether or not the bow rises in the water or falls when the boat is in motion1 also how much such rise or fall may amount to4 ,the suitability of a certain shape of vessel1 moreover1 can to a certain extent be seen by observing the commotion which it makes in the water4 ,everyone has noticed the way in which a ship throws up a wave at its bows1 and that bow-wave1 as it is termed1 represents so much energy being wasted4 ,the power of the engines is absorbed to a certain extent in making that wave4 ,it is impossible to make anything which when forced through the water will not make some wave1 but certain forms cause less of it than others1 and the designer of a ship seeks to find that form which will make the smallest bow-wave4 ,in like manner the eddies which a ship leaves in its wake are the result of wasted energy1 and the ship must be so shaped that they too will be reduced to a minimum4 ,shipbuilders find that there are three things which retard a ship's movement3 skin friction1 or friction between the water and the sides of the ship2 wave making at the bow and eddy making at the stern4 ,the first depends largely upon the smoothness of the ship's surface1 the second and third depend upon its shape4 ,if a model behaves badly in the tank the fault may be either too much wave making or too much eddy making1 and which of these it is the dynamometer does not of course tell4 ,in many cases the experienced eye of the tank officials furnishes the clue to the trouble1 but in some cases a cinematograph is used to make a complete series of photographs of the model and the water around it as it rushes from end to end4 ,these can then be studied in conjunction with the chart and the cause of the fault discovered4 ,the real aim1 it is obvious1 of all these tank experiments is to find out the lowest horse-power necessary to drive the ship1 or the best form of ship to get the highest speed out of a given horse-power4 ,the cost of keeping up these large tanks and making the models and conducting the experiments is very great1 for not only are the premises very large 7,i know one in which the water alone cost nearly a hundred pounds7 but a highly skilled staff is necessary4 ,the saving effected in the cost of ships and the superior efficiency of the ships makes it well worth while however4 ,there is still one other point about this matter which will possibly be puzzling the observant reader4 ,what are the models made of and how are they made8 ,they are made of paraffin wax1 and a very important department of the experimental tank is that where the models are formed4 ,first of all a rough mould is fashioned by hand in modelling clay and into this is poured melted wax1 the result being a very rough model of the ship4 ,this is then placed in the model-making machine4 ,those of my readers who are familiar with an engineer's shop will know what a planing machine is like1 and from that they can form an idea of the general structure of this remarkable tool4 ,there is1 first of all1 a travelling table which1 as the machine works1 travels to and fro4 ,spanning this table is a beam which carries on its under side two revolving cutters1 so that as the table passes beneath them the cutters can operate upon anything placed upon the table4 ,another part of the machine is a board upon which is placed the drawing showing the external shape of the proposed ship1 and working over this board is a pointer connected by a system of rods and levers to the cutters just mentioned4 ,the rough block of wax1 then1 having been placed upon the table and the to and fro motion set going1 the attendant guides the pointer along the lines of the drawing1 and as he does so the cutters so move as to carve away the soft wax into the precise shape of the model4 ,a little smoothing by hand is all that is necessary to complete the conversion of the rough piece of wax into a perfect model4 ,it is then placed in the water and ballasted with little bags of shot until it floats at just the correct depth1 and finally a light wooden frame is fitted to it for the purpose of making the connection to the lever by which it is pulled along4 ,thus1 after much thought and experiment1 the designs for a new ship are completed4 ,tracings are then made of them on semi-transparent paper or cloth1 which tracings are then used as negatives1 from which a number of photographic prints are made1 just as the amateur photographer makes prints from his negatives4 ,at least that is how they used to be done1 in a huge printing frame1 but nowadays a machine is more often employed which passes the tracing or negative with a piece of photographic paper behind it slowly past an electric light1 thus doing the work more quickly and more conveniently1 for the drawings of ships are often very long and would either require an enormous frame or else would have to be made in pieces and joined together4 ,the prints are finally passed out to the works to be translated in terms of iron1 steel and wood4 ,perhaps the most important part of a shipyard is the mould loft1 a large apartment on the floor of which the ship is drawn out full size4 ,then from these full-size drawings moulds or templets are made of wood or soft metal1 showing the exact size and shape of the various parts4 ,the moulds or templets go thence to the workshops1 where the bars and plates of steel are cut to the right shape and perforated with holes1 and some of the pieces are there joined together with rivets4 ,illustration3 ,,the ,,tripod ,,mast4 ,here we see one leg of the tripod mast of a warship4 ,these masts have greater stability and freedom from vibration than others4 ,they are used for observation and range-finding1 and have a fighting-top on which guns of small calibre are mounted4 ,here is shown a sailor carrying a wounded comrade4 ,from the workshops the various pieces or parts go to the yard where the slip is on which the vessel is being built4 ,this slip is by the water's edge1 conveniently placed with a view to the fact that later on the great structure1 weighing possibly thousands of tons1 has got to slide down into the water4 ,where the keel of the ship is to go a row of timber blocks is placed a few feet apart1 and upon these blocks the plates of steel which form the lowest part of the ship are laid4 ,upon them are laid other parts1 and upon them others1 the joints being made by riveting4 ,thus the great ship grows from the keel upwards4 ,as she gets bigger and bigger there comes the danger of her tipping over1 and that is provided against by the use of props or shores along both sides4 ,by the time the hull is ready for launching it is often of great weight1 all of which is borne upon the wooden blocks underneath the keel4 ,consequently1 if the ground be not good1 piles have to be driven in or concrete foundations laid to enable the huge mass of the ship to be supported4 ,for this reason a large vessel cannot be built anywhere but only on a properly prepared slip1 and it is the possession of a large number of such places which enables ,great ,britain to build so many ships at once4 ,along each side of the slip there is usually a row of tall masts with a beam projecting out sideways near the top of each1 forming cranes by which the heavier parts can be hoisted into position4 ,in other yards1 again1 there is a tall iron structure called a gantry along each side of the slip1 while travelling cranes span across from one to the other over where the growing ship lies4 ,these travelling cranes1 worked by electricity1 permit heavy weights to be handled with ease and safety4 ,other subsidiary cranes1 meanwhile1 carry the heavy hydraulic riveting machines by which riveting is done4 ,much riveting is done by hand1 men working together in squads of four4 ,of these one1 often quite a boy1 heats the rivets in a small furnace1 after which he throws them one by one to man number two1 who inserts each as he receives it in its proper hole and holds it there with a big heavy hammer or else a tool called a dolly4 ,number two is called the holder-up1 since he holds the rivet up in its place while the remaining two hammer it over with alternate blows of their hammers4 ,in many cases1 however1 the two last described men give place to one1 who is armed with a tool in shape much like a pistol and operated by compressed air obtained through a flexible tube4 ,when he presses a trigger a little hammer inside the pistol gives a rapid series of blows to the rivet1 completing the job more quickly than the two men can do with hand hammers4 ,a third way of doing this operation so important in the building of a ship is by the hydraulic machine suspended from the cranes4 ,to the casual onlooker this has the notable feature of being silent1 whereas riveting by hand and still more by a pistol hammer is terribly noisy4 ,the reason for this is that the hydraulic riveter does not hammer at all1 but1 like a huge mechanical hand1 it takes the rivet between finger and thumb and just squeezes it down4 ,one strange result of all this hammering in of rivets is that every ship by the time it leaves the slip has become a huge magnet1 with somewhat disconcerting effects upon its own compasses1 but of that more later on4 ,thus the great ship grows1 being made piece by piece in the workshops to the shapes indicated from the mould loft and put together and riveted on the slip1 until finally in due time it is ready to take its first journey4 ,the launching of a big ship always strikes me as about the boldest and most daring thing which is ever done in the course of industry4 ,for the huge structure1 naturally top-heavy1 weighing hundreds or thousands of tons1 is just allowed to slide at its own sweet will4 ,from the moment it starts until it is well in the water it is in charge of itself1 so to speak1 and if anything were to go wrong no power on earth could stop it once it had got a start4 ,that nothing ever does go wrong1 or scarcely ever at all events1 is due to the care with which all preparations are made before that critical moment when the ship is let loose and to the skill and experience of those in charge4 ,as the hull reaches that degree of completion when it can safely be put in the water1 strong wooden structures termed launching ways are constructed one on each side of her4 ,these really act like huge rails upon which in due course there will slide a gigantic toboggan4 ,tremendously solid and strong they have to be1 as they have each to carry half the total weight of the ship4 ,under each side of the ship and upon the launching ways there is built a timber framework capable of raising the ship bodily off the blocks upon which until now it has reposed4 ,these two frames1 being connected together by chains passing beneath the keel1 constitute what is called the cradle1 the toboggan which is to slide down the ways1 bearing the ship upon it4 ,it is easy to see that being top-heavy something must be done to give the ship support before the shores on either side can be taken away1 and it is equally clear that these latter must be removed before she can slide down to the water4 ,neither would it do to let the vessel slide upon her own plates1 so we see that the cradle fulfils a twofold purpose1 first enabling the ship to reach the water without ripping holes in her own plates1 and secondly giving it the necessary side support to prevent it from toppling over on the way4 ,when all is ready1 but a short time before the hour appointed for the launch1 a curious operation is performed4 ,between the main part of the cradle and the part which actually slides upon the ways wedges are inserted1 hundreds of them1 and they are all driven in simultaneously4 ,their purpose is to make the cradle slightly higher and so to lift the ship off the blocks upon which it was built4 ,if they were driven in one at a time each would only dig its way into the timber and nothing else would happen1 but being driven all together a most powerful lifting action is produced which actually raises the mighty ship4 ,so hundreds of men stand1 each with his hammer ready to strike a wedge1 while the foreman stands by with a gong4 ,at a stroke on the gong the hundreds of hammers strike as one1 and so the ship is raised off the blocks1 which can then be removed1 to facilitate which they too are built of wedge-shaped pieces which can easily be knocked apart4 ,the shores1 too1 have ceased to serve any useful purpose and can be taken away until at last all shores and all blocks are gone and the vessel rests upon the cradle only4 ,meanwhile tons of grease have been put on the ways1 and the ship1 urged by its own weight1 is straining to get down the greasy slope into the element for which all along it has been intended4 ,at this stage the only thing which restrains it is a kind of trigger arrangement on either side which locks the cradle in its place4 ,in some yards elaborate mechanical catches controlled by electricity are used for this1 but in many the old device of dog shores is still used4 ,these are simply two stout wood props which fit between a projection on the ways and one on the cradle1 there being one dog shore on either side4 ,just over each dog shore there hangs a weight4 ,the person who performs the ceremony cuts the cord which holds the weights1 the weights fall1 the dog shores are knocked away1 and the ship is free4 ,slowly at first1 but gathering speed every moment1 she moves majestically downwards into the water1 being ultimately brought to rest by means of chains4 ,whether done by the simple dodge of cutting a cord or by the more refined method of pressing an electric push1 the launching is generally preceded by the breaking of a bottle of wine against the bows and the pronouncement of the vessel's name4 ,once safely afloat1 the vessel is towed away and berthed alongside a wharf whereon are cranes and other machines which lightly drop on board of her the massive turbines and boilers which in time will propel her1 and the guns with which she will fight4 ,all the multitudinous little finishing touches are here put into her until at last she sallies forth on her trial trips to show what she is capable of1 after which follow trials of her guns1 and then she takes her place in the fleet4 ,thus1 briefly sketched1 we see the history of the warship from her inception in the minds of her designers till she is ready to meet the foe4 ,,chapter ,,xviii ,,the ,,torpedo ,in parts of ,south ,america there lives a little fish1 which1 if you touch its nose1 gives you a severe electric shock4 ,the natives call it the torpedo4 ,when an artificial fish came to be invented1 capable of giving a very nasty shock to anyone touching its snout1 that name was bestowed upon it too4 ,even more than the submarine1 the torpedo resembles a fish with its graceful outlines and its fins and tail1 the chief difference being that the tail of the torpedo carries a couple of little rotating propellers4 ,looked at another way we may say that the torpedo is an automatic submarine4 ,as a matter of fact1 we all know it best as the weapon of the submarine4 ,it was originally invented by an ,austrian who took it to a ,mr4 ,whitehead1 an ,englishman who then had an engineering works at ,fiume4 ,this gentleman took up the idea and developed it into the ,whitehead torpedo1 which is to-day used by half the navies in the world1 the rest using something very similar4 ,it is curious to note that the ,german variety is called the ,schwartzkopf1 the meaning of which is blackhead4 ,the smooth1 steel1 fish-like body consists of two separate parts1 which can be detached from each other4 ,the front part called the head is made in two kinds1 the war-head and the peace-head4 ,the former contains a large quantity of explosive and the mechanism for firing it on coming into contact with any hard body4 ,it is only used in actual warfare4 ,the peace-head is precisely the same shape and weight as the other but is quite harmless1 so that when it is fitted to the torpedo the latter can be handled with perfect safety1 a valuable feature during the frequent exercises through which our sailors go in their efforts to attain perfection in the use and handling of these valuable weapons4 ,so much for the head4 ,the body of the torpedo contains a beautiful little engine precisely similar to a steam-engine but on a small scale1 which is driven by compressed air1 a store of which is carried in a compartment provided for the purpose4 ,then there is an automatic steering apparatus controlled by a gyroscope1 the purpose of which is to keep the torpedo steered in precisely that direction in which it is started4 ,if any outside force1 such as current or tide1 deflects it from its path the gyroscope1 acting through a rudder at the tail1 brings it back again4 ,like the submarine1 moreover1 it has rudders which can steer it upwards or downwards and these again are controlled automatically so that having been set to travel at a certain depth the torpedo can be launched into the water with the practical certainty that it will descend to that depth and then maintain it4 ,this remarkable result is attained by the use of two devices acting in combination1 namely1 a hydrostatic valve and a pendulum4 ,either of these alone would set the thing going by leaps and bounds1 at one time above the required depth and at another equally below it1 and so on alternately4 ,the hydrostatic valve consists of a flexible diaphragm1 one side of which is in contact with the water outside1 so that since the pressure increases with increasing depth1 it is bent inwards more or less as the depth varies4 ,this deflection is made to control the horizontal rudders4 ,suppose that things are adjusted for the rudders to steer the torpedo horizontally when at a depth of ten feet3 if it descends to twelve feet the increased deflection of the diaphragm will so change the rudders that they will tend to steer slightly upwards3 if1 on the other hand1 it rises to eight feet the contrary will happen1 with the result that it will descend4 ,as has been said already1 this alone would result in a continually undulating course1 so the pendulum is introduced to check the too decided changes in direction and so produce a practically straight course4 ,there is an interesting feature1 too1 about the propeller4 ,it is twin but not1 as in ships1 two screws side by side4 ,instead1 they are both set upon one shaft or rather upon two concentric shafts1 like the two hands of a clock4 ,the hour-hand of a clock is on one shaft1 a solid one1 which itself turns inside the shaft of the minute hand1 which is hollow4 ,the propellers of the torpedo are likewise1 one on a tubular shaft and the other on a solid shaft inside it4 ,these two shafts turn in opposite directions1 but since the two propellers are made opposite hands they both equally push the torpedo along4 ,the reason for this arrangement is that without it the action of a single propeller would tend to turn the torpedo over and over4 ,instead of the torpedo turning the propeller the propeller would to some extent turn the torpedo4 ,the range of the torpedo depends1 clearly1 upon the quantity of compressed air which it is able to carry and that is limited by certain practical considerations4 ,one of these is the space required to store it1 and a very ingenious method has been invented whereby the limited supply is eked out so that in effect its quantity is increased4 ,as the air is used up the pressure in the air-chamber naturally falls and when that has gone on to a certain extent chemicals come into action which generate heat1 whereby the remaining air is raised in temperature4 ,this1 of course1 increases the volume of air and the result is just the same as if a greater quantity were carried to commence with4 ,the explosion is brought about by the pressing in of a pin which normally projects from the nose or point of the torpedo1 and it would be very easy to knock this accidentally1 causing a premature explosion1 were not precautions taken to prevent it4 ,these take the form of a little fan which is turned by the water as the torpedo proceeds through it4 ,the firing-pin is locked by means of a screw so that it cannot be operated until it has been released by the withdrawal of the screw and that can only be done by the fan4 ,thus1 while on the submarine or whatever ship carries it1 the torpedo cannot be fired3 it only becomes capable of explosion after it has passed through the water for a certain distance1 far enough1 that is1 for the fan to have undone the screw4 ,thus the maximum of safety is combined with the maximum of sensitiveness when the object aimed at is struck4 ,there are other forms of torpedo which although little used are by no means lacking in interest4 ,there is the ,brennan1 for example1 at one time much favoured in the ,british ,navy4 ,its propellers were operated from the shore1 by the pulling of two very flexible steel wires4 ,the effect was much as if the thing were driven by reins1 as a horse is driven4 ,on shore was a powerful engine with two large drums on which the wires could be wound and by which they could be drawn in at a very high speed4 ,by pulling one more than the other the torpedo could be steered and it is said that such a torpedo could be made to follow a ship through complicated evolutions and fairly hunt it down1 finally overtaking and striking it4 ,the purpose of such weapons was clearly to defend a port or roadstead against enemy craft which might try to rush in4 ,it needed to be controlled by someone perched upon an eminence of some sort from which he could watch its course and guide it as might be necessary4 ,compare this with the ease with which the ,whitehead torpedo is just slipped into the water and then left to itself4 ,a submarine has in its bows either one or two tubes just large enough to hold the torpedo easily4 ,at the front is a flap door which is kept closed while the torpedo is slipped into its place4 ,then the similar door at the rear of the tube is closed after which the front one can be opened4 ,water of course flows in and surrounds the torpedo when this takes place and a little push from some compressed air sends it floating out4 ,as it emerges from the tube the engines are set going automatically and likewise the gyroscope which steers it1 after which it continues to proceed in a straight line1 soon seeking and maintaining the desired depth4 ,other vessels besides submarines have submerged torpedo-tubes like these1 but others again have tubes of a different kind4 ,these are fixed on the deck and have the advantage that they can be pointed in any direction almost like a gun1 whereas the others are either fixed rigidly in the vessel or are only slightly movable4 ,in the case of these other tubes the torpedo is shot over the side of the ship1 off which it leaps into the water somewhat like a man diving4 ,one other kind of steerable torpedo may be mentioned because of its ingenuity1 although so far as is known it is not in actual use4 ,it is called the ,armorl1 a compound of the names of its inventors1 ,messrs4 ,armstrong and ,orling4 ,it is controlled by wireless telegraphy in a very simple but effective manner4 ,the rudder which steers it is connected to a small crank in such a way that as the crank revolves it turns the helm first to one side and then to the other4 ,suppose that1 to commence with1 the rudder is straight3 a quarter of a revolution of the crank sets it to one side1 say1 the right3 another quarter sets it straight again3 a third quarter sets it to the left3 and so on4 ,the crank is turned by a wound-up spring1 the effect of which is1 however1 normally held in check by a catch4 ,when a wireless impulse comes along the catch is lifted for a moment1 the crank slips round a quarter of a turn and the rudder is moved accordingly4 ,every impulse changes the position of the rudder and by sending suitable series of impulses it can be set as desired and changed at any moment4 ,a difficulty with all these guided torpedoes is that they must carry some indication whereby their place at any moment will be made visible to the man in control4 ,a little mast and flag would do1 for example1 but it would be a fair mark for the enemy's guns and being shot away would leave the torpedo uncontrollable4 ,the same objection seems to apply to the wireless antenna which this last type must carry with which to receive their guiding impulses1 but that can be made light and almost invisible4 ,it is when the thing is clearly visible that the danger arises1 and1 of course1 to serve its purpose it must be visible4 ,the way in which this difficulty was overcome by ,messrs4 ,armstrong and ,orling is a beautiful example of ingenuity4 ,they cause a jet of water to be blown upwards by compressed air1 something like the spouting of a whale1 so familiar in books of natural history4 ,that forms a mast which is clearly visible1 yet the enemy may blaze away at it to their heart's content without damaging it in the least4 ,,chapter ,,xix ,,what ,a ,,submarine ,,is ,,like ,the precise details of the submarines of our own navy or of any other for that matter are wrapped in mystery4 ,those who might tell do not know and those who know must not tell4 ,true1 there have been fully descriptive articles in many books and magazines1 but it may be safely asserted that those descriptions are nothing more than what this chapter avowedly is1 reflections by the authors on what such a craft must be like1 more or less4 ,it is just as well that this should be clearly understood1 and the following description does not claim to be any more than that4 ,just as an aeroplane follows the general design of a bird of the swallow type1 which soars without flapping its wings1 so the submarine necessarily follows much the lines of a fish4 ,it has fins which help to guide it1 it has rudders which compare with the fish's tail1 and while it cannot use either fins or tail to push itself along as the fishes do1 it has one or more propellers which serve that purpose admirably4 ,it is rather remarkable that1 while we often imitate nature very closely1 there is one very important mechanical feature which almost invariably distinguishes man-made schemes from natural ones--that is1 that man uses rotary motion for many purposes whereas nature practically never does4 ,to be perfectly honest1 the natural mechanisms are far too difficult for us to copy or ,i expect we should do so4 ,for example1 watch a goldfish and see how cleverly it uses its tail4 ,man could never hope to make anything so perfect as that tail4 ,absolutely under its owner's control1 it serves a double purpose of propelling and steering in a manner which is equally beautiful and impossible to imitate4 ,for certain definite purposes1 however1 a rotary propeller is quite as good as anything which the fishes can show us4 ,as