,,the ,,children',s ,,library ,,of ,,work ,,and ,,play ,,carpentry ,,and ,,woodwork ,by ,edwin ,w4 ,foster ,,electricity ,,and ,,its ,,everyday ,,uses ,by ,john ,f4 ,woodhull1 ,ph4,d4 ,,gardening ,,and ,,farming ,by ,ellen ,eddy ,shaw ,,home ,,decoration ,by ,charles ,franklin ,warner1 ,sc4,d4 ,,housekeeping ,by ,elizabeth ,hale ,gilman ,,mechanics1 ,,indoors ,,and ,,out ,by ,fred ,t4 ,hodgson ,,needlecraft ,by ,effie ,archer ,archer ,,outdoor ,,sports1 ,,and ,,games ,by ,claude ,h4 ,miller1 ,ph4,b4 ,,outdoor ,,work ,by ,mary ,rogers ,miller ,,working ,,in ,,metals ,by ,charles ,conrad ,sleffel ,illustration3 ,photograph by ,underwood ,underwood ,a ,,motor ,,boat ,,model ,in the making of little models of this kind1 you will encounter many things that will tax your skill and ingenuity1 as amateur workmen4 ,the ,library of ,work and ,play ,,mechanics1 ,,indoors ,,and ,,out ,,by ,,fred ,t4 ,,hodgson ,illustration3 ,cover ,page ,garden ,city ,new ,york ,,doubleday1 ,,page ,,company #aiaa ,,all ,,rights ,,reserved1 ,,including ,,that ,,of ,,translation ,,into ,,foreign ,,languages1 ,,including ,,the ,,scandinavian ,,copyright1 #aiaa1 ,,by ,,doubleday1 ,,page ,,company ,,acknowledgment ,the publishers wish to acknowledge their indebtedness to the ,horace ,mann ,school for their courtesy in permitting certain of the photographs to be taken for this volume4 ,,contents ,,part ,i ,,chapter ,,page ,i4 ,a ,pathway of ,cement #c ,purchasing property1 ,river ,passaic--,removing rocks and other obstacles--,preparing for cement sidewalk--,digging trench and purchasing materials--,making1 laying1 and properly placing concrete--,the lever and roller and application--,moving heavy bodies with lever and roller--,finishing the cement sidewalk--,how to make good concrete walks4 ,,ii4 ,building of a ,boat ,house #cf ,qualities of the inclined plane--,dismantling an old barn and out-houses--,blocks and tackle1 ropes and pulleys--,strength and care of ropes--,building a boat-house1 using old materials--,strength of timber floors--,method of construction--,holding power of nails--,doors and windows for boat-house--,the use of rollers in moving heavy weights--,sliding ways for boat--,how heavy stones were raised to tops of ,egyptian ,pyramids4 ,,iii4 ,bridge and ,boat ,work #fe ,dimensions of the launch--,arrival of ,the ,mocking-,bird--,an interesting boat talk--,a sail on the river--,building a small foot-bridge--,the same completed--,some rules for sailing a launch--,fitting up boat-house and dock--,preparing block for keel--,the winch and its construction--,the wheel and axle as a mechanical power--,the fusee1 and what it means--,some problems solved4 ,,iv4 ,making a ,gasolene ,launch #hd ,arrival of boat material--,laying keel and keelson--,setting up the boat and giving her shape--,laying engine bed--,installing engine and propeller--,nailing on planking--,table of offsets--,gasolene engine and carburetor--,dimensions of engine and propeller--,gas engines1 generally--,danger of using gasolene--,the proper use of yacht flags for signalling4 ,v4 ,a ,talk ,about ,engines #aaj ,water around the cylinder--,the carburetor and spark coil--,running the engine in boat-house--,varnishing the boat--,a steamboat on the river--,a story of the first steam engine--,how the steam acted in the case--,the slide valve1 piston and steam chest--,internal and external engine heaters--,horse-power and how calculated--,foot pounds1 dry steam and condensation--,expansion of gases1 turbines--,gilding the name--,constructing picnic tables and seats--,height of tables1 chairs and benches4 ,,vi4 ,propeller and ,other ,screws #acf ,the launch of the ,caroline--,trial of the new boat--,description of the screw as a power--,the wheel and worm and endless screw--,formula for counting power of wheel and worm screws of various kinds--,archimedian screw and water lifter--,some data of power of wheel and worm--,the screw propeller1 with data--,how to calculate force of propeller screws--,finding pitch and other lines for propeller--,the screw auger or boring tool--,adhesion of ordinary wood screws--,how to loosen and withdraw rusty screws4 ,,vii4 ,aeroplanes #aeh ,seats for riverside--,model aeroplane for the ,fourth--,dimension on construction of planes--,why a monoplane rises from the earth--,the gyroscope as a balancer--,the biplane and its construction--,aeroplanes generally--,the ,french aeroplane ,demoiselle--,how to make a model aeroplane--,illustrations and details of model aeroplane--,some general remarks4 ,,viii4 ,kites1 ,sundials1 ,patents #ahe ,the theory of kite-flying--,the highest kite ascent--,the flat plane kite--,the kite a small aeroplane--,a box kite of common type--,cellular kites of various kinds--,pairs and bevies of kites--,bird flight and motion--,war kites of various kinds--,wind gauges and wind force--,patents and how to secure them--,a simple sundial--,how to make an oval flower bed4 ,,ix4 ,tides #bab ,the why of the tides explained--,globular form of the earth proved--,day and night--,phases of the moon--,attraction of the sun and moon--,newton's theory of the tides--,height of tides--,a simple hygrometer--,the ,australian boomerang--,theory of the pump4 ,x4 ,wall ,making and ,plumbing #bcg ,protecting the river bank--,concrete retaining walls--,big dams in the ,west--,galveston sea wall--,the great dam across the ,nile--,proposed irrigation works in ,babylon--,some properties of light and sound--,hints on amateur plumbing--,the peppermint test--,barometers of various kinds--,thermometers1 and their uses--,something about steel springs--,how to make a cross-bow--,the gyroscope and its uses4 ,,part ,,ii ,i4 ,some ,practical ,advice #bga ,the inventor1 ancient and modern--,barriers to mechanical progress in the past--,laws of gravitation--,how to adjust sewing machines4 ,,ii4 ,mechanical ,movements #cjf ,coffee mills--,pulleys--,pumps--,pistons--,leve rs--,steam engine and water wheel governors1 etc4 ,,iii4 ,the ,weather and ,indoor ,work #cdi ,how to make a rain gauge--,hail--,snow--,designing1 making and inflating paper balloons--,magnetized watches--,a boy's wheelbarrow--,vacuum cleaners4 ,,iv4 ,motors and ,typewriters #chg ,motors1 gasolene and steam--,automobile frames--,the modern typewriter--,directions for securing copyrights4 ,,illustrations ,a ,motor-,boat ,model ,frontispiece ,,facing ,,page ,boat-,house and ,workshop #db ,the ,creek #gj ,making a ,motor ,launch #hh ,finishing the ,motor ,launch #aab ,the ,monoplane ,model ,complete #afj ,making an ,aeroplane ,model #ahj ,making ,kites #aij ,a ,sundial ,made of ,concrete #bjh ,,part ,i ,i ,a ,,pathway ,,of ,,cement ,i do wish papa would buy the land from ,mr4 ,breigel4 ,the weather will soon be fine enough to play out of doors6 ,so said ,jessie ,gregg1 a rosy-cheeked girl of twelve1 to her eldest brother1 ,fred1 one evening in ,march1 as they stood in the porchway of their home1 situated near the bank of the ,passaic ,river1 a few miles from the city in which ,mr4 ,gregg had his business offices4 ,why1 ,jessie1 said ,fred1 papa told me this morning1 at breakfast1 he expected to close the deal1 that is1 get the deed of the property1 this afternoon4 ,i am just as anxious as you are to have the matter settled1 for if he gets the land1 ,i will have a lot of work to do1 and ,i want to commence it right away4 ,the land must be ours1 for papa is later than usual this evening4 ,oh6 there's the train just coming in2 he will be here in a few minutes1 and then we'll know4 ,oh1 ,fred6 he and ,george are coming now4 ,i see them at the turn of the road4 ,i'll run to meet them4 ,away she scampered1 and almost upset her father by jumping into his arms1 as she was quite a plump1 husky girl and evidently a pet1 for her father kissed her fervently as she slid from his arms to the ground4 ,then the three trudged homeward4 ,jessie1 said ,george1 a younger brother1 ,i have a secret for you if you won't tell ,fred1 until papa has told him4 ,what is it8 ,papa has bought the land1 and has got it in his pocket4 ,oh6 ,i am so glad1 said ,jessie1 but how can he have it in his pocket4 ,george means that ,i have there the papers1 deeds1 conveyances1 and receipts1 giving me the sole ownership of the land1 and all that is on it1 including the trees1 old barn1 and other structures2 so1 girlie1 you can get down to the river now without having to climb a fence4 ,fred met his father on his arrival at the house1 but was too well behaved to ask him about the land1 though he was as anxious to know as he could be4 ,his father saw the boy's anxiety and after tea asked him to go with him into his den1 a little room nicely fixed up some time previous1 containing many articles of wood1 brass1 and plaster of ,paris1 ,fred and ,george had made during the past winter4 ,jessie1 also1 had contributed many little things toward the decoration of the lion's den1 as she called the room into which her father retired to have his evening smoke1 to take a friend1 or to do a little private business4 ,when seated1 ,mr4 ,gregg called ,fred to his desk1 and talked over some home affairs before he said3 ,now1 my boy1 since ,i have secured the property behind us1 as you children desired1 ,i shall expect you and ,george to help by your labour1 and by the knowledge you obtained at the training school1 in making the improvements on the land and the water front we have talked of so often4 ,i am sure1 with my advice and assistance1 you will be able to do most of the work1 or at least to superintend it in such a way that the labour and expenditure will not be wasted4 ,you know1 ,fred1 ,i am not a rich man1 so cannot afford to waste money on experiments4 ,indeed1 father1 said ,fred1 ,i will do all ,i can4 ,you may count on my giving my best attention to whatever work and improvements you entrust me with4 ,that is well said1 my boy1 and what ,i expected from you4 ,we will begin operations by putting down a cement pathway from the walk now leading to the house from the street1 and continue it to the river1 where you must build a small boat house and workshop1 as ,i intend either to purchase a small gasoline launch for our own use1 or have you build one1 if you feel equal to that4 ,oh6 father1 you are so good1 said ,fred4 ,there is nothing ,i'd like better than to do this work1 and particularly to build a boat4 ,i'm sure ,i can do that with your help and advice4 ,as to putting down the pathway1 that ,i can do very well1 after my good training in cement works4 ,all right1 my son4 ,we'll see in the morning what old material we have on the two places which can be used4 ,there must be quite a quantity of lumber1 timber1 bricks1 hard mortar1 and plaster in and about the old barn and the smaller buildings4 ,the next morning ,george evidently had something on his mind1 and seemed to be on the point of explosion4 ,mrs4 ,gregg noticed this and said to him1 ,why are you so restless this morning8 ,why don't you finish your breakfast8 ,oh6 mother1 he exclaimed1 ,i am too glad4 ,i am so full of the good things ,fred told me last night and this morning ,i haven't any room for breakfast4 ,what did ,fred say to you8 asked the mother4 ,oh6 he told me he was going to build a cement walk right from the door here to the river1 and do lots of other things2 and best of all1 mother1 he is going to build a boat1 a real boat1 that will be driven by a gasoline engine1 just like ,walter ,scott's4 ,that will be glorious6 ,i can take you and ,jessie up the river to ,belville to see aunty1 whenever you want to go4 ,very well1 ,george2 we will see about that after the boat is ready to take on passengers4 ,breakfast over1 the whole family walked out to see the newly acquired property4 ,they had all seen and walked over the grounds often1 but never before with that feeling of pride in ownership which possession creates4 ,as there could be no objection to the removal of the line fence between the newly acquired property and the homestead1 ,fred got a handsaw1 and cut down a part of it1 making an opening some nine or ten feet wide1 so that all could pass into the new place without climbing or stumbling4 ,the old barn was the first thing examined1 and it was found to be in a state of good preservation1 and quite large4 ,it had been built--perhaps in ,colonial times--of heavy timber1 oak1 chestnut1 and pine1 and it contained enough timber and lumber to build two or three small cottages4 ,there was a big pile of broken bricks and mortar lying against one side of the barn2 and another large pile of bowlders1 or field stones1 near the fence4 ,these1 ,fred said1 will be fine to build a little landing place or pier for the boat4 ,the broken bricks and hard mortar will make grand stuff for the foundation of the cement pathway4 ,there were also two or three small buildings on the place4 ,one had been used for a poultry house1 another for a tool house1 and a third seemed to have been a sort of cattle shed4 ,mr4 ,gregg suggested their removal1 of which all approved4 ,there were quite a number of good-sized trees on the grounds1 and these rendered it a little difficult to set out a straight line to the river for the cement walk1 without cutting down several1 which could not be considered4 ,there was one direction1 however1 that would admit of a walk1 about four feet wide1 but there were some big rocks or bowlders in the way1 that would have to be removed before a straight path could be made4 ,still it was decided to put it there4 ,the rocks1 said the father1 can be removed by blasting1 by lifting them out of their beds and rolling them aside1 or moving them down to the river1 where they will form a good protection against both current and ice4 ,i think they can be moved1 said ,fred1 if ,i can get levers and rollers2 and they will make fine breakwater stones4 ,jessie found two suitable trees1 upon which ,fred promised to put up a strong rope swing1 as soon as the place could be cleaned up and made tidy4 ,now1 ,fred1 said the father1 this cement walk should be commenced at once1 so that it will be dry and hard before you go on with other work4 ,i will employ a labouring man to help you1 one who will do the heavy work1 as ,i do not want you to over-exert yourself4 ,you have a number of tools now in the shed1 and1 when ,i come home from the office this evening1 we will make out a list of the other tools and materials you will require to finish the intended work4 ,in the meantime you and ,george can be making a number of wooden stakes1 about eighteen inches long and two inches square4 ,point them sharply at one end so that they may be driven into the ground their whole length4 ,you will require thirty or forty of these4 ,after getting them1 take a clothes line1 old halyard1 or any rope or heavy string your mother can find for you1 and stretch it from the house down to the river1 at the point we decided upon4 ,drive in a stake near the river1 tie one end of the rope to it1 pull tightly1 and stretch the rope from the river to the house4 ,it will then show you where one edge of the walk is to be4 ,after that is done1 get another rope or string and1 starting from the house end of the walk1 measure off four feet for the proposed width4 ,drive in a stake at that point1 and tie one end of the second rope to it2 then go toward the river with the other end1 making the rope extend the whole length of the path and drive in another stake which must be four feet from the first rope4 ,to this stake tie the end of the rope and make it tight4 ,be sure to have the two ropes exactly four feet apart at each end1 as well as along the whole length4 ,you will find it to your advantage to get a straight strip of wood1 say1 one or two inches thick both ways1 and cut it exactly four feet long4 ,it can then be used as a