a straightforward1 simple1 forward-pushing device it is equal to anything that a fish possesses4 ,it has to be given that one duty1 however1 and no other1 the steering being the task of a separate device1 the rudder4 ,there again1 too1 we see how nature does two things with one kind of mechanism while we have to use two1 for the fish steers itself to right and to left with its tail in a vertical plane1 but if it wants to steer upwards or downwards it twists its tail over somewhat towards a horizontal plane4 ,the submarine1 however1 needs two distinct and separate rudders1 one for right and left steering and one for up and down1 the latter being generally a pair1 one each side the vertical rudder for the sake of symmetry and balance4 ,so we find that a submarine has a body like that of a fish except that it is rather more rotund1 perhaps1 than the most portly fish usually seen4 ,it has certain fixed fins projecting from its sides1 which together with the rudders enable it to be guided4 ,it has also certain long fins called bilge keels for the purpose of keeping it from rolling too much4 ,also1 it has one or more propellers and the two kinds of rudder already referred to4 ,a fish1 never wishing to get outside itself and walk about upon its own upper surface1 needs no deck1 in which the submarine differs from it1 for the crew require somewhere where they can enjoy a breath of fresh air when opportunity offers4 ,it is not a very commodious place1 one could not exactly take a long walk upon it1 nor even play deck-quoits1 but on the back of the submarine there is an undoubted deck where the men can get out and upon which they can stand when she is on the surface4 ,a fish1 moreover1 takes little heed of things upon the surface3 its interests lie almost entirely below4 ,hence it has no conning-tower or periscope1 but without these the submarine would be useless4 ,the former is a little oblong tower something like a chimney1 which projects upward from the deck1 while projecting to a higher level still is the tall hollow mast with prism and lenses at the top called the ,periscope1 through which the commander of the submarine1 himself comparatively inconspicuous1 can sweep the horizon for enemies or victims4 ,the problem of constructing a ship to travel under water is quite different from making one to travel on the surface in the ordinary way4 ,when deep down the pressure of the water tending to crush the vessel is something enormous4 ,roughly speaking1 it is a pound per square inch for every two feet in depth1 so that if a submarine dives to a depth of fifty feet the water presses upon it with a force of about twenty-five pounds upon every square inch of its surface4 ,on a square foot1 that means over a ton4 ,and there are many square feet of the surface in even a small submarine4 ,consequently1 the whole shell of the ship has to be of very substantial construction4 ,moreover1 there are curious strains which come upon the vessel when it dives to which surface ships are not subject4 ,all these have to be reckoned as far as possible and allowed for4 ,the size of the modern submarine is not known with any certainty1 but we may put it down roughly as two hundred feet long and at least a thousand tons displacement1 which means that that is its actual weight1 including everything and everybody on board1 when it is just about to submerge4 ,of course1 a submarine1 alone among boats1 has two tonnages4 ,when it is on the surface it is comparatively light4 ,indeed1 running light is the technical term describing it when it is riding upon the surface of the water like an ordinary ship4 ,then1 by increasing its weight1 it can cause itself to sink until the little promenade or deck called the superstructure is just submerged and little can be seen above water except the conning-tower4 ,that is termed the awash position1 and it is clear that it is then displacing more water than when running light1 and hence its displacement tonnage must be more4 ,when it is desired to sink1 the vessel is set in motion in the awash position1 from which it is gradually steered downwards by the diving rudders1 until only the periscope1 or it may be not even that1 is left showing above4 ,then the maximum of water is being displaced4 ,it is then actually displacing more than its own weight of water1 for if left to itself it will rise rapidly and it is only the speed and the action of the rudders which keep it under4 ,we see1 then1 that the action of a submarine in submerging itself is a real genuine dive4 ,it sinks upon an even keel until it is awash1 after which it goes under head-first1 just as a swimmer does4 ,it also rises bow first4 ,this tendency to rise when the combined action of movement and rudder ceases constitutes a very considerable safeguard1 for should anything happen to the propelling machinery the vessel simply rises4 ,at one time weights were attached to the under side of the hull which could be detached from the inside so that in the event of the vessel descending against the wish of her commander1 she could be simply forced to the surface by the great excess of buoyancy resulting from shedding these safety weights4 ,of course1 in the event of a serious perforation of the hull neither of these forms of surplus buoyancy would bring the boat up4 ,let us now trace the operations of diving right through1 supposing that our submarine is first running light4 ,in that condition she is being driven by the oil engines which constitute her primary propelling power4 ,the hatch or door at the top of the conning-tower is open1 as also1 it may be1 is the one lower down1 just at the foot of the tower4 ,men are standing upon the little platform formed by the tower1 and one of them is steering by means of a wheel1 keeping his eye1 moreover1 upon a compass also provided there1 that being in fact1 to the submarine when light1 what the bridge is to the ordinary steamer4 ,other members of the crew may be upon the superstructure or deck just below1 while others again are down inside1 attending to their duties there4 ,under these conditions the inside is by no means an unpleasant place4 ,plenty of fresh air comes down through the open hatches and through the ventilators1 it being drawn down through the latter by means of a fan4 ,preparations are then made for submerging4 ,the hand-rail along the little deck is removed4 ,the upper steering wheel and compass are covered up or shut away into the coverings provided for them1 the wireless apparatus1 if provided1 is removed and the mast shut down4 ,hatches are securely closed and valves in the ventilating pipes are closed4 ,in fact every opening is shut and made water-tight so that no risk shall be run of diving prematurely and taking in water accidentally4 ,the quarter-master transfers himself to the steering wheel inside1 where he has another compass to guide him1 not of the magnetic variety this time but a cunning application of the gyroscope4 ,the commander1 too1 having descended before the last hatch was closed down1 takes his stand at the eyepiece of the periscope1 since that is now his only means of seeing what is going on above4 ,another man takes his place at the wheel which controls the diving rudder1 conveniently near to which is a pressure gauge so connected to the outer water that as the ship dives its depth is recorded upon its dial3 that in effect is to him what the compass is to his comrade at the other wheel4 ,with every movement of men there needs to be adjustment made to keep the ship on an even keel4 ,otherwise she would go down by the bow or down by the stern according as the men's weight shifted towards either end4 ,this is arranged for by two small tanks formed in the structure of the vessel1 one at either end4 ,connected together by pipes and controlled by compressed air1 water can be transferred from one to the other at will and so the balance be always kept4 ,quite simple manipulations of a valve serve to accomplish this delicate balancing performance4 ,it is perhaps not of such importance at this stage1 but in a moment1 when the whole vessel will be under water1 a very little movement indeed will suffice to upset the equilibrium4 ,next water ballast is admitted into certain other spaces in the ship's structure1 these spaces being called1 because of the use to which they are put1 ballast tanks4 ,gradually1 as the incoming water increases the weight of the vessel1 she sinks until she is awash4 ,then the diving rudders are set at the right angle 7a pendulum serves to show the angle at which the boat points7 and down she goes4 ,as the pressure-gauge indicates the approach to the required depth the rudder is flattened out a little until just that position is found which keeps the boat under at the desired depth4 ,of course1 when all hatches and openings were closed the supply of fresh air was cut off and after that the crew had to depend upon the air contained in the submarine4 ,also1 they had to stop the engine1 for without air it cannot work3 nor can it work without giving off fumes1 which1 if admitted to the ship1 would soon suffocate the crew4 ,just before closing up1 therefore1 the engine is stopped and electric motors take up the task of driving the ship4 ,now suppose that1 while running submerged1 the commander espies1 through his periscope1 an unsuspecting enemy4 ,he tries forthwith to get as close as he can4 ,having noted the direction of the vessel and which way she is going and as far as possible her speed1 he submerges more deeply1 in all probability1 lest the white streak which represents the wake caused by his periscope should reveal his presence4 ,for possibly she is one of those terrible destroyers in fair fight with which he has but a poor chance4 ,his only safety lying in complete invisibility1 he therefore submerges entirely1 trusting to his calculations to lead him in the desired direction4 ,thus he attempts and1 if he have good luck1 he succeeds in getting reasonably near to his foe4 ,then he must try so to manoeuvre that his bow shall at the right moment be pointing towards the quarry1 for his torpedo tubes are in the bow and they are fixed1 or nearly so at all events1 so that he can only fire them in a direction nearly1 if not precisely1 in the direction of the centre line of his ship4 ,nay1 he must do even more than that4 ,it will not do to fire the torpedo directly at the ship1 for a torpedo is comparatively slow4 ,suppose it is capable of forty miles an hour1 and the other ship is a mile away3 the torpedo will take ninety seconds to reach it4 ,and in that time it may have travelled a mile or so itself4 ,so the submarine man has to allow for that4 ,occasionally1 therefore1 he comes up a little for a moment in the hope of getting a sight of the enemy while not revealing his own presence4 ,or perhaps he may decide to risk being seen and caught1 trusting to the chance of getting his own blow in first4 ,he needs to be a most resourceful man1 with clear and keen judgment and supreme self-confidence1 or he can never grapple with such a task4 ,supposing1 then1 that he succeeds in getting undetected into a favourable position1 as he thinks2 at the critical moment the other ship may change its course1 and the whole scheme goes awry4 ,perhaps he then tries to follow1 but that is bad1 for the end of a ship is not nearly so good a target as the side and the part hit is not so vulnerable4 ,the first torpedo may1 however1 so disable the vessel as to give him chance to get into position for a second and better shot4 ,anyway1 when he thinks he has got his best chance he lets off a torpedo1 immediately diving to be safe out of harm's way for a while4 ,then he rises to see the result of his work4 ,if successful he would be sure to hear the sound1 for water is an excellent sound-conductor and a submarine is like a gigantic telephone ear-piece4 ,it must be a nerve-racking job at the best of times1 for the submarine is a very vulnerable craft4 ,a member of the crew of a ,german submarine captured during the war is reported to have said that out of ten submarines attacked1 nine were sunk4 ,that may or may not be true1 but it is certain that a very little damage1 which would hardly affect an ordinary craft1 is enough to sink a submarine4 ,that is because1 in order to be able to sink at will1 the reserve of buoyancy has to be very low4 ,an ordinary surface ship has at least as much of its bulk above water as below3 hence it can take on board a weight of water almost equal to1 if not exceeding its own weight before it sinks4 ,at the best a submarine has not more than #cj per cent of excess and so it sinks if water amounting to only #cj per cent of its weight gets into it4 ,in other words1 the reserve in one case is at least #ajj per cent3 in the other at most #cj per cent4 ,during the war a submarine saw and tried to track down1 somewhat after the manner described1 a slow1 steady-going collier which plies between ,london and the north carrying coal for a ,london gas-works4 ,having1 as it thought1 got into position for discharging its torpedo it rose for a final look when 7it must have been to the amazement of the crew7 the collier was seen making straight for them4 ,what they really thought no one will ever know1 for the collier had the best of the encounter1 the submarine was crushed beneath her blunt bows and sank1 no doubt1 for ever4 ,the mere fact that a slow1 clumsy1 heavily-laden collier could ever thus vanquish an up-to-date submarine is eloquent testimony to their vulnerability4 ,many a submarine1 too1 has fallen to the shells of an armed fishing trawler simply because the shells of the latter were so much quicker in action than a torpedo1 coupled with the fact that one well-placed shot1 by preventing a submarine from diving1 renders it almost helpless4 ,some submarines1 however1 have a gun on the deck1 so that when light they can fight like a destroyer or other lightly-armed vessel4 ,the gun shuts down into a cavity when the vessel goes below4 ,the periscope1 which forms such an important part of the submarine's equipment1 is really very little more than a telescope4 ,on the top there is a little mirror1 or more probably a prism or three-cornered piece of glass which serves precisely the same purpose in that it reflects exactly as a mirror does4 ,this is so placed that it throws the light from distant objects down the tube into the interior of the ship4 ,in the tube are lenses very like those of an ordinary telescope and the light may be made to throw a picture upon a little table or screen or else can be viewed through another prism directly by the eye4 ,in either case the periscope is just like an ordinary telescope set up vertically with a prism at the top so that it can see at right angles1 and possibly another at the bottom so that the picture can be viewed at right angles to the direction of the tube4 ,the latter is necessary only for the convenience of the observer1 since otherwise he would have to be upon his back to look up the tube4 ,the whole apparatus can be rotated mechanically and a scale forms a means of measuring the precise direction in which the prism or mirror is at any moment pointed4 ,this is useful for measuring roughly the position of the prey1 and it may even be used as a rough means of getting the range4 ,another feature is the gyroscope compass1 to which a passing reference has already been made4 ,it is fairly well known that an object when spinning exhibits properties quite different from those which it possesses when still4 ,a boy's top is a familiar illustration1 for while spinning it will stand perfectly steady1 supported only upon a tall peg with a sharp point1 a pose which it will absolutely refuse to maintain when not spinning4 ,now fortunately for the present purpose it so happens that one of the peculiarities of the gyroscope or spinning-wheel is this3 that if mounted in a certain way it persists in placing its axis in the same plane as that in which the axis of the earth lies4 ,if you imagine for a moment a plane or flat surface of which the earth's axis forms a part you will see that wherever that plane cuts the surface of the earth will be a line in a north and south direction4 ,consequently1 if any horizontal object has its axis in that same plane it1 too1 will always point north and south4 ,a wheel1 small but heavy1 is therefore mounted with its axis supported horizontally upon a little metal raft floating in a trough of mercury and driven round at a very fast speed by a small electric motor fixed in it4 ,whatever its position may be to start with1 this revolving wheel will in a short time slew itself round upon the supporting mercury until its own axis is in the same plane as the axis of the earth3 until1 in fact1 its axis points due north and south4 ,arrived in that position1 it will remain there no matter how the ship upon which it stands may turn4 ,since it floats freely upon mercury the motion of the ship has little effect upon it1 so little indeed1 that it has no difficulty in following its own peculiar bent1 even if the ship be describing circles4 ,the advantages of this are various3 two of them may be stated4 ,first1 the apparatus points to the actual geographical north and not to the magnetic north1 which is a slightly different direction and one1 moreover1 subject to frequent variation4 ,second1 it is absolutely unaffected by the presence of iron or other magnets1 a very fruitful source of error in the magnetic compass when used upon an iron ship close to steel guns and electrical machinery4 ,surrounded with iron as is the compass in the interior of a submarine1 the magnetic needle practically refuses to work at all1 so that1 although employed on other ships1 it is on the submarine that the gyro-compass finds its most important field of usefulness4 ,the pressure-gauge or manometer1 which indicates the depth1 is probably not different in any respect1 except in its dial1 which is marked in feet-depth instead of in pounds-pressure1 from the pressure-gauge used on steam boilers4 ,it has either a little cylinder with a piston in it which the water presses upwards more or less against the force of a spring1 a diaphragm which is bent more or less1 or a bent tube which tries to straighten itself out as the pressure inside it increases4 ,the older submarines derived their power from petrol engines similar to those which drive high-power motor-cars1 but nowadays these have given place to engines of the type invented by the unfortunate ,diesel who1 after making one of the most brilliant and successful inventions of modern times1 committed suicide1 apparently in the height of his success4 ,these engines burn cheap heavy oil in place of the costly refined petrol3 they are exceedingly reliable and well-behaved1 and are free from many of the troubles which affect the petrol motor4 ,they are referred to in more detail in another chapter4 ,in twin-screw boats there are two distinct engines1 one for each propeller4 ,each engine1 too1 is coupled to a dynamo by which it can generate electric current1 which is stored in large accumulator batteries until required and then withdrawn to drive the dynamos as motors while the boat is submerged1 for if you feed a dynamo with current it becomes a motor4 ,a great deal of work is done1 on the submarine1 by compressed air1 of which large stores are carried in strong steel cylinders4 ,for example1 the ballast is ejected from the ballast tanks1 when the boat is required to rise1 not by pumps but by the action of compressed air from a cylinder4 ,the simple movement of a tap thus suffices to blow out the water in a very short time4 ,the torpedoes1 too1 are given their initial push which sends them out of their tube into the water by compressed air4 ,in other ways1 too1 compressed air is employed and to facilitate its use there are many tubes and valves whereby the cylinders and other apparatus are connected4 ,like all things human1 these tubes and valves have their defects1 which in this case means that they leak somewhat1 but this defect is of value since the leaking air helps to keep pure and sweet the air inside the boat which1 when submerged1 the men have to breathe4 ,to what extent it is used ,i do not know1 but it is a fact that certain chemicals1 caustic soda for instance1 have the power to absorb the objectionable carbonic acid which makes tightly-shut rooms seem close and uncomfortable1 and if something of that sort be employed1 it1 together with the fresh air which thus leaks in by accident1 is undoubtedly enough to enable men to live under water for many hours at a stretch4 ,on the other hand1 several instances are on record in which strong healthy young officers have1 after a course of service on a submarine1 been found to be suffering seriously from chest and lung trouble1 brought on1 no doubt1 by long spells of duty in this unhealthy atmosphere4 ,it used to be the custom to keep some white mice on board a submarine to give warning of the impurities in the air4 ,being very susceptible to the smell of petrol vapour1 which used to be a source of considerable danger1 and also to carbonic acid1 these little creatures squeaked with anxiety some time before the conditions became really dangerous1 thus giving timely warning4 ,there is an instrument1 however1 which will give an indication of this sort and probably it has been brought in to reinforce the mice if not actually to supplant them4 ,this interesting little instrument1 which the gasworks people use for detecting leakage1 consists of a metal drum with a porous diaphragm4 ,normally the pressure of the atmosphere upon the diaphragm is equalled and balanced by the pressure of the air inside the drum1 but if there be gas in the air this balance is upset1 the diaphragm is bulged in or out and a finger is thereby moved1 which movement forms a measure of the amount of gas present4 ,in conclusion1 we may fittingly take a glance at what happens when a submarine founders4 ,only a few years ago this occurred with lamentable frequency1 though now it is quite rare except under the actual stress of warfare4 ,several interesting schemes were therefore invented to give the men at least a sporting chance of getting to safety4 ,one was to make the conning-tower detachable and water-tight1 so that the men could get into it1 fasten themselves in and float up to the surface4 ,the practical difficulties in the way prevented this being a success4 ,for example1 if sufficiently detachable in an emergency it was difficult to make it sufficiently water-tight in ordinary use4 ,another and better device provided the men with small helmets and jackets1 like the dress of a diver very much simplified4 ,one of these for each man was stored in an accessible place in the boat and partitions were devised inside the hull itself in order that whatever happened there should be air entrapped somewhere wherein the men could live for a time and put on their helmets in safety4 ,then1 thus provided1 they could crawl out through the hatchway and float up to the surface4 ,arrived there they could inflate their jackets by blowing into them1 open the window of the helmet and float upon the surface in comparative safety until rescued4 ,this apparatus was largely installed in ,british submarines and a tank was built at ,portsmouth where the men could actually practise with it under water4 ,a third device may also be mentioned4 ,this takes the form of a buoy fitted into a recess in the boat's upper surface4 ,sufficient line is coiled up inside it and when the occasion arises it can be released from inside4 ,this does not in itself save the crew but it may go a long way towards ensuring their safety by letting those above know just where the sunken craft is and guiding them in their efforts to raise it4 ,the torpedo1 the weapon without which the submarine would be practically useless1 is dealt with in another chapter4 ,enough has been said here to give a good general idea of these interesting craft1 their fittings1 their uses and the sort of life which befalls those who man them4 ,,chapter ,,xx ,,the ,,story ,,of ,,wireless ,,telegraphy ,for ages people were puzzled as to the nature of light4 ,pythagoras1 that old ,greek who invented what we now call the forty-seventh proposition of ,euclid1 thought that the bright body shot off streams of tiny particles which literally hit the observer in the eye4 ,sir ,isaac ,newton thought the same1 but for once the greatest scientist of all time was wrong4 ,for when the ,danish astronomer1 ,romer1 discovered that light travelled at the rate of somewhere about #ahf1jjj miles per second it dawned upon people that it was scarcely believable that particles of any kind could by any means be made to move so fast4 ,so they set about searching for a new explanation1 and they found it in the idea that light was conveyed from the bright body to the observer's eye by means of waves1 and as there cannot be waves of nothing they had to imagine a something to exist in all the vacant spaces of the universe capable of forming the waves of light4 ,this something was called the luminiferous ether or light-bearing ether4 ,we can neither see1 feel1 taste nor hear it4 ,our senses tell us nothing about it4 ,indeed1 if it does really exist it must be so very different from anything that we do know by our senses that one is often tempted to doubt its existence4 ,still1 it explains so many things which are otherwise unexplainable and enables us so correctly to reason from one phenomenon to another that our reason forces us to accept it as a fact1 at all events until something better comes along4 ,this wave theory in regard to light was finally set at rest by the curious discovery about a century ago by ,dr4 ,thomas ,young of ,london that if two lots of light were brought together in a certain way they produced darkness4 ,now if a ray of light were a stream of particles1 two such rays would inevitably and always1 if added together1 produce a doubly brilliant light1 and under no conceivable circumstances could they do anything else4 ,but two lots of waves can1 and do1 under the proper conditions1 neutralize each other so as to produce rest4 ,this mutual action upon each other of two sets of waves can be very simply exhibited by two violin strings tuned to nearly but not quite the same note4 ,if you have a violin handy1 try it and you will find that when either string is plucked separately it gives a steady continuous sound1 but if both be plucked at the same time they give a throbbing sound4 ,that is because1 periodically1 as one string is coming up the other is going down1 so that they neutralize each other1 while at other times1 owing to the fact that one is vibrating faster than its fellow1 both are rising and falling together4 ,when neutralizing each other there is a momentary silence1 