measuring stick or gauge1 for the distance between the ropes1 which is to be the width of the walk1 and by using it you will have a parallel and uniform path from start to finish4 ,mr4 ,gregg had passed an examination in the ,massachusetts ,school of ,technology1 and had won a position as civil engineer in ,new ,york which later he abandoned for the profession of law2 hence his knowledge of practical mechanics and engineering4 ,after ,jessie and ,george had gone to school1 ,fred started on his new undertaking with enthusiasm4 ,he found quite a number of pieces of wood1 out of which he made over forty stakes1 and pointed them nicely with the large hatchet he always kept sharp and in good order4 ,by tying several pieces together1 it did not take him long to find cord enough to set out the whole walk4 ,an old halyard that had been taken from the flag pole and replaced by a new one answered the purpose admirably4 ,driving a stake into the ground1 near the house1 he tied one end of his cord to that1 and stretched it down to the river bank to the point chosen for the end of the walk1 where another stake was driven in and the cord tied to it4 ,the long stretch between the two stakes would not allow the cord to be tight enough to make a straight line between the two points1 but ,fred left it as it was1 to be adjusted when his father came4 ,with his rod he measured off four feet from the first stake1 across the intended path1 and drove in another stake to which he attached another cord4 ,then going down to the river he measured off the width of the walk from the long cord1 and drove in another stake4 ,he was now ready to have his father examine the work he had done1 and to make suggestions or changes if such were deemed necessary4 ,jessie and ,george arrived home from school1 having run most of the way1 to help ,fred make the walk1 and were quite disappointed to be told there was nothing they could do until the work was further advanced4 ,we might1 perhaps1 commence taking down the old buildings1 said ,fred1 and pile the lumber where it will be snug and dry4 ,all right1 said ,george2 so the three of them went over to the poultry house and ,fred began by taking out the two or three small windows1 and removing the doors by unscrewing the hinges4 ,george's desire to pull1 tear1 and smash the old material was held in check by ,fred1 who advised him to be careful1 and not break or destroy anything that could be used4 ,after the doors had been taken off and laid nicely away--to be used on the boat house--and the windows and frames placed in a dry spot1 ,fred began to remove the old siding1 or clapboards4 ,he found this a rather difficult job1 as they were nailed on with old-fashioned wrought-iron nails which could not readily be drawn1 and1 in trying to get the boards loose1 the ends kept breaking and splitting2 so he stopped1 went inside the building1 and took off the lining there2 this also was a little difficult to do1 but1 as the boards were an inch thick1 he did not split many of them4 ,he then sawed off the boards alongside the studs1 on the corners1 and at the doorways to relieve the siding at the ends1 and give him a good chance to wedge off the boards wherever they were nailed4 ,with the help of ,george1 he succeeded in getting most of them loose without serious damage4 ,of course1 he had to begin tearing the boards off at the top of the wall1 as they lapped over each other like the scales of a fish4 ,mr4 ,gregg arrived1 went over the ground1 and was well pleased with the results of ,fred's day's work4 ,he assisted in straightening the long cords1 and made a number of suggestions for the boys to follow4 ,he had a strong-looking man with him1 who he told ,fred was to help him4 ,he was an ,italian1 named ,nicolo1 called ,nick for short1 a kindly fellow1 who could speak ,english fairly1 for he had been employed in ,newark1 as a handy labouring man for years4 ,he1 ,fred1 and ,george soon became good companions1 and even ,jessie1 though a little shy at first1 soon became quite friendly toward him4 ,when it was explained what was wanted of him1 he was quite satisfied1 and agreed to begin work in the morning4 ,next day ,fred and ,george were at work before their father was out1 and soon ,nick arrived1 bringing a spade1 a crowbar1 and a pick4 ,he was immediately set to work by ,fred1 digging a shallow trench for the pathway1 a little over four feet wide and about eight inches deep4 ,the stretched cord and the four-foot rod were the guides4 ,illustration3 ,fig4 #a4 ,section of sidewalk ,there were a number of rocks to be removed from the trench1 one of them near the river bank weighing over a ton4 ,these were left to be removed later4 ,their father1 on coming out1 was glad to see them all at work2 he showed ,fred and ,nick how to prepare the edges of the trench by putting planks along them1 as shown in ,fig4 #a4 ,the boards1 about twelve inches wide1 and from twelve to sixteen feet long1 had been taken from the old barn4 ,after breakfast ,fred worked along with his man1 and got the trench well cleaned out1 except for a few of the larger rocks4 ,the smaller bowlders were wheeled down to the river and rolled over the bank to the water's edge4 ,near one side of the walk grew a large tree1 whose main root ran under the proposed path4 ,mr4 ,gregg had noticed this in the morning and had told ,fred to see that the root was cut off close to the line on both sides and pulled out altogether4 ,if it isn't cut off1 it will grow larger1 lift up the cement flags1 and perhaps break them4 ,fred saw the force of this1 so had the root cut off and taken out4 ,the operation would not kill the tree1 though it might do it some injury4 ,now came the process of taking out the big stones1 and a lever1 ten or twelve feet long1 was brought from the barn1 in the shape of a red cedar pole1 five or six inches in diameter at the larger end4 ,nick took an axe and chopped the big end a little flat on two sides1 so that it could be shoved under the stone4 ,a flat plank was next laid behind the stone on the ground1 on which a fulcrum was to be placed1 in order to get what is termed by workmen a purchase4 ,on the side of the stone next to the river1 three planks taken from the floor of the barn were laid down flat at the bottom of the trench4 ,three other planks were laid on the top of the first layer1 thus making a bed in the trench1 two planks in thickness1 on which the big stone was to be rolled4 ,a fulcrum1 consisting of an old fence post1 was laid upon the plank1 and forced up as close to the stone as possible4 ,everything was now ready for lifting the bowlder out of the bed1 where it had lain perhaps for thousands of years4 ,as had been arranged1 the work at this stage was suspended1 and other work gone on with1 until ,mr4 ,gregg made his appearance4 ,upon his arrival all hands went to the stone1 ,jessie included4 ,having approved what had been done1 the father suggested that rollers be placed between the two thicknesses of plank to increase the ease of moving the stone to the river when it was started4 ,fred and ,nick went to the barn1 and among a big pile of old planks1 boards1 and timber found eight or ten old fence posts1 six or eight inches in diameter1 and long enough to make two rollers1 each three feet long1 when cut in two4 ,these were quickly stripped of bark by ,george and ,jessie1 while ,nick and ,fred1 with axe and hatchet1 soon had a number of them round enough to serve as rollers4 ,the father then directed that the ends nearest the river1 of the top layer of planks1 be raised up1 and one of the rollers placed between the two layers of plank near the stone1 while the ends of planks nearest the stone should be left resting on the bottom ones4 ,another roller was placed nearer the river end of the planks1 and all was made1 as shown at ,fig4 #b--where fulcrum1 lever1 stone1 planks1 and rollers may be seen4 ,illustration3 ,fig4 #b4 ,raising rock with lever ,all was now ready2 the lever was adjusted in place under the stone and on the fulcrum4 ,mr4 ,gregg1 ,nick1 and the children were gathered about the lever1 each one pushing down1 and the stone began to move1 as the top end of the lever came down1 much to the delight of ,jessie and ,george1 who kept shouting1 ,there she goes6 ,up she goes6 ,finally the great stone turned over on the plank1 and was moved to near the centre4 ,now came the labour of getting the monster down to the bank4 ,this was made easier by raising the ends of the upper planks under the stone and inserting another roller1 five or six feet from the end4 ,the planks holding the stone were now resting on rollers1 as seen in ,fig4 #c1 and it was found easy to move1 but in order to get it to the bank of the river the runway1 or lower planks1 had to be laid down that distance2 this would take too many planks1 so it was decided to lay only a second length on the ground1 and then when the load had travelled to this length1 the plank behind the stone should be carried forward and laid down again4 ,this was continued until the load was slid into the water4 ,mr4 ,gregg called the children and told them to push against the stone1 and they all were filled with wonder to see this great stone move along so easily on the rollers4 ,illustration3 ,fig4 #c4 ,moving rock on rollers ,fred and ,nick got more rollers to put between the planks as the stone was pushed forward1 for1 of course1 these were continually coming out at the rear end of the loaded planks4 ,the rollers had also to be watched and kept square across the plank or they would slide1 making it hard to move the load4 ,when the river bank was reached1 ,fred and ,nick made a rough slide of old timber down to its side from the trench4 ,getting the lever properly adjusted under the planks and stone1 the latter was turned over on the slide1 when it plunged into the river with a great splash1 causing the water to fly and sprinkle each one of the workers1 much to the delight of ,george1 who thought it fine fun to see his father1 ,fred1 and ,nick get a wetting4 ,it was decided that the stone as it lay in the water should form the end of the pier for the boat1 as it was nicely situated and the proper distance out1 being about a foot out of the water at high tide4 ,the other stones were easily removed from the trench by ,fred and his man1 and were either rolled or wheeled down to the river1 where ,nick built them as well as he could on both sides of the big rock1 leaving a hollow space between the walls1 to be filled in afterward with small stones1 mortar1 and broken bricks1 for the making of a good1 strong boat pier4 ,mr4 ,gregg then took out his note-book and pencil1 and figured out the quantity of cement1 sand1 and gravel required to complete the cement work4 ,he found there was good sand1 clean and sharp1 on one corner of the new lot4 ,a big pile of gravel and broken stones out on the street had been left over from the building of a two-story concrete house nearby1 so he concluded to buy it1 if not too dear4 ,measuring the trench1 he found it to be #cjj feet long1 by #d feet wide1 making a surface of #a1bjj feet to be laid with cement1 concrete1 and gravel1 or broken stones4 ,he calculated that every #ajj superficial feet of the concrete walk would require about a barrel and a third of ,portland cement2 and that the top dressing of cement and sand1 or fine crushed stone1 required another third of a barrel2 which totaled up to #bj barrels1 all told4 ,the concrete to be used was to be proportioned as follows3 ,one part of cement1 two parts of good1 clean sand1 and five parts of gravel1 or broken stones1 which should be small enough to pass through a ring having a diameter of not more than two inches4 ,this mass should be well mixed1 dry1 on a wooden floor or movable platform1 and then wetted just enough to have stones1 sand1 and cement1 well moistened4 ,all should be again mixed before being placed in the trench1 and it should not be thrown in place1 but shovelled in gently4 ,mr4 ,gregg ordered the cement by telephone1 to be delivered at once1 either in barrels or bags2 and he got into communication with the owner of the gravel1 and bought the whole pile4 ,he then engaged a team of horses1 wagon1 and driver1 to commence work the next day4 ,by this time ,nick had gone home1 and the children came rushing into the house1 anxious to tell their mother all the work they had done that day4 ,the keen appetites of the younger folks gave positive proof of their having earned their supper1 by actual work1 and1 when the meal was over1 the father invited ,jessie and the boys into his little room4 ,george was asked to take with him his portable blackboard1 some chalk1 and a ruler1 and all marched into their father's den4 ,now1 said ,mr4 ,gregg1 ,i have often told you ,i would explain to you some things about the mechanical powers1 and this seems to be the most appropriate time to begin1 as you have fresh in your minds the application of the lever as we used it to-day in raising and moving the big rock4 ,i am glad to see that ,fred grasped the idea so readily1 for that encourages me to let him use his own judgment while doing this job4 ,the lever is known to accomplished mechanics1 as 'the first mechanical power'1 and ,archimedes said of it1 if he only had one long and strong enough1 together with a suitable fulcrum1 he could1 alone1 lift the earth from its place4 ,this ,archimedes was a celebrated ,greek philosopher and mathematician1 who lived from about #bhg to #bab ,b4 ,c4 ,the discovery of the law of specific gravity1 which ,i will some day tell you about1 is attributed to him4 ,i think ,george can tell you something about this great man1 as ,i saw him and ,jessie the other day reading ,plutarch's ',lives1' in which he is mentioned4 ,illustration3 ,fig4 #d4 ,principle of lever and fulcrum ,a lever may be formed of any strong1 stiff material1 wood1 iron1 steel1 or similar stuff1 and it may be of any length1 or dimensions1 according to the purpose for which it is to be used4 ,in theory1 it is supposed to have no weight1 and is simply figured as a straight line having neither breadth nor thickness4 ,in practice1 however1 a lever may be a handspike1 a pry1 a crowbar1 a fire poker1 a windlass bar1 or any other appliance or instrument that can be used for prying4 ,while we may not know the proper name of the little steel tool the dentist employs when preparing one's teeth to receive the filling1 by cleaning out the cavities1 we are safe in calling it a small lever4 ,when your mother stirs the fire in the grate1 she makes a lever of the poker1 and bars of the fireplace become fulcrums4 ,the fulcrum is the fixed point on which the lever rests when in use4 ,the force applied is called the power and the object to be acted upon is called the weight4 ,the spaces from the power and the weight1 respectively1 to the fulcrum1 are called the arms of the lever4 ,there are three different ways of using the lever1 according to the relative positions of power1 weight1 and fulcrum4 ,this rough sketch ,i am drawing on the blackboard 7,fig4 #d7 shows the lever being used to raise one end of a heavy stone4 ,suppose ,w is a big rock1 ,c will be the fulcrum1 ,b the end of the lever under the stone1 and ,o the power4 ,the weight thrown on the lever by the man at ,o1 raises the stone so that it can be blocked up1 the lever and fulcrum arranged for another lift1 and the process repeated4 ,this can be continued until the stone is raised to the height required1 or until it is turned over4 ,this method applies to the raising of any sort of weight1 engine1 boiler1 heater1 etc4 ,in this sketch the distance from ,b to ,c shows the short arm of the lever1 and the distance from ,c to ,o shows the length of the long arm4 ,a lever1 