while in between the silences come the times when both are acting together and therefore producing a specially loud sound4 ,and so as the vibrations of the faster keep gaining upon those of the slower string one hears a continual crescendo and then diminuendo repeated over and over again4 ,so two sets of sound waves sometimes produce silence4 ,and in like manner two sets of light waves can be made so to interfere 7that is the technical term7 that together they produce darkness4 ,so for a hundred years or more people have1 generally speaking1 accepted the idea that light consists of waves in a medium called ,the ,ether4 ,heat also is brought to us from the sun and from any distant hot body by similar means1 the difference between light waves and heat waves being simply in their wave length or the distance apart4 ,the different colours of light1 too1 are to be accounted for by different wave lengths4 ,you have of course seen how a magnet can act upon a piece of iron at a distance4 ,you may1 too1 have tried the experiment of jerking a magnet past a piece of wire1 thereby generating an electric current in the wire4 ,both those things need1 for explanation1 that we assume the existence of a something invisible and undetectable by our senses between the magnet and the iron and between the magnet and the wire1 by which the action of one is conveyed to the other4 ,so people imagined another ,ether capable of acting like a link between the magnet and the iron and between the magnet and the wire4 ,now just about half a century ago a celebrated professor of ,cambridge ,university brought all these facts about light1 heat1 magnetism and electricity together and by skilful reasoning showed that but one ,ether sufficed to explain all these things4 ,he showed how magnetic and electric forces acting together could produce waves like those of light and heat4 ,and finally he demonstrated by figures that waves so formed would necessarily travel at the very speed at which light and heat are known to move4 ,this is known as the electro-magnetic theory of light4 ,and not content with showing the nature of things already known1 ,professor ,clerk-,maxwell added a prophecy that there were other waves in existence of longer wave length1 which no one then knew how to make or to detect if made4 ,following up this prophecy many investigators sought these waves1 and the first to find them was ,professor ,hertz of ,carlsruhe in ,germany4 ,fortunately for his position in the minds of ,english people he died before the ,war1 so that his name is not sullied by the stupidities of which ,german professors in more recent days have been guilty4 ,on the contrary1 his writings show him to have been a kindly1 modest1 genial soul1 and particularly gratifying is his generous assertion in one of his books that had he not himself discovered these waves he is certain ,sir ,oliver ,lodge would have done so4 ,he seemed quite anxious to share the credit of his discovery with his ,english colleague as he called him4 ,let us see then how these ,hertzian waves are produced4 ,in the year #agdh a ,dutch experimenter named ,cuneus thought he would try to electrify water4 ,he got a glass flask and filled it with water into which he let drop one end of a chain connected to an old-fashioned frictional electrical machine4 ,thus he stood with the flask in his hand while a friend worked the machine4 ,after a short time the friend stopped and ,cuneus took hold of the chain to lift it out1 when to his astonishment he received a shock which knocked him over1 broke his flask and sent him to bed to recover4 ,unwittingly ,cuneus had invented what became known thereafter as a ,leyden jar1 ,leyden being the town in which he lived4 ,it consisted1 you will notice1 of two conductors1 the water and his hand1 with an insulator1 the glass1 in between4 ,to understand or rather to give ourselves a useful working explanation of how such an apparatus comes to be charged we must first imagine that everything contains a certain normal amount of electricity which we can by certain means add to or take away from at will4 ,when we add some to anything we say we have given it a positive charge3 when we subtract some we say that we have imparted a negative charge4 ,clearly1 if we add some to one thing we must first obtain it from something else1 and if we take some away from one thing we must do something with what we have taken1 and so we add it to something else4 ,therefore whenever we charge anything positively we must charge something else negatively and vice versa4 ,now the ease with which we can thus charge two bodies seems to depend upon their nearness to each other1 so that the easiest things to charge are two plates of metal separated by the thinnest possible insulator4 ,modern ,leyden jars are usually formed of a thin glass jar with a lining inside and out of tinfoil4 ,the ,leyden jar is1 however1 only one form of the piece of electrical apparatus known as an electrical condenser1 and many other forms exist4 ,for example1 a flat sheet of glass with foil above and below1 or several such piled one on top of another4 ,an eminent electrician whom ,i know has recently made some of two tin patty pans put bottom to bottom1 nearly but not quite touching1 the whole being enclosed in a solid block of paraffin wax4 ,and ,i might describe many other forms1 but whatever they may be every one is essentially two conductors with an insulator between4 ,now when a condenser has been charged its charges remain for a considerable time unless they be given a chance to escape4 ,suppose you have a charged condenser and that you take a wire and with it touch simultaneously both the conductors1 the surplus on one plate will rush through the wire and make good the deficiency upon the other2 it will thus in an instant become discharged4 ,now several scientific men had suggested1 before ,hertz's time1 that when that occurred something else happened too4 ,they thought that the charge did not simply rush from one plate to the other instantly1 but that it oscillated to and fro for a period2 that the surplus rushing round overshot the mark1 so to speak1 and not only made up the deficiency but caused a surplus on the opposite plate1 after which this new surplus rushed back again through the wire1 doing the same thing1 though to a less and less degree1 several times over before a condition of perfect rest was reached4 ,to use a simple analogy1 it was thought that the surplus swung to and fro like the swinging of a pendulum4 ,we know that a pendulum swings because of its inertia1 and electricity possesses a property very like inertia which1 it was thought1 would cause it to behave in the same way4 ,the ,ether waves travel at the rate of #ahf1jjj miles per second1 so that if1 as was thought1 a sudden current of electricity gives rise to a wave1 currents which succeed each other at the rate of one per second would produce waves #ahf1jjj miles apart4 ,a hundred currents per second would give a wave length of #ahfj miles4 ,a thousand per second would give #ahf miles4 ,but a thousand succeeding currents per second are difficult to produce1 and #ahf miles is so very much greater than the tiny fraction of an inch1 which is the length of the light and heat waves1 that ,hertz had to find some way of making currents succeed each other faster even than a thousand times per second4 ,so he thought of these oscillating currents which were supposed to occur when a condenser was discharged1 and he rigged up a condenser with an induction coil and a spark gap in a way which he thought would do what he wanted4 ,there is not room here to explain the ,induction ,coil1 indeed it is so well known that it will be quite sufficient to state that it is an apparatus which takes steady current from a battery and gives back instead a lot of little spurts or splashes of current at a rate of1 say1 fifty or one hundred splashes per second1 according as we adjust the little vibrating spring which forms a part of the coil4 ,we can so connect this to a condenser that each splash will charge it up2 and we can combine with it a spark-gap1 that is to say1 a gap between two knobs1 so that every time it is charged it immediately discharges again through this gap4 ,thus we may have1 say1 one hundred splashes per second1 and each splash is followed by several oscillations across the air-gap1 the oscillations taking place at the rate of perhaps a million per second4 ,each series of oscillations is called a train4 ,now a million per second gives a wave-length somewhere about what ,hertz wanted1 so he arranged his apparatus as just described4 ,for a condenser he used two metal plates a little distance apart1 the air between forming the insulating material4 ,he set up his apparatus in a large room1 and having started the coil he moved about with a nearly complete hoop of wire1 the ends of which nearly touched4 ,working in darkness he found after a while that sometimes he could see little sparks1 very small but just visible across the gap between the ends of the bent wire4 ,those sparks only occurred when the coil was in action1 and so he knew that the one was the result of the other's work4 ,by careful painstaking experiment he found that the sparks were unquestionably caused by waves1 and that the waves moved with the same speed as light1 also that they could be reflected and refracted just on precisely the same principles as those which control light4 ,moreover1 he measured the wave-length4 ,at first sight it seems incredible that anyone could measure the distance apart of waves which travel at such a speed as #ahf1jjj miles per second1 but fortunately1 by a special application of interference1 it is possible to make the waves stand still and tamely submit to measurement4 ,an example of this can be seen by simply tapping a glass of water1 when the ripples being reflected off the sides interfere with each other and become stationary4 ,stationary waves are half the wave-length of the original waves1 and by using this method ,hertz was able to make a measurement which at first sight seems beyond the bounds of possibility4 ,thus ,hertz discovered how to make the waves which ,clerk-,maxwell had predicted and also how to detect them when made4 ,it was not long before the idea arose of using these waves for signalling to a distance4 ,many experiments were made but with no very striking success until #ahif when ,marconi first came to ,england4 ,hertz had noticed that the farther apart he placed the plates of his condenser the farther could he get his tell-tale spark1 so ,marconi saw that the plates of his condenser1 too1 must be far apart4 ,he also found that the earth could be used as one of the plates1 that in fact there was a great advantage in so using it4 ,so1 one plate having to be the earth itself and the other removed as far as possible from it1 the tall masts of the wireless antenna came into being4 ,illustration3 ,,listening ,,for ,,the ,,enemy4 ,special sensitive cylinders are sunk into the ground to which the usual telephonic apparatus is fixed4 ,this enables the sappers to detect any underground operations by the enemy4 ,when ,marconi came to ,england he was taken under the kindly wing of ,sir ,william ,preece1 the veteran engineer of the ,post ,office1 and the facilities which ,sir ,william was able to give no doubt helped largely in his subsequent rapid progress4 ,after a few experiments in ,london he got to work across the ,channel1 sending messages from the ,north ,foreland ,lighthouse to ,wimereux on the coast of ,france1 including congratulatory messages between the ,french authorities and good ,queen ,victoria4 ,a little later he was signalling from ,niton in the ,isle of ,wight to the mainland and to the far west at the ,lizard4 ,the first wireless telegram which was actually paid for was sent by ,lord ,kelvin1 the father of cable telegraphy1 from ,niton to the mainland1 whence it was transmitted by land wires to ,sir ,george ,stokes4 ,this incident1 so interesting because of its marking a stage in the history of this great invention1 also because of the persons concerned1 occurred in #ahih4 ,but ,marconi was quickly increasing the range of his apparatus far beyond anything already mentioned4 ,he journeyed in the ,italian warship ,carlo ,alberto as far north as ,cronstadt and as far east as ,italy1 keeping in communication with ,england all the time4 ,then he crossed the ,atlantic1 again keeping up communication with ,england the greater part of the journey4 ,raising his wires to a great height by means of kites he was soon able to signal from ,nova ,scotia to the great station just previously built at ,poldhu in ,cornwall1 and then wireless telegraphy from land to land across the great ocean became an accomplished fact4 ,we all know how things have progressed since then4 ,a telegram by ,marconi is as commonplace to-day as a telegram by cable4 ,the ,british ,government is now engaged upon a series of stations dotted about the globe in such a way that every part of the widely separated ,british ,empire shall be in constant touch with every other part by wireless telegraphy4 ,in other words1 the range of the system has now become such that nothing further is needed4 ,the ,british ,admiralty has a few wires slung to posts on the top of the offices in ,london1 and those few wires enable touch to be maintained with ships4 ,as almost every intelligent newspaper reader in ,great ,britain knows1 the ,germans were in the habit1 during the war1 of sending news to the ,united ,states by wireless telegraphy1 which news was always picked up by the ,admiralty installation and circulated to the ,british newspapers1 often to the amusement of their ,british readers4 ,the famous ,emden1 too1 which had such a run of success until it encountered the ,australian cruiser ,sydney1 met its end entirely through the intervention of wireless telegraphy4 ,these incidents give us a good idea of the usefulness of wireless in naval warfare4 ,in military work it is used chiefly in connection with air-craft1 but of that more will be said in another chapter4 ,illustration3 ,,transmitter4 ,,receiver4 ,,diagram ,,showing ,,the ,,principle ,,by ,,which ,,the ,,aerials ,,are ,,connected ,,to ,,the ,,apparatus4 ,,chapter ,,xxi ,,wireless ,,telegraphy ,,in ,,war ,the history of this wonderful invention has been described in the preceding chapter4 ,now we will see how it is applied in warfare4 ,let us take first its uses in connection with the ,navy4 ,the aerial wires or antenna are stretched to the top of the highest mast of the vessel4 ,where there are two masts they often span between the two4 ,ships which have masts for no other reason are supplied with them for this special purpose4 ,in the case of submarines1 the whole thing1 mast and wires included1 is temporary and can be taken down or put up quickly and easily at will4 ,the stations ashore are equipped much after the same manner as are the ships1 except that sometimes they are a little more elaborate1 as they may well be since they do not suffer from the same limitations4 ,for example1 the well-known antenna over the ,admiralty buildings in ,london consists of three masts placed at the three corners of a triangle with wires stretched between all three4 ,however these wires may be arranged and supported they are very carefully insulated from their supports1 for when sending they have to be charged with current at a high voltage and need good insulation to prevent its escape1 while1 in receiving1 the currents induced in them are so very faint that good insulation is required in order that there may not be the slightest avoidable loss4 ,the function of these wires1 it will be understood1 is to form one plate of a condenser1 the earth being the other plate and the air in between the dielectric or insulator4 ,in the case of ships the earth is represented by the hull of the vessel4 ,it makes a particularly good earth since it is in perfect contact with a vast mass of salt water1 and that again is in contact with a vast area of the earth's surface4 ,salt water is a surprisingly good conductor of electricity4 ,in land stations earth consists of a metal plate well buried in damp ground4 ,the whole question of conduction of electricity through the earth is very perplexing4 ,there seems to be resistance offered to the current at the point where it enters the ground1 but after that none at all4 ,consequently the resistance between two earth plates a few yards apart and between similar ones a thousand miles apart is about the same4 ,though the earth is made up mainly of what1 in small quantities1 are very bad conductors indeed1 taking the earth as a whole it is an exceedingly good conductor4 ,that makes it all the more important that where the current enters should be made as good a conductor as possible1 and the construction and location of the earth plates is therefore very carefully considered so as to get the best results4 ,wires1 of course1 connect the antenna to the earth1 thereby forming what is called an oscillatory circuit4 ,the ordinary electric circuit is a complete path of wire or other good conductor around which the current can flow in a continuous stream4 ,an oscillatory circuit is one which is incomplete1 but the ends of which are so formed that they constitute the two plates of a condenser4 ,in that way1 according to theory1 the circuit is completed between the two ends by a strain or distortion in the ,ether between them4 ,a continuous current will not flow in such a circuit1 but an alternating1 intermittent or oscillating current will flow in it in many respects as if there were no gap at all but a complete ring of wire4 ,at some convenient point in this oscillatory circuit are inserted the wireless instruments1 one set for sending and the other set for receiving1 either being brought into circuit at will by the simple movement of a switch4 ,in small installations the central feature of the sending apparatus is an ,induction ,coil operated by a suitable battery or by current from a dynamo4 ,connected with it is a suitable spark gap consisting of two or three metal balls well insulated and so arranged that the distance between them can be delicately adjusted4 ,this is generally done by a screw arrangement with insulating handles1 so that the operator can safely adjust them while the current is on4 ,the current from the battery or dynamo to the coil is controlled by a key similar to those used in ordinary telegraphy1 the action being such that on depressing the key the current flows and the coil pours forth a torrent of sparks between the knobs of the spark-gap1 but on letting the key up again the sparks cease4 ,since the sparks send out etherial waves which in turn affect the distant receiving apparatus it follows that a signal is sent whenever the key is depressed4 ,moreover1 if the key be held down a short time a short signal is sent1 but if it be kept depressed for a little longer a long signal is sent1 by which means intelligible messages can be transmitted over vast distances4 ,certain specified wave lengths are always used in wireless telegraphy4 ,that is to say1 the waves are sent out at a certain rate so that they follow each other at a certain distance apart4 ,in other words1 it is necessary to be able to adjust the rate at which the currents will oscillate between the antenna and earth4 ,every oscillatory circuit possesses two properties which are characteristic of it4 ,these two properties are known as ,capacity and ,inductance4 ,it is not necessary to explain here what these terms mean precisely4 ,it is quite sufficient just to name them and to state that the rate at which oscillations take place in such a circuit depends upon the combined effect of these two properties4 ,consequently1 if we can arrange things so that capacity or inductance or both can be added to a circuit at will and in any quantity within limits1 we can within those limits obtain any rate of oscillation which we desire and consequently send out the message-bearing waves at any interval we like2 in other words1 we can adjust the wave-length at will4 ,fortunately1 it is very easy to add these properties to an oscillatory circuit in a very simple manner4 ,a certain little instrument called a tuner is connected up in the circuit and by the simple movement of a few handles the desired result can be obtained quickly even by an operator with but a moderate experience4 ,he has certain graduated scales to guide him1 and he is only called upon to work according to a prearranged rule in order to obtain any of the regulation wave-lengths4 ,as a matter of fact1 the instruments are not directly inserted in the antenna circuit1 the circuit that is which is formed by the aerial wires1 the earth and the inter-connecting wires4 ,instead1 the two sides of the spark-gap are connected together so as to form a separate circuit of their own1 the local circuit as we might call it1 and then the two circuits1 the antenna circuit and the local circuit1 are connected together by induction4 ,a coil of wire is formed in each1 and these two coils are wound together so that currents in one winding induce similar currents in the other winding1 and by that means the oscillations set up by the coil in the local circuit are transformed into similar oscillations in the antenna circuit4 ,this transformation involves certain losses1 but it is found in practice to be by far the most effective arrangement4 ,both the circuits have to be tuned to the desired wave length1 but that is done quite easily by the operation of the handles in the tuner already referred to4 ,it is to this coupling together of tuned circuits that ,marconi's most famous patent relates4 ,it is registered in the ,british ,patent ,office under the number #gggg1 and hence is known as the four sevens patent4 ,it has been the subject of much litigation1 which proves its exceptional importance1 and it is to the fact that the ,marconi ,company have been able to sustain their rights under it that they owe their commanding position to-day in the realm of wireless telegraphy4 ,the ,receiving ,apparatus also consists of a separate local circuit which can be coupled when desired to the antenna circuit through a transformer4 ,the same simple tuning arrangement is made to affect this circuit also1 so that the multiple tuner1 as the instrument is called1 controls all the circuits both for sending and for receiving4 ,the oscillations caused in the antenna circuit by the action upon it of the etherial waves flowing from the distant transmitting station pass through one winding of the transformer and thereby induce similar oscillations in the local receiving circuit which are made perceptible by the receiving instrument4 ,reference has already been made to the original form of receiving apparatus called the ,coherer4 ,this1 however1 has been very largely superseded by the ,magnetic ,detector of ,marconi and the ,crystal ,detector1 both of which make the signals perceivable as buzzing sounds in the telephone4 ,the magnetic detector owes its existence to the fact that oscillations tend to destroy magnetism in iron4 ,it is believed that every molecule of iron is itself a tiny magnet4 ,if that be so one would expect every piece of iron to be a magnet1 which we know it is not4 ,we can always make a piece of iron into a magnet by putting another magnet near it1 but when we take the other magnet away the iron loses its power1 or to be precise it almost loses it4 ,a piece of even the best and softest iron having once been magnetized retains a little magnetic power which we call residual magnetism4 ,all this is easily explained if we remember first that a heap of tiny magnets lying higgledy-piggledy would in fact exhibit no magnetic power outside the heap4 ,if1 however1 we brought a powerful magnet near them it would have the effect of pulling a lot of them into the same position1 of arranging them in fact so that instead of all more or less neutralizing each other they could act together and help each other4 ,then the heap would become magnetic4 ,on removing the powerful magnet1 however1 a lot of the little ones would be sure to fall down again into their old places and so the heap would at once lose a large part of its power1 yet some would remain and so it would retain a certain amount of residual magnetism4 ,if1 then1 you were to give the table on which the little magnets rest a good shake1 the higgledy-piggledyness would be restored and even the residual magnetism would vanish4 ,so we believe that the little molecules lie just anyhow1 wherefore they neutralize each other and the mass of iron is powerless4 ,when another magnet comes near1 however1 they are more or less pulled into the right position and the iron becomes magnetized4 ,when the magnet is removed the magnetism which it produced is largely lost1 and if last of all we give the iron a smart blow with a hammer even the residual magnetism vanishes too4 ,now1 oscillations taking place in the neighbourhood of a piece of iron possessing residual magnetism have much the same effect as the blow of a hammer4 ,probably because of its rapidity an oscillating current shakes the molecules up and strews them about at random1 entirely destroying any orderly arrangement of them4 ,and ,marconi used that fact in detecting oscillations4 ,two little coils of wire are wound together1 one inside the other4 ,through the centre of the innermost there runs an endless band of soft iron wire4 ,stretched on two rollers this band travels steadily along1 the motive power being clockwork1 so that it is always entering the coil at one end and leaving it at the other4 ,as it travels it passes close to two powerful steel magnets1 so that as it enters the coil it is always slightly magnetized4 ,the oscillations are passed through one of the two concentric coils1 and their action is to remove suddenly the residual magnetism in that part of the moving wire which is at the moment passing through4 ,that sudden demagnetization then affects the second of the concentric coils1 inducing currents in it1 not of an oscillating nature but of an ordinary intermittent kind which can make themselves audible in a telephone which is connected with the coil4 ,this arrangement1 then1 causes the oscillations1 which will not operate a telephone1 to produce other currents of a different nature which will4 ,the reason why oscillations have no effect in a telephone is no doubt because they change so rapidly1 at rates1 as has been mentioned already1 of the order of a million per second4 ,the telephone diaphragm1 light and delicate though it is1 is far too gross and heavy to respond to such rapidly changing impulses as that4 ,in the magnetic detector the difficulty is overcome by making them change the magnetic condition of some iron wire which change in turn produces currents capable of operating a telephone4 ,the ,crystal ,detector achieves the same result in another way4 ,there are certain substances1 of which carborundum is a notable example1 which conduct electricity more readily in one direction than the other4 ,most of these substances are crystalline in their nature1 and hence the detector in which they are used gets its name4 ,carborundum1 by the way1 is a sort of artificial diamond produced in the electric furnace and largely used as a grinding material in place of emery4 ,it is easy to see that by passing an oscillating current1 which is a very rapidly alternating current1 through one of these one-direction conductors one half of each oscillation is more or less stopped4 ,oscillations1 again1 are surgings to and fro3 the crystal tends to let the tos go through and to stop the fros4 ,that does not quite explain all that happens4 ,it is not fully understood4 ,the fact remains1 however1 that by putting a crystal in series with the telephone the oscillations become directly audible4 ,the term in series with means that both crystal and telephone are inserted in the local receiving circuit so that the currents in that circuit pass through both in succession4 ,the resistance of the crystal being very great1 a special telephone is needed for use with it4 ,it is quite an ordinary telephone1 however1 except in that it is wound with a great many turns of very fine wire and is therefore called a high-resistance telephone4 ,whichever of these detectors be used1 then1 the operator sits1 with his telephone clipped on to his head1 and with his tuner set for that wave length at which his station is scheduled to work1 listening for signals4 ,he may go for hours without being called up1 and in the meantime he may hear many signals intended for others4 ,he knows they are not for him1 since every message is preceded by a code signal indicating to whom it is addressed4 ,under the conditions of warfare there is far more listening than there is sending1 but when a station wishes to send the operator just switches over1 cutting out his receiving apparatus and bringing his transmitting instruments into operation1 and1 having adjusted his tuner for the wave length of the station to which he desires to communicate1 he flings out his message4 ,in war-time1 too1 there is much listening for the signals of the enemy1 which is the reason why as few messages are sent out as possible4 ,in this case the man sits with his telephone on his head carefully changing his tuner from time to time in the endeavour to catch any message in any wave-length which may be travelling about4 ,this searching the ether for a chance message of the enemy must be at times a very wearisome job1 but it must be varied with very exciting intervals4 ,on aircraft it is clear that no earth connection is possible4 ,the antenna in that case usually hangs vertically down from the machine or airship4 ,under these conditions the valuable effect of the earth connection is of course lost4 ,as will be remembered1 the earth-connected apparatus sends forth waves which cling more or less to the neighbourhood of the earth's surface1 while those from the non-earthed apparatus as used by aircraft tend to fly in all directions4 ,the latter apparatus is in fact almost precisely similar to that which ,hertz used in his first experiments4 ,hence the range is comparatively poor under these conditions1 but it is good enough for very valuable work in warfare4 ,communication between airman and artillery by this means has revolutionized the handling of large guns in the field4 ,to save the airman from the accidental catching of his aerial wire in a tree or on a building there is sometimes fitted a contrivance of the nature of wire-cutters so that he can at any moment cut himself free from it4 ,so far we have dealt almost exclusively with the naval and aerial use of this wonderful invention4 ,it is employed1 though in a lesser degree1 in land warfare4 ,in such cases the aerial may be merely a wire thrown on to and caught up on a high tree4 ,more elaborate devices are used1 however1 such as a high telescopic tower similar to the tall fire-escape ladders of the fire-brigades4 ,anyone who has seen the ladders rush up to a burning building and commence to erect themselves almost before they have stopped will realise how valuable such a machine must be for forming a temporary and easily movable wireless antenna4 ,the power which causes the tall tower to extend itself erect in a few seconds is compressed air carried in cylinders upon the machine1 while the power which takes it from place to place is a petrol motor1 and since the latter can be made to re-charge the storage cylinders it is clear that in it we have a marvellously convenient adjunct to the wireless apparatus4 ,but apart from such carefully prepared devices the men of the ,royal ,engineers are past masters in the art of rigging up1 according to the conditions of the moment1 all sorts of makeshift apparatus whereby signalling over quite long ranges can be carried on by wireless4 ,such improvisations1 could they be recorded1 would constitute war inventions of a high order4 ,,chapter ,,xxii ,,military ,,telegraphy ,telegraphy plays a very important part in warfare4 ,the commander of even a small unit cannot see all that his men are doing or suffering1 but is kept posted by telegraph or telephone1 while communication between units depends very largely indeed upon such means4 ,wireless telegraphy1 in land warfare1 is largely devoted to communication between aircraft and the artillery batteries with which they are working1 and to avoid interference with that important work telegraphy by wire is employed for most other purposes4 ,right at the front this communication is kept up by means of that type of instrument which the soldiers call a buzzer1 for the good and sufficient reason that that is really what it does4 ,in view of the fact that soldiers speak of their home-land1 for which they are enduring all manner of risk and hardship1 and to which they are longing to return1 by the contemptuous-sounding name of ,blighty1 we might expect that what they call a buzzer has nothing whatever to do with making sound1 but in this case the name describes the thing very aptly4 ,its sole purpose and intent is to make buzzing sounds of either long or short duration4 ,perhaps the simplest way in which ,i can describe this useful and interesting invention is by telling you how you can make one for yourself4 ,it is nothing more than an electric-bell mechanism connected up in a certain way4 ,as most people know1 an electric bell contains a magnet made of two round pieces of iron placed parallel and yoked together at one end by means of a third piece of iron1 generally flat1 while on to each round piece is threaded a bobbin of insulated wire4 ,the iron becomes a magnet when1 and only when1 current flows through the wire4 ,near the free ends of the round pieces1 or the poles of the magnet1 to use the orthodox term1 is placed another little piece of iron called the armature1 carried upon a light spring4 ,when the current flows in the wire the armature is pulled towards the poles against the force of the spring1 but when the current ceases the magnet lets go and the armature1 urged by the spring1 swings back again4 ,behind the armature is a little post through which passes a screw tipped with platinum1 and in operation this screw is advanced until its point touches a small plate of platinum carried by the armature4 ,connection for the current is made to this contact screw whence it passes to the armature1 through the spring to the wire upon the magnet1 through that and away4 ,on completing the circuit1 then1 as when you push the button at the front door1 current flows and energizes the magnet4 ,a moment later1 however1 the armature moves1 breaks the contact with the screw and stops the current4 ,then the magnet lets go and the armature springs back1 making contact once more and setting the current flowing again4 ,these actions repeat themselves over and over again quite automatically1 and the hammer which is attached to the armature vibrates accordingly4 ,that is the ordinary familiar electric bell4 ,cut off the hammer and you have a buzzer with which excellent telegraph signals can be sent4 ,so much for the sending apparatus4 ,the receiving device is simply an ordinary telephone receiver4 ,there is sometimes a little confusion in people's minds because of this4 ,a telephone is used1 but it is used as a telegraph instrument4 ,the sounds heard in it are not speech but long and short buzzing sounds which1 being interpreted according to the code of ,morse1 deliver up their message4 ,now the telephone1 by which term is always meant the receiver 7the sending part of the telephone apparatus being a microphone71 is one of the most remarkable pieces of electrical apparatus which the mind of man has ever conceived4 ,it is astonishingly robust4 ,with ordinary care you cannot damage it4 ,there is no need whatever to keep it wrapped in cotton wool or even to keep it in a case4 ,without harm you can put it loose in your pocket4 ,within reason you may even drop it a few times without harm4 ,its cost is only a few shillings4 ,yet its sensitiveness is simply astounding4 ,it will detect the existence of currents so small that any other type of instrument to deal with them has to be extremely delicate and costly4 ,it consists of a magnet fitted into a little brass case with a little piece of soft iron fixed on each pole1 while each of these pole-pieces is surrounded by a tiny coil of wire4 ,the lid of the box is a disc of thin sheet-iron1 and things are so proportioned that the pole pieces nearly but not quite touch this sheet-iron diaphragm4 ,an outer cover1 generally of ebonite1 serves to catch the sound-waves caused by any movement of the diaphragm and convey them to the ear4 ,the action of the permanent magnet tends to pull the diaphragm inwards--to bulge it in slightly--so that it is in a state of very unstable equilibrium4 ,because of this instability a very tiny current flowing through the coils and either adding to or subtracting from the strength of the magnet is sufficient either to draw it still closer or to let it recede a little4 ,whether it approaches or recedes depends upon the direction of the current through the coils and makes no difference to the sound4 ,the movement of the diaphragm is great or small according as the current is strong or weak3 any variation in the current causes a perfectly corresponding movement in the diaphragm4 ,even those very small and very complex changes in air-pressure which give us the sensation of sound are very faithfully followed by this simple bit of sheet iron1 so that the sounds are faithfully reproduced for our benefit4 ,at the moment1 however1 we are not dealing with speech but with buzzing sounds1 which are very simple1 being merely a rapid succession of ticks4 ,the telephone1 it must be remembered1 takes no notice of a steady current1 except when it starts and stops4 ,but each time that occurs it gives a tick4 ,hence1 if we start and stop a current very rapidly1 or to use another term1 make it rapidly intermittent1 we get a rapid succession of ticks1 and if rapid enough they form a humming1 buzzing1 or singing sound4 ,if very fast you can get a positive shriek4 ,the precise character of the sound depends entirely upon the rapidity of the intermittency4 ,now it is easy to see that the current passed through an electric-bell mechanism is intermittent4 ,it is the very nature of the apparatus to make the current intermittent4 ,it is by so doing that it works4 ,therefore1 if we pass the same current which works a bell through a telephone we get a buzzing or humming sound according to the speed of interruption4 ,the vibration of the armature itself also causes a humming sound of a similar note or tone to that heard in the telephone1 but it must be clearly understood that these two sounds are quite different4 ,one is the result of mechanical motion1 the other is the result of electrical action producing motion in the diaphragm of the telephone4 ,when you listen in the telephone it is not that you hear the sound of the bell mechanism1 you hear another sound altogether1 although1 since both have the same origin1 both have the same note or tone4 ,take any old bell1 then1 which you may happen to have or be able to procure and an old telephone such as can be bought for a shilling or so at a second-hand shop1 and these together with a pocket-lamp battery can be formed into a military field telegraph4 ,the way to connect these up is to run a wire from one of the copper strips on the battery to one of the terminal screws on the bell1 a second wire from the other screw on the bell to one of the flexible wires of the telephone1 which may be a mile away if you like1 a third wire returning from the other flexible wire of the telephone back to the battery4 ,to send signals all you have to do is to touch the return wire upon the second strip of the battery for short or long intervals1 thereby making the dot-and-dash signals4 ,or a simple form of key can easily be contrived for the purpose4 ,every time you complete the circuit the buzzer will buzz1 in other words1 it will permit an intermittent current to pass round the circuit and a buzzing or humming sound will be heard in the telephone1 no matter how far away it may be4 ,this arrangement1 however1 involves two wires between the two stations1 and in practice only one is usual4 ,this could be arranged by running the third wire from the telephone not back to the sending station but to a peg driven into the earth1 connecting the second pole of the battery in like manner to an earth pin at the sending end4 ,thus the return wire would be done away with and the earth utilized instead4 ,to do that1 unfortunately1 you would need to increase very greatly the power of your battery1 for although the path through the earth itself offers practically no resistance at all to the current1 the actual places where the current passes to earth and from earth1 especially if they be simply temporary pegs driven into the ground1 offer very considerable resistance1 so that in order to get enough current through the buzzer to make it work would need a powerful battery4 ,there is another way1 however1 by which that difficulty can be overcome quite easily4 ,probably all my readers know something of the induction or shocking coil1 wherein intermittent currents in one part of the coil induce intermittent currents of a somewhat different kind in another part of the coil4 ,few people realize1 however1 that the same effect can be attained1 within limits1 in a single coil such as the winding upon the magnet of an electric bell4 ,watch a bell at work and you will notice a bright spark at the place where the contact is made and broken4 ,that spark is due to a sudden rush of current which takes place in the coil when the original current is stopped1 in other words1 when the contact is broken4 ,it is as if the coil gives a rather vicious kick every time the current is stopped4 ,there is not much electricity in this kick current1 but it is very forceful1 and it is that force which makes it actually jump across the gap after contact has been broken1 thereby causing the spark4 ,now we can capture most of that energy and make it go a long distance through wire and through earth carrying our messages for us4 ,to do this we need to make a new connection on the bell at the place where the spring is fixed4 ,then we can make two circuits4 ,one is between the two terminal screws of the buzzer1 in which circuit we must include the battery and the key4 ,that circuit will be just as it would be if we were fixing the buzzer to announce our visitors at the front door4 ,the second circuit is different3 lead one wire from the new connection just made and take it to a pin driven into the ground4 ,if the ground is just a shade moist a wire meat-skewer will answer admirably4 ,then lead a second wire from that one of the two terminal screws which is connected directly to the winding of the magnet 7not to that one which is connected to the contact screw7 and lead it away to your distant station4 ,at the other station connect the single wire to the telephone as before and the other end of the telephone to a pin in the earth4 ,you will find that the kicks from the coil will traverse wire and earth-return quite easily1 while there will be no difficulty about working the bell1 for the small battery will do that quite well4 ,in fact1 after cutting the hammer off and so converting a bell into a buzzer1 ,i have got quite good results with one-third of a pocket-lamp battery4 ,the little flat batteries so familiar to us all if divested of their outer covering will be found to consist of three little dry cells any one of which is quite capable of sending messages in the way described as far as any amateur is likely to want to send4 ,to be able to send and receive at either end it is only necessary to connect both telephones and both coils in series4 ,that is to say1 connect one end of the coil to the long wire and the other to one wire of the telephone1 the other wire of the telephone being connected to earth4 ,if this be done at both ends signals can be sent and received both ways4 ,many young readers1 scouts1 members of cadet corps and the like1 will find great pleasure and interest in constructing and working this apparatus1 besides which it shows precisely what the official buzzer is like4 ,although beautifully made1 of course1 the army instrument is essentially just that and little more4 ,it has an additional feature1 however1 namely1 a microphone1 so that when desired it can be used as a speaking telephone for transmitting verbal messages4 ,it also has the bottom of the case made of a brass plate so that earth pins are often unnecessary1 the case dumped down upon the ground being a good enough earth4 ,buzzers are not used for very long lines3 forty miles is about the limit1 and usually the distances are very much less4 ,that is because long lines rather object to rapidly changing currents flowing through them4 ,why1 you say1 what currents could change more rapidly than telephone currents carrying speech1 yet they go for hundreds of miles8 ,true1 but in that case there are two wires1 flow and return1 twisted together all the way1 under which conditions they interact upon each other in such a manner as to abolish the difficulty to which ,i am referring4 ,buzzers and indeed all the telegraph circuits consist of one wire and the earth1 which is quite different4 ,another objection to the buzzer is that it is apt to interfere with others4 ,for instance1 if two buzzer sets are at work anywhere near each other and the wires run parallel for a distance they will be able to hear each other's signals as well as their own4 ,if two such sets are earthed near together the same thing happens1 the signals of one are picked up by the other1 a very annoying state of affairs for the operators4 ,right at the front1 however1 amid the rough and tumble of the actual fighting1 the buzzer is supreme4 ,the wire used is sometimes plain copper enamelled3 more often1 however1 it is a mixture of steel and copper strands twisted together and covered with a strong insulating covering4 ,this is carried on reels in properly fitted carts which can advance at a gallop1 paying out the wire as they go4 ,the inner end of the wire is connected to the axle of the reel in such a way that a telegraphist in the cart is in communication all the time with the starting-point1 the wheels of the cart providing him with an earth connection4 ,when laying these wires another interesting little device is often used--an earth plate on the operator's heel4 ,thus1 while carrying the wire along1 laying it as he goes1 he can still be in communication with the starting-point every time he puts his heel to the ground4 ,for the longer lines away back from the fighting the methods employed are just the same as those of peace4 ,sounder instruments are used1 ,wheatstone automatic machines1 duplex and quadruplex systems1 whereby two and four messages are sent simultaneously over the same wire1 indeed all the contrivances and refinements of the home telegraph office are to be found in the field telegraph offices4 ,but it would hardly be fitting to describe them here4 ,some information on the subject will be found in ,the ,romance of ,submarine ,engineering1 where their application to cable telegraphy is dealt with4 ,a genuine speciality of warfare1 however1 is the methods by which makeshift arrangements can be set up1 such as sending telegraph messages over a telephone wire without interfering with the latter4 ,imagine that ,a and ,b are the two wires of a telephone circuit running 7for the sake of simplicity7 from north to south4 ,at the south end ,i connect a telegraph set to both wires while you1 we will imagine1 do the same at the north end4 ,you and ,i can then signal to each other without the telephone man hearing us at all4 ,to him the two wires are flow and return1 to us they are both flow1 the earth being our return4 ,thus our signals never reach his instruments at all4 ,but when we each connect to both his wires1 do we not short-circuit or connect them to each other1 thereby destroying his circuit8 ,no1 we are too cunning for that4 ,we first connect the two wires ,a and ,b together with a coil of closely wound wire1 having1 in scientific language1 much inductance1 and telephone currents shun a coil of that sort4 ,then we make our connection to the centre of that coil so that our currents go to ,a through half the coil and to ,b through the other half4 ,this enables us to use the apparatus without interfering with the other fellow at all4 ,for this1 by the way1 we must use ordinary telegraph instruments4 ,we cannot employ a buzzer1 for these coils which we use to obstruct the passage of the other man's telephone currents would also obstruct the changing currents from a buzzer4 ,the slow1 steady currents of the ordinary telegraph pass quite easily1 however4 ,again1 suppose you and ,i want to communicate by buzzer and there is already a wire laid passing both of us but in use already for ordinary telegraphy4 ,we only need to add a condenser to our apparatus and we can manage all right4 ,as a matter of fact1 the service instruments generally have condensers partly for this very purpose4 ,each of us then connects his instrument to the wire and to earth1 after which we can signal to each other while the telegraphist is unaware of the fact4 ,the reason that is possible is the reverse of what we saw just now4 ,there we had a coil which obstructed buzzer or telephone currents but passed ordinary telegraph currents4 ,here we use condensers which will pass our buzzer currents but not the ordinary telegraph currents4 ,thus the soldier telegraphist is up to many dodges whereby he can save time or save material1 both of which may be precious4 ,as in bridge building and other branches1 he needs to be quick to adapt himself to circumstances1 to utilize to the full any opportunities which may present themselves4 ,but his principles are quite simple and do not differ in any way from those of peace4 ,it is only in applying them that the differences arise4 ,,chapter ,,xxiii ,,how ,,war ,,inventions ,,grow ,the inventor of one of the devices described later on in this book modestly claims that he did not invent it but it invented itself4 ,what he means is that he worked step by step1 from simple beginnings1 each step when complete suggesting the next4 ,to put it another way1 many inventions grow in the inventor's mind1 sometimes from unpromising beginnings1 the most unlikely start often resulting in the most successful ending4 ,who has not heard of the tanks which made such a name for themselves when they suddenly appeared in ,northern ,france8 ,the ,british ,commander-in-,chief simply mentioned that a new type of armoured car had come into use with good results1 but the newspaper men set the whole non-,teutonic world laughing with droll stories of huge monsters suggestive of prehistoric animals which suddenly began to crawl through the slime and mud of the battle-field1 pouring death and destruction upon the astounded ,germans4 ,how they came to be called tanks no one seems to know clearly but that is how they will be known for all time4 ,it has been suggested that they were so named because tank is one of the things which they certainly are not1 the intention being thereby to add to the mystification of the enemy4 ,that is by the way1 however1 for we are more concerned with the things than with their name4 ,their precise origin is wrapped in mystery but we have it on excellent authority that they grew out of the peaceful tractor1 originally intended to drag a plough to and fro across a field in the service of the farmer4 ,an illustration of one of these interesting machines will be seen in this book which will well repay a little study4 ,it consists of a steel frame or platform upon which is mounted a four-cylinder petrol engine with a reservoir above to carry the supply of fuel and with a radiator in front to cool the water which keeps the engine from becoming too hot4 ,towards the back of the vehicle is what is called by engineers a worm-gear1 the function of which is to reduce the one thousand revolutions per minute of the engine to somewhere near the slow speed required of the wheels of the tractor4 ,this worm-gear is simply a wheel with suitable teeth on its edge in conjunction with a screw so made that its thread can engage comfortably with the teeth4 ,this latter1 because of the wriggling appearance which it presents when it is revolving is called a worm1 which name it gives to the whole apparatus4 ,both wheel and worm are mounted in bearings which form part of a case enclosing the whole so that dirt is excluded while1 the case being filled with oil1 ample lubrication is assured4 ,the shafts of both wheel and worm emerge through holes in the case4 ,it will easily be seen that each single turn of the worm will propel the wheel one tooth1 so that if the wheel have fifty teeth1 for example1 the worm will turn fifty times to the wheel's once4 ,thus a great reduction in speed is attainable with this device and what is equally valuable1 a great increase of power also results4 ,thus a small engine1 working at a high speed1 is able by means such as this to pull very heavy loads at a slow speed4 ,it is evident1 however1 that the reduction necessary in this case cannot be attained even by a worm-gear1 for there are other wheels visible which show that ordinary tooth gearing is also employed to reduce the speed even further before it is applied to