used in this way1 is called a lever of the first kind1 because of its simplicity and easy adaptation to many purposes4 ,i saw ,george digging in the garden the other day1 making a flower bed for his mother4 ,the spade he used formed an excellent lever4 ,he forced it into the ground to its full depth1 pried the handle toward him1 and broke loose the soil1 after which he turned over the earth in the bed4 ,now1 in this case1 the top of the blade or foot-plate of the spade1 rested on the hard ground1 which was the fulcrum2 the soil dug up was the weight1 and ,george's hand at the top of the spade handle1 furnished the power4 ,i am sure you all understand the working of a lever of this kind1 but ,i will give you another illustration4 ,illustration3 ,fig4 #e4 ,lever as a mechanical power ,illustration3 ,fig4 #f4 ,double lever as scales ,here's another sketch 7,fig4 #e71 in which ,a1,b1,c1 together show the lever1 also the power ,a1 the fulcrum ,b1 and the weight ,c4 ,if ,i should place the fulcrum ,b so that it would be in the middle between the ends ,a ,c1 there would be what is termed an equilibrium between the weight and the power1 and if they are equal there will be a perfect balance maintained4 ,it is on this principle that scales for druggists are made1 the lever being suspended in the centre of its length1 as ,i show in the sketch 7,fig4 #f74 ,these scales are very nicely adjusted1 and the chains and receivers are made as nearly alike in weight as possible4 ,the arms of the lever being of equal length from the centre1 or pivot1 permit the lever to stand in a perfectly horizontal position1 unless disturbed by having a weight placed in either one or other of the receivers4 ,in this case1 the pivoted point ,p is the fulcrum1 and the two points ,o and ,x may be taken as the power and the weight4 ,if one pound is placed in the receiver at ,o1 it will tip the scale down1 and that will become the weight1 while any commodity placed in the receiver at ,x1 until the lever is again brought level1 or horizontal1 may be called the power4 ,as another illustration ,i'll tell you of something that took place the other day4 ,in the vacant lot are several piles of bricks1 stones1 and planks4 ,george1 seeing this1 took one of the planks and threw it across several others1 making a ',teeter ,tauter1' or1 as some children call it1 a ',seesaw4' ,he balanced the plank nicely1 and then invited ,jessie and her cousin to sit on it1 one at each end4 ,the two girls were about the same weight1 and ,george held the plank until both were seated4 ,it remained level and balanced1 until ,george got on the top of it1 and stood on the centre of its length1 placing his feet so that one was on one side of the centre1 or fulcrum1 and the other on the other4 ,by causing his weight to rest on his right foot1 the right end of the plank would dip downward2 then by throwing his weight on his left foot1 the movement of the plank would be reversed1 and the motion continued until ,george ceased to exert any extra pressure on either of his feet4 ,what do you call the boy or girl who stands on the plank8 ,sometimes1 said ,jessie we call him a 'candlestick' and sometimes 'the balancer'4 ,this teeter tauter and the explanation of the druggist scales1 said the father1 show you that many of our conveniences are due to the lever in one way or another4 ,these are but a few of the thousands of instances ,i could name4 ,take a nut-cracker1 for instance4 ,there we have a sort of double lever1 the joint being the fulcrum1 the nut the weight1 and the two handles the combined power or lever4 ,by pressing the handles or levers1 we crack the nut or overcome the weight1 by crushing it4 ,we owe many of our amusements to the lever in one form or another4 ,even our pianos would be impossible were it not for the combination of levers in the adjustment of the keys4 ,machinery and all kinds of moving instruments1 including watches1 clocks1 and other fine mechanism1 could not be perfected without the lever4 ,the common every-day wheelbarrow is a good illustration of the use of the lever combined with the wheel4 ,george fills up his barrow with stones or other materials that weigh two or three times the amount he could lift easily4 ,yet he gets away with the load1 apparently with very little trouble4 ,the handles form the lever or power1 the wheel the fulcrum1 and the stones the weight4 ,george raises the handles1 and throws the greater part of the weight on the fulcrum1 which is the wheel1 and this latter1 acting as a roller1 is easily moved around its own axle1 thus enabling ,george to move his threefold load with ease4 ,this example shows you how1 by a simple combination of mechanical devices1 labour may be reduced4 ,the roller is related to the wheel and axle class--another of the mechanical powers4 ,in your bicycles you have a fine illustration of the application of the roller principle1 in the ball-bearings4 ,the little round balls1 over which the axle of the wheel runs1 are simply rollers rounded in every direction1 and placed there to destroy friction1 which they do almost entirely4 ,another excellent illustration of the use of the roller is seen in the hanging of the grindstone we have in our back shed4 ,the axle passing through the stone rests on two pairs of wheels or rollers1 one pair at each side of the stone4 ,if you turn the stone on its axis1 you will notice the wheels turn also1 and the effort required to turn the stone is hardly noticeable4 ,if the grindstone were well balanced and true1 and the little wheels the same1 so that they could be run without friction on their bearings1 the stone1 by giving it one good turn with the hand1 would keep revolving a very long time4 ,so you see how much we are indebted to the mechanical powers for our present state of civilization4 ,next morning being ,saturday1 ,george was up early1 put on a pair of overalls his mother had bought1 and1 when breakfast was over1 all but the mother went out to the new property4 ,they found ,nick helping a teamster to unload gravel1 also a load of cement1 which was placed in a dry and convenient place1 for once damp or wet in the least it becomes of little use1 unless worked up immediately4 ,george was full of glee4 ,he got his wheelbarrow and wanted to commence work without delay4 ,the father took ,fred and ,nick to the trench and explained what was to be done and the way to do it4 ,the trench is now eight inches deep1 he said1 and you must wheel gravel1 broken bricks1 hard mortar1 or cinders into it so that there will be about five inches of it in the trench from one end to the other4 ,put all the larger stones at the bottom1 but before throwing in any1 tamp or pound the ground at the bottom of the trench until it is solid and hard1 making a good bottom for the stones to rest on1 and ensuring the walk from settling or sinking in spots4 ,where the big root and rocks are taken out1 the holes must be filled up level1 and tamped solid4 ,rake off the largest of the gravel1 and let ,george wheel as much of it as he can1 and dump it in the trench1 while ,nick or you wheel in the balance4 ,finish the top of the gravel off with smaller sized stones1 and after you have filled in about five inches1 throw water on the whole with the garden hose until quite wet1 and then pound the gravel down until it is compact and firm4 ,this bed forms a good foundation for the concrete which must be laid on it about four inches thick1 and well tamped4 ,after you have raked off the larger gravel1 take a wire sieve1 with meshes not larger than four to the inch1 and sift the finer gravel out1 to save for the top finish4 ,before filling in the concrete1 strips of wood having straight edges on top must be nailed to the stakes on both sides of the walk1 as ,i showed you on the blackboard in ,fig4 #a1 marked ,a ,a4 ,these strips must be placed at proper grade in their length1 and level across from one to the other4 ,a straight edge made of wood1 and long enough to reach over the walk1 and the strips as well1 must be provided1 and it may be notched out as ,i show at ,x1 in ,fig4 #a4 ,this straight edge is to be used in levelling off the top or finishing coat1 by keeping both ends on the strips ,a ,a1 and moving it along lengthwise of the walk4 ,if the top of the walk is to be below the edges of the strips1 you may notch the ends1 as shown1 to suit whatever depth may be required4 ,fred told his father he thoroughly understood the process as far as explained1 and the latter then left4 ,by this time ,nick and ,george--and1 we might add1 ,jessie--had wheeled into the trench quite a lot of gravel1 but for the want of a proper tamper they had to stop4 ,so ,fred cut two pieces off a fence post1 each about a foot long1 and with an auger or boring tool1 made a hole in the centre of the end of each1 about eight inches deep1 into which he inserted a round wooden handle1 about three feet long4 ,these made excellent tampers1 not too heavy for ,george to use4 ,jessie1 persuaded ,fred to make her just a little one1 but he told her not to use it much or her hands would get sore and too stiff to practise her music4 ,the strips for the stakes were prepared1 nailed on1 and properly adjusted1 and then it was time to commence the real work4 ,nick had nailed some boards on three pieces of scantling about six feet long1 which made a good mixing table for the concrete4 ,this was carried up near the top end of the walk1 and placed where it would be handy4 ,a pailful of cement was put on the board1 next two pailfuls of nice clean sand1 and then five pails of gravel that had no stones in it larger than would pass through a ring having a clear diameter of two inches4 ,all this gravel1 sand1 and cement being in one heap on the board1 ,fred and ,nick worked at it steadily for more than ten minutes1 mixing it up until the sand and cement were thoroughly and evenly blended with the gravel4 ,fred then sprinkled the mixture with clean water from the hose1 while ,nick kept shovelling it over and over until the whole was damp1 but not so much so that the cement and sand were washed from the gravel4 ,the whole mass looked like a pile of dirty stones that had just been under a light shower4 ,this1 said ,fred to ,nick1 is a very important process1 for if we make the stuff too wet1 it will starve the concrete by washing away the cement1 and if we leave it too dry the work will be rotten and crumble away4 ,fred might also have added that the proper proportioning of the materials was as essential as the proper mixing1 and in this case1 where we are making it one of cement1 two of sand1 and five of gravel--all by measurement--we must adhere closely to the rule or the walk will be uneven in texture and colour4 ,the concrete being properly mixed1 ,fred and ,nick began to shovel it into the trench1 spread it to about four inches in thickness1 and tamped it down until the top mass looked sloppy and muddy4 ,while in this condition1 a new lot of cement mixture was made1 consisting of one part of cement and two parts of sand and the fine of the gravel that had been sifted4 ,all were mixed thoroughly while dry1 and afterward wet to the consistency of thick mortar4 ,this was spread over the concrete to about one inch in thickness and levelled down by the notched straight edge until the proper thickness and level were obtained4 ,the surface was then ready to smooth1 or float1 as the workman calls it1 which always gives to the top of the work a nice1 even1 level appearance1 and makes it solid and firm4 ,the floating is done with a tool made of wood1 as shown in ,fig4 #g1 and may be finished off with a plasterer's steel float1 merely to give the surface a better finish4 ,illustration3 ,fig4 #g4 ,floats and trowels ,the floating operation is laborious1 for it must be done at once1 while the operator is on his knees4 ,fred and ,nick1 however1 worked away at it until they made a good job of the portion that they were putting down4 ,all of the walk they could finish at one time was about sixteen or eighteen feet1 so that the whole job required a number of days to complete4 ,the first instalment being done1 so far as the floating was concerned1 it was now in order to make joints in the walk across the face1 firstly for the purpose of marking it off into flag sizes1 four feet square2 secondly to prevent expansion4 ,if there were no joints made in the walk1 it would lift up1 crack1 break1 and ultimately be destroyed4 ,fred1 who knew that the walk would contract in cold and expand in warm weather1 explained this peculiarity to ,george and ,nick1 and having a jointer along with the floats which the father had sent1 he1 with ,nick's help1 ran some joints1 at four-foot intervals1 across the walk1 while ,nick pushed his spade through the joints to the ground1 actually cutting cement and concrete into sections of four feet each4 ,this would allow for expansion or contraction1 and even admit the raising of some of the sections above the others1 without cracks or breaks occurring4 ,the first instalment of the walk being made1 it was left to ,george to wheel damp sand and scatter it over the face of the walk about an inch thick1 to keep the sun and rain from injuring it4 ,then he received instructions to wet the surface every morning for a week4 ,at the end of two or three days the cement was hard1 or set enough to bear walking on1 and in a week it was cleaned off for use4 ,one peculiarity about concrete or cement work is1 that it improves and gets stronger with age4 ,the walk was complete in due time1 in sections of about sixteen feet long1 and proved quite satisfactory4 ,mr4 ,gregg was pleased with it1 and he explained to ,fred1 ,george1 and ,jessie that it might have been made more ornamental1 as there were many tools for rounding off the edges1 indenting the surface1 to make it less slippery1 or for laying the flags off in panels2 but in this case all were pleased with the way the boys had finished it4 ,,ii ,,building ,,of ,a ,,boat ,,house ,the cement walk being finished to the satisfaction of all concerned1 and the admiration of the neighbours1 ,fred turned his thoughts to the building of a boat house and workshop4 ,it was decided to make it #af feet wide and #bb feet long1 as these dimensions would suit the timbers in the old barn1 and be ample for stowing away the boat and allowing space for a work bench4 ,lines for a foundation were set out1 and stakes driven in the ground at the corners1 alongside the cement walk and pier4 ,a trench about two feet deep was dug on the two sides and ends2 and in this were laid large rocks and stones1 in a single course all round4 ,nick1 who was quite handy at this kind of work1 built up a wall of smaller stones laid in cement mortar4 ,this mortar was composed of one part of cement to five of sand1 and made quite thin and easy to spread4 ,when the wall was high enough1 about level with the highest part of the ground1 it was levelled off by using smaller stones and plenty of cement mortar4 ,the level was obtained by laying a straight plank flat on the top of the cement finishing1 and then applying an ordinary spirit-level4 ,any errors in the level of the wall showed at once1 and were made right by adding more mortar1 or by taking some off the top of the wall4 ,illustration3 ,fig4 #h4 ,framing studding ,timbers from the old barn were next pressed into service1 chestnut wood that had served as girths and beams4 ,two pieces were cut1 #bb feet long1 and two of #af feet4 ,the ends were then halved1 as shown in ,fig4 #h--the simplest method of framing a corner--and the timbers were spiked and so squared as to make right angles at the corners4 ,fred then took the old window and door frames1 and measured off on the foundation timbers the outside distance where