driving the tractor along4 ,practically all the other gear which we see in the picture1 above the platform1 consists of the controlling apparatus4 ,the object with a screw-like appearance just behind the engine is not really a screw but is a flexible coupling joining the engine to the worm-gear1 its flexibility enabling the two to work sweetly together even though by chance they may get just a little out of line with each other4 ,but by far the most interesting part of the machine is that which is underneath the frame4 ,at one end we see a pair of ordinary-looking wheels and between them the gear for swinging them to right or left for steering purposes1 but even they are somewhat unusual1 since they will be seen to have flanges or rims round the edge for the purpose of biting into the earth1 so that they may be able to guide the machine the better in soft ground4 ,the back wheels1 however1 are quite peculiar1 for there is a pair on each side and round each pair is a chain somewhat after the fashion of a huge bicycle chain4 ,the links of this chain are made of tough steel and they are two feet wide1 so that each chain forms a broad track upon which the machine moves4 ,the links of this track-chain will be seen to be tooth-shaped so that they grip or bite deeply into the yielding ground4 ,the teeth1 moreover1 are shaped like those of a saw and they are so placed as best to help the tractor forward4 ,between the two chain-wheels will be noticed a row of smaller wheels and it is these which largely support the weight of the machine1 the chains forming tracks upon which they run4 ,the wheels actually turned by the power of the engine are the chain-wheels1 and their action is such as to keep on laying down and then taking up again two broad firm tracks along which1 at the same time1 they keep propelling the other wheels which carry the weight above4 ,the effect1 really1 is just as if the machine had a pair of driving wheels two feet wide and of enormous diameter1 of such diameter1 in fact1 that the part in contact with the ground is almost flat4 ,thus there is always a broad bearing surface to prevent sinking in soft earth1 while the tooth-like shape of the links gives a firm hold even under very adverse conditions4 ,this form of construction has been used for some few years now under the name of caterpillar or centipede traction4 ,a glance at the picture will explain those names1 particularly if the chain-driven part of the vehicle be imagined to be a little longer than it is in the particular machine shown4 ,the idea of armouring a vehicle with bullet-proof plates is also a fairly old conception4 ,armoured trains were used again and again during the ,south ,african ,war1 and armoured motor-cars became familiar to most people4 ,in the case of cars1 however1 the armour could only be very light and the guns carried were limited practically to a single machine-gun and some rifles4 ,moreover1 the operations of a car are very largely confined to such places as are blessed with good roads or smooth plains4 ,an armoured car of the older type would have cut a poor figure amid the shell-holes and mine-craters of ,northern ,france4 ,it would have had to keep to the roads and so it was little used4 ,but the idea of an armoured vehicle was good and a good idea is never entirely lost4 ,sooner or later some genius puts it to good use4 ,thus the idea of an armoured vehicle came to be associated with the idea represented in the centipede tractor and the result was the tank4 ,why not armour a large centipede1 said someone8 ,make it very big and strong4 ,it will trample down the barb-wire entanglements as if they were grass4 ,if made long enough and rightly balanced it will pass over the trenches like a moving bridge4 ,nothing but a direct hit from a heavy gun will do it much harm4 ,for1 observe1 the mechanism can be entirely covered up1 all the vital parts can be well protected1 and the chain tracks can be so strong as to be almost undamageable4 ,illustration3 ,by permission of ,messrs4 ,foster and ,co4 ,,the ,,parent ,,of ,,the ,,tank4 ,here we see an innocent agricultural tractor with caterpillar hind wheels4 ,it is out of such a machine that the idea of the formidable tank was evolved4 ,thus we get a glimpse of the growth of this simple peaceful agricultural machine into one of the most striking mechanical achievements of the ,great ,war4 ,another thing which seems to have grown more or less of itself is the bomb or grenade4 ,before the time of modern accurate fire-arms hand-grenades were quite a recognized weapon4 ,the ,grenadier ,guards owe their title to this fact and carry the design of a bursting grenade upon their uniforms4 ,yet until a few years ago everyone thought that such things were done with for ever3 that with modern rifles soldiers would seldom get near enough together to use grenades and that if they did the bayonet would be the weapon to be used4 ,when1 however1 the ,germans were driven back at the battle of the ,marne and found themselves compelled to entrench in order to avoid further disaster1 it soon became evident that neither rifle nor bayonet nor both together entirely filled the needs of the infantryman4 ,since the ,allies were not powerful enough to drive the ,germans from their trenches forthwith1 they1 too1 had to entrench4 ,gradually the trenches drew nearer and nearer together and at the same time skill in entrenching increased4 ,thus a time soon arrived when both rifle and bayonet were largely useless for purposes of offence4 ,then the hand-grenade came into its own again1 for the men could throw it from the depths of their own trench high into the air in the hope that it would fall into the trenches of the enemy4 ,the call for these quickly produced the supply4 ,there is little need to describe them here1 for who among us has not intimate friends who used them again and again8 ,this much may be said1 however4 ,they were little hollow balls of cast iron1 sometimes chequered so that when they burst they flew into many fragments4 ,inside was a charge of explosive with a suitable fuse or firing mechanism4 ,some were fixed to the end of a stick for convenience in throwing1 while others were simply handled like a cricket-ball4 ,they serve to show us1 however1 how an old idea may under fresh conditions be revived into what is practically a new invention4 ,another example of the same sort is the revival of chain mail4 ,who1 but a few years ago1 would have thought it possible that modern soldiers would go to battle sheathed in shirts consisting of little metal plates cunningly connected by wire links and so overlapping each other as to form a perfect shield for all the more vital parts of the body8 ,to what extent these were worn ,i do not know1 for the ,british soldier is a very shy fellow in some ways and there are few who would not be a trifle ashamed to let their comrades see them thus garbed4 ,they would feel that it was a confession of fear1 and however afraid an ,englishman may be he will never admit it4 ,he is really a pious fraud1 for the more he is really afraid inwardly the more courageously will he act just to hide his fear4 ,since1 however1 the bullet-proof helmet is worn officially nowadays there seems no reason whatever why the bullet-proof waistcoat should not be adopted officially too4 ,it is very light and very flexible and it is claimed that it is quite effectual in stopping rifle and machine-gun bullets4 ,thus we see in what different ways inventions grow4 ,some are warlike from first to last1 like the gun and the torpedo1 but we find a vast range of peaceful things growing into implements of warfare1 as the farmer's tractor has been developed into the tank1 while not less interesting are the old ideas revived and adapted to modern needs1 exemplified by the hand-grenade and the chain armour4 ,,chapter ,,xxiv ,,aeroplanes ,of all the great inventions perhaps the most striking because of the suddenness with which they have come upon us are those relating to the navigation of the air4 ,until a few years ago to fly was taken to typify the impossible4 ,now we see men flying every day and there is scarcely anyone who has not had a friend or relative in the ,flying ,corps4 ,recent experience1 too1 has shown that this one invention has revolutionized warfare in several important departments1 particularly in the use of very heavy long-range artillery4 ,huge guns1 hidden in a hollow or behind a hill1 have been set to throw shells on to an unseen target1 while a man in an aeroplane above watches the result and signals back by wireless4 ,thus by the aid of aircraft the power of artillery has been immensely increased4 ,again1 aircraft have superseded cavalry for reconnaissance purposes1 that is to say1 for finding out the enemy's strength and preparedness4 ,only a few years ago a ,general who needed information as to his foe would send forward a screen of cavalrymen who would cautiously creep forward until1 judging by what they could see and by what sort of a reception they got1 they were able to form some idea of the foe's arrangements4 ,nowadays1 however1 the airmen sail over his head and take photographs of him and his positions4 ,a careful commander to-day not only screens his men and his guns from view along the land but he also tries his best to make them invisible from above4 ,and1 speaking of inventions1 the soldiers have shown a degree of ingenuity in making themselves and their guns invisible which almost merits a volume to itself4 ,the airman1 therefore1 goes up and sails over the enemy4 ,he may be simply observing for some particular unit of artillery1 or he may be sent to find out things generally--nothing in particular1 but anything which seems likely to be of use4 ,he looks out intently and carefully1 moreover he not only looks with his own eyes3 as has just been mentioned1 he takes photographs1 which can be developed on his return and studied minutely at leisure4 ,he may1 or may not1 according to circumstances1 send back reports of an urgent nature by wireless telegraphy4 ,in some cases these duties are all carried out by one man1 but in others there are two3 one the pilot who looks after the working of the machine1 and the other the observer whose whole attention can thus be devoted to scrutinizing the enemy4 ,of course1 when aeroplanes go on scouting expeditions like this they are apt to be attacked by the enemy both by anti-aircraft guns and also by other aeroplanes4 ,the former can only be met by high speed and the steering of a somewhat erratic course so as to confuse the gunners and prevent them from taking good aim4 ,the other aeroplanes1 however1 must be met by actual fighting4 ,the only way to defeat them is to go for them and attack them1 a machine-gun being the most usual weapon4 ,besides those who go up for definite scouting operations or to spot1 as it is termed1 for the artillery1 there are other machines whose sole duty is fighting4 ,these go up for the purpose of driving off those machines of the enemy which may come prying1 or to keep the ground1 so to speak1 for the scouting machines and enable them to do their work unmolested4 ,then there are1 of course1 still others whose function is to carry out bombing expeditions4 ,all these different duties call for different types of machine1 but ,i do not propose to go into the differences here since changes are so rapid in this particular field that only the general principles remain unchanged for any length of time4 ,what has just been hinted1 however1 as to the different kinds of work which the aeroplane is called upon to do will enable the reader to see why different kinds of machines are needed4 ,so far we have only spoken of aeroplanes4 ,there is a kind of machine sometimes called a hydroplane but which we are gradually getting to call a sea-plane4 ,the latter term is much to be preferred1 since the former is also in use to denote a special kind of high-speed boat4 ,now a sea-plane only differs from an aeroplane in that it has floats instead of wheels4 ,the aeroplane has wheels to enable it to alight upon and arise from the ground3 the sea-plane has floats by which it can alight upon the water and arise from the water also4 ,in some instances this float idea is made so pronounced a feature of the machine that it becomes a flying boat4 ,sea-planes are therefore really only aeroplanes specially adapted for a certain purpose4 ,they are really just as much aeroplanes as those machines which go by that name4 ,it is somewhat unfortunate1 therefore1 that a separate term is used to describe them4 ,but there it is3 names grow in a very curious way1 not always in a logical way1 and a name having once stuck to a thing in the mind of the public it is very difficult to make any alteration4 ,aeroplanes1 then1 may be said to include a subdivision known as sea-planes1 and for the rest of this chapter what is said of aeroplanes will apply to sea-planes also4 ,without doubt1 these are the fastest vehicles in existence4 ,many of them can exceed a speed of a hundred miles an hour4 ,consequently1 the pilot lives while he is aloft in the equivalent of a furious gale1 and it would seem as if that must produce such a degree of cold as to be almost unendurable4 ,moreover1 it appears that this cold is almost as bad in summer as in winter1 for the temperature high up in the air is much the same all the year round4 ,the consequent muffling up with thick clothes and gloves1 while it mitigates the cold1 must add greatly to the pilot's difficulties in managing his machine4 ,the protection for his eyes and ears which is made necessary by the same conditions must likewise add to his difficulties or at any rate to his discomfort4 ,on the other hand1 the effect of gliding at a very high speed over a perfectly smooth track1 for that is in effect what it is1 is very exhilarating1 which to some extent compensates for the other drawbacks4 ,moreover1 the handling of such a machine in the air1 particularly if a fight is included in the programme1 appeals strongly to the sporting instincts of young men1 so much so that during the ,war1 in spite of the dangers and hardships1 and the continual loss of life1 there was never a dearth of men anxious to become pilots4 ,owing to these considerations1 too1 it follows that the best aviators are to be found in those lands where the people are most devoted to sports4 ,hence1 as we have it on excellent authority1 the young men of ,great ,britain and the ,united ,states1 with their love of adventure and their strong sporting instincts1 make better men in the air than the ,germans4 ,but really we are more concerned here with the machines than with the men1 so let us get back to our subject4 ,the aeroplane consists of one or more planes or surfaces which1 on being held at a certain slant and then pushed forward rise or remain supported in the air4 ,therefore the plane or planes need to be supplemented by first a tail and horizontal rudder to hold them at the correct slant1 and an engine and propeller to drive them forward4 ,it is not necessary1 here1 to go over the history of the aeroplane1 as that has been told so often4 ,it is not of much interest1 moreover1 except to those who are particularly concerned with small details of construction1 for in a general way the machine of to-day is very little different from one pictured by ,sir ,george ,cayley a hundred years ago4 ,it is only the perfecting of the details which has transformed a dream into a very real thing4 ,so we will look only at the construction of the aeroplane in a general way1 to do which we must first consider why it flies at all4 ,it is due to the well-established law that action is always accompanied by a reaction equally strong and in the opposite direction4 ,when a gun is fired the explosion not only drives the shell forward but equally drives the gun itself backward4 ,the backward energy of the recoil is precisely equal to the forward energy of the shell4 ,the two are equal but in opposite directions4 ,in like manner a rocket ascends because the hot gases from the paper cylinder blow forcibly downwards1 thereby producing an equal reaction upwards4 ,now the plane of a flying machine is held with its forward edge a little higher than its rear edge1 so that as it is pushed along it tends to catch the air and throw it downwards4 ,hence the reaction tends to lift the plane upwards4 ,when the machine starts the reaction is not sufficient to overcome gravity1 which is trying to hold the machine down upon the ground1 but as the speed increases and the air is thrust down with more and more violence the point is ultimately reached when the reaction is able to overcome gravity and the machine ascends4 ,when a sufficient height is reached1 the pilot alters the position of his horizontal rudder or elevator so as to make the position of the plane more flat1 with the result that it throws the air downwards to a less extent1 and the reaction is thereby reduced until it is only just sufficient to keep the machine at the same height4 ,to descend1 the position of the plane is made still flatter1 the reaction is reduced still more and gravity has its way once again1 bringing the machine to earth4 ,in other words1 the machine acts under the influence of two forces3 the downward pull of gravity and the upward reaction due to the action of the machine in throwing the air downward4 ,the former never varies1 the latter can be varied by the pilot at will3 he can increase it by increasing the speed or by increasing the tilt of his plane or planes3 he can reduce it by diminishing the speed or the tilt4 ,since generally speaking the speed of his engine will remain constant1 he rises1 remains at the same height or falls1 at will1 by the simple manipulation of the elevator through which he can change the tilt or inclination4 ,most machines have a fixed tail as well as a horizontal rudder or elevator1 the same being so set that it tends to keep the plane in a certain normal inclination1 the elevator being called in to increase that or diminish it as may be required4 ,in addition to the elevator there is also another rudder of the ordinary kind1 such as every ship and boat has1 for guiding the machine to right or left4 ,the elevator steers up and down1 the rudder steers to either hand4 ,provision is also made for balancing the machine4 ,this is sometimes in the form of two small planes hinged to the main plane1 one at either end1 connected together and to a controlling lever by wires1 so that by their use the pilot can steer the right-hand side of his machine upwards and the left-hand downward1 or vice versa1 if through any cause he finds a tendency to capsize4 ,in some machines the same effect is produced not by separate planes but by pulling the main plane itself somewhat out of shape1 but precisely the same principle is involved4 ,the planes are usually made with a slight curve in them1 so that they may the better catch the air and scoop it downwards1 so to speak4 ,they usually consist of fabric specially made for the purpose1 stretched upon a light wooden framework4 ,the whole framework is usually of wood with metal fittings frequently made of aluminium for the sake of lightness4 ,the engines have been mentioned in another chapter4 ,the propeller which is almost invariably fixed directly upon the shaft of the engine has two blades only and not three as is usual with those of ships4 ,precisely why this should be so is not clear1 but experience shows that two-bladed propellers are preferable for this work4 ,they are made of wood1 several layers being glued together under pressure1 the resulting log being then carved out to the required shape4 ,this makes a stronger thing than it would be if cut out of a single piece of wood4 ,all parts1 engine1 elevator1 rudder and balancing arrangement1 are controlled by very simple means from the pilot's seat4 ,in monoplanes there is but one main plane1 resembling a pair of bird's wings4 ,or if we care to look upon it as two planes1 one each side of the body1 then we must call it a pair4 ,since the name mono indicates one it is best to think of it as one plane although it may be in two parts4 ,the biplane has1 as its name implies1 two planes1 but in that case there can be no doubt1 since they are placed one above the other4 ,machines have been made with three planes and even with as many as five1 but monoplanes and biplanes appear to hold the field4 ,it is not possible for an aeroplane to be in any sense armoured for protection against bullets3 for defence the pilot has to depend upon his own cunning manoeuvres combined with the fast speed at which he can move4 ,for offensive purposes he usually has a machine gun mounted right in front of him with which he can pour a stream of bullets into an opponent or even1 by flying low1 he can attack a body of infantry4 ,it is recorded that one ,german prisoner during the war1 speaking of the daring of the ,british pilots in thus attacking men on foot1 exclaimed1 ,they will pull the caps off our heads next4 ,some of the aeroplanes have their propeller behind the pilot and some have it in front4 ,the latter1 to distinguish them1 are called ,tractor machines1 since in their case the propeller pulls them along4 ,now it is easy to see that a difficulty arises in such cases through the best position for the gun being such that it throws its bullets right on to the propeller4 ,but that has been overcome in a most simple yet ingenious way4 ,the gun is itself operated by the engine with the result that a bullet can only be shot forth during those intervals when neither blade of the propeller is in the way4 ,the propeller is moving so fast that it cannot be seen and the bullets are flying out in a continuous rattle1 yet every bullet passes between the blades and not one ever touches4 ,it is easy to see that when an aeroplane is manned by a single man1 as is often the case1 he must have his hands very full indeed1 what with the machine itself and the gun as well4 ,in fact1 he often has to leave the machine for a short time to look after itself while he busies himself with the gun4 ,now there we see a sign of the wonderful work which has been done in the course of but a few years in the perfecting of the aeroplane1 the result of a series of improvements in detail which make but a dreary story if related but which make all the difference between the risky1 uncertain machine of a few years ago and the safe1 reliable machine of to-day4 ,modern machines are inherently stable4 ,the older ones had the elements of stability in them but they were so crudely proportioned that these inherent qualities did not have a chance to come into play4 ,if one drops a flat card edgewise from a height it seems as if it ought to fall straight down to the ground4 ,yet we all know from experience that it seldom does anything of the kind4 ,instead1 it assumes a position somewhere near horizontal and then descends in a series of swoops from side to side4 ,there we see the principle at work which1 in a well-designed aeroplane1 causes inherent stability4 ,the explanation is as follows4 ,the aeroplane is sustained in the air through the upward pressure of the air resisting the downward pull of gravity4 ,that has been fully explained already4 ,now gravity1 as we all know1 acts upon every part of a body whether it be an aeroplane or anything else4 ,but for practical purposes1 we may regard its action as concentrated at one particular point in that body1 called the centre of gravity4 ,likewise1 the upward pressure of the air acts upon the whole of the under surface of the plane or planes1 yet we may regard it as concentrated at a certain point called the centre of pressure4 ,further1 we all know from experience that a pendulum or other suspended body is only still when its centre of gravity is exactly under the point of suspension4 ,if we move it to either side it will swing back again4 ,in just the same way1 the only position in which an aeroplane will remain steady is that in which the centre of gravity is exactly under the point of suspension or1 in other words1 the centre of pressure4 ,for the centre of pressure in the aeroplane is precisely similar to the point of suspension of a pendulum4 ,let us1 then1 picture to ourselves an aeroplane flying along on a horizontal course with this happy state of things prevailing4 ,something we will suppose occurs to upset it with the result that it begins to dive downwards4 ,it is then in the position of sliding downhill and instantly its speed increases in consequence4 ,that increase of speed causes the air to press a little more strongly than it did before upon the front edge of the planes4 ,in other words1 the centre of pressure shifts forward a little1 with the result that the centre of gravity is then a little to the rear of the centre of pressure4 ,a moment's reflection will show that with the centre of pressure 7or point of suspension7 in advance of the centre of gravity there is a tendency for the machine to turn upwards again1 or1 in other words1 to right itself4 ,if1 on the other hand1 the initial upset causes it to shoot upwards the speed instantly falls off and the centre of pressure retreats1 turning the machine downwards once more4 ,and the same principle applies whatever the disturbance may be4 ,instantly and automatically a turning force comes into play which tends to check and ultimately to correct what has gone wrong4 ,this principle explains the behaviour of the card dropped from an upstairs window and1 no doubt1 as has been said1 it operated also in the early flying machines1 but in their case other factors caused disturbing elements with which the self-righting tendency was not strong enough to cope4 ,as time went on1 however1 experience taught the makers how to avoid these disturbing factors until at last the self-righting tendency was able to act effectively1 thus producing the aeroplane which is inherently stable and which will1 for short periods at all events1 fly safely without attention from its pilot4 ,each little improvement in this direction was an invention4 ,of course1 there were certain men whose names stand out prominently in the history of the aeroplane1 notable among whom are the ,wright brothers1 but the final result is due to innumerable inventions1 many of them by unknown men4 ,but perhaps someone will say1 how can you possibly talk about final results in a matter which is still in its infancy8 ,the answer to that is that so far as the safe1 flyable machine is concerned1 it has arrived4 ,little now remains to be done in that direction4 ,further improvements there will1 of course1 be1 but the great fundamental problems of flight have been solved4 ,,chapter ,,xxv ,,the ,,aerial ,,lifeboat ,balloons had not long been invented when the idea arose of a device by means of which