each one was to be placed4 ,he put the double doors in the end of his boat house1 next to the river front4 ,the other door and windows were set in the best places to provide an entrance opening on the cement walk1 light above the work bench1 and views over the river and grounds4 ,fred decided to build his house ten feet high2 so a quantity of studding1 #b #d inches in section1 was taken out from the walls of the barn1 and cut exactly ten feet long4 ,these were to form the side walls between the corners1 doors1 and windows4 ,heavier studs were found in the barn1 and ,fred wisely used them next to the windows and doors4 ,illustration3 ,fig4 #i4 ,side of boat house frame ,these heavy studs were set up in the places marked on the timber sills1 also at the four corners1 and were toe-nailed at the bottom to hold them in place4 ,they were then made vertical or plumb1 by aid of a spirit-level1 and the corners were braced temporarily to hold them in that position4 ,the picture 7,fig4 #i7 shows how the side of the building next to the cement work looked when the studding was all in place4 ,the dark ends shown are the joists on which the floor is laid4 ,the lower joists were made from timbers taken from the barn floor1 #b #h inches wide and long enough to reach across the building4 ,the joists on top were #b #f inches1 by #af feet long4 ,these latter floor beams were set about #ae inches apart1 ready to receive the flooring plank1 which was nailed solid to them4 ,you will notice that cross pieces of studding are nailed between the studs at the window openings4 ,these form the tops and bottoms of the window frames4 ,the spaces above and below are also filled in with short pieces of studding1 to nail the clapboards to1 as shown4 ,the ends of the building were finished as shown in ,fig4 #aj1 a small window being left in each to admit light and air1 also lumber1 poles1 or other stuff that could be put into the loft through these openings4 ,inside the building a trapdoor was to be left1 so that ,fred or ,george could get up to take in or hand out the stuff4 ,illustration3 ,fig4 #aj4 ,end of boat house frame ,the end 7,fig4 #aj7 shows how ,fred and ,nick1 with ,george's help1 built that portion1 the collar beam1 ,o ,o1 and the rafter being seen1 while the details in ,fig4 #h give larger sketches of the manner of doing the work4 ,the stone-work1 as built by ,nick1 for foundation walls1 is shown in both ,figs4 #i and #aj4 ,all the clapboards having been taken off the barn and old sheds1 the better portions were selected for covering the outside of the new frame1 and a lot of old boards were used for lining the inside of the walls and nailing on to the rafters4 ,the next thing was to lay on the shingles4 ,these had been provided some days before by ,mr4 ,gregg1 who had figured out the number required4 ,he found the roof would measure #bd feet in length1 including the projections over the ends of gables1 and that the length of the rafters was #ag feet each1 including the overhanging eaves or cornice4 ,this made the whole stretch of length on both sides of the roof #cd feet4 ,multiplied by #bd feet1 the length of the roof1 this was #haf feet4 ,to cover an area of #haf feet about #h1jjj shingles would be required1 as #ajj surface feet require nearly #a1jjj shingles1 laid #d inches to the weather1 according to the usual custom4 ,mr4 ,gregg explained to ,fred what is meant by the term weathering1 applied to shingles1 clapboards1 slates1 or anything similar4 ,the weathering part of a shingle is that portion of it exposed to the weather1 when in place on the roof4 ,it makes no difference how wide or how narrow a shingle may be1 it is that portion showing from the lower end of one shingle to the lower end of the next one above it1 that is the weathering4 ,this is generally four inches wide and it runs from end to end of the roof4 ,another thing ,mr4 ,gregg explained--the term1 a square of shingling4 ,in this case1 as in flooring1 clapboarding or similar work1 a square is an area #aj #aj feet2 or #ajj superficial feet4 ,in nailing down shingles1 went on ,mr4 ,gregg1 the nails should be driven so that the next course or layer will cover up the nail heads1 thus protecting them from rain and damp1 and preventing them from rusting4 ,when laying the shingles1 after the first courses are on1 which should be laid double at the eaves1 a string or chalk line must be stretched from one end of the roof to the other1 four inches up from the ends of the first courses4 ,this string or chalk line may first be rubbed over with chalk or soft charcoal1 and when drawn tight from each end1 it may be 'struck' or 'snapped' by raising it up in the middle and letting it strike the roof suddenly so that a mark will be left on the shingles from end to end4 ,this will be the guide for the thick ends of the shingles to be laid against when nailing on the next course1 and the process must be continued until the ridge1 or top of the roof1 is reached4 ,when you paint your boat house1 don't forget the roof1 for a good coat of paint on the shingles will lengthen the life of the roof fully five years4 ,fred1 to whom these instructions were more particularly given1 told his father he understood the whole matter1 and he was directed to go on with the work4 ,in the meantime the father ordered the shingle-nails required2 five pounds for each thousand shingles1 or forty pounds altogether4 ,the building being small1 the whole work was soon completed1 windows put in1 doors hung1 and floors laid2 and ,mr4 ,gregg was greatly pleased with the manner in which ,fred had managed the job4 ,illustration3 ,photograph by ,frank ,h4 ,taylor ,,boat ,,house ,,and ,,workshop ,a ,good ,coat of ,paint on the ,shingles ,will ,lengthen the ,life of the ,roof ,fully ,five ,years4 ,the next thing was to take down the heavy timbers of the barn1 still standing4 ,fred saw at once that they were too heavy to be removed without mechanical aid or more human help1 so he brought from his father's stable a rope and set of pulley-blocks like the ones shown in ,fig4 #aa4 ,nick1 who had seen some service at sea1 hooked the block into a loop formed by a short piece of rope tied over a limb projecting from one of the trees4 ,the question of lifting the timber now was an easy one1 as another short rope was tied to the heavy post ,w1 in this case the weight ,p being the power4 ,each of the blocks shown contains pulleys which make the relation of the weight to the power as one to four4 ,the weight being sustained by six cords1 each bears a sixth and a weight of six pounds will be kept in equilibrium by a power of one pound4 ,the blocks used in a system of this character are called single if there is one pulley in each1 double if there are two1 treble if there are three1 and quadruple if there are four4 ,fred1 ,george1 ,nick1 and ,jessie who liked to help whenever she could1 counted for four times their number when they all pulled together on the rope ,p4 ,it was astonishing to the youngsters how easily the heavy timbers were taken down and piled in a nice heap4 ,two timbers1 each about twenty-five feet long1 were chosen and marked1 to be used for slides or ways1 on which the proposed boat could be hauled in and out of the boat house4 ,it was quite a distance from the timber to the river end of the boat house1 and1 the former being heavy1 ,fred decided to make an inclined plane of planks--of which there was an abundance--so that the timbers could be slid or rolled down to the river4 ,it took but a few minutes to lay the planks1 and as the incline was gentle1 rollers were used and the timbers went down as easily as the big rock had done4 ,this pleased the younger children very much4 ,when papa comes home1 said ,jessie1 ,i'm going to get him to tell me about the 'inclined plane' as well as the ropes and pulleys4 ,the two timbers were rolled into the river and floated to the boat house1 where one end of each was raised to the floor level at the doorway and made fast2 the other end sank to the bottom1 where ,nick dug down and made a bed for it to rest in4 ,these beds were made deep enough to bury the ends1 and large stones were then thrown in to keep them from moving1 but these were not allowed to reach within #ah inches of the surface of the water1 which was then at its lowest mark4 ,the timbers were kept about three feet apart1 ample space to admit of any ordinary launch or row boat being taken into the boat house4 ,oh1 ,fred1 said ,jessie1 do you think those two sticks will be strong enough to hold the boat while you are pulling it up8 ,why1 yes2 strong enough to hold a dozen boats no larger than the one we intend having made4 ,i don't know how much weight these timbers will support1 nor how heavy our boat will be with the engine in it1 but ,i'm sure the timbers are strong enough4 ,jessie's question1 however1 caused ,fred to think over the matter1 and he set to work to find out how to tell the strength of timber beams4 ,he discovered that to be able to determine the strength of beams and wooden pillars under all sorts of conditions required considerable training in mechanics and mathematics1 but that the case before him was comparatively easy4 ,a general rule for finding the safe carrying capacity of wooden beams of any dimensions1 for uniformly distributed loads1 is to multiply the area of section in square inches1 by the depth in inches1 and divide their product by the length of the beam in feet4 ,if the beam is of hemlock1 this result is to be multiplied by seventy1 ninety for spruce and white pine1 one hundred and twenty for oak1 and one hundred and forty for yellow pine4 ,the product will be the number of pounds each beam will support4 ,for short-span beams1 the load may be increased considerably4 ,fred1 who had some knowledge on the subject1 acquired at the training school1 determined to pursue his studies in this direction4 ,in talking over the matter of nails with his father1 their holding power was mentioned1 and ,mr4 ,gregg told ,fred of a test that had been made some time ago by the ,u4 ,s4 ,ordnance ,department1 where cut and wire nails had been tested respectively1 showing a decided superiority for the former1 both in spruce1 pine1 and hemlock4 ,thus in spruce stock nine series of tests were made1 comprising nine sizes of common nails1 longest #f inches1 shortest #a-c_/h inches2 the cut nails showed an average superiority of #dg4ea per cent42 in the same wood six series of tests1 comprising six sizes of light common nails1 the longest #f inches and the shortest #a-a_/h inches1 showed an average superiority for cut nails of #dg4dj per cent42 in #ae series of tests1 comprising #ae sizes of finishing nails1 longest #d inches and shortest #a-a_/h inches1 a superiority of #gb4bb per cent4 average was exhibited by the cut nails2 in another six series of tests1 comprising six sizes of box nails1 longest #d inches and shortest #a-a_/d inches1 the cut nails showed an average superiority of #ej4hh per cent42 in four series of tests1 comprising four sizes of floor nails1 longest #d inches and shortest #b1 an average superiority of #hj4jc per cent4 was shown by the cut nails4 ,in the #dj series of tests1 comprising #dj sizes of nails1 longest #f inches and shortest #a-a_/h inches the cut nails showed an average superiority of #fj4ej4 ,speaking of the ropes used in blocks1 while taking down the old barn timbers1 ,mr4 ,gregg suggested that it would not be a bad idea if the boys were taught a few general items concerning hempen ropes2 so he asked them to memorize the following3 ,a rope #a_/d inch in diameter will carry #dej pounds1 and #ej feet of it will weigh one pound4 ,if #e_/h inch in diameter1 it will carry #c1jjj pounds and #g feet will weigh one pound4 ,when a rope is #c_/d inch in diameter1 it will carry #c1ijj pounds1 and #f feet will weigh #a pound4 ,a rope one inch in diameter1 the same as we have in our blocks1 will carry #g1jjj pounds1 and #c feet #f inches will weigh one pound4 ,it is not likely that sizes greater than these will ever be used by you4 ,if they are1 you can obtain a fair knowledge of their strength by finding their areas1 and comparing them with the areas of the ropes given1 taking the rope having one inch in diameter1 as a constant example4 ,wire ropes are much stronger than hempen ones1 whether made of steel1 brass1 or bronze4 ,the care and preservation of ropes is deserving of consideration1 particularly in localities where the atmosphere is destructive to hemp fibre4 ,such ropes should be dipped when dry into a bath containing #bj grains of sulphate of copper per gallon of water1 and kept soaking in this solution some four days1 before they are dried4 ,the ropes will thus have absorbed a certain quantity of sulphate of copper1 which will preserve them for some time1 both from the attacks of animal parasites and from rot4 ,the copper salt may be fixed in the fibres by a coating of tar or by soapy water4 ,in order to do this the rope is passed through a hot bath of boiled tar1 drawn through a ring to press back the excess of tar1 and suspended afterwards on a staging to dry and harden4 ,the figures given are intended for new manila ropes1 and do not hold good for ropes made of inferior hemp4 ,it is always safer never to load a rope to more than #fj per cent4 of its capacity1 and not even this much when it is old and weathered4 ,jessie reminded her father of his promise to give them some information regarding the power of blocks and tackle and the qualities of the inclined plane4 ,accordingly1 ,fred1 ,george1 and ,jessie joined their father in his den after supper1 and ,george placed his blackboard in a convenient place with chalk1 rule1 and other requisites4 ,when all were seated1 the father said3 ,some time ago ,i tried to explain to you the uses of the lever in quite a number of different situations2 to-night ,i'm going to show you how the various ropes and pulley blocks are made to do service for mankind4 ,these devices are used very generally1 especially in building operations1 where heavy beams1 girders1 or blocks of stone have to be raised4 ,on board ship1 it is the favourite mechanical power by which rigging is raised1 cords and ropes tightened1 and goods lifted from or lowered into the hold4 ,illustration3 ,fig4 #aa4 ,blocks and tackle ,the pulley1 the main feature of the third mechanical power1 may be explained almost on the same principle as the lever1 as you will see upon examining the sketch 7,fig4 #aa7 ,i now make on the blackboard4 ,the pulleys seen in the blocks around which the rope runs may be considered so many levers whose arms are equal1 and whose centres are fulcrums4 ,in describing this power1 it will perhaps be better to begin with the first and simplest form of the combination4 ,the pulley1 weight1 and rope ,i show now 7,fig4 #ab7 is the simplest form of making use of this power4 ,it is called a snatch-block and often employed for drawing water from wells1 or for hoisting light weights4 ,it is very handy1 but we do not get any additional power from it1 though we get a change of direction and quick movement4 ,from its portable form1 its low cost1 and the handiness with which it can be applied1 this arrangement is one of the most useful of our mechanical contrivances4 ,illustration3 ,fig4 #ab4 ,theory of block and tackle ,when pulleys are adjusted1 as ,i show you in this sketch 7,fig4 #ac71 the block which carries the weight is called a movable pulley1 and the whole1 as shown1 a system of pulleys4 ,illustration3 ,fig4 #ac4 ,double block and tackle ,in this illustration1 suppose the weight is #bj pounds4 ,it is supported by two cords1 ,a and ,b2 that is1 the two sections of the cord support #aj pounds each4 ,now1 the cord being continuous1 the power must be #aj pounds4 ,we leave out of consideration the weight of pulley and the friction of the various parts4 ,we have seen that the weight is sustained by two cords2 if1 therefore1 it has been raised two feet1 each cord must be shortened two feet4 ,to do this1 the power ,p must run down four feet4 ,to get the full value of this machine the cords must be parallel4 ,if we increase the number of movable pulleys1 as sketched at ,fig4 #ad1 to three1 the relation of ,p to ,w will be as #a to #h and the distance through which ,p will travel will be eight times that through which ,w is raised4 ,illustration3 ,fig4 #ad4 ,multiple blocks and tackle ,if we apply this principle to the sketch 7,fig4 #aa71 which illustrates the blocks you used to-day in lifting the large timbers1 and which is the usual form of pulley employed to lift heavy weights1 you will notice that there is a four-sheave block at the top1 and a three-sheave block at the bottom1 with the end of the rope fixed from the top block4 ,the three-sheave block is movable4 ,a power of #aj pounds will1 with this form of pulley1 balance a weight of #fj pounds4 ,suppose a block of stone weighing #h1jjj lbs4 is to be raised to the top of a wall and we use a system of pulleys where each of the two blocks has four pulleys2 we shall find that it will require a power of #a1jjj pounds to raise it4 ,now1 as to the inclined plane3 this is called the fourth mechanical power1 and it is not in any way related to the lever1 but is a distinct principle4 ,some writers on the subject reduce the number of mechanical powers to two1 namely1 the lever and the inclined plane4 ,the advantages gained by this are many for just so much as the length of the plane exceeds its perpendicular height is an advantage gained4 ,suppose ,a ,b ,c 7,fig4 #ae71 ,i make in the sketch1 is a plane standing on the table4 ,if length ,a ,b is three times greater than the perpendicular height ,c ,b then a cylinder at ,r ,p may be supported upon the plane ,a ,b by a power equal to a third of its own weight4 ,that is1 a block of that weight would prevent the roller or cylinder from going farther4 ,from this we gather that one third of the force required to lift any given weight in a perpendicular direction will be quite sufficient to raise it the same height on the plane2 allowance1 of course1 must be made for overcoming the friction1 but then1 you see1 you will have three times the space to pass over1 so that what you gain in power1 you will lose in time4 ,we see the use of the inclined plane every day we pass a building under construction1 where the workmen wheel bricks1 mortar1 and other materials from the street to the floors above1 using long planks for the plane or tramway4 ,merchants1 too1 often make use of an inclined plane when rolling heavy boxes and packages from the street to the floors of their warehouses4 ,illustration3 ,fig4 #ae ,an excellent1 practical illustration was given you to-day when ,nick and ,fred built the ways on which the proposed boat is to be slid into the new house4 ,it would require five or six strong persons to lift the boat bodily into the new house2 but ,i expect two or three will easily slide it up into the building on the ways2 and by arranging a winch--another mechanical contrivance--at one end of the boat house1 ,fred1 or ,george1 for that matter1 will be able to haul the boat up4 ,the winch for this purpose will be a very simple affair1 merely a ready adaptation of the wheel and axle1 as ,i will show you later4 ,now1 however1 we are talking about inclined planes1 and to illustrate its early application to the building arts1 it is only necessary to tell a few things we know regarding the moving and raising of the great stones used in building the ,pyramids4 ,for centuries it was a mystery how the heavy stones in these structures had been placed in their present positions4 ,recent investigations have led many scientific men to believe the stones were taken up inclined planes1 on rollers1 and then put in place by the workmen1 who moved them to the different sides of the building on strong timber platforms1 where rollers1 or rolling trucks1 carried the load4 ,according to one authority1 there are the remains of the approach to an inclined plane near the ,great ,pyramid1 which1 if continued at the angle1 as now seen1 would rise to the apex4 ,according to this writer1 the foot of the plane was more than a mile from the building1 fifty or sixty feet wide1 and had been one huge embankment1 formed of earth1 sand1 and the clippings and waste of stone made by the workmen4 ,this1 of course1 would be an expensive and a tedious method1 but in those days time and labour went for little4 ,every time a course of stones was laid and completed1 the plane was raised another step1 to the height of the next tier of stones4 ,the same angle of incline was probably maintained during the whole period of erection1 and this angle1 you may rest assured1 was made as low and easy as possible2 for the ,egyptian engineers were not slow in adapting the easiest and quickest methods available4 ,this method of conveying the heavy stones to their places in the ,pyramids was simple and effective1 with no engineering difficulties that could not be readily overcome4 ,moreover1 it was really the very best method considering the narrow limits of their appliances4 ,you may ask1 ',how were these big stones carried to the foot of the inclined plane8' ,the quarries1 in some cases1 were five hundred miles distant1 and most of the stones had to be brought across the ,nile to the works4 ,we know from the monuments1 and from the papyrii that have come down to us from remote periods1 that many of the stones were brought down the river on large rafts or floats1 and on barge-like vessels2 and we also know that many of the larger ones were hauled or dragged down from the quarries at ,assowan to ,memphis1 alongside the river1 a distance of #ehj miles4 ,this is particularly true of the obelisks1 for all along an old travelled road evidences have lately been found that these stones had been taken that way1 and that resting places for the labourers had been provided at stations about twelve miles apart1 along the whole distance4 ,it has been estimated that a gang of men--say forty--well provided with rollers1 timbers1 ropes1 and necessary tools1 could easily roll an obelisk like that in ,central ,park1 ,new ,york1 twelve miles in twelve hours2 and doubtless this was the system employed in conveying those immense stones that great distance4 ,a large number of obelisks were erected near ,memphis1 though there are none there now1 for the ,greek and ,roman engineers1 at the command of the rulers1 took a number down and carried them to the city of ,alexandria2 but we have less knowledge of how these later engineers transferred the stones to the newer city1 than we have of the methods of the older4 ,the beautiful column known as ,pompey's ,pillar was once an obelisk1 and was transformed into a pillar1 by either ,greek or ,roman artisans1 it is not clear which4 ,the work of putting those huge stones in place was not easy1 as ,commander ,gorringe discovered when he stood the ,new ,york obelisk in the place it now occupies4 ,but let us get back to our inclined plane4 ,i have shown you how a weight or roller acts on the incline1 but ,i did not explain it clearly1 nor in a scientific way1 as ,i do not want to puzzle or confuse you with terms and problems you cannot understand4 ,i will1 however1 give you another illustration or two on the subject1 in which another factor plays a part1 namely--gravitation4 ,let us suppose you have two golf balls laid on a table that is perfectly horizontal or level in every direction2 they will remain at rest wherever placed1 but if we elevate the table so that the raised end is half the length of the top higher than the lower end1 the balls will require a force half their weight to sustain them in any position on the table4 ,but suppose they are on a plane perpendicular to the table top1 the balls would descend with their whole weight1 for the plane would not contribute in any respect to support them2 consequently they would require a power equal to their whole weight to hold them back4 ,it is by the velocity with which a body falls that we can estimate the force acted upon it1 for the effect is estimated by the cause4 ,suppose an inclined plane is thirty-two feet long1 and its perpendicular height sixteen feet1 what time should a ball take to roll down the plane1 and also to fall from the top to the ground by the force of gravity alone8 ,we know that by the force of attraction or gravitation1 a body will be one second in falling sixteen feet perpendicularly1 and as our plane in length is double its height at the upper end1 it will require two seconds for the ball to roll down from top to bottom4 ,suppose a plane sixty-four feet in perpendicular height1 and three times sixty-four feet1 or one hundred and ninety-two feet long2 the time it will require a ball to fall to the earth by the attraction of gravitation will be two seconds4 ,the first it falls sixteen feet1 and the next forty-eight feet will be travelled in the same time1 for the velocity of falling bodies increases as they descend4 ,it has been found by accurate experiments that a body descending from a considerable height by the force of gravitation1 falls sixteen feet in the first second1 three times sixteen feet in the next2 five times sixteen feet in the third2 seven times sixteen feet in the fourth second of time2 and so on1 continually increasing according to the odd numbers1 #a1 #c1 #e1 #g1 #i1 #aa1 etc4 ,usually1 the increase of velocity is somewhat greater than this1 as it varies a trifle in different latitudes4 ,in the example before us we find that the plane is three times as long as it is high on a perpendicular line2 so that it will take the ball to roll down that distance 7#aib ft47 three times as many seconds as it took to descend freely by the force of gravity1 that is to say1 six seconds4 ,the principle of the inclined plane is made use of in the manufacture of tools of many kinds1 as in the bevelled sides of hatchets1 axes1 chisels and other similar tools1 the examples of which are in a great measure related to this power1 though many of them partake largely of the wedge1 of which we shall now have something to say4 ,illustration3 ,fig4 #af4 ,action of the wedge ,the wedge may be a block of wood1 iron1 or other material1 tapered to a thin edge1 forming a sort of double inclined plane1 ,a ,p ,b1 7,fig4 #af7 where their bases are joined1 making ,a ,b the whole thickness of the wedge at the top4 ,in splitting wood as is shown in the illustration1 ,r ,r being the wood1 the wedge must be driven in with a large hammer or heavy mallet which impels it down and forces the fibres of the wood to separate and open up4 ,the wedge is of great importance in a vast variety of cases where the other mechanical powers are of no avail1 and this arises from the momentum of the blow given it2 which is greater beyond comparison than the application of any dead weight or pressure employed by the other mechanical powers4 ,hence1 it is used in splitting wood1 rocks1 and many other things4 ,even the largest ships may be raised somewhat by driving wedges below them4 ,often1 in launching a vessel1 wedges are used to start it on its way4 ,and they are also used for raising beams or floors of houses where they have given way by reason of having too much weight laid upon them4 ,in quarrying large stones1 it is customary to wedge or break off the rock by first drilling a number of holes on the line of cleavage4 ,wooden wedges are then driven tightly into these and left there until they get wet1 when they expand and split off the rock as required4 ,this method of quarrying large stones was well known to the old ,egyptians1 and employed by them in quarrying their famous obelisks4 ,owing to the fact that the power applied to force a wedge is not continuous1 but a series of impulses1 the theory of the wedge is less exact than that of the other mechanical powers4 ,considering the power and the resistance on each side1 however1 as three forces in equilibrium1 it may be demonstrated that the ,resistance 7,r7 equals ,p ,length of equal side_/,back of wedge ,then the mechanical advantage will be-- ,r_/,p equals ,length of equal side_/,back of wedge ,so that by diminishing the size of the back and increasing the length of the side--that is1 diminishing the angle of penetration--the mechanical power of the wedge is increased4 ,while ,i did not intend to inflict you with arithmetical or algebraical formul1 ,i have been compelled to give you that simple example which ,i know you can all work out1 as it is concise1 and the same would be long and tedious if rendered in text4 ,next morning1 as ,fred and his father were out on the new place early1 looking over the boat house1 the slide for the boat1 and some other matters1 ,mr4 ,gregg suggested that a winch be placed at the upper end of the house1 to haul the boat out of the water4 ,he also suggested that ,fred prepare for work on the boat at once1 and provide himself with all the tools and materials necessary4 ,he promised to call on a friend of his in the city1 who is a noted boat builder1 and ask him the best method to adopt in building the craft4 ,perhaps1 said the father1 it might be a good plan to buy a full set of shapes or patterns from some one of the professional boat builders who advertise such4 ,they are sold at a very low rate--being made of paper--and many firms sell all the material that is required to build a boat complete2 with the sweeps1 ribs1 and curved stuff cut out to the required shape and numbered all ready to set up4 ,what we want1 ,fred1 continued the father1 is a boat sixteen or eighteen feet long1 just the size of the one belonging to your friend1 ,walter ,scott2 that is plenty large enough for all our purposes4 ,his boat can stand as a kind of a model for you to work after in case you do not thoroughly understand the patterns you are to get1 or the manner of arrangement4 ,the gasolene motor we'll order from some manufacturer1 with whom we'll arrange to install it1 with a suitable propeller and necessary attachments4 ,fred was quite satisfied with all his father had said and started to get ready4 ,jessie began to question him about several things she did not fully understand in her father's talk the night previous4 ,fred explained matters1 made them quite clear to her1 and then asked her to get her memorandum book and write down the following1 which he said1 she would often find useful3 ,there are six mechanical powers1 two of which father has not told us about1 but will no doubt do so1 before long4 ,these are called1 the ,lever1 ,pulley1 ,wheel and ,axle1 ,inclined ,plane1 ,wedge1 and ,screw4 ,the ,screw and the ,wheel and ,axle1 you have yet to hear about4 ,now1 study carefully the following rules3 ,the ,lever4--,rule3 ,the power required is to the weight as the distance of the weight from the fulcrum is to the distance of the power from the fulcrum4 ,the ,pulley4--,a fixed pulley gives no increase of power4 ,with a single movable pulley the power required will equal half the weight1 and will move through twice the distance4 ,increasing the number of pulleys1 diminishes the power required4 ,rule3 ,the power is equal to the weight1 divided by the number of folds of rope passing between the pulleys4 ,the ,wheel and ,axle4--,rule3 ,the power is to the weight as the radius of the axle is to the length of the crank or radius of the wheel4 ,the ,inclined ,plane4--,rule3 ,the power is to the weight as the height of the plane is to the length4 ,wedge4--,rule3 ,half the thickness of the head of the wedge is to