an aeronaut who found himself in difficulties might be able to reach the ground in safety4 ,in other words1 the need was felt for something which should play towards the balloon the part which the lifeboat does to the ship4 ,the original idea of a parachute was even older than that1 since we are told of a man away back in the seventeenth century who amused the ,king of ,siam by jumping from a height and steadying his descent by means of a couple of umbrellas4 ,it was not1 however1 until the very end of the eighteenth century or the beginning of the nineteenth that descents were made from really considerable heights from balloons4 ,the usual arrangement then was to have the parachute hanging at full length fastened below the basket1 or tied to one side of the balloon in such a manner that it could be detached by cutting the cords that held it up4 ,when the parachute was carried below the balloon basket the man was already in the cradle or seat of the parachute ready to be dropped1 but when the seat was tied to the side of the car of the balloon the aeronaut1 when he wished to make a descent1 first got from the car into the seat1 and1 casting himself adrift from the car1 swung out from under the centre of the balloon so that when he was hanging clear another man in the balloon cut the cords or pulled a slip-knot which set the parachute free4 ,there were different ways of doing this and when a man was by himself he had to get into the sling of the parachute and1 on finding himself clear of everything1 he would give a tug to a cord which would release a catch holding up the parachute and allow it to drop to earth4 ,the parachute1 at the very first1 was but a simple affair1 being little more than a circular sheet of cotton or similar fabric1 but it was very soon found necessary to make it a bag or it would not properly hold the air4 ,cords were attached at regular intervals all around the edge of this bag1 these cords being gathered together and attached to the edge of a basket which carried the man4 ,sometimes only a sling was used1 or a simple light seat after the fashion of the bosun's chair upon which a sailor is sometimes hauled to the top of an unclimbable mast1 or a steeplejack to the top of a chimney4 ,thus1 when it was dropped1 the weight of the man1 pulling upon all the cords simultaneously1 drew down the edge of the bag1 which1 catching the air in its fall1 acted as a powerful brake and reduced the rate of falling to such an extent that if all went well the man alighted in safety if not comfort4 ,as has already been remarked in another chapter1 air1 which seems to us sometimes to be so exceedingly light as to have practically no weight at all1 really has weight and also the property which we call inertia1 by virtue of which things at rest prefer to stay at rest4 ,now when this open air-bag1 of considerable area1 is pulled downwards it causes a very considerable disturbance in the air4 ,as it descends the air inside and beneath it is first pushed downwards and compressed a little1 then it commences to move outwards1 towards the edge1 round which it finally escapes to fill the slight vacuum in the space just above the descending parachute4 ,all this the air objects to do because of its inertia4 ,the parachute has to force it to act thus and in that way it uses up some of the force of gravity which all the time is pulling the man earthwards4 ,in other words1 that force1 instead of dragging the man downwards at such a speed as to dash him to pieces1 is so far employed in churning up the air that what is left only brings him down quite slowly and ends with just a gentle bump4 ,that is the scientific explanation of what happens1 although expressed in somewhat homely language4 ,to anyone who thinks of this matter it will be clear that a relatively heavy weight like a man1 suspended from a parachute1 is like a very delicately poised pendulum1 and consequently it is not surprising to hear that the early parachutes oscillated very considerably from side to side1 so much so1 indeed1 that this oscillation became a decided danger1 for before the proper shape of the air-bag was found out they sometimes skidded and even turned inside out4 ,it was found1 however1 at quite an early stage that this instability could be to some extent cured by making a hole right in the centre or crown of the parachute through which the air compressed inside could blow upwards in a powerful jet4 ,at first sight it seems as if this would much weaken the parachute and cause it to descend too quickly1 but quite a large hole can be safely made1 and to make such a hole is only the same thing as slightly reducing the area and that can be easily remedied by slightly increasing the diameter4 ,reading of this many years ago1 ,i have often been puzzled as to why the presence of the hole should have this steadying effect1 the explanation given in the old scientific textbook from which ,i learnt it being obviously very unsatisfactory4 ,of recent years1 however1 this subject of parachutes has been very deeply studied by an eminent engineer of ,london1 ,mr4 ,e4 ,r4 ,calthrop1 the inventor of the ,guardian ,angel parachute to which these remarks are leading up1 and he has hit upon what is undoubtedly the explanation4 ,he says that the big jet of air shooting upwards through the crown of the parachute forms in effect a rudder which steers the parachute in a straight downward course1 just as the rudder guides a boat upon the surface of the water4 ,it is quite possible that thus far the impression conveyed to the reader's mind is that the parachute and its use are very simple1 straightforward matters4 ,one may be inclined to think that it is only necessary to get a circular sheet of fabric1 to fasten the cords to it1 to connect them to a suitable seat and then to descend from any height at any time in perfect safety4 ,if you make a model from a flat sheet of cotton1 then one made like a bag1 and drop them with little weights attached from the top window of your house you will see what funny things the air can do4 ,after having tried these little ones1 you will begin to suspect that the big parachute is full of waywardness3 and1 as a matter of fact1 until recent years1 it has been very largely a delusion and a snare4 ,by its refusal to act and open at the right moment it has sacrificed many lives4 ,although apparently so simple1 there were conditions existing and forces at work which for a century or more had never been properly considered and investigated1 and it is only now that we have arrived at a parachute whose certainty of action and general trustworthiness entitle it to be called the lifeboat of the air4 ,the troubles with the older parachutes were two4 ,first1 although often it opened quite quickly1 and carried its load as perfectly as could be desired1 it sometimes had the habit of delaying its opening1 and unless the fall were from a very great height it was unsafe to take the risk1 indeed1 it sometimes refused to open at all1 and the poor parachutist suffered a fearful death4 ,it had to be carried in a more or less folded-up state4 ,often it was hung up by its centre to the side of a balloon1 when it was very like a shut-up umbrella4 ,consequently the power of opening quickly and certainly was of the first importance1 and the lack of that power and the uncertainty of its action were a very serious defect4 ,it has always suffered from an ill reputation as to reliability4 ,the second fault lay with the cords4 ,they would persist in getting entangled4 ,everyone knows how a dozen cords hanging near together will get entangled with each other on the slightest provocation4 ,such cords if blown about by a strong wind would be much worse even than when still1 and if1 as must often be the case with parachutes1 they be coiled up1 we all know from our own experience that some of them would be almost sure to get knotted and tangled together when1 in a sudden emergency1 the attempt was made to pull them all out of their coils in a second or two4 ,just picture to yourself what it means3 a dozen coiled cords all close together1 themselves all coiled up in loops1 suddenly pulled4 ,something awkward appears almost inevitable4 ,and the result of even one rope going awry may be fatal1 for it may prevent the parachute opening out fully1 probably giving it a lop-sided form incapable of gripping the air effectually and consequently allowing the unfortunate man to fall with a velocity which means certain death4 ,this second cause of failure to open1 through entanglement of cordage1 has happened in a number of cases1 with fatal results4 ,so much for the faults of the old primitive parachute4 ,now let us consider for a moment the urgent need for a parachute which is free from such faults4 ,the man who goes up in a balloon on a ,saturday afternoon feels so sure of his craft that he thinks he needs no lifeboat1 yet men in ordinary free balloons have been killed for want of them4 ,the spectators at country fairs no longer appreciate a parachute descent as a great and extraordinary spectacle4 ,but in warfare1 with kite balloons by the dozen1 with dirigible balloons by the score and aeroplanes by the hundred1 the call for parachutes is urgent and irresistible4 ,at all events1 ,mr4 ,calthrop found an irresistible call to devote years of close study1 unceasing toil and considerable sums of money to the task of perfecting an improved parachute which would always open and open quickly1 and whose cords would never get entangled4 ,he has the satisfaction of knowing that by so doing he has provided an appliance that in the air is as reliable as a lifeboat is at sea1 and that at all times1 and from every kind of aircraft1 can be depended upon in case of accident to save the lives of gallant airmen who but for his work would be dashed to death4 ,the ,great ,war has taught us to regard life somewhat cheaply4 ,for years we were more concerned with taking life than with saving it1 yet surely to save the life of one's own men is equivalent to taking the lives of one's opponents1 so that even from the point of view of warfare the saving of life may be a help towards victory4 ,this is particularly so when the lives saved are those of the choicest spirits1 and among the most highly trained4 ,it has been reckoned that to make a fully-trained pilot costs as much as #aejj1 so that to save but a few1 even in their preparatory nights on the training-grounds where so many accidents happen1 makes quite an appreciable difference in the cost of a war1 without considering the main question of the men's lives4 ,many inventions arise through a man thinking of an idea and then seeking and finding some application for it4 ,elsewhere in this book1 ,i give examples of such cases4 ,here we have an instance of the opposite1 for ,mr4 ,calthrop found his thoughts strongly directed in this direction by the death of a personal friend1 the ,hon4 ,c4 ,s4 ,rolls1 one of the early martyrs in the cause of aviation1 not to mention others who shared the same risks and in some cases the same fate4 ,his interest thus aroused1 he first studied all the records which could be found relating to parachute accidents1 so as to ascertain1 if possible1 what were the causes of failure4 ,then he commenced a long series of experiments with a view to removing these causes4 ,improvement after improvement was tried1 unexpected difficulties were discovered and grappled with1 the kinematograph was called in to record the movements of the falling objects1 a task for which it is far better fitted than the human eye1 and after years of this there emerged the finished parachute1 automatic in its action1 perfectly reliable and a true safeguard1 which ,i am about to describe4 ,the parachute's body consists of the finest quality silk carefully cut into gussets of such a shape that when sewn together somewhat after the manner of the cover of an umbrella1 they form a shallow bag1 parabolic in section1 of that particular shape which the material would assume naturally were it perfectly elastic when enclosing its resisting body of compressed air4 ,at intervals round the edge are fastened twenty-four ,v-shaped tapes4 ,these are only a few feet long and the lower end of each ,v-shaped pair is attached to a long main tape4 ,there are twelve of these main tapes1 and their lower ends unite in a metal disc from which is suspended the sling and harness by which the man is supported4 ,illustration3 ,,the ,,guardian ,,angel ,,parachute4 7#a7 ,shows the airman in the harness by which he is attached to the parachute4 ,by means of the star-shaped buckle he can instantly release himself4 7#b7 ,shows the parachute two seconds after the airman has jumped from the aeroplane4 ,in 7#c7 he is seen nearing the ground4 7,by permission of ,e4 ,r4 ,calthrop1 ,esq47 ,so the twenty-four short tapes form twelve ,v's to the points of which are attached the twelve long tapes which support the man4 ,the reason why tapes are used in this particular parachute and not cords will be referred to later4 ,in the crown of the silk body there is the usual hole for the purpose of forming the air-rudder to steady the parachute in its descent4 ,and now we can consider the first great feature of this wonderful invention and ask ourselves these questions3 ,by what means is it made to open8 ,what makes it more reliable than others8 ,to answer that we must first see why the others sometimes refused to open4 ,in whatever way an ordinary parachute may be packed it must1 when coming into use1 assume the state of a shut umbrella with a hole in the top4 ,in this condition it is assumed that as it falls the air will find a way in through the lower end and will blow the parachute open in precisely the same way that a strong wind will sometimes blow out the folds of an umbrella4 ,but1 as a matter of fact1 the loose folds of a parachute1 when the edge of the gussets is gathered in1 are sure to overlap and enfold each other more or less4 ,thus1 when in the shut-umbrella state1 it sometimes happens that air which is inside can escape upwards through the hole more easily than fresh air can get in from below4 ,the parachute1 in such a state1 is1 let us imagine1 falling rapidly through the air4 ,the result is just the same as if it were still and the air were rushing upwards past it4 ,and the upward rush past the top hole tends to suck air out through the hole faster than fresh air can find a way in at the bottom4 ,this is the principle of the ejector1 which engineers have put to many uses4 ,for example1 the vacuum brakes employed on many large railways owe all their power to stop a train to a vacuum caused by an ejector4 ,there is a short tube or nozzle1 placed in the centre of another tube through which steam blows4 ,the action of the steam in the outer tube as it rushes past the end of the inner tube drags after it the air which is in the inner tube so effectively as to produce quite a good vacuum4 ,and in precisely the same way1 the upward rush of air past the parachute1 or what is just the same1 the falling of the parachute through stationary air1 can suck the air from inside the latter and create a vacuum in it if the gussets gathered together at the mouth unfortunately overlap one another and are thus locked together by the pressure of the air striving to get in4 ,thus1 instead of the downward fall causing the ordinary parachute to open1 as in most cases it will do quite well1 the fall under these particular conditions actually binds its folds together and prevents it from opening4 ,it is true this does not often happen1 but the risk is always present at every drop1 and this unreliability has cost the lives of brave men and women1 and the knowledge of this constant risk has led others to write down the parachute a failure1 by reason of its known unreliability to open instantly4 ,even when it does open the depth it falls before it opens is so variable1 by reason of the fight between vacuum and pressure1 that it may be one hundred feet one time and one thousand feet next time with the same parachute4 ,now the ,guardian ,angel is designed so that those conditions cannot occur4 ,its silken covering is first laid out on the ground and into the centre is introduced a beautifully-designed disc of aluminium1 somewhat like a large inverted saucer1 of exceeding lightness but of ample strength for what it has to do4 ,then the silk body is pleated and folded back over the upper part of this launching-disc and gradually packed so that it occupies but a very small space upon the upper surface of the disc4 ,it is so folded that its edge comes in the topmost layer and also in such a manner that on the tapes being pulled the silk unfolds easily and regularly1 flowing down as it were over the edge of the disc almost as water flows if allowed to fall from a tap upon the centre of an inverted saucer4 ,after the folding is complete another aluminium disc is placed above the packed silk body which shields it from the enormous air pressure when it is being released from an aeroplane flying at top speed4 ,the upper and lower fabric covers are then superimposed and sealed and the ,guardian ,angel parachute is ready for use4 ,the tapes1 likewise1 are folded up1 in a special way upon the bottom cover1 which is sprung over the bottom of the disc4 ,the bottom cover with the tapes upon it1 is pulled away by the weight of the airman as he makes his jump to safety1 and the tapes are so arranged that a pull upon them causes them to draw out steadily and smoothly1 almost like water falling from a height4 ,if we regard the silk as forming a shallow bag inverted1 we may say that it is folded upon the disc inside out and the function of the disc is to cause it to spread and enclose a wide column of air as it is pulled from its folds4 ,to commence with it is nothing more than so much folded-up silk1 but from the first moment of action it becomes a bag with a wide-open mouth1 for its open mouth cannot be smaller than the disc4 ,therefore1 from the first instant it begins to grip the air and the ejector action never gets a chance to commence4 ,the pressure of air inside is from the very commencement of the fall greater than that of the surrounding air4 ,moreover1 the disc covers the hole until the parachute is actually open1 thereby making ejector action doubly impossible4 ,the widely-opened mouth of the air-bag 7,i cannot help repeating that term for it is so expressive7 swallows up more and more air as the thing falls rapidly1 with the result that the air inside is instantly compressed and the increasing pressure as the silk is more and more fully drawn out causes it to expand until the whole is fully extended like a huge umbrella4 ,the instant compression of the enclosed column of air is what causes it always to open automatically4 ,when once it is pointed out it is easy to see what a difference the presence of this disc makes4 ,it is so simple that it cannot fail to act and having once produced that open mouth all the rest is due to the action of natural forces which can be absolutely relied upon4 ,the ordinary parachute with its hopeless irregularities has1 in fact1 been converted into a machine whose action can never fail4 ,the disc is fastened to the balloon or aeroplane and is left behind when the parachute falls1 having done its work4 ,and now let us consider the tapes4 ,as has already been remarked1 a series of coiled cords cannot be relied upon to pull out straight without possibility of entanglement1 but a tape1 if folded to and fro like a ,chinese cracker1 will invariably do so4 ,so packed tapes have been substituted for coiled corded rigging1 with the certainty that they cannot be entangled in the fiercest air current4 ,and now we come to another interesting feature4 ,the man is not suspended directly from the small disc to which the tapes are attached but by a non-spinning sling which contains a shock absorber4 ,this latter consists of a number of strands of rubber and it is owing to its action that the aviator who trusts his life to the parachute suffers little or no shock2 even when the instant opening of the parachute begins to arrest his fall4 ,and not only does it save him from shock1 but it also avoids the possibility of too great a stress coming suddenly upon the parachute or its rigging of tapes4 ,the aviator himself is attached to the parachute through the shock-absorber sling1 by means of a harness which he wears constantly throughout his flight1 so that in the event of trouble he only has to jump overboard and the parachute automatically does the rest4 ,this harness consists of two light but strong aluminium tubular rings through which he places his arms1 combined with a series of straps which can be so adjusted that the stress of carrying him comes upon those parts of his body best adapted to bear it4 ,this improved parachute is the only one which is capable of being used instantly and without preparation for descent from an aeroplane flying at top speed4 ,it is easy to see that it is one thing to drop from a stationary or nearly stationary balloon and quite another to dive from an aeroplane at one hundred miles per hour4 ,the latter is equivalent to suddenly trusting oneself to a parachute during the strongest gale4 ,it has been found1 by experiment1 however1 that high speed is no bar to the use of this parachute since it only causes the parachute to open a little more quickly than usual1 which means that it can be used with safety from an even lower height4 ,under the worst conditions this wonderful parachute can be relied upon always to open and carry its load at a height of only one hundred feet1 and its use is safe in all circumstances when dropped from two hundred feet above the ground4 ,after it has once got into operation and taken charge of affairs1 so to speak1 the man descends at the rate of only fifteen feet per second1 which is just about the same as dropping from a height of a little over three feet4 ,in other words1 he will arrive on the ground with no worse bump than you would get by jumping off the dining-room table4 ,but suppose that there were a wind blowing3 would not the parachute come down in a slanting direction and then drag the man along8 ,or may he not alight upon a tree or the roof of a house1 only to be pulled off again and flung headlong8 ,quite true he might1 were not proper provision made for such occurrences4 ,embodied in the harness is a lock which can be instantly undone1 by a simple movement of a lever in the hand1 and by its aid the man on touching earth or on alighting upon anything solid can release himself instantly1 after which the parachute can sail away whither it will1 but he will be safe and sound4 ,what ,mr4 ,calthrop has accomplished by the invention of his ,guardian ,angel parachute may be summarised briefly by saying that he has reduced the minimum height from which a parachute could be dropped from two thousand to two hundred feet1 and that he has made it possible to launch a parachute1 with the certainty of safety1 from any kind of aircraft flying at the slowest or highest speed of which they are capable4 99 99 99 99 99 ,you are only a boy now1 but when in years to come you are quite old and have grey hair you may become a ,member of the ,air ,board and--who knows--it may become your duty to decide that this great invention shall be always used on the training grounds to save the lives of the young men1 not yet born1 who are then learning to fly4 ,during the ,war1 one was killed every day1 #cfe in a year1 many of whom might have been saved had more ,guardian ,angels been in use4 ,,index ,acetone1 #cf1 #eg1 #eh ,acetylene1 #eh ,aeroplanes1 types of1 #bhe1 #bhf ,air-raft equipment1 #hi ,alcohols1 #di1 #ej1 #ea1 #eb1 #ee1 #aci ,aluminium1 #aeg ,anchors for floating bridges1 #hj ,anti-aircraft guns1 #aai ,aquitania1 s4s41 #aig ,armourer1 #ag ,austrian heavy mortars1 #aaa1 #aad1 #aag ,bamboo1 bridges made of1 #hg ,basic steel1 #aja ,becquerel1 ,h41 #dj ,benzene1 #ce ,bessemer1 ,sir ,henry1 #ic1 #ih1 #ii1 #ajj1 #ajb ,blast-furnace1 #id1 #ie ,boilers in warships1 #agf ,breech-block of guns1 #aca1 #acb ,brennan torpedo1 #bai ,calthrop1 ,e4 ,r41 #cjj1 #caa ,canet1 ,gustave1 #abi ,canvas boats1 #hf ,carbolic acid1 #ce ,carbon1 #bh1 #ej1 #id1 #ih ,carbon in steel1 #ajf ,carbon monoxide1 #ie ,carriages of guns1 #aaf ,cast iron1 #if1 #ig ,catamaran bridge1 #ij1 #ia ,caustic soda1 #bb1 #bc1 #bd ,chloride of lime1 #bc ,chlorine1 #ah1 #ai1 #ba1 #bc1 #eb ,chloroform1 #ei ,clerk-,maxwell1 ,professor ,j41 #bdc ,coal dust explodes1 #bi ,coal tar1 #cd ,contact-firing mines1 #fe ,copper1 #adg ,cordite1 #cf ,cotton explosives1 #cb1 #cc ,countermining1 #fc1 #gc ,crucible steel1 #ajd ,curie1 ,madame1 #da ,detonator1 #cg ,diastase1 #ee ,diesel engine1 #agh1 #bcf ,dreadnought1 ,h4,m4,s41 #aid ,driving-band on shells1 #adb ,dynamite1 #ca ,electricity1 positive and negative1 #bj1 #ba ,electrodes1 #ai ,electrolysis of salt1 #ah1 #ai ,electrolyte1 #ai ,electrons1 #db ,electroscope1 #dc ,elia mines1 #gj ,ethane1 #ea ,ether1 #eh1 #ei ,explosion1 force of1 #cj ,field guns1 #ajh1 #aad ,flotilla leaders1 #ahi ,fractional distillation1 #ce1 #eg ,french field artillery1 #ajh ,froude1 ,william1 #bjc ,fulminate of mercury1 #cg ,glycerine1 #be ,gravity1 action of upon shells1 #abb1 #abc1 #abd ,guardian ,angel parachute1 #cjj ,gun-cotton1 #cb1 #cc ,gunpowder1 #bg1 #cj ,gyroscope1 uses of1 #baf1 #bcd ,helium1 #db ,hertzian waves1 #bdc ,high explosives1 #cf1 #ach ,high-explosive shells1 #acg ,high-speed steel1 #aje ,hop-pole bridges1 #hh ,horse artillery1 #ajh1 #aad ,howitzers1 #aaa1 #aad1 #aae ,hydrostatic valve1 #fh1 #bag ,hydroxyl1 #eb1 #ec ,interference of waves1 #bda1 #bdh ,invincible1 ,h4,m4,s41 #aif ,ionogens1 #bj ,ions of common salt1 #ai ,iron ore1 #ic ,kieselguhr1 #cb ,ladysmith1 guns at1 #aji ,launching a ship1 #baa ,limit gauges1 #adj ,line-of-battle ships1 #aia ,lion1 ,h4,m4,s41 #aig ,lyddite1 #ce ,machine guns1 #aae ,magnetic detector1 #beg ,malt1 #ee ,marconi1 #bdh ,methane1 #ea ,methylated spirit1 #ed ,mine1 submarine1 #fc et seq4 ,mine1 subterranean1 #fa ,mortars1 #aaa1 #aab1 #aac1 #aad1 #aah ,naval guns1 #aab1 #abj et seq4 ,naval shells1 #acf1 #acg ,nitrate of potassium1 #cj ,nitro-benzene1 #ce ,nitro-glycerine1 #bf1 #ca1 #cb ,nitrogen1 action of1 #bf1 #cj ,observation mines1 #fe ,oil fuel1 #agg ,olympic1 s4s41 #aig ,organic substances1 #bf ,orion1 ,h4,m4,s41 #aic ,parachutes1 #big ,paraffins1 #ea ,periscope1 #bbe1 #bcc ,petrol engine1 #aha1 #ahb ,phenol1 #ce ,picric acid1 #ce ,pig iron1 #ie1 #ig ,poison gas1 #bc ,pontoons for bridging1 #gg ,propellants1 #cf1 #abe1 #ach ,radio-activity1 #da ,radium1 #ci et seq4 ,rays from radium1 #da1 #db ,reeds1 bridges made of1 #he ,repulse1 ,h4,m4,s41 #aib ,rheumatism and radium1 #dg ,rifling in guns1 #adc ,rolling mills1 #ih1 #aci ,salt and explosives1 #ah ,saltpetre1 #bg1 #bi1 #cj ,scott1 ,sir ,percy1 #aji ,sea-planes1 #bhg ,shell-steel1 #adf ,shrapnel shells1 #acg1 #add1 #ade ,siemens steel1 #ajb1 #ajc ,sights for guns1 #acc ,smokeless powder1 #ca ,soap1 #be ,sodium1 #ah1 #bb ,soluble seal used in mines1 #gb ,spinning action of shells1 #adb ,stability of aeroplanes1 #bic ,steam-engines1 #agj ,steel for guns1 #abf ,sulphuric acid1 #ca1 #cb1 #aej ,suspension bridges1 #hc ,tanks1 #bgf ,telephone used in telegraphy1 #bff ,tin1 #aeb1 #aec ,t4,n4,t41 #ce ,toluene1 #ce ,torpedo boats1 #ahd ,trajectory1 #abb ,trench mortars1 #aah ,trestle bridges1 #hj1 #hc ,tri-nitro-benzene1 #ce ,tri-nitro-phenol1 #ce ,tri-nitro-toluene1 #ce ,tungsten1 #aje1 #aec ,tuning wireless telegraph apparatus1 #bee ,turbine1 steam1 #ag ,uranium1 #da ,whitehead torpedo1 #bae ,wire-wound guns1 #abh ,wolfram1 #aec ,wood spirit1 #eg ,wrought iron1 #ig ,wyoming1 ,u4,s4 battleship1 #aie ,x-rays1 #db1 #dc ,zeppelin v4 aeroplane1 #df ,zinc1 #adi1 #aej1 #aea ,,printed ,,by ,,william ,,brendon ,,and ,,son1 ,,ltd41 ,,plymouth1 ,,england4 #aiag ,great ,classics for ,little ,children ,,the ,,children',s ,,odyssey ,,told ,,for ,,little ,,children ,,by ,,prof4 ,a4 ,j4 ,,church1 ,m4,a4 ,with ,fourteen ,illustrations4 ,extra ,crown #hvo1 #es4 ,a really charming volume in all respects4 ,no writer has done work of this kind so well since ,kingsley first set the fashion in his masterpiece1 ,the ,heroes4--,guardian4 ,the stories could not be told more simply and directly1 or in a way better fitted to delight and interest children1 than they are in this charming book4 ,we are delighted to see the book embellished with ,flaxman's exquisite illustrations4 ,greatly daring 444 they have been coloured in simple colours1 like those of classical wall paintings4 ,the effect is quite excellent4--,spectator4 ,,the ,,children',s ,,iliad ,,told ,,for ,,little ,,children ,,by ,,prof4 ,a4 ,j4 ,,church1 ,m4,a4 ,with ,fourteen ,illustrations4 ,extra ,crown #hvo1 #es4 ,what need nowadays to praise ,prof4 ,church's skill in presenting classical stories to young readers8 ,this is a capital example of the cultured1 simple style4 ,a delightful gift-book4--,athenum4 ,prof4 ,church has written as good a book as can ever be produced for ,english children from the literary treasures of ,greece4 ,the illustrations are worthy of the writing4--,sheffield ,independent4 ,with delightful simplicity of style ,prof4 ,church retells the story of the ,siege of ,troy so that it ceases to be 'history1' and becomes an engrossing narrative4 ,the handsome volume has a dozen excellent illustrations4--,dundee ,courier4 ,,the ,,children',s ,,neid ,,told ,,for ,,little ,,children ,,by ,,prof4 ,a4 ,j4 ,,church1 ,m4,a4 ,with ,fourteen ,illustrations in ,colours4 ,extra ,crown #hvo1 #es4 ,professor ,church has probably done more than any other man living to bring the classics of ,greece and ,rome within the comprehension of young folks4 ,he has a simple style that must be the envy of writers for children4--,dundee ,advertiser4 ,a delightful gift-book4--,athenum4 ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,the ,,romance ,,of ,,animal ,,arts ,,crafts ,,describing ,,the ,,wonderful ,,intelligence ,,of ,,animals ,,revealed ,,in ,,their ,,work ,,as ,,masons1 ,,paper ,,makers1 ,,raft ,,diving-,,bell ,,builders1 ,,miners1 ,,tailors1 ,,engineers ,,of ,,roads ,,bridges1 ,c4 ,c4 ,,by ,h4 ,,coupin1 ,d4,sc41 ,,john ,,lea1 ,b4,a4 7,,cantab47 ,with ,thirty ,illustrations4 ,extra ,crown #hvo41 #es4 ,will carry most readers1 young and old1 from one surprise to another4--,glasgow ,herald4 ,a charming subject1 well set forth1 and dramatically illustrated4--,athenum4 ,it seems like pure romance to read of the curious ways of ,nature's craftsmen1 but it is quite a true tale that is set forth in this plentifully illustrated book4--,evening ,citizen4 ,,the ,,romance ,,of ,,insect ,,life ,,describing ,,the ,,curious ,,interesting ,,in ,,the ,,insect ,,world ,,by ,,edmund ,,selous ,author of ,the ,romance of the ,animal ,world1 c4 ,with ,sixteen ,illustrations4 ,extra ,crown #hvo1 #es4 ,an entertaining volume1 one more of a series which seeks with much success to describe the wonders of nature and science in simple1 attractive form4--,graphic4 ,offers most interesting descriptions of the strange and curious inhabitants of the insect world1 sure to excite inquiry and to foster observation4 ,there are ants white and yellow1 locusts and cicadas1 bees and butterflies1 spiders and beetles1 scorpions and cockroaches--and especially ants--with a really scientific investigation of their wonderful habits not in dry detail1 but in free and charming exposition and narrative4 ,an admirable book to put in the hands of a boy or girl with a turn for natural science--and whether or not4--,educational ,times4 ,,the ,,romance ,,of ,,the ,,animal ,,world ,,describing ,,the ,,curious ,,and ,,interesting ,,in ,,natural ,,history ,,by ,,edmund ,,selous ,with ,sixteen full-page ,illustrations4 ,extra ,crown #hvo1 #es4 ,mr4 ,selous takes a wide range in ,nature2 he has seen many wonders which he relates4 ,open the book where we will we find something astonishing4--,spectator4 ,it is in truth a most fascinating book1 as full of incidents and as various in interest as any other work of imagination1 and1 beyond the pleasure in the reading there is the satisfaction of knowing that one is in the hands of a genuine authority on some of the most picturesque subjects that natural history affords4 ,mr4 ,selous' method is strong1 safe1 and sound4 ,the volume has numerous illustrations of a high order of workmanship and a handsome binding of striking design4--,school ,government ,chronicle4 ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,the ,,romance ,,of ,,modern ,,electricity ,,describing ,,in ,,non-,,technical ,,language ,,what ,,is ,,known ,,about ,,electricity ,,many ,,of ,,its ,,interesting ,,applications ,,by ,,charles ,r4 ,,gibson1 ,a4,i4,e4,e4 ,,author ,,of ,,electricity ,,of ,,to-,,day1 ,,etc4 ,extra ,crown #hvo4 ,with #cd ,illustrations and #aa ,diagrams4 #es4 ,everywhere ,mr4 ,charles ,r4 ,gibson makes admirable use of simple analogies which bespeak the practised lecturer1 and bring the matter home without technical detail4 ,the attention is further sustained by a series of surprises4 ,the description of electric units1 the volt1 the ohm1 and especially the ampere1 is better than we have found in more pretentious works4--,academy4 ,mr4 ,gibson's style is very unlike the ordinary text-book4 ,it is fresh1 and is non-technical4 ,its facts are strictly scientific1 however1 and thoroughly up to date4 ,if we wish to gain a thorough knowledge of electricity pleasantly and without too much trouble on our own part1 we will read ,mr4 ,gibson's 'romance4'--,expository ,times4 ,a book which the merest tyro totally unacquainted with elementary electrical principles can understand1 and should therefore especially appeal to the lay reader4 ,especial interest attaches to the chapter on wireless telegraphy1 a subject which is apt to 'floor' the uninitiated4 ,the author reduces the subject to its simplest aspect1 and describes the fundamental principles underlying the action of the coherer in language so simple that anyone can grasp them4--,electricity4 ,,the ,,romance ,,of ,,the ,,ship ,,the ,,story ,,of ,,her ,,origin ,,and ,,evolution ,,from ,,the ,,earliest ,,times ,,by ,e4 ,,keble ,,chatterton1 ,b4,a4 ,,oxon4 ,,author ,,of ,,sailing ,,ships ,,and ,,their ,,story1 ,,etc4 ,,etc4 ,with #cd ,illustrations4 ,price #es4 ,one of the most instructive and intelligent treatises on sea-life that it has yet been our lot to peruse4--,syren and ,shipping4 ,there is not a doubt about this volume being the best of its kind yet published4--,dundee ,courier4 ,absorbingly interesting and highly instructive4--,liverpool ,daily ,post4 ,,the ,,romance ,,of ,,modern ,,astronomy ,,by ,,hector ,,macpherson1 ,,junior ,with #cb ,illustrations ,diagrams4 ,extra ,crown #hvo4 ,price #es4 ,we can conceive no book better adapted than this handsomely got up and beautifully illustrated volume to attract the young1 and even older people to the study of the sublimest of sciences4--,edinburgh ,news4 ,described in popular language1 yet with a thoroughness which will give the reader a surprisingly complete grasp of the subject4--,christian4 ,an ideal book for presentation1 as indeed all ,messrs4 ,seeley's ,romance books are4--,eastern ,morning ,news4 ,an excellent compendium of the most interesting facts in astronomy1 told in popular language4 ,great care has evidently been taken to secure accuracy4 ,the illustrations are exceedingly good4--,the ,athenum4 ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,stories by ,prof4 ,a4 ,j4 ,church ,the ,headmaster of ,eton 7,dr4 the ,hon4 ,e4 ,lyttelton7 advised his hearers1 in a recent speech at the ,royal ,albert ,institute1 to read ,professor ,a4 ,j4 ,church's ,stories from ,homer1 some of which1 he said1 he had read to ,eton boys after a hard school day1 and at an age when they were not in the least desirous of learning1 but were anxious to go to tea4 ,the stories were so brilliantly told1 however1 that those young ,etonians were entranced by them1 and they actually begged of him to go on1 being quite prepared to sacrifice their tea time4 ,profusely illustrated4 ,extra ,crown #hvo1 #es4 each ,the ,children's neid ,the ,children's ,iliad ,the ,children's ,odyssey ,the ,faery ,queen and her ,knight ,the ,crusaders ,greek ,story and ,song ,stories from ,homer ,stories from ,virgil ,the ,crown of ,pine ,stories from ,greek ,tragedians ,stories of the ,east from ,herodotus ,story of the ,persian ,war ,stories from ,livy ,roman ,life in the ,days of ,cicero ,with the ,king at ,oxford ,count of ,saxon ,shore ,the ,hammer ,story of the ,iliad ,story of the ,odyssey ,stories from ,greek ,comedians ,heroes of ,chivalry and ,romance ,helmet and ,spear ,stories of ,charlemagne ,extra ,crown #hvo1 illustrated1 and other sizes #cs4 #f;d4 ,last ,days of ,jerusalem ,the ,burning of ,rome ,the ,fall of ,athens ,stories from ,english ,history ,patriot ,hero #bs4 #f;d4 ,the ,chantry ,priest of ,barnet ,heroes of ,eastern ,romance ,three ,greek ,children ,to the ,lions ,a ,young ,macedonian #bs4 ,heroes of ,eastern ,romance #as4 #f;d4 ,heroes and ,kings ,greek ,gulliver ,nicias ,story of the ,iliad and neid ,to the ,lions #as4 ,story of the ,iliad ,story of the ,odyssey ,story of the ,iliad and neid #f;d4 ,last ,days of ,jerusalem ,story of the ,iliad ,story of the ,odyssey ,stories from ,virgil ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,a ,catalogue of ,books for ,young ,people1 ,published by ,seeley1 ,service ,co ,limited1 #ch ,great ,russell ,street1 ,london ,some of the ,contents ,adventure1 ,the ,library of #ab ,bedford ,library1 ,the #b ,church1 ,stories by ,professor #c ,giberne1 ,books by ,miss #f ,heroes of the ,world ,library1 ,the #h ,marshall1 ,stories by ,miss ,beatrice #i ,marshall1 ,stories by ,mrs4 #i ,missionary ,biographies #aj ,olive ,library1 ,the #aj ,pink ,library1 ,the #aa ,prince's ,library1 ,the #aa ,romance1 ,the ,library of #ac ,royal ,library1 ,the #ab ,russell ,series1 ,the #ab ,scarlet ,library1 ,the #ad ,science for ,children #ad ,sunday ,echoes #b ,wonder ,library1 ,the #af ,the ,publishers will be pleased to send post free their complete ,catalogue or their ,illustrated ,miniature ,catalogue on receipt of a post-card ,,seeley1 ,,service ,,co4 ,,limited 99 99 99 99 99 ,,catalogue ,,of ,,books ,arranged alphabetically under the names of ,authors and ,series ,,aguilar1 ,,grace4 ,,the ,,days ,,of ,,bruce4 ,with ,illustrations4 ,extra crown #hvo1 #bs4 7,,scarlet ,,library47 ,,andersen1 ,,hans4 ,,fairy ,,tales4 ,with ,illustrations4 #as4 #f;d41 #bs41 and #cs4 #f;d4 7,,scarlet ,,and ,,prince',s ,,libraries47 ,,alcott1 ,l4 ,m4 ,,little ,,women ,,and ,,good ,,wives4 ,with ,illustrations4 #bs4 7,,scarlet ,,library47 ,also ,,little ,,women1 ,extra crown #hvo1 #as4 #f;d42 and ,,good ,,wives1 ,extra crown #hvo1 #as4 #f;d4 ,,arabian ,,nights' ,,entertainments4 ,with ,illustrations1 #as4 #f;d4 7,,pink ,,library72 #bs4 7,,royal ,,scarlet ,,libraries72 #cs4 #f;d4 7,,prince',s ,,library74 ,,ballantyne1 ,r4 ,m4 ,,the ,,dog ,,crusoe ,,and ,,his ,,master4 ,with ,illustrations by ,h4 ,m4 ,,brock1 ,r4,i4 ,extra crown #hvo1 #bs4 and #bs4 #f;d4 ,,bedford ,,library ,,for ,,boys ,,and ,,girls1 ,,the4 ,a ,series of books describing the ,adventures1 ,bravery1 and ,resource of ,soldiers1 ,sailors1 and others in all ,parts of the ,world4 ,sq4 ,crown #hvo1 with many ,illustrations in ,colour1 #cs4 #f;d4 ,,daring ,,deeds ,,of ,,famous ,,pirates4 ,by ,lieut4 ,e4 ,,keble ,,chatterton1 ,r4,n4,v4,r41 ,author of ,sailing ,ships and their ,story1 c4 c4 ,,daring ,,deeds ,,of ,,hunters ,,and ,,trappers4 ,by ,,ernest ,,young1 ,b4,sc41 ,f4,r4,g4,s41 ,author of ,the ,king of the ,yellow ,robe1 c4 c4 ,,berthet1 ,e4 ,,the ,,wild ,,man ,,of ,,the ,,woods4 ,with ,illustrations1 #as4 #f;d4 ,,blake1 ,m4 ,m4 ,,the ,,siege ,,of ,,norwich ,,castle4 ,with ,illustrations1 #es4 ,,boisragon1 ,major ,,alan ,m4 ,late ,royal ,irish ,fusiliers4 ,,jack ,,scarlett1 ,sandhurst ,cadet4 ,with ,coloured ,illustrations4 ,extra crown #hvo1 #es4 ,,brock1 ,mrs4 ,,carey4 ,,dame ,,wynton',s ,,home4 ,a ,story ,illustrative of the ,lord's ,prayer4 ,with ,eight ,illustrations4 ,crown #hvo1 #as4 #f;d4 ,,my ,,father',s ,,hand1 and other ,stories4 ,crown #hvo1 #bs4 ,,sunday ,,echoes ,,in ,,weekday ,,hours4 ,a ,series of ,illustrative ,tales4 ,seven ,vols4 ,crown #hvo1 #cs4 #f;d4 each4 ,i4 ,the ,collects4 ,,ii4 ,the ,church ,catechism4 ,,iii4 ,journeyings of the ,israelites4 ,,iv4 ,scripture ,characters4 ,v4 ,the ,epistles and ,gospels4 ,,vi4 ,the ,parables4 ,,vii4 ,the ,miracles4 ,,working ,,and ,,waiting4 ,crown #hvo1 #es4 ,,brown ,,linnet4 ,,the ,,kidnapping ,,of ,,ettie1 and other ,tales4 ,with ,sixteen ,illustrations4 ,crown #hvo1 #es4 ,,bunyan1 ,,john4 ,,the ,,pilgrim',s ,,progress4 ,with ,illustrations4 ,extra crown #hvo1 #bs4 7,,scarlet ,,library74 ,,carter1 ,miss ,j4 ,r4 ,m4 ,,diana ,,polwarth1 ,,royalist4 ,a ,story of the ,life of a ,girl in ,commonwealth ,days4 ,with ,eight ,illustrations4 ,crown #hvo1 #cs4 #f;d4 ,,charlesworth1 ,miss4 ,,england',s ,,yeomen4 ,crown #hvo1 #bs4 #f;d4 ,,oliver ,,of ,,the ,,mill4 ,with ,eight ,illustrations4 ,cr4 #hvo1 #bs4 #f;d4 ,,ministering ,,children4 #a4 ,olive ,library4 ,crown #hvo1 cloth gilt1 #bs4 #f;d4 #b4 ,scarlet ,library4 ,crown #hvo1 cloth1 #bs4 #c4 ,with #d ,illustrations4 ,cloth1 #as4 #f;d4 ,,ministering ,,children3 ,a ,,sequel4 ,with ,illustrations4 ,cloth1 #as4 #f;d4 ,also with ,eight ,illustrations4 ,cloth1 #bs4 and #bs4 #f;d4 ,,the ,,broken ,,looking-,,glass4 ,crown #hvo1 #as4 ,,the ,,old ,,looking-,,glass ,,and ,,the ,,broken ,,looking-,,glass2 or1 ,mrs4 ,dorothy ,cope's ,recollections of ,service4 ,in one volume4 ,with ,eight ,illustrations4 ,crown #hvo1 #as4 #f;d4 ,,chatterton1 ,e4 ,,keble4 ,,the ,,romance ,,of ,,the ,,ship4 ,with #cc ,illus4 ,ex4 cr4 #hvo1 #es4 ,,the ,,romance ,,of ,,piracy4 ,many ,illus4 ,ex4 cr4 #hvo1 #es4 ,,church1 ,professor ,,alfred ,j4 ,the ,headmaster of ,eton 7,dr4 the ,hon4 ,e4 ,lyttelton7 advised his hearers1 in a recent speech at the ,royal ,albert ,institute1 to read ,professor ,a4 ,j4 ,church's ',stories from ,homer1' some of which1 he said1 he had read to ,eton boys after a hard school day1 and at an age when they were not in the least desirous of learning1 but were anxious to go to tea4 ,the stories were so brilliantly told1 however1 that those young ,etonians were entranced by them1 and they actually begged of him to go on1 being quite prepared to sacrifice their tea time4 ,,the ,,children',s ,,neid4 ,told for ,little ,children4 ,with ,twelve ,illustrations in ,colour4 ,extra crown #hvo1 #es4 ,,the ,,children',s ,,iliad4 ,told for ,little ,children4 ,with ,twelve ,illustrations in ,colour4 ,extra crown #hvo1 #es4 ,,the ,,children',s ,,odyssey4 ,told for ,little ,children4 ,with ,twelve ,illustrations in ,colour4 ,extra crown #hvo1 #es4 ,,the ,,crown ,,of ,,pine4 ,a ,story of ,corinth and the ,isthmian ,games4 ,with ,illustration in ,colour by ,,george ,,morrow4 ,ex4 cr4 #hvo1 #es4 ,,the ,,count ,,of ,,the ,,saxon ,,shore4 ,a ,tale of the ,departure of the ,romans from ,britain4 ,with ,sixteen ,illustrations4 ,crown #hvo1 #es4 ,,the ,,faery ,,queen ,,and ,,her ,,knights4 ,stories from ,spenser4 ,with ,eight ,illustrations in ,colour4 ,extra crown #hvo1 #es4 ,,stories ,,of ,,charlemagne ,,and ,,the ,,twelve ,,peers ,,of ,,france4 ,with ,eight ,illustrations in ,colour4 ,crown #hvo1 #es4 ,,the ,,crusaders4 ,a ,story of the ,war for the ,holy ,sepulchre4 ,with ,eight ,illustrations in ,colour4 ,extra crown #hvo1 #es4 ,,stories ,,from ,,the ,,greek ,,tragedians4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,greek ,,story4 ,with #af ,illustrations in ,colour4 ,crn4 #hvo1 #es4 ,,stories ,,from ,,the ,,greek ,,comedians4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,the ,,hammer4 ,a ,story of ,maccabean ,times4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,the ,,story ,,of ,,the ,,persian ,,war1 from ,herodotus4 ,with ,coloured ,illustrations4 ,crown #hvo1 #es4 ,,heroes ,,of ,,chivalry ,,and ,,romance4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,stories ,,of ,,the ,,east1 from ,herodotus4 ,coloured ,illustrations4 ,crown #hvo1 #es4 ,,helmet ,,and ,,spear4 ,stories from the ,wars of the ,greeks and ,romans4 ,with ,eight ,illustrations by ,g4 ,,morrow4 ,crown #hvo1 #es4 ,,the ,,story ,,of ,,the ,,iliad4 ,with ,coloured ,illustrations4 ,crown #hvo1 #es4 ,also ,thin ,paper ,edition1 cloth1 #bs4 nett2 leather1 #cs4 nett4 ,cheap ,edition1 #f;d4 nett2 also cloth1 #as4 ,,roman ,,life ,,in ,,the ,,days ,,of ,,cicero4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,stories ,,from ,,homer4 ,coloured ,illustrations4 ,crn4 #hvo1 #es4 ,,stories ,,from ,,livy4 ,coloured ,illustrations4 ,crn4 #hvo1 #es4 ,,story ,,of ,,the ,,odyssey4 ,with ,coloured ,illustrations4 #es4 ,also ,thin ,paper ,edition1 cloth1 #bs4 nett2 leather1 #cs4 nett4 ,cheap ,edition1 #f;d4 nett4 ,also cloth1 #as4 ,,stories ,,from ,,virgil4 ,with ,coloured ,illustrations4 ,crown #hvo1 #es4 ,cheap edition1 sewed1 #f;d4 nett4 ,,with ,,the ,,king ,,at ,,oxford4 ,a ,story of the ,great ,rebellion4 ,with ,coloured ,illustrations4 ,crown #hvo1 #es4 ,crown #hvo1 #c_/f each4 ,,the ,,fall ,,of ,,athens4 ,with ,illustrations4 ,crown #hvo1 #cs4 #f;d4 ,,the ,,burning ,,of ,,rome4 ,a ,story of ,nero's ,days4 ,with ,sixteen ,illustrations4 ,cheaper ,edition4 ,crown #hvo1 #cs4 #f;d4 ,,the ,,last ,,days ,,of ,,jerusalem1 from ,josephus4 ,crown #hvo1 #cs4 #f;d4 ,also a ,cheap ,edition4 ,sewed1 #f;d4 ,,stories ,,from ,,english ,,history4 ,with many ,illustrations4 ,cheaper ,edition4 ,revised4 ,crown #hvo1 #cs4 #f;d4 ,,patriot ,,and ,,hero4 ,with ,illustration4 ,crown #hvo1 #cs4 #f;d4 ,extra crown #hvo1 #b_/f each4 ,,to ,,the ,,lions4 ,a ,tale of the ,early ,christians4 ,with ,coloured ,frontispiece and other ,illustrations4 #bs4 #f;d4 ,,heroes ,,of ,,eastern ,,romance4 ,with ,coloured ,frontispiece and ,eight other ,illustrations4 ,extra crown #hvo1 #bs4 7,,royal ,,library72 #bs4 #f;d4 ,a ,,young ,,macedonian ,,in ,,the ,,army ,,of ,,alexander ,,the ,,great4 ,with ,illustrations4 ,extra crown #hvo1 #bs4 #f;d4 ,,the ,,chantry ,,priest4 ,with ,illustrations4 #bs4 #f;d4 ,,three ,,greek ,,children4 ,extra crown #hvo1 #bs4 #f;d4 ,crown #hvo1 #a_/f each4 ,a ,,greek ,,gulliver4 ,illustrated4 ,crown #hvo1 #as4 #f;d4 ,,heroes ,,and ,,kings4 ,stories from the ,greek4 ,illus4 #as4 #f;d4 ,,the ,,stories ,,of ,,the ,,iliad ,,and ,,the ,,neid4 ,with ,illustrations4 #afmo1 sewed1 #as42 cloth1 #as4 #f;d4 ,also without ,illustrations1 cloth1 #as4 ,,to ,,the ,,lions4 ,a ,tale of the ,early ,christians4 ,with ,illustrations4 ,crown #hvo1 #as4 #f;d4 ,,cody1 ,rev4 ,h4 ,a4 ,,on ,,trail ,,and ,,rapid4 ,by ,dog-sled and ,canoe4 ,a ,story of ,bishop ,bompas's ,life among the ,red ,indians and ,esquimo4 ,told for ,boys and ,girls4 ,with ,twenty-six ,illustrations4 ,extra crown #hvo1 #bs4 #f;d4 ,,apostle ,,of ,,the ,,north1 ,,an4 ,memoirs of ,bishop ,bompas4 ,with #db ,illustrations and a ,map4 #gs4 #f;d4 nett4 ,new and ,cheaper ,edition4 ,with ,illustrations4 ,extra crown #hvo1 #es4 nett4 7,,crown ,,library47 ,,coolidge1 ,,susan4 ,,what ,,katy ,,did ,,at ,,home ,,and ,,at ,,school4 ,illustrations in ,colour by ,h4 ,m4 ,,brock1 ,r4,i4 ,crown #hvo1 #bs4 7,,scarlet ,,library47 ,,what ,,katy ,,did ,,at ,,home4 ,extra crown #hvo1 #as4 #f;d4 ,,coupin1 ,h41 ,d4,sc41 and ,j4 ,,lea1 ,m4,a4 ,,the ,,romance ,,of ,,animal ,,arts ,,and ,,crafts4 ,with ,twenty-five ,illustrations4 ,extra crown #hvo1 #es4 ,,cowper1 ,f4 ,,caedwalla3 or1 ,the ,saxons in the ,isle of ,wight4 ,with ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 7,,prince',s ,,library47 ,,the ,,island ,,of ,,the ,,english4 ,a ,story of ,napoleon's ,days4 ,with ,illustrations by ,,george ,,morrow4 ,crown #hvo1 #bs4 #f;d4 ,,the ,,captain ,,of ,,the ,,wight4 ,with ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,craik1 ,mrs4 ,,john ,,halifax4 ,illustrated4 ,extra cr4 #hvo1 #bs4 7,,scarlet ,,liby47 ,,currey1 ,commander ,e4 ,,hamilton1 ,r4,n4 ,,ian ,,hardy1 ,,naval ,,cadet4 ,coloured ,illus4 ,ex4 cr4 #hvo1 #es4 ,,ian ,,hardy1 ,,midshipman4 ,a stirring story for boys4 ,with ,coloured ,illustrations4 ,extra crown #hvo1 #es4 ,,ian ,,hardy1 ,,senior ,,midshipman4 ,with ,col4 ,illus41 #es4 ,,davidson1 ,n4 ,j41 ,b4,a4 ,a ,,knight-,,errant ,,and ,,his ,,doughty ,,deeds4 ,the ,story of ,amadis of ,gaul4 ,col4 ,illus4 by ,h4 ,m4 ,,brock1 ,r4,i4 ,crown #hvo1 #es4 ,,the ,,romance ,,of ,,the ,,spanish ,,main4 ,ex4 crown #hvo4 ,with many ,illustrations1 #es4 ,,things ,,seen ,,in ,,oxford4 ,cloth1 #bs4 nett2 leather1 #cs4 nett and #es4 nett4 ,,dawson1 ,rev4 ,canon ,e4 ,c4 ,,heroines ,,of ,,missionary ,,adventure4 ,with ,twenty-four ,illustrations4 ,extra crown #hvo1 #es4 ,,lion-,,hearted4 ,bishop ,hannington's ,life ,retold for ,boys and ,girls4 ,illustrated4 ,crown #hvo1 #cs41 #bs4 #f;d4 7,,olive ,,library71 and #as4 #f;d4 ,,in ,,the ,,days ,,of ,,the ,,dragons4 ,crown #hvo1 #as4 #f;d4 ,,missionary ,,heroines ,,in ,,many ,,lands4 ,ex4 cr4 #hvo1 #as4 #f;d4 ,,missionary ,,heroines ,,of ,,the ,,cross4 ,with ,illus41 #bs4 #f;d4 ,,defoe1 ,,daniel4 ,,robinson ,,crusoe4 ,with ,illustrations4 ,extra crown #hvo1 #bs4 and #cs4 #f;d4 7,,scarlet ,,and ,,prince',s ,,libraries47 ,,elliott1 ,miss4 ,,copsley ,,annals ,,preserved ,,in ,,proverbs4 ,with ,illustrations4 ,crown #hvo1 #cs4 #f;d4 ,,mrs4 ,,blackett4 ,her ,story4 ,fcap4 #hvo1 #as4 ,,elliot1 ,prof4 ,g4 ,f4 ,,scott1 ,m4,a41 ,b4,sc41 ,f4,r4,g4,s41 ,f4,l4,s4 ,,the ,,romance ,,of ,,plant ,,life4 ,describing the curious and interesting in the ,plant ,world4 ,with #cd ,illustrations4 ,ex4 crown #hvo1 #es4 ,popularly written by a man of great scientific accomplishments4 ,,the ,,outlook4 ,,the ,,romance ,,of ,,savage ,,life4 ,with ,forty-five ,illustrations4 ,extra crown #hvo1 #es4 ,,the ,,romance ,,of ,,early ,,british ,,life3 ,from the ,earliest ,times to the ,coming of the ,danes4 ,with #cj ,illustrations4 ,ex4 crown #hvo1 #es4 ,,everett-,,green1 ,,evelyn4 ,a ,,pair ,,of ,,originals4 ,with ,coloured ,frontispiece and ,eight other ,illustrations4 ,extra crown #hvo1 #bs4 #bs4 #f;d4 ,,field1 ,rev4 ,,claud1 ,m4,a4 ,,heroes ,,of ,,missionary ,,enterprise4 ,with many ,illustrations4 ,extra crown #hvo1 #es4 ,,missionary ,,crusaders4 ,with many ,illustrations and a ,frontispiece in ,colour1 #bs4 #f;d4 ,,gardiner1 ,,linda4 ,,sylvia ,,in ,,flowerland4 ,with #af ,illustrations ,cr4 #hvo1 #cs4 #f;d4 ,,gaye1 ,,selina4 ,,coming2 or1 ,the ,golden ,year4 ,a ,tale4 ,third ,edition4 ,with ,eight ,illustrations4 ,crown #hvo1 #es4 ,,the ,,great ,,world',s ,,farm4 ,some ,account of ,nature's ,crops and ,how they are ,grown4 ,with a ,preface by ,professor ,,boulger1 and ,sixteen ,illustrations4 ,second ,edition4 ,crown #hvo1 #es4 ,,giberne1 ,,agnes4 ,,the ,,romance ,,of ,,the ,,mighty ,,deep4 ,with ,illustrations4 #es4 ,most fascinating4--,,daily ,,news4 ,,among ,,the ,,stars2 or1 ,wonderful ,things in the ,sky4 ,with ,coloured ,illustrations4 ,eighth ,thousand4 ,crown #hvo1 #es4 ,,duties ,,and ,,duties4 ,crown #hvo1 #es4 ,,the ,,curate',s ,,home4 ,crown #hvo1 #bs4 #f;d4 ,,the ,,ocean ,,of ,,air4 ,meteorology for ,beginners4 ,illustrated4 ,crown #hvo1 #es4 ,,the ,,starry ,,skies4 ,first ,lessons on ,astronomy4 ,with ,illustrations4 ,crown #hvo1 #as4 #f;d4 ,,sun1 ,,moon1 ,,and ,,stars4 ,astronomy for ,beginners4 ,with a ,preface by ,professor ,,pritchard4 ,with ,coloured ,illustrations4 ,twenty-sixth ,thousand4 ,revised and ,enlarged4 ,crown #hvo1 #es4 ,,the ,,world',s ,,foundations4 ,geology for ,beginners4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,beside ,,the ,,waters ,,of ,,comfort4 ,crown #hvo1 #cs4 #f;d4 ,,gibson1 ,,charles ,r41 ,f4,r4,s4,e4 ,,our ,,good ,,slave ,,electricity4 ,with many ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,the ,,great ,,ball ,,on ,,which ,,we ,,live4 ,with ,coloured ,frontispiece and many other ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,the ,,stars ,,and ,,their ,,mysteries4 ,with a ,coloured ,frontispiece and #ai ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,romance ,,of ,,scientific ,,discovery4 ,illustrated4 #es4 ,,heroes ,,of ,,the ,,scientific ,,world4 ,an ,account of the ,lives and ,achievements of ,scientists of all ages4 ,with #af ,illustrations4 #es4 ,,autobiography ,,of ,,an ,,electron4 ,long #hvo4 #cs4 #f;d4 nett4 ,,the ,,wonders ,,of ,,electricity4 ,with ,eight illustrations4 ,extra crown #hvo1 #bs4 ,,the ,,wonders ,,of ,,modern ,,manufacture4 ,illustrated4 #bs4 ,,wireless ,,telegraphy4 ,many ,illustrations4 #bs4 nett4 ,,the ,,romance ,,of ,,modern ,,electricity4 ,describing in non-technical language what is known about electricity and many of its interesting applications4 ,with ,forty-one ,illustrations4 ,ex4 crown #hvo1 #es4 ,admirable 444 clear1 concise4--,,the ,,graphic4 ,,the ,,romance ,,of ,,modern ,,photography4 ,the ,discovery and its ,application4 ,with many ,illustrations4 ,extra crown #hvo1 #es4 ,,the ,,romance ,,of ,,modern ,,manufacture4 ,with ,twenty-four ,illustrations and ,sixteen ,diagrams4 ,extra crown #hvo1 #es4 ,,how ,,telegraphs ,,and ,,telephones ,,work4 ,explained in non-technical language4 ,with many ,diagrams4 ,crown #hvo1 #as4 #f;d4 nett4 ,,gilliat1 ,,edward1 ,m4,a4 ,formerly ,master at ,harrow ,school4 ,,forest ,,outlaws4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,heroes ,,of ,,modern ,,crusades4 #bd ,illus4 ,ex4 cr4 #hvo1 #es4 ,,in ,,lincoln ,,green4 ,illustrated4 ,crown #hvo1 #es4 ,,the ,,king',s ,,reeve4 ,illustrated by ,,sydney ,,hall4 #cs4 #f;d4 ,,wolf',s ,,head4 ,with ,eight ,illustrations4 ,crown #hvo1 #cs4 #f;d4 ,,the ,,romance ,,of ,,modern ,,sieges4 #af ,illus4 ,ex4 cr4 #hvo1 #es4 ,,heroes ,,of ,,the ,,elizabethan ,,age4 #af ,illus4 ,ex4 cr4 #hvo1 #es4 ,,heroes ,,of ,,modern ,,africa4 #af ,illus4 ,ex4 cr4 #hvo1 #es4 ,,heroes ,,of ,,modern ,,india4 ,with many ,illustrations4 ,extra crown #hvo1 #es4 ,,heroes ,,of ,,the ,,indian ,,mutiny4 ,with many ,illustrations4 ,extra crown #hvo1 #es4 ,,stories ,,of ,,elizabethan ,,heroes4 ,with ,coloured and other ,illustrations4 ,extra crown #hvo1 #bs4 #f;d4 ,,stories ,,of ,,great ,,sieges4 ,with ,illus4 ,ex4 cr4 #hvo1 #bs4 #f;d4 ,,stories ,,of ,,indian ,,heroes4 ,with ,illus4 ,ex4 cr4 #hvo1 #bs4 #f;d4 ,,golden ,,reciter1 ,,the4 ,see ,,reciters1 ,,the ,,golden4 ,,grew1 ,,edwin1 ,m4 ,a4 7,oxon474 ,,the ,,romance ,,of ,,modern ,,geology4 ,a popular account in non-technical language4 ,with ,twenty-four ,illustrations4 ,ex4 crown #hvo1 #es4 ,,grimm',s ,,fairy ,,tales4 ,with ,illustrations4 ,extra cr4 #hvo1 #bs4 and #cs4 #f;d4 7,,scarlet ,,and ,,prince',s ,,libraries72 also ,,pink ,,library1 #as4 #f;d4 99 99 99 99 99 ,,heroes ,,of ,,the ,,world ,,library ,each ,volume lavishly ,illustrated4 ,extra crown #hvo1 #es4 ,,heroes ,,of ,,the ,,indian ,,mutiny4 ,by the ,rev4 ,,edward ,,gilliat4 ,,heroes ,,of ,,the ,,scientific ,,world4 ,by ,c4 ,r4 ,,gibson1 ,f4,r4,s4,e4 ,,heroes ,,of ,,modern ,,africa4 ,by ,rev4 ,,edward ,,gilliat4 ,,heroes ,,of ,,missionary ,,enterprise4 ,by ,rev4 ,,claud ,,field1 ,m4,a4 ,,heroes ,,of ,,pioneering4 ,by ,rev4 ,,edgar ,,sanderson1 ,m4,a4 ,,heroines ,,of ,,missionary ,,adventure4 ,by ,rev4 ,,canon ,,dawson1 ,m4,a4 ,,heroes ,,of ,,modern ,,crusades4 ,by ,rev4 ,,edward ,,gilliat4 ,,heroes ,,of ,,modern ,,india4 ,by ,rev4 ,e4 ,,gilliat4 ,,heroes ,,of ,,the ,,elizabethan ,,age4 ,by ,rev4 ,e4 ,,gilliat4 ,,hughes1 ,,thomas4 ,,tom ,,brown',s ,,schooldays4 ,with ,illustrations4 ,extra crown #hvo1 #bs4 and #bs4 #f;d4 7,,scarlet ,,and ,,olive ,,libraries47 ,,hyrst1 ,h4 ,w4 ,g4 ,extra crown #hvo1 price #es4 ,,adventures ,,in ,,the ,,great ,,deserts4 ,with #af ,illustrations4 ,,adventures ,,in ,,the ,,great ,,forests4 ,with #af ,illustrations4 ,,adventures ,,among ,,wild ,,beasts4 ,with #bd ,illustrations4 ,,adventures ,,in ,,the ,,arctic ,,regions4 ,with #af ,illustrations4 ,,adventures ,,among ,,red ,,indians4 ,with #af ,illustrations4 ,,stories ,,of ,,red ,,indian ,,adventure4 ,with ,coloured and other ,illustrations4 ,extra crown #hvo1 #bs4 #f;d4 ,,stories ,,of ,,polar ,,adventure4 ,extra crown #hvo1 #bs4 #f;d4 ,,kingsley1 ,,charles4 ,,westward ,,ho6 ,with ,illustrations4 ,extra crown #hvo1 #bs4 #bs4 #f;d4 7,,scarlet ,,and ,,olive ,,libraries47 ,,knight-,,errant ,,and ,,his ,,doughty ,,deeds4 ,the story of ,amadis of ,gaul4 ,edited by ,n4 ,j4 ,,davidson1 ,b4,a4 ,with ,eight ,coloured ,illustrations by ,h4 ,m4 ,,brock1 ,r4,i4 ,sq4 ex4 crown #hvo1 #es4 ,,lamb1 ,,charles and ,,mary4 ,,tales ,,from ,,shakespeare4 ,with ,illustrations4 ,ex4 crown #hvo1 #bs4 7,,scarlet ,,library47 ,,lambert1 ,rev4 ,,john1 ,m4,a41 ,d4,d4 ,,the ,,romance ,,of ,,missionary ,,heroism4 ,true ,stories of the ,intrepid ,bravery and ,stirring ,adventures of ,missionaries in all ,parts of the ,world4 ,with ,thirty-nine ,illustrations4 ,extra crown #hvo1 #es4 ,,missionary ,,heroes ,,in ,,asia4 ,illustrated4 ,cr4 #hvo1 #as4 #f;d4 ,,missionary ,,heroes ,,in ,,africa4 ,illustrated4 ,cr4 #hvo1 #as4 #f;d4 ,,missionary ,,heroes ,,in ,,oceania4 ,illustrated4 ,cr4 #hvo1 #as4 #f;d4 ,,missionary ,,heroes ,,of ,,north ,,and ,,south ,,america4 ,illustrated4 ,crown #hvo1 #as4 #f;d4 ,,missionary ,,knights ,,of ,,the ,,cross4 ,with many ,illustrations and a ,frontispiece in ,colour4 #bs4 #f;d4 ,,lea1 ,,john1 ,m4,a4 7,oxon47 ,,the ,,romance ,,of ,,animal ,,arts ,,and ,,crafts4 ,see ,,coupin4 ,,the ,,romance ,,of ,,bird ,,life4 ,with ,twenty-six ,illustrations4 #es4 ,,wonders ,,of ,,bird ,,life4 ,extra crown #hvo1 #bs4 ,,leyland1 ,j4 ,,for ,,the ,,honour ,,of ,,the ,,flag4 ,a ,story of our ,sea ,fights with the ,dutch4 ,with ,illustrations by ,,lancelot ,,speed4 ,crown #hvo1 #es4 ,,macpherson1 ,,hector1 ,jun4 ,,the ,,romance ,,of ,,modern ,,astronomy4 ,with ,twenty-four ,illustrations4 ,extra crown #hvo1 #es4 ,,wonders ,,of ,,modern ,,astronomy4 ,ex4 crown #hvo1 #bs4 ,,marryat1 ,captain4 ,,masterman ,,ready4 ,with ,illustrations by ,h4 ,m4 ,,brock1 ,r4,i4 #bs4 7,,scarlet ,,library47 ,,marshall1 ,,beatrice4 ,,his ,,most ,,dear ,,ladye4 ,a ,story of the ,days of the ,countess of ,pembroke1 ,sir ,philip ,sidney's ,sister4 ,illustrated4 ,extra crown #hvo1 #es4 ,,the ,,siege ,,of ,,york4 ,a ,story of the ,days of ,thomas1 ,lorde ,fairfax4 ,with ,eight ,illustrations4 ,crown #hvo1 #es4 ,,an ,,old ,,london ,,nosegay4 ,gathered from the ,day-,book of ,mistress ,lovejoy ,young4 ,with ,eight ,illustrations4 ,crown #hvo1 #es4 ,,old ,,blackfriars4 ,in the ,days of ,van ,dyck4 ,a ,story4 ,with ,eight ,illustrations4 ,crown #hvo1 #es4 ,,the ,,queen',s ,,knight-,,errant4 ,a ,story of the ,days of ,sir ,walter ,raleigh4 ,with ,eight ,illustrations4 ,extra crown #hvo1 #es4 ,,marshall1 ,,emma4 ,crown #hvo1 #e_/- ,,in ,,colston',s ,,days4 ,a ,story of ,old ,bristol4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,in ,,four ,,reigns4 ,the ,recollections of ,althea ,allingham1 #aghe-ahdb4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,in ,,the ,,choir ,,of ,,westminster ,,abbey4 ,a ,story of ,henry ,purcell's ,days4 ,with ,illustrations4 ,crown #hvo1 #es4 and at #cs4 #f;d4 ,,in ,,the ,,east ,,country ,,with ,,sir ,,thomas ,,browne1 ,,knight4 ,with ,illustrations4 ,crown #hvo1 #es4 ,a ,,haunt ,,of ,,ancient ,,peace4 ,memories of ,mr4 ,nicholas ,ferrar's ,house at ,little ,gidding4 ,with ,illustrations by ,t4 ,,hamilton ,,crawford4 ,crown #hvo1 #es4 ,,kensington ,,palace4 ,in the ,days of ,mary ,,ii4 ,with ,illustrations4 ,crown #hvo1 #cs4 #f;d4 and #es4 ,,the ,,master ,,of ,,the ,,musicians4 ,a ,story of ,handel's ,day4 ,with ,illustrations4 ,crown #hvo1 #es4 and at #cs4 #f;d4 ,,the ,,parson',s ,,daughter1 and ,how she was ,painted by ,mr4 ,romney4 ,with ,eight ,illustrations4 ,crown #hvo1 #es4 and at #cs4 #f;d4 ,,penshurst ,,castle4 ,in the ,days of ,sir ,philip ,sidney4 ,with ,illustrations4 ,crown #hvo1 #cs4 #f;d41 #es4 ,,cheap ,,edition4 ,demy #hvo1 #f;d4 ,,winchester ,,meads4 ,in the ,days of ,bishop ,ken4 ,with ,illustrations4 ,crown #hvo1 #cs4 #f;d41 #es4 ,,cheap ,,edition4 ,demy #hvo1 #f;d4 ,,under ,,salisbury ,,spire4 ,in the ,days of ,george ,herbert4 ,with ,illustrations4 ,crown #hvo1 #cs4 #f;d41 #es4 ,,cheap ,,edition4 #f;d4 ,,under ,,the ,,dome ,,of ,,st ,,paul',s4 ,in the ,days of ,sir ,christopher ,wren4 ,with ,illustrations4 ,crown #hvo1 #es4 ,crown #hvo1 #e_/- ,,under ,,the ,,mendips4 ,a ,tale of the ,times of ,hannah ,more4 ,with ,illustrations4 ,crown #hvo1 #es4 ,,constantia ,,carew4 ,crown #hvo1 #es4 ,crown #hvo1 #c_/f ,,castle ,,meadow4 ,a ,story of ,norwich a ,hundred ,years ,ago4 ,,an ,,escape ,,from ,,the ,,tower4 ,,life',s ,,aftermath4 ,,now-,a-,,days4 ,,on ,,the ,,banks ,,of ,,the ,,ouse4 ,,winifrede',s ,,journal4 ,extra crown #hvo1 #b_/f ,,the ,,old ,,gateway4 ,,millicent ,,legh4 ,,violet ,,douglas4 ,,helen',s ,,diary4 ,crown #hvo1 #a_/f ,,brothers ,,and ,,sisters4 ,,brook ,,silverstone4 #a_/- ,,the ,,first ,,light ,,on ,,the ,,eddystone4 99 99 99 99 99 ,,missionary ,,biographies4 ,with many ,illustrations and a ,frontispiece in ,colour4 ,price1 #bs4 #f;d4 ,extra crown #hvo4 #a4 ,a ,,hero ,,of ,,the ,,afghan ,,frontier4 ,being the ,life of ,dr4 ,t4 ,l4 ,pennell1 of ,bannu1 told for ,boys and ,girls4 ,by ,a4 ,m4 ,,pennell1 ,m4,b41 ,b4,s4 7,lond471 ,b4,sc4 #b4 ,,missionary ,,crusaders4 ,by ,,claude ,,field1 ,m4,a41 sometime ,c4,m4,s4 ,missionary in the ,punjab4 #c4 ,,judson1 ,,the ,,hero ,,of ,,burma4 ,the ,life of ,judson told for ,boys and ,girls4 ,by ,,jesse ,,page1 ,f4,r4,g4,s4 #d4 ,,on ,,trail ,,and ,,rapid ,,by ,,dogsled ,,and ,,canoe4 ,by the ,rev4 ,h4 ,a4 ,,cody1 ,m4,a4 #e4 ,,missionary ,,knights ,,of ,,the ,,cross4 ,by ,rev4 ,j4 ,g4 ,,lambert4 #f4 ,,missionary ,,heroines ,,of ,,the ,,cross4 ,by ,,canon ,,dawson4 99 99 99 99 99 ,,the ,,olive ,,library4 ,stories by well-known ,authors4 ,extra crown #hvo4 ,with ,coloured and other ,illustrations1 #bs4 #f;d4 each4 ,,andersen1 ,,hans4 ,,fairy ,,tales4 ,r4 ,m4 ,,ballantyne4 ,,the ,,dog ,,crusoe4 ,,charlesworth1 ,miss4 ,,ministering ,,children4 ,a ,,sequel ,,to ,,ministering ,,children4 ,,england',s ,,yeomen4 ,,oliver ,,of ,,the ,,mill4 ,,church1 ,prof4 ,a4 ,j4 ,,the ,,chantry ,,priest4 ,,heroes ,,of ,,eastern ,,romance4 ,a ,,young ,,macedonian4 ,,three ,,greek ,,children4 ,,to ,,the ,,lions4 ,a ,tale of the ,early ,christians4 ,,dawson1 ,rev4 ,canon ,e4 ,c4 ,,lion-,,hearted4 ,the ,story of ,bishop ,hannington's ,life told for ,boys and ,girls4 ,,everett-,,green1 ,,evelyn ,a ,,pair ,,of ,,originals4 ,,hughes1 ,t4 ,,tom ,,brown',s ,,schooldays4 ,,kingsley1 ,,chas4 ,,westward ,,ho6 ,,marshall1 ,mrs4 ,,the ,,old ,,gateway4 ,,helen',s ,,diary4 ,,brothers ,,and ,,sisters4 ,,violet ,,douglas4 ,,millicent ,,legh4 ,,mulock1 ,miss4 ,,john ,,halifax4 ,,stowe1 ,mrs4 ,,beecher4 ,,uncle ,,tom',s ,,cabin4 ,,wilberforce1 ,bishop4 ,,agathos1 ,,the ,,rocky ,,island1 and other ,sunday ,stories4 ,,philip1 ,,james ,c41 ,d4,sc41 ,ph4,d4 ,,the ,,romance ,,of ,,modern ,,chemistry4 ,with ,twenty-nine ,illustrations4 ,extra crown #hvo1 #es4 99 99 99 99 99 ,,the ,,pink ,,library4 ,stories by well-known ,authors4 ,crown #hvo4 ,with many ,illustrations1 #as4 #f;d4 ,,church1 ,prof4 ,a4 ,j4 ,to the ,lions4 ,the ,greek ,gulliver4 ,,marshall1 ,mrs4 ,brothers ,sisters4 ,brook ,silvertone4 ,,charlesworth1 ,miss4 ,ministering ,children4 ,the ,sequel to ,ministering ,children4 ,the ,old the ,broken ,looking-,glass4 ,,dawson1 ,canon ,e4 ,c4 ,lion-,hearted4 ,missionary ,heroines in many ,lands4 ,,lambert1 ,rev4 ,j4 ,g4 ,missionary ,heroes of ,n4 ,s4 ,america4 ,missionary ,heroes in ,asia4 ,missionary ,heroes in ,oceania4 ,missionary ,heroes in ,africa4 ,,wilberforce1 ,bishop4 ,agathos ,the ,rocky ,island4 ,,alcott1 ,l4 ,m4 ,little ,women4 ,good ,wives4 ,,berthe1 ,t4 ,e4 ,the ,wild ,man of the ,woods4 ,,seeley1 ,e4 ,the ,world before the ,flood4 ,,andersen1 ,,hans4 ,fairy ,tales and ,stories4 ,,grimm1 ,the ,brothers4 ,fairy ,tales and ,stories4 ,,coolidge1 ,,susan4 ,what ,katy did at ,home ,,by ,,various ,,authors ,the ,life of a ,bear4 ,only a ,dog4 ,the ,life of an ,elephant ,the ,arabian ,nights4 99 99 99 99 99 ,,the ,,prince',s ,,library4 ,with ,coloured ,frontispiece and other ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,patriot ,,hero4 ,by ,prof4 ,a4 ,j4 ,,church4 ,,cranford4 ,by ,mrs4 ,,gaskell4 ,,the ,,vicar ,,of ,,wakefield4 ,by ,,oliver ,,goldsmith4 ,,the ,,arabian ,,nights' ,,entertainments4 ,,andersen',s ,,fairy ,,tales4 ,,grimm',s ,,fairy ,,tales4 ,,the ,,wolf',s ,,head4 ,by the ,rev4 ,e4 ,,gilliat4 ,,the ,,last ,,of ,,the ,,white ,,coats4 ,by ,g4 ,i4 ,,whitham4 ,,diana ,,polwarth1 ,,royalist4 ,by ,j4 ,r4 ,m4 ,,carter4 ,,the ,,fall ,,of ,,athens4 ,by ,professor ,a4 ,j4 ,,church4 ,,the ,,king',s ,,reeve4 ,by the ,rev4 ,e4 ,,gilliat4 ,,the ,,cabin ,,on ,,the ,,beach4 ,by ,m4 ,e4 ,,winchester4 ,,the ,,captain ,,of ,,the ,,wight4 ,by ,,frank ,,cowper4 ,,caedwalla4 ,by ,,frank ,,cowper4 ,,robinson ,,crusoe4 ,by ,,daniel ,,defoe4 ,,reciter1 ,,the ,,golden4 ,a volume of ,recitations ,readings in ,prose ,verse selected from the works of ,,rudyard ,,kipling1 ,r4 ,l4 ,,stevenson1 ,,conan ,,doyle1 ,,maurice ,,hewlett1 ,,christina ,,rossetti1 ,,thomas ,,hardy1 ,,austin ,,dobson1 ,a4 ,w4 ,,pinero1 c41 c4 ,with an ,introduction by ,,cairns ,,james1 ,professor of ,elocution at the ,royal ,college of ,music and the ,guildhall ,school of ,music4 ,extra crown #hvo1 #gjd pp41 #cs4 #f;d4 ,also ,thin ,paper ,edition for the ,pocket1 with gilt edges4 ,small crown #hvo1 #es4 ,an admirable collection in prose and verse4--,,the ,,spectator4 ,,reciter1 ,,the ,,golden ,,humorous4 ,edited1 and with an ,introduction by ,,cairns ,,james1 ,professor of ,elocution at the ,royal ,college of ,music4 ,recitations and ,readings selected from the writings of ,f4 ,,anstey1 ,j4 ,m4 ,,barrie1 ,s4 ,r4 ,,crockett1 ,,major ,,drury1 ,,jerome ,k4 ,,jerome1 ,,barry ,,pain1 ,a4 ,w4 ,,pinero1 ,,owen ,,seaman1 ,g4 ,b4 ,,shaw1 c4 ,over #gjj pages1 extra crown #hvo1 cloth1 #cs4 #f;d4 ,also a ,thin ,paper ,edition1 with gilt edges1 small crown #hvo1 #es4 ,,robinson1 ,commander ,c4 ,n4 ,,for ,,the ,,honour ,,of ,,the ,,flag4 ,a ,story of our ,sea ,fights with the ,dutch4 ,with ,illustrations by ,,lancelot ,,speed4 ,crown #hvo1 #es4 ,,sanderson1 ,rev4 ,e4 ,,heroes ,,of ,,pioneering4 ,true ,stories of the ,intrepid ,bravery and ,stirring ,adventures of ,pioneers in all ,parts of the ,world4 ,with ,sixteen ,illustrations4 ,extra crown #hvo1 #es4 ,,stories ,,of ,,great ,,pioneers4 ,with ,coloured and other ,illustrations4 ,extra crown #hvo1 #bs4 #f;d4 99 99 99 99 99 ,,royal ,,library ,,for ,,boys ,,and ,,girls1 ,,the4 ,a ,series of handsome ,gift ,books by ,celebrated ,authors4 ,illustrated by ,h4 ,m4 ,,brock1 ,,lancelot ,,speed1 and other well-known artists4 ,ex4 crown #hvo1 #bs4 each4 #a4 ,a ,,pair ,,of ,,originals4 ,by ,,evelyn ,,everett-,,green4 #b4 ,,john ,,halifax4 ,by ,miss ,,mulock4 #c4 ,,uncle ,,tom',s ,,cabin4 ,by ,h4 ,,beecher-,,stowe4 #d4 ,,westward ,,ho6 ,by ,,charles ,,kingsley4 #e4 ,,robinson ,,crusoe4 ,by ,,daniel ,,defoe4 #f4 ,,tom ,,brown',s ,,school-,,days4 ,by ,,thomas ,,hughes4 #g4 ,,grimm',s ,,fairy ,,tales4 ,a ,new ,translation4 #h4 ,,the ,,arabian ,,nights' ,,entertainments4 #i4 ,,andersen',s ,,fairy ,,tales4 #aj4 ,,what ,,katy ,,did ,,at ,,home ,,and ,,at ,,school4 ,by ,,susan ,,coolidge4 #aa4 ,,heroes ,,of ,,eastern ,,romance4 ,by ,prof4 ,a4 ,j4 ,,church4 #ab4 ,,lion ,,hearted4 ,by the ,rev4 ,canon ,e4 ,c4 ,,dawson4 #ac4 ,,the ,,adventures ,,of ,a ,,cavalier4 ,by ,g4 ,i4 ,,whitham4 99 99 99 99 99 ,,the ,,library ,,of ,,adventure ,with many ,illustrations4 ,extra crown #hvo1 #es4 each4 ,delightful books of adventure1 beautifully printed and tastefully got up4--,,educational ,,times4 ,,adventures ,,of ,,missionary ,,explorers4 ,by ,r4 ,m4 ,a4 ,,ibbotson4 ,,adventures ,,in ,,southern ,,seas4 ,by ,,richard ,,stead1 ,b4,a4 ,,adventures ,,among ,,trappers ,,hunters4 ,by ,e4 ,,young1 ,b4,sc4 ,,adventures ,,in ,,the ,,arctic ,,regions4 ,by ,h4 ,w4 ,g4 ,,hyrst4 ,,adventures ,,among ,,wild ,,beasts4 ,by ,h4 ,w4 ,g4 ,,hyrst4 ,,adventures ,,on ,,the ,,high ,,seas4 ,by ,r4 ,,stead1 ,b4,a4 ,,adventures ,,in ,,the ,,great ,,deserts4 ,by ,h4 ,w4 ,g4 ,,hyrst4 ,,adventures ,,on ,,the ,,great ,,rivers4 ,by ,,richard ,,stead4 ,,adventures ,,in ,,the ,,great ,,forests4 ,by ,h4 ,w4 ,g4 ,,hyrst4 ,,adventures ,,on ,,the ,,high ,,mountains4 ,by ,r4 ,,stead4 ,,adventures ,,among ,,red ,,indians4 ,by ,h4 ,w4 ,g4 ,,hyrst4 99 99 99 99 99 ,,russell ,,series ,,for ,,boys ,,girls1 ,,the4 ,coloured and other ,illustrations4 ,extra crown #hvo1 #bs4 #f;d4 ,,stories ,,of ,,polar ,,adventure4 ,by ,h4 ,w4 ,g4 ,,hyrst4 ,,stories ,,of ,,great ,,pioneers4 ,by ,,edgar ,,sanderson1 ,m4,a4 ,,stories ,,of ,,elizabethan ,,heroes4 ,by the ,rev4 ,e4 ,,gilliat4 ,,stories ,,of ,,red ,,indian ,,adventure4 ,by ,h4 ,w4 ,g4 ,,hyrst4 ,,stories ,,of ,,indian ,,heroes4 ,by ,e4 ,,gilliat1 ,m4,a4 ,,stories ,,of ,,great ,,sieges4 ,by ,e4 ,,gilliat1 ,m4,a4 99 99 99 99 99 ,,the ,,library ,,of ,,romance ,fully ,illustrated4 ,bound in blue1 scarlet1 and gold4 ,extra crown #hvo1 #es4 each4 ,splendid volumes4--,,the ,,outlook4 ,gift books whose value it would be difficult to overestimate4--,,standard4 ,,the ,,romance ,,of ,,the ,,spanish ,,main4 ,by ,n4 ,j4 ,,davidson1 ,b4,a4 7,oxon47 ,,the ,,romance ,,of ,,piracy4 ,by ,e4 ,,keble ,,chatterton1 ,b4,a4 7,oxon474 ,with many ,illustrations4 ,,the ,,romance ,,of ,,scientific ,,discovery4 ,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,,the ,,romance ,,of ,,submarine ,,engineering4 ,by ,,thomas ,w4 ,,corbin4 ,,the ,,romance ,,of ,,aeronautics4 ,by ,,charles ,c4 ,,turner4 ,,the ,,romance ,,of ,,the ,,ship4 ,the story of its origin and evolution4 ,by ,e4 ,,keble ,,chatterton4 ,with ,thirty-three ,illustrations4 ,,the ,,romance ,,of ,,modern ,,astronomy4 ,by ,,hector ,,macpherson1 ,jun4 ,with ,twenty-four ,illustrations4 ,,the ,,romance ,,of ,,modern ,,chemistry4 ,by ,j4 ,c4 ,,philip1 ,d4,sc41 ,assistant ,professor of ,chemistry1 ,south ,kensington4 ,,the ,,romance ,,of ,,modern ,,manufacture4 ,by ,c4 ,r4 ,,gibson1 ,f4,r4,s4,e4 ,,the ,,romance ,,of ,,early ,,british ,,life4 ,by ,prof4 ,g4 ,f4 ,,scott ,,elliot1 ,m4,a41 ,b4,sc4 ,with #cj ,illustrations4 ,,the ,,romance ,,of ,,modern ,,geology4 ,by ,e4 ,s4 ,,grew1 ,m4,a4 7,oxon474 ,,the ,,romance ,,of ,,bird ,,life4 ,by ,,john ,,lea1 ,m4,a4 ,,the ,,romance ,,of ,,modern ,,photography4 ,its ,discovery and its ,application4 ,by ,c4 ,r4 ,,gibson1 ,a4,i4,e4,e4 ,with #fc ,illustrations4 ,,the ,,romance ,,of ,,modern ,,sieges4 ,by the ,,rev4 ,e4 ,,gilliat4 ,with #bd ,illustrations4 ,,the ,,romance ,,of ,,savage ,,life4 ,by ,professor ,g4 ,f4 ,,scott ,,elliot1 ,m4,a41 ,b4,sc41 c4 ,with #de ,illustrations4 ,,the ,,romance ,,of ,,the ,,world',s ,,fisheries4 ,by ,,sidney ,,wright4 ,with #bd ,illustrations4 ,,the ,,romance ,,of ,,animal ,,arts ,,crafts4 ,by ,h4 ,,coupin1 ,d4,sc41 and ,j4 ,,lea1 ,m4,a4 ,with #bd ,illustrations4 ,extremely fascinating4--,,liverpool ,,courier4 ,,the ,,romance ,,of ,,early ,,exploration4 ,by ,a4 ,,williams1 ,b4,a41 ,f4,r4,g4,s4 ,with #af ,illustrations4 ,we cannot imagine a book that a boy would appreciate more than this4--,,daily ,,telegraph4 ,,the ,,romance ,,of ,,missionary ,,heroism4 ,by ,,john ,c4 ,,lambert1 ,b4,a41 ,d4,d4 ,with #ci ,illustrations4 ,about #cej pages of the most thrilling missionary lives ever collected in one volume4--,,methodist ,,times4 ,,the ,,romance ,,of ,,plant ,,life4 ,by ,prof4 ,g4 ,f4 ,,scott ,,elliot1 ,b4,a4 7,cantab471 ,b4,sc4 7,edin474 ,with #cd ,illustrations4 ,besides being entertaining1 instructive and educative4--,,liverpool ,,courier4 ,,the ,,romance ,,of ,,polar ,,exploration4 ,by ,g4 ,,firth ,,scott4 ,with #bd ,illustrations4 ,thrillingly interesting4--,,liverpool ,,courier4 ,,the ,,romance ,,of ,,insect ,,life4 ,by ,,edmund ,,selous4 ,,the ,,romance ,,of ,,modern ,,mechanism4 ,by ,a4 ,,williams4 ,genuinely fascinating4 ,mr4 ,williams is an old favourite4--,l',,pool ,,courier4 ,,the ,,romance ,,of ,,modern ,,electricity4 ,by ,c4 ,r4 ,,gibson1 ,f4,r4,s4,e4 ,revised ,edition4 ,admirable 444 clear and concise4--,,the ,,graphic4 ,,the ,,romance ,,of ,,the ,,animal ,,world4 ,by ,,edmund ,,selous4 ,a very fascinating book4--,,graphic4 ,,the ,,romance ,,of ,,modern ,,exploration4 ,by ,a4 ,,williams4 ,a mine of ,information and stirring incident4--,,scotsman4 ,,the ,,romance ,,of ,,modern ,,invention4 ,by ,a4 ,,williams4 ,revised ,edition4 ,an ideal gift book for boys1 fascinatingly interesting4--,,queen4 ,,the ,,romance ,,of ,,modern ,,engineering4 ,by ,a4 ,,williams4 ,an absorbing work with its graphic descriptions4--,,standard4 ,,the ,,romance ,,of ,,modern ,,locomotion4 ,by ,a4 ,,williams4 ,crisply written1 brimful of incident not less than instruction4 ,should be as welcome as a ,ballantyne story or a ,mayne ,reid romance4--,,glasgow ,,herald4 ,,the ,,romance ,,of ,,modern ,,mining4 ,by ,a4 ,,williams4 ,boys will revel in this volume4--,,city ,,press4 ,,the ,,romance ,,of ,,the ,,mighty ,,deep4 ,by ,,agnes ,,giberne4 ,most fascinating4--,,daily ,,news4 99 99 99 99 99 ,,scarlet ,,library1 ,,the ,,illustrated4 ,large crown #hvo1 cloth1 gilt4 ,with ,eight original ,illustrations by ,h4 ,m4 ,,brock1 ,,lancelot ,,speed1 and other leading ,artists4 ,price #bs4 per volume4 ,,the ,,pilgrim',s ,,progress4 ,,the ,,wide1 ,,wide ,,world4 ,,uncle ,,tom',s ,,cabin4 ,,ben ,,hur4 ,,gen4 ,,lew ,,wallace4 ,,westward ,,ho6 ,,kingsley4 ,,john ,,halifax4 ,by ,mrs4 ,,craik4 ,,robinson ,,crusoe4 ,,defoe4 ,,little ,,women and ,,good ,,wives4 ,,the ,,history ,,of ,,henry ,,esmond4 ,by ,w4 ,m4 ,,thackeray4 ,,the ,,swiss ,,family ,,robinson4 ,,grimm',s ,,fairy ,,tales4 ,,poe',s ,,tales ,,of ,,mystery ,,and ,,imagination4 ,,don ,,quixote4 ,by ,,cervantes4 ,,gulliver',s ,,travels4 ,,swift4 ,,the ,,days ,,of ,,bruce4 ,,tom ,,brown',s ,,schooldays4 ,,tales ,,from ,,shakespeare4 ,,lamb4 ,,hans ,,andersen',s ,,fairy ,,tales4 ,,the ,,arabian ,,nights' ,,entertainments4 ,,the ,,scalp ,,hunters4 ,by ,captain ,,mayne ,,reid4 ,,ministering ,,children4 ,,ministering ,,children4 ,a ,sequel4 ,,the ,,dog ,,crusoe4 ,,ballantyne4 ,,masterman ,,ready4 ,,marryat4 ,,what ,,katy ,,did ,,at ,,home ,,and ,,at ,,school4 ,by ,,susan ,,coolidge4 ,,the ,,old ,,gateway4 ,e4 ,,marshall4 ,,millicent ,,legh4 ,e4 ,,marshall4 ,,vicar ,,of ,,wakefield4 99 99 99 99 99 ,,science ,,for ,,children ,,our ,,good ,,slave ,,electricity4 ,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,with many ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,the ,,great ,,ball ,,on ,,which ,,we ,,live4 ,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,with ,coloured ,frontispiece and many other ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,the ,,stars ,,and ,,their ,,mysteries4 ,with ,illustrations4 ,extra crown #hvo1 #cs4 #f;d4 ,,scott1 ,g4 ,,firth4 ,,the ,,romance ,,of ,,polar ,,exploration4 ,illustrated ,extra crown #hvo1 #es4 ,thrillingly interesting1 excellently illustrated4--,,liverpool ,,courier4 ,,seeley1 ,a4 ,,this ,,great ,,globe4 ,first ,lessons in ,geography4 #as4 #f;d4 ,,seeley1 ,m4 ,,the ,,world ,,before ,,the ,,flood4 ,stories from the ,best ,book4 ,with ,illustrations by ,g4 ,p4 ,,jacomb ,,hood4 ,crown #hvo1 #as4 and #as4 #f;d4 ,,selous1 ,e4 ,,the ,,romance ,,of ,,the ,,animal ,,world4 ,illustrated4 ,ex4 crown #hvo1 #es4 ,a very fascinating book4--,,graphic4 ,,the ,,romance ,,of ,,insect ,,life4 ,illustrated4 ,ex4 cr4 #hvo41 #es4 ,mr4 ,selous1 the well-known naturalist1 writes in purely informal style4--,,the ,,globe4 ,,wonders ,,of ,,animal ,,life4 ,extra crown #hvo1 #bs4 ,,wicks1 ,m4 ,,to ,,mars ,,via ,,the ,,moon4 ,an ,astronomical ,story4 ,with ,eight ,illustrations4 ,extra crown #hvo1 #es4 ,,wilberforce1 ,bishop ,s4 ,,agathos4 ,with ,illustrations4 ,fcap4 #hvo1 sewed1 #f;d42 cloth1 #as4 ,,agathos1 ,,the ,,rocky ,,island1 and other ,sunday ,stories4 ,with ,sixteen ,illustrations4 ,extra crown #hvo1 #as4 #f;d41 #bs4 #f;d4 ,,the ,,rocky ,,island ,,and ,,other ,,similitudes4 ,with ,illustrations4 ,fcap4 #hvo1 sewed1 #f;d42 cloth1 #as4 ,,winchester1 ,m4 ,e4 ,,adrift ,,in ,a ,,great ,,city4 ,illustrated4 ,crown #hvo1 #es4 ,a ,,city ,,violet4 ,crown #hvo1 #es4 ,,the ,,cabin ,,on ,,the ,,beach4 ,illustrated4 ,crown #hvo1 #cs4 #f;d4 ,a ,,nest ,,of ,,skylarks4 #es4 ,a ,,nest ,,of ,,sparrows4 ,crown #hvo1 #es4 ,a ,,wayside ,,snowdrop4 ,crown #hvo1 #bs4 #f;d4 ,,chirps ,,for ,,the ,,chicks4 #bs4 #f;d4 ,,williams1 ,,archibald1 ,b4,a4 7,oxon471 ,f4,r4,g4,s4 ,,the ,,romance ,,of ,,early ,,exploration4 ,illustrated4 #es4 ,a companion volume to ',the ,romance of ,modern ,exploration1' and if possible1 more full of ,romance4--,,evening ,,standard4 ,,the ,,romance ,,of ,,modern ,,exploration4 ,illustrated4 #es4 ,a mine of information and stirring incident4--,,scotsman4 ,,the ,,romance ,,of ,,modern ,,mechanism4 ,illustrated4 #es4 ,mr4 ,williams is an old favourite2 a genuinely fascinating book4--,,liverpool ,,courier4 ,,the ,,romance ,,of ,,modern ,,invention4 ,with #bd ,illustrations4 ,an ideal gift book for boys1 fascinatingly interesting4--,,queen4 ,,the ,,romance ,,of ,,modern ,,engineering4 ,illustrated4 ,an absorbing work with its graphic descriptions4--,,standard4 ,,the ,,romance ,,of ,,modern ,,locomotion4 ,illustrated4 ,crisply written and brimful of incident4--,,glasgow ,,herald4 ,,the ,,romance ,,of ,,modern ,,mining4 ,with #bd ,illustrations4 ,boys will revel in this volume4--,,city ,,press4 ,,the ,,wonders ,,of ,,modern ,,engineering4 ,ex4 crown #hvo1 #bs4 ,,whitham1 ,g4 ,i4 ,,the ,,last ,,of ,,the ,,white ,,coats4 ,a ,story of ,cavaliers and ,roundheads4 ,illustrated in colour by ,,oscar ,,wilson4 ,ex4 crown #hvo1 #cs4 #f;d4 99 99 99 99 99 ,,the ,,wonder ,,library ,with ,eight ,illustrations4 ,extra crown #hvo4 ,price #bs4 ,,wonders ,,of ,,animal ,,life4 ,,edmund ,,selous4 ,,the ,,wonders ,,of ,,modern ,,manufacture4 ,by ,c4 ,r4 ,,gibson1 ,f4,r4,s4,e4 ,,the ,,wonders ,,of ,,savage ,,life4 ,by ,professor ,g4 ,f4 ,,scott ,,elliot1 ,m4,a41 ,b4,sc4 ,,the ,,wonders ,,of ,,astronomy4 ,by ,,hector ,,macpherson1 ,junr41 ,m4,a4 ,,the ,,wonders ,,of ,,invention4 ,by ,a4 ,williams1 ,b4,a4 ,revised and brought up to date by ,t4 ,w4 ,,corbin4 ,,the ,,wonders ,,of ,,modern ,,chemistry4 ,by ,,james ,c4 ,,philip1 ,d4,sc4 ,,the ,,wonders ,,of ,,electricity4 ,by ,,charles ,r4 ,,gibson1 ,f4,r4,s4,e4 ,,the ,,wonders ,,of ,,animal ,,ingenuity4 ,by ,h4 ,,coupin1 ,d4,sc41 and ,,john ,,lea1 ,m4,a4 ,,the ,,wonders ,,of ,,mechanical ,,ingenuity4 ,by ,,archibald ,,williams1 ,b4,a41 ,f4,r4,g4,s4 ,,the ,,wonders ,,of ,,asiatic ,,exploration4 ,by ,,archibald ,,williams1 ,b4,a41 ,f4,r4,g4,s4 ,,the ,,wonders ,,of ,,the ,,plant ,,world4 ,by ,g4 ,f4 ,,scott ,,elliot1 ,m4,a41 ,b4,sc41 ,f4,l4,s41 c4 ,,the ,,wonders ,,of ,,modern ,,railways4 ,by ,,archibald ,,williams1 ,b4,a41 ,f4,r4,g4,s4 ,,the ,,wonders ,,of ,,the ,,insect ,,world4 ,by ,e4 ,,selous4 ,,the ,,wonders ,,of ,,modern ,,engineering4 ,by ,,archibald ,,williams1 ,b4,a4 7,oxon47 ,,the ,,wonders ,,of ,,bird ,,life4 ,by ,,john ,,lea1 ,m4,a4 99 99 99 99 99 ,,wright1 ,,sidney4 ,,the ,,romance ,,of ,,the ,,world',s ,,fisheries4 ,with many ,illustrations4 ,extra crown #hvo1 #es4 ,,young1 ,,ernest4 ,,adventures ,,among ,,trappers ,,and ,,hunters4 ,with ,sixteen ,illustrations4 ,ex4 crown #hvo1 #es4 99 99 99 99 99 ,transcriber's note3 ,the following changes have been made to the text3 ,page #c3 added missingopen quotation mark3 7,it is no exaggeration to say that ,commander ,currey bears worthily the mantle of ,kingston and ,captain ,marryat47 ,page #c3 added missing open quotation mark 7,by writing this series the author is doing national service1 4447 ,page #ff3 added missing word on 7,needless to say1 that ship went on no more excursions47 ,page #gg3 changed bridginv to bridging 7 444 certain engineering field companies1 and bridging trains1 4447 ,page #adg3 changed ,chili to ,chile 7 444 notably in the ,united ,states1 ,chile and ,spain47 ,page #aef3 changed alumimium to aluminium 7,alumina1 too1 is oxide of aluminium47 ,page #ahg3 changed comma to period at end of sentence 7444 if the mild steel ordinarily employed for shipbuilding were used47 ,page #ahh3 ,deleted spurious comma following experience 7444 as experience shows1 a very considerable degree of safety47 ,page #bcf3 changed nutil to until 7 444 which is stored in large accumulator batteries until required 4447 ,page #bcg3 added missing period 7 444 by long spells of duty in this unhealthy atmosphere47 ,page #cjg3 changed aliminium to aluminium 7 444 another aluminium disc 4447