the length of one of its sides as the power which acts against its head is to the effect produced on its side4 ,the ,screw4--,rule3 ,as the distance between the threads is to the circumference of the circle described by the power1 so is the power required to the weight4 ,fred told ,george also to copy the foregoing in his memorandum book1 so that he would be able to work out any problems for himself4 ,,iii ,,bridge ,,and ,,boat ,,work ,the next day ,fred and his father talked over the proposed boat1 the result being that ,walter ,scott was asked over the telephone if he would come down in his launch to the ,gregg property in the evening1 as ,mr4 ,gregg and ,fred would like to see the craft1 hear all about it1 and find out if it had any defects that might be avoided in the building of another one4 ,walter said he'd be glad to sail down1 and would take his sister to see ,jessie4 ,in the meantime some addresses of boat builders were handed to ,fred1 with instructions to write and ask for catalogues1 prices of materials1 and the other information usually sent out to prospective customers4 ,fred immediately wrote to a number of firms1 including several who manufactured motors and other requisites for small launches4 ,a little after the city clock struck four1 ,jessie1 who was home from school1 saw ,the ,mocking-,bird sailing down the river at good speed1 with ,walter1 his sister ,grace1 and their mother on board4 ,fred went down to the water's edge1 and helped ,walter haul the boat to the unfinished landing place1 where ,mrs4 ,scott and ,grace were safely landed4 ,fred and ,walter soon became deep in boat talk1 and kept it up until the arrival of ,mr4 ,gregg1 who began to make inquiries regarding the speed1 capacity1 and safety of ,the ,mocking-,bird4 ,all his questions were intelligently and favourably answered by ,walter1 a bright and earnest little fellow4 ,he was some months the senior of ,fred1 but was not so strong or robust looking4 ,she's just #ah feet long over all1 said he1 with a #e-;foot beam1 a draft aft of about #ah inches1 and a forward draft of #a foot4 ,she is fitted with a #f-;horse-power gasolene engine1 and her speed is from #h to #i miles an hour4 ,an illustration of her1 as she appeared when partly built1 is shown in ,fig4 #ag1 where a plan and a section of her length may be seen4 ,the manner of her construction is also shown1 also the lines of ribs1 portion of inside lining1 position of motor1 rudder1 and propeller4 ,illustration3 ,fig4 #ag4 ,plan and section of ,the ,mocking-,bird ,mr4 ,gregg also ascertained from ,walter that his father had sent to a firm who made a business of preparing the complete wood-work for many kinds of boats on the knockdown system1 selling the whole material ready to set up without the aid of an expert4 ,printed instructions came along with each boat1 so that the buyer would have but little difficulty in setting up the wood-work and making it ready for use4 ,an expert workman had been engaged by ,walter's father to install the engine1 line up the propeller shaft1 and connect the wheel and shaft to the engine4 ,on the arrival of the materials--within a week after the order was sent--,walter had gone to work2 and inside of fourteen days1 ,the ,mocking-,bird took to the water4 ,so fully and so satisfactorily did ,walter explain to ,mr4 ,gregg all that he asked about1 that ,fred was able at once to order the material for a similar launch1 to be sent on immediately4 ,in order to hurry matters1 a cheque was inclosed with the order1 and ,fred1 ,walter1 and ,george walked over to the postoffice with the letter1 so that it went by the night mail4 ,on returning1 it was suggested that the boys1 ,grace1 and ,jessie go for a sail on the river1 and all were soon at the landing4 ,walter adjusted his engine and made all ready as ,george and the girls got on board1 while ,fred cast off the rope which held the boat to the dock1 then stepped after them4 ,the engine was started1 ,fred took the tiller1 and they were soon afloat1 sailing with the tide in their favour at a rapid speed1 and returning to the landing place inside of an hour1 well pleased with their little outing4 ,fred showed ,walter his new boat-house and workshop1 explained to him how ,nick and he1 with the help of ,george and the advice of his father1 had completed the work and the building4 ,he also pointed out other work he was going to do as soon as his boat was finished4 ,though not yet dark1 it was getting rather late1 and ,walter's mother advised that they start for home as soon as he was ready4 ,so wishing ,fred every success in the building of his boat1 ,mrs4 ,scott1 her daughter1 and ,walter left for home4 ,well1 ,fred1 said ,mr4 ,gregg1 when his family were all seated in the living room1 you are now in for quite a job1 one that will test your working qualities2 but ,i am sure you will come out with flying colours4 ,you will meet difficulties1 but you must overcome them1 and when the boat is finished1 painted1 and ready to name1 you can have some of your friends up for the launching4 ,mother will have a special tea for you all1 and we'll christen the new craft4 ,meantime we must think over the matter of a name1 and decide upon one we shall all like4 ,next morning1 ,fred and his father went down to the river's edge to examine the little ravine that had been cut out by the spring and fall freshets4 ,it was a small affair1 only about six feet deep and ten or twelve feet wide4 ,at present1 the opposite side was reached by crossing a couple of planks1 safe enough while the land had been in a measure unoccupied4 ,to leave it so now would be a different matter1 as ,jessie or her mother1 attempting to cross1 might easily fall over2 so it was decided to have a foot-bridge built over the creek1 which was nearly dry the greater part of the year4 ,there was plenty of material on the ground for the purpose1 and ,fred was asked by his father to get ,nick to help1 so that the bridge might be ready as soon as possible4 ,fred felt he was getting to be quite an important person when his father trusted him with work which must necessarily entail considerable expense1 but he accepted the responsibility with pleasure1 and promised to commence at once1 so as to have it finished by the time the material for the boat arrived4 ,so1 when ,nick arrived1 operations began immediately4 ,illustration3 ,the ,creek ,taking a tape line1 ,fred sent the ,italian to the other end of it1 and they picked out a favourable location to measure across1 making it over #aa feet at the narrowest spot from one edge to the other4 ,allowance was then made for bearings five feet on either side of the span1 so that timbers #ba feet long would be required to cross the chasm4 ,this width would require three string-pieces1 or chords1 to run across1 one on each side1 and one in the centre4 ,these1 covered with three-inch plank from end to end1 would make a good1 solid deck sufficient for all purposes4 ,the planks were cut off seven feet long1 to have the deck of the bridge1 over all1 exactly seven feet wide4 ,among the timbers taken from the old barn were nine pieces1 measuring #bb feet in length1 #h #aj inches in section1 so ,fred decided to make use of three of these just as they were1 without cutting1 and to place them on their edges to get the most strength out of them4 ,he then had six posts cut off the old cedar fence posts1 about two feet long1 which were sunk into the ground their whole length1 as shown in ,fig4 #ah1 three on each side of the creek1 and the tops made level1 so that a flat timber or plank would rest on them1 touching each one4 ,this plank was made nine feet long1 so as to project over the posts about a foot at each end4 ,this was1 of course1 the same at each end of the bridge4 ,after the flat timbers had been laid on the ends of the posts and fastened with spikes1 there were laid the three long timbers spanning the gully4 ,the spaces between were equally divided1 and then covered with three-inch planks taken from the floor of the old barn4 ,the boards were cut off to the proper length and fastened down on the three timbers with spikes five inches long1 the planks not laid close together1 but kept about three-eighths of an inch apart1 in order to let the water run off after a rain1 as well as to allow air to circulate underneath and between the joints to prevent the planks from decay4 ,illustration3 ,fig4 #ah4 ,frame of foot-bridge ,in order to make the bridge safe1 it was necessary to build a rail on each side4 ,two pieces of timber about #bj feet long and #f #f inches square were used for the rails1 while posts and braces were made of timber of about the same dimensions4 ,the bottoms of the posts were halved1 so that they could be spiked or nailed to the long outside string-pieces1 as shown in the illustration4 ,tenons were made on the top of these posts1 and these fitted into mortises made in the top rails1 and all were then put together and fastened with wooden pins4 ,nick dug away the surplus earth from the approaches to the bridge1 and made an easy grade to its deck4 ,this completed the work all but the painting1 which was left to be done some other day4 ,mr4 ,gregg inspected the bridge1 pronounced it all right1 and congratulated ,fred on his workmanship1 at the same time saying a good word to ,nick and ,george1 both of whom had helped very much to make the effort a success4 ,in the evening ,mr4 ,gregg told ,fred and ,george that a friend of his had given him a copy of the rules to be observed when running a launch1 so he asked the boys to get their note-books1 and take these down as he read them out4 ,even ,jessie1 too1 he thought1 ought to be acquainted with the rules1 as she might be called upon some time to make use of them1 so three pencils were soon at work1 as the father read out the following3 #a4 ,when at the wheel1 remember as a first consideration1 that you cannot entertain the boat's occupants as well as steer4 #b4 ,keep your course1 and know what that course is4 #c4 ,regulate your speed to the company you are in4 ,marine motors are1 as a rule1 very flexible4 #d4 ,do not cut corners4 #e4 ,when approaching a landing1 learn to judge exactly the distance your boat will travel after your propeller has stopped1 so as to run alongside without using your reverse gear4 ,this requires some practice1 but is amply rewarded by time saved1 in the long run1 and decrease of wear and tear on engine1 gear1 and propeller4 ,any one can get to a landing in time by alternately running full speed ahead and then astern4 #f4 ,when aboard your boat1 and facing the bow your right hand is starboard1 your left1 port4 ,keep to the right4 ,should you be overtaking any one1 it is your duty to pass clear on their left4 ,the above applies only to narrow waters4 #g4 ,when going up or down stream1 should you wish to cross over to the other side and return1 and another boat is overtaking you on your left1 don't attempt to cross its bow2 slow down until it has passed4 #h4 ,keep clear of non-engined crafts4 ,you have greater freedom of action than they2 it costs you nothing1 and their occupants appreciate your courtesy4 #i4 ,do not tow canoes or skiffs alongside4 ,if towed at all1 they should be right aft with as short a towline as possible4 #aj4 ,finally2 remember the rules of the road-- ',green to green or red to red ,perfect safety--go ahead ,if to starboard red appear ',tis your duty to keep clear4 ,when upon your port is seen ,a steamer's starboard light of green1 ,there's not so much for you to do ,as green to port keeps clear of you4' ,the children all promised to memorize these rules4 ,as the stuff for the boat was not expected for some days1 ,fred and ,nick kept at work about the new boat house1 and building up the landing dock4 ,the former fitted up a work bench1 and put his little shop in readiness for actual use4 ,fred also hunted for a nice stick of timber among the old barn ruins1 on which to set up the boat4 ,a good piece found1 he cut it to a length of #bj feet1 and then he and ,nick got it into the boat house1 where ,fred planed it off a little with a rough jack plane1 keeping a sharp lookout for nails1 sand1 or gravel4 ,nothing destroys the cutting edges of tools more than nails1 bits of iron1 glass1 sand1 or small pebbles1 which sometimes escape the vigilance of the workman4 ,especially is this true of saws1 which ,fred knew quite well since he had once run a good sharp saw against a nail1 while cutting a piece of timber in two4 ,this taught him a lesson he never forgot1 and whenever he had to cut up old material1 he was always careful to examine it all round1 and to scrape or brush off all the dirt and sand from the parts through which the saw teeth had to travel4 ,in planing1 or dressing the stick of timber1 the same precautions were taken1 and the surface of the wood was made as clean and free from dirt and sand as it possibly could be4 ,notwithstanding all this1 ,fred found it almost impossible to keep the cutting iron of his jack plane sharp enough to take off shavings4 ,he had to sharpen it every few minutes4 ,this is nearly always the case when working up wood which has previously been used4 ,however1 he managed to dress his stick very nicely1 and after finishing it1 laid it down along the middle of the floor of the shop1 putting blocks of wood under it here and there to raise it up from the floor five or six inches4 ,it was then made level on top and fastened down so that it would not move or get out of line4 ,this was about all they could do on the boat until the materials arrived4 ,nick had managed to fill in the space between the two walls of the little pier with heavy bowlders1 and had strengthened the whole with coarse rubble-stone work in such a manner that there was little danger of injury from floating ice or flood tides2 and he had covered the whole over with small stones1 gravel1 and a good thick layer of cement concrete1 which made it correspond with the cement walk4 ,the question of a winch was then taken up with ,mr4 ,gregg and it was decided to construct a simple affair at the end of the boat-house opposite the large doors1 where the boat would have to enter4 ,illustration3 ,fig4 #ai4 ,winch and crank ,mr4 ,gregg suggested1 in order to make the end of the building strong enough1 that two upright posts be set up1 well braced by being fastened to both floor and ceiling1 and that the winch be attached to them in a way that would be easy to work1 as shown in ,fig4 #ai1 room enough being left between the posts and the wall for the crank to turn without the hand of the operator striking the boards4 ,the cylinder around which the rope should wind ought to be about six inches in diameter1 and the crank or handle on the end1 not less than fifteen or sixteen inches long4 ,the longer the crank1 the less force it would require to haul in the boat4 ,if desired1 a crank could be fitted to the other end of the cylinder so that two persons could work at one time1 pulling in the weight4 ,in the evening ,mr4 ,gregg asked the boys and ,jessie to visit his room1 and he would try to explain the principle and advantages of the wheel and axle1 as the winch they were to make was in a measure related to that principle4 ,mr4 ,gregg began by saying3 ,the wheel and axle is merely a modification of the lever and consists of a couple of cylinders turning on a common axis1 the larger cylinder is usually called the wheel1 the lesser one the axle4 ,this arrangement1 which ,i draw on the blackboard herewith1 forms a kind of lever of the first or second class4 ,considered as a lever1 the fulcrum is at the common axis1 while the arms of the lever are the radii of the wheel and of the axle4 ,the fulcrum is at ,c1 the centre4 ,the arm of the weight is ,w ,w1 and the arm of the power is ,a ,c4 ,in ,fig4 #bj the arm of the power is the spoke of the wheel1 while the arm of the weight is the radius of the axle4 ,fig4 #ai shows the ordinary winch1 often used in well-digging for hauling up dirt and rock1 and also for raising planks1 shingles1 rafters1 and other light stuff1 to the roofs and upper floors of buildings4 ,often it is made more powerful by adding spur or geared wheels to the end of the shaft1 consisting of a pinion and a larger spurred wheel4 ,the crank or handle is attached to the pinion1 and the power is increased according to the difference in diameters of the spur wheels4 ,the machine is then called a 'crab' and it is often used for lifting safes and other heavy weights to elevated situations4 ,in ,fig4 #bj the length of the crank 7in a straight line7 is the arm of the power4 ,illustration3 ,fig4 #bj4 ,wheel and axle ,the mechanical advantage of the wheel and axle equals the ratio between the diameter of the wheel and of the axle4 ,illustration3 ,fig4 #ba4 ,capstan and hand bars ,it is not necessary that an entire wheel be present4 ,in the case of the windlass and the capstan 7,fig4 #ba71 the power may be applied to a single arm or to a number of arms placed in the holes shown4 ,the cable or rope on the barrel of the capstan is hauled in by turning the capstan on its axis1 with handspikes or bars4 ,the capstan is prevented from turning back by a pawl attached to its lower part1 working in a circular ratchet on the base4 ,illustration3 ,fig4 #bb4 ,compensating fusee ,as an illustration of the lever action1 and of work put into and got out of a machine1 there is no better illustration than the ingenious contrivance termed the fusee 7,fig4 #bb74 ,in good watches and clocks1 where the elastic force of a coiled spring is used to drive the works1 the fusee compensates the gradually diminishing pull of the uncoiling spring4 ,the driving of the works at a constant rate is the object for which a watch or clock is designed4 ,this usually entails a constant resistance to be overcome1 but since one of the most compact and convenient forms of mechanism into which mechanical force can be stored is that of the coiled spring1 and since the very nature of the spring is such that its force decreases as it uncoils1 we must employ some compensating device between this variable driving force and the constant resistance4 ,the fusee does this in a most accurate and complete manner4 ,as the fusee to the right is to compensate for the loss of force of the spring as it uncoils itself1 the chain is on the small diameter of the fusee when the watch is wound up1 as the spring has then the greatest force4 ,in the differential1 or ,chinese windlass 7,fig4 #bc71 different parts of the cylinder have different diameters1 the rope winding upon the larger and unwinding from the smaller4 ,by one revolution the load is lifted a distance equal to the difference between the circumference of the two parts4 ,illustration3 ,fig4 #bc4 ,chinese winch and pulley ,there are many other contrivances and appliances of the wheel and axle for performing various services1 but ,i think the examples ,i have shown you will be sufficient to enable you to make use of the device to perform any duty you may be called upon to attempt in ordinary life1 but1 should you enter professional life as civil1 mechanical1 naval1 or mining engineer or architect1 you will be obliged to pursue the study of these subjects further4 ,before closing ,i may add a few problems for you to solve at your leisure by the application of the rules ,i have given you when describing the other mechanical powers4 ,the pilot wheel of a boat is #c feet in diameter2 the axle is #f inches2 the resistance of the rudder is #bdj pounds4 ,what power applied to the wheel will move the rudder8 ,here the difference between the axle and wheel is #ah inches4 ,four men are hoisting an anchor of #c1jjj pounds' weight2 the barrel of the capstan is #h inches in diameter2 the circle described by the handspikes is #g feet #f inches in diameter4 ,how great a pressure must each of the men exert8 ,with a capstan four men are raising a #ajjj-pound anchor2 the barrel of the capstan is a foot in diameter2 the handspikes used are #e feet long2 friction equals #aj per cent4 of the weight4 ,how much force must each man exert to raise the anchor8 ,the circumference of a wheel is #h feet2 that of its axle is #af inches2 the weight1 including friction1 is #he pounds4 ,how great a power will be required to raise it8 ,a power of #gj pounds on a wheel whose diameter is #aj feet balances #cjj pounds on the axle4 ,give the diameter of the axle4 ,an axle #aj inches in diameter fitted with a winch #ah inches long is used to draw water from a well4 ,how great a power will it require to raise a cubic foot of water1 which weighs #fb-a_/b pounds8 ,the first mail in the morning brought word that the whole of the partly prepared stuff for the boat had been shipped by fast freight1 and that it would reach its destination in the course of a few days4 ,the paper patterns1 directions1 and all necessary instructions for building would be mailed at once4 ,,iv ,,making ,a ,,gasolene ,,launch ,two or three days after ,mr4 ,gregg had talked over the principles of the wheel and axle1 with the children1 ,fred received notice that a consignment of wood-work was at the station awaiting his orders4 ,mr4 ,gregg made immediate arrangements with the railway people1 and by the time he got home from his office1 the stuff was being unloaded by the boys1 who carried it piece by piece into the workshop1 each section being laid by itself in the order in which it was to be put in place in the boat4 ,printed instructions were in the equipment for laying the keel1 setting up the frames1 and even for taking the stuff out of the packages and putting it in heaps1 so that it could be readily picked out when wanted for use4 ,each rib was numbered1 and marked or stamped right or left1 and all the pieces were cut off to the right length and to the right bevel or angle to suit the positions they were to occupy1 as specified in the printed instructions4 ,this made the setting up an easy matter1 requiring only care1 patience1 and a fair knowledge of the use of wood-working tools4 ,that ,fred possessed these qualities1 was partly due to the training he had received in the technical school1 and partly to his natural aptitude for picking up methods1 ideas1 and new applications4 ,fred1 ,george1 and ,mr4 ,gregg himself1 were much interested in the selection of the various materials1 and when the plank that was to form the keel had been unpacked1 ,george was anxious that it should be laid down on the bed that had been prepared for its reception4 ,he was quite disappointed when he found it considerably shorter than he had expected the boat to be4 ,it was explained to him1 however1 that the overhanging of the stern1 and therefore shortening of the forefoot1 or stem1 necessitated the keel being shorter than the boat would be when measured over all on top4 ,the keel was found to be a fine piece of tough oak1 nicely dressed1 made the proper shape at each end1 bored and gained to receive the stern post1 the stern ribs1 and side stanchions4 ,everything was marked1 and each timber was sized so that it would fit in place snugly without using a tool on it1 except a hammer or mallet4 ,at tea time ,george felt it difficult to keep reasonably quiet1 he was so enthusiastic about the boat--much to the amusement of his father1 who knew exactly how the boy felt4 ,illustration3 ,fig4 #bd4 ,stem of launch ,after tea1 all walked to the boat house1 and the father assisted ,fred to set up the keel1 which was in two pieces1 halved together midway and well fastened with screws4 ,the joint was painted with a heavy coat of white lead and linseed oil paint1 before being put together and screwed up4 ,the keel is the lowest timber in a boat or ship1 and it runs nearly the length of the craft4 ,sometimes there is a keelson placed on the top of the keel1 and the ribs of the boat1 or stanchions1 are made fast to that timber1 as shown in the illustration1 7,fig4 #bd17 in which the gains for the ribs or moulds are made4 ,this portion of the boat was put together temporarily1 so ,fred had no difficulty in assembling the various pieces4 ,the stem1 keel1 keelson1 and deadwood were all made of oak1 and looked strong4 ,the keel and keelson were properly laid and adjusted1 and after some explanations by ,mr4 ,gregg the manner of setting up the ribs was thoroughly understood4 ,fred decided to telephone ,walter ,scott to come down next day1 as it was ,saturday1 and help him to set up the skeleton4 ,as the weather was getting warm1 the whole family spent the evening on the veranda and ,george introduced the question of naming the boat4 ,he suggested ,red ,bird1 but this did not seem to take well1 and several others were proposed but none seemed to suit everybody4 ,jessie sat quietly on the steps till asked by ,fred what her choice would be4 ,i would like it called after mamma1 ,caroline4 ,that's a good idea1 ,jessie1 said her father1 and if the boys or your mother don't object1 ,i think we'll settle on ,caroline4 ,early next morning the boys were out watching for ,the ,mocking-,bird1 which very soon made its appearance4 ,fred and ,walter tied the boat up to the new dock and went into the boat house1 where the latter began to examine the boat stuff1 and to explain the manner of setting it up and fastening it in place4 ,nick1 who was on hand to help1 did the heavy work1 and helped to put up the stanchions4 ,walter seemed quite familiar with the work1 and he and ,fred soon had the boat so well in hand that it seemed to grow under their fingers4 ,the ribs were easily selected1 as they were tied together in pairs and numbered4 ,they were then set in their places according to their numbers and were fastened to the keelson with the strong copper nails4 ,all the nails required for the boat were of copper1 because that metal is less likely to corrode than iron or steel4 ,it was found necessary to brace the ribs in order to keep them in line4 ,thin pieces of lath were tacked on the tops to hold the ribs the proper distance apart1 and longer and stronger strips of wood were used for bracing the boat sideways4 ,these were nailed to the joints in the ceiling or high up on the walls of the boat house4 ,illustration3 ,copyright1 #aiaa1 by ,underwood ,underwood1 ,n4 ,y4 ,,making ,a ,,motor ,,launch ,all the ,nails ,required for the ,boat ,were of ,copper1 ,because ,that ,metal is ,less ,likely to ,corrode ,than ,iron or ,steel ,illustration3 ,fig4 #be4 ,section of launch--abeam ,at noon the boys had the skeleton of the boat well advanced1 and to one standing in front of the bow1 it presented an appearance like the sketch shown at ,fig4 #be4 ,illustration3 ,fig4 #bf4 ,methods of sheathing ,the launch might be called carvel ribbon built1 or nearly so1 and it would have a displacement of #ad or #ae hundred-weight when fairly loaded4 ,this weight would bring her down to the third ,w4 ,l41 as shown in the end sketch4 ,to load her to the fourth ,w4 ,l41 would give her a load far beyond these figures4 ,the sections had to be closely spaced1 and the ribbons or slats let into the temporary section moulds before the outside boarding could be put on1 the edges of the boarding being clinch fastened1 as shown in the ribbon carvel1 ,fig4 #bf4 ,other styles of sheathing boats1 as shown1 are often used1 but the ,caroline was ribbon carvel4 ,it is usual to lay off the sheer profile on a suitable floor1 and line in the rebate line1 scarf of stem1 deadwoods1 fork timbers1 etc41 making thin moulds of each member to be lined off1 sawn1 and bolted together4 ,the section moulds1 from which the boat derives its shape1 are also laid off1 and the planking1 #c_/h-;in4 thick1 deducted when making them4 ,the stem1 of crooked oak1 was #b-a_/d in4 thick by about #c in41 shaped as shown in ,fig4 #bd4 ,the fore deadwood was #b-a_/b in4 thick1 moulded about #c in41 and through-bolted to the stem and keel with #c_/h-;in4 copper bolts2 and the stern-post1 #c-a_/b in4 thick1 was wrought to shape1 as shown4 ,the centre line of the shaft1 as shown1 is subject to alteration1 since different makes of motors have different sizes of propellers and flywheels4 ,the fork timbers were let into the stern-post1 and carried the transom1 wrought out of a flitch of elm #c-a_/b in4 thick4 ,the planking1 of #c_/h-;in4 cedar1 was closely jointed and varnished1 and secured to the ribbons4 ,the timbers were of rock elm1 #g_/h in4 by #a_/b in41 steamed and bent or sawn to shape1 and through-fastened at the top and bottom edges of the planking4 ,these were spaced on #g-a_/b-;in4 centres1 with two clinch nails into the ribbons between them4 ,three or four solid floorings should be worked into the motor space2 fitting of the motor bed thwartships gives great support to the boat4 ,the thwarts were of oak1 #h in4 wide and #a in4 thick1 with the side seats1 #g_/h in4 thick1 supported by turned legs of oak4 ,the decks at each end should be of #a_/b-;in4 oak or cherry reeded into #c in4 widths1 and filled with marine glue4 ,the covering board1 #b-a_/b in4 wide1 with a nosing worked on the edges1 and #a_/b in4 thick1 was carried by a clamp or binding stake1 #b-a_/b in4 by #e_/h in41 through-fastened at every timber4 ,the knees were of oak1 #a in4 thick1 about #aj in4 on the foot by about #c in4 at the head1 and through-fastened4 ,a breast hook #b in4 thick should be fitted4 ,the floor boards may be of #c_/d-;in4 spruce1 elm1 or ash grating1 as preferred4 ,the centre of the motor was at ,no4 #f section1 as indicated1 the gasolene being stored in a strong tank under the forward deck1 just high enough to feed by gravitation4 ,after being cleaned off and sandpapered1 a coat of good shellac varnish1 may be followed1 if desired1 by three coats of best yacht varnish4 ,the spacing of the sections was3 ,no4 #a1 from face to stem1 #a foot #b in42 ,no4 #b1 from ,no4 #a1 is #a ft4 #b in41 the other sections to ,no4 #aa each #a ft4 #f in42 ,no4 #ab was #a ft4 #a in4 from ,no4 #aa 7see ,fig4 #be74 ,the water-lines were #e in4 apart1 and the buttock-lines1 ,a and ,b1 #a ft4 and #a ft4 #i in4 respectively from the middle line4 ,the boys followed these directions1 and with the help of the following table1 managed to get the boat ready to varnish and finish up4 ,the following table1 which refers more particularly to the section shown in ,fig4 #be1 shows the sheer lines1 counting from ,l ,w ,l 7low water line74 ,while all the work and calculations regarding the plan had been already done1 ,mr4 ,gregg1 who had watched the work's progress for a week1 thought they should know the principles on which the craft was being built1 and therefore advised them to examine the illustration and table1 so that they would have some knowledge of the science required to build a boat intelligently4 ,fred and ,george did this1 and were helped along by ,walter1 who seemed to have mastered the subject pretty thoroughly4 ,,table ,,of ,,offsets ,stem ,section ,numbers ---------------------------------------- -------------------- #a #b #c #d ---------------------------------------- -------------------- ft4 in4ft4 in4ft4 in4ft4 in4ft4 in4 ,sheer heights above ,l4,w4,l4 #a #g #a #f #a #e #a #d-a_/h #a #c-a_/d ,l4,w4,l4 to rebate line #g #h-c_/d #i #i-a_/d ,half-breadths at gunwale #h-a_/d #a #c-a_/h #a #i-a_/b #b #a-a_/h ,half-breadths at #d ,w4,l4 #f-g_/h #a #a-a_/b #a #h #b #j-a_/b ,half-breadths at #c ,w4,l4 #e-g_/h #aa-e_/h #a #f-c_/h #a #aa ,half-breadths at ,l4,w4,l4 #d-c_/h #i-c_/h #a #c-e_/h #a #h-c_/d ,half-breadths at #a ,w4,l4 #b-a_/b #e-c_/d #aj-a_/b #a #c ,buttock ,a from ,l4,w4,l4 #e-a_/b #d-a_/h #f-c_/h ,buttock ,b from ,l4,w4,l4 #c_/h ---------------------------------------- -------------------- ,section ,numbers ---------------------------------------- -------------------- #e #f #g #h #i ---------------------------------------- -------------------- ft4 in4ft4 in4ft4 in4ft4 in4ft4 in4 ,sheer heights above ,l4,w4,l4 #a #b-c_/d #a #b-a_/d #a #b-a_/h #a #b-a_/h #a #b-a_/b ,l4,w4,l4 to rebate line #i-a_/b #i-g_/h #aj #aj-a_/b #aj-c_/d ,half-breadths at gunwale #b #c-a_/b #b #d-a_/b #b #d-c_/h #b #c-e_/h #b #b-a_/h ,half-breadths at #d ,w4,l4 #b #b-g_/h #b #d #b #c-g_/h #b #c-a_/d #b #a-c_/d ,half-breadths at #c ,w4,l4 #b #b #b #c-a_/d #b #c-a_/d #b #b-a_/b #b #j-c_/d ,half-breadths at ,l4,w4,l4 #b #j #b #a-a_/b #b #a-a_/b #b #j-e_/h #a #i-a_/b ,half-breadths at #a ,w4,l4 #a #f-c_/d #a #h-a_/b #a #h-a_/b #a #f-a_/b #a #j-g_/h ,buttock ,a from ,l4,w4,l4 #g-e_/h #h #h #g-a_/b #e-a_/d ,buttock ,b from ,l4,w4,l4 #c-c_/h #d-c_/d #d-c_/d #c-a_/b #c_/h ---------------------------------------- -------------------- ,end of ,section ,numbers ,transome ---------------------------------------- ----------- #aj #aa #b ---------------------------------------- ----------- ft4 in4ft4 in4ft4 in4ft4 in4 ,sheer heights above ,l4,w4,l4 #a #c #a #c-e_/h #a #d-a_/d #a #f ,l4,w4,l4 to rebate line #aa ,half-breadths at gunwale #b #j #a #i-a_/b #a #f-c_/d ,half-breadths at #d ,w4,l4 #a #aa-c_/h #a #g-a_/d ,half-breadths at #c ,w4,l4 #a #i-a_/d #h-a_/b ,half-breadths at ,l4,w4,l4 #a #b-a_/h ,half-breadths at #a ,w4,l4 #e-c_/d ,buttock ,a from ,l4,w4,l4 #a #f #aa-c_/d ,buttock ,b from ,l4,w4,l4 ---------------------------------------- ----------- ,it was necessary1 before installing the motor1 that a foundation should be laid for it1 so varnishing and the final finish were left over until the engine and propeller should be put in and tried4 ,illustration3 ,fig4 #bg4 ,starboard side of motor ,illustration3 ,fig4 #bh4 ,port side of motor ,the engine was brought to the boat house from ,newark1 and the expert1 engaged by ,mr4 ,gregg some time previous1 came along with it1 bringing such tools as he might want4 ,he examined the bed for the engine1 and saw that all was properly fastened and in good condition to place the engine and the propeller shaft4 ,mr4 ,watts 7the machinist7 laid off a line for the propeller shaft and with a long auger bored a hole from the engine bed through to the stern-post1 large enough to permit the shaft of the propeller to revolve in it easily4 ,a bearing1 or box1 was adjusted to the stern-post in which the shaft ran1 and the box was made water-tight to prevent any inflow4 ,the propeller was made of bronze1 had been nicely fitted to the shaft before it came1 and had a set screw in its hub to hold it firmly on the shaft4 ,the diameter of the propeller wheel measured #ae inches and it had two blades4 ,the shaft and wheel being properly adjusted1 the next thing was to place the engine1 which weighed about #bjj lbs4 ,the blocks and tackle used in taking down the old barn were rigged up to the ceiling by cutting a hole through the floor1 laying a short timber across the joists1 hitching a rope around the timber1 and letting a loop hang down through the hole made in the floor4 ,the hook of the upper block was attached to the loop1 a sling was fastened to the engine1 the whole was hoisted by ,nick with the greatest ease1 and the machine dropped on its bed4 ,as it did not lie quite level1 it was raised again and held suspended until the bed was trued up1 when it was permanently lowered into place and fastened down4 ,two views of the engine are shown in ,figs4 #bg and #bh4 ,illustration3 ,fig4 #bi4 ,carburetor ,in shop talk1 the engine may be described as follows--,bore of cylinder #d-a_/b in4 ,stroke #d-a_/b in4 ,crank shaft #a-c_/h in4 ,revolutions per minute from #fj to #gej4 ,propeller shaft one inch4 ,about #ae or #af horse-power4 ,a float-feed carburetor1 ,fig4 #bi1 was installed at the same time4 ,this carburetor is an excellent one4 ,it insures a regular supply of gasolene and air1 in proper proportion1 and prevents trouble when the motor is in use4 ,the float guarantees an even level of gasolene in the float chamber at all times4 ,the proper balance of the cork float closes the supply of gasolene automatically when it reaches the proper level4 ,this prevents waste of fuel1 every drop being thoroughly vaporized and mixed with the proper amount of air4 ,the spraying nozzle is higher than the gasolene in the float chamber1 and prevents the gasolene from getting into the engine1 unless it is running4 ,the throttle valve on the carburetor gives the operator the power to change instantly the speed1 without changing the timer1 and affords him absolute control of the engine4 ,when all the machinery was in place1 and the propeller attached1 ,mr4 ,watts told the boys that he would finish up the work of installing the next day1 and would then run the engine dry for an hour or two1 to get everything working nicely before declaring the ,caroline ready for sea4 ,it was just two weeks from the day the stuff arrived when the engine was finally installed4 ,that's pretty quick work1 declared ,walter1 and if the boat were varnished1 we could have her in the water in a couple of days4 ,in the evening1 as all the ,greggs were seated on the veranda1 ,fred tried to explain to his father the installation of the engine1 but he failed to make himself quite clear4 ,mr4 ,gregg said to him3 ,you seem to have grasped the theory of the matter1 but ,i see you don't understand some important points1 so ,i think a few suggestions may be of use to you4 ,i will not confine myself to marine motors altogether1 as gasolene engines are used for many purposes1 more and more every day4 ,with regard to installing an engine in a boat1 the first question is the bed1 as you have seen in your own case1 where your foundation is made good and solid4 ,small engines may be supported upon a single cross piece at each end of the bed1 but this method should be employed only for the smallest sizes4 ,the heaviest1 and in most cases the hardest1 pipe to fit up is the exhaust4 ,it runs from the exhaust nozzle on the engine to the muffler and thence outboard4 ,the muffler is commonly placed in the stern with the outlet directly outboard4 ,it may1 however1 be in any convenient position1 like under the seats in the standing room1 and the piping led outboard4 ,in any case1 the piping for the exhaust should be as direct and as free from sharp bends as possible4 ,when the motor is near the middle of the boat1 a good practice is to lead the exhaust pipe out through the bottom1 and along it to a point near the stern1 where it again enters the boat and connects with the muffler4 ,the outlet from the muffler then leads directly outboard as before4 ,this method1 especially on a large cabin boat1 avoids much loss of space and the disagreeable heat of the exhaust pipe4 ,the surrounding water quickly cools the exhaust1 reduces the pressure and makes the exhaust almost noiseless4 ,the particular function of the muffler is to afford a comparatively large space into which the exhaust may pass and expand1 greatly reducing the pressure4 ,the gas1 under the reduced pressure1 then passes out with little disturbance4 ,the muffler need be of no particular shape1 as long as the volume is sufficient4 ,it is usually made of cast iron in the smaller sizes and of sheet iron in the larger4 ,in many cases a long piece of rather large pipe will answer the same purpose4 ,the muffler may be dispensed with and much space saved by carrying the exhaust directly through the bottom of the boat and exhausting under water4 ,although this is a very convenient and many times satisfactory way1 great care must be used or poor results will be obtained4 ,when the exhaust leads directly out1 a certain amount of pressure is used in displacing the water4 ,this pressure is1 of course1 supplied by the piston and is a 'back pressure1' retarding the piston and decreasing its power4 ,a small expansion chamber or muffler should be provided between the engine and the outlet1 in order to break up the violent pulsations and make the flow fairly constant4 ,some form of shield should be fitted over the outer end of the exhaust pipe to guide the stream of the exhaust aft and prevent the water being forced into it by the movement of the boat4 ,several forms of these are on the market in the shape of brass castings which bolt on to the outside of the hull and have a thread on the inside to take the exhaust pipe4 ,when the under water exhaust is fitted1 a pet cock should be put in the exhaust pipe near the engine4 ,this is opened when the engine is stopped1 thus preventing the water from being drawn up into the cylinders by the vacuum caused by the cooling of the gases in the pipe and cylinders4 ,the under water exhaust is a very neat and simple method1 when correctly installed1 as all noise and heat from the exhaust pipe are avoided4 ,the exhaust may be considerably cooled and the noise reduced by dispersion4 ,with regard to stationary engines1 used for domestic or other purposes1 any old place is considered good enough to put them in4 ,now1 this is one of the biggest and most expensive mistakes one can make1 for as soon as some small screw gets loose in the far corner1 the engine1 salesman and manufacturer are unjustly blamed1 simply because the present owner has not left enough room to make the small adjustments necessary in every engine and piece of machinery4 ,therefore1 it pays always to install the engine in a light1 dry place1 easy of access and with sufficient space all round to enable all parts to be reached and to give plenty of room for turning the fly wheels in starting4 ,whenever possible1 place the engine on the ground floor4 ,on an upper floor1 the necessary provision should be made to avoid vibration2 if installed in the basement1 place it in the best light4 ,without a good foundation1 an engine may be expected to give more or less trouble from vibration1 since it is subjected to forces1 suddenly and repeatedly exerted1 which produce violent reactions4 ,care should be taken to excavate down to good soil and to line the bottom with a substantial thickness of concrete in order to form a single mass of artificial stone4 ,the foundations may then be built up of either concrete1 brick1 or stone4 ,anchor plates should be extended to the bottom of the masonry and fastened so as to prevent turning while the nuts are being screwed up4 ,place gas pipes or tubes with an inside diameter twice the diameter of the bolts around them1 while the foundation is being built2 this allows the bolts to be adjusted1 and any variations between the tubes may be filled with thin cement after the engine is set4 ,the top of the foundation should be finished perfectly flat and level with a dressing of cement1 and after this is thoroughly dry the engine may be placed in position4 ,when bolting down the engine1 it is better to draw each bolt down a little at a time until all are tight and thus avoid straining the engine crank4 ,after the nuts are drawn tight1 if the crank turns unreasonably hard without loosening the main bearing caps1 it may indicate an uneven foundation1 which is a strain in the engine bed casting4 ,when setting up large engines1 for farm or other purposes1 especial care must be taken to avoid straining the bed castings4 ,foundations hung from an upper floor1 or built upon it1 should be placed as close to the wall as possible4 ,for the smaller sizes of engines it is a good plan to lay wooden beams on top of the foundations and then to place the engine on top of them so that when the frame is bolted down it beds itself into the timber4 ,the timber cap often saves an annoying vibration when it can be overcome in no other way4 ,all the connections should be as short and as free from turns as possible1 and no mistake can be made by having plenty of unions1 so as to disconnect with ease4 ,the gasolene tank should be set as near the engine as is convenient1 with the top of the tank1 preferably1 not more than a foot or two below the base of the engine4 ,in cases where the gasolene tank must be set from forty to fifty feet away1 it is necessary to place a check valve in the suction pipe near the tank4 ,both suction and overflow pipes must have a gradual rise all the way from the tank to the pump and should be as straight as possible to avoid the air traps1 which prevent a steady flow of gasolene4 ,it is most essential to clean thoroughly all pipes and fittings before they are put together1 by hammering lightly to loosen any scale and washing out with gasolene1 as solid matter of this nature may be responsible for some of the simple1 but hard-to-get-at troubles common to gasolene engines4 ,shellac is best for joints in gasolene piping1 but when this cannot be obtained common laundry soap will answer the purpose just about as well4 ,remember1 also1 that gasolene is a rubber solvent1 and should never be applied to joints where rubber is used4 ,in some cases it will be found advisable to use gravity feed instead of a pump1 except in the case of the tank1 which must be so arranged that its lowest point is slightly above the generator valve4 ,the exhaust pipe must be of full size1 free from turns and short as possible1 since the shorter it is the more economically the engine will run4 ,it will be found advisable to place the muffler and exhaust piping away from combustible material1 and never to turn the exhaust into any chimney or flue4 ,there are two general methods of supplying the water1 the first being that of the cooling tank commonly used with small engines4 ,for convenience in piping1 the tank should be slightly elevated1 and both pipes1 having as few bends as possible1 should slope from the tank to the engine1 a valve being placed in the bottom pipe near the tank4 ,by using a circulating pump1 fitted to the engine or shaft1 water may be used from an underground cistern or tank4 ,the other method is to use a continuous cooling stream from water-works or other source4 ,when city water is used1 it is a good plan to have a break and funnel inserted in the drain pipe so that the current of water flowing through the cylinder jacket may be seen4 ,for making joints in water pipes1 either thick lead or graphite may be used with almost equal success4 ,it may be well to place particular emphasis on the fact that it will pay to get into the habit of always shutting off the water at the tank and draining the cylinder every time the engine is stopped--not necessary in summer1 but absolutely essential in winter--as a fair percentage of gasolene users know to their cost4 ,the greatest care must be employed in using and handling gasolene1 as it is dangerous and highly explosive4 ,it has been known to explode when #bj or #cj feet from light1 the vapours having reached the fire in the way of a gas1 igniting and firing the liquid4 ,and1 now1 right here1 let me impress on you this warning2 never handle gasolene near a fire or light under any circumstances1 and be very careful with it under all conditions4 ,fortunately1 there are few accidents resulting from gasolene1 when we consider the large amount used since it has become almost a universal fuel for engines1 and it is also used largely for domestic heating and lighting4 ,it is a product of petroleum1 of which in its crude form about #gf per cent4 is turned into kerosene1 #aa per cent4 into gasolene1 #c per cent4 into lubricating oils1 and the balance into vaselines1 paraffine1 coke and so forth4 ,different petroleums produce different proportions of the various products1 some of them being considerably richer in gasolene than #aa per cent4 ,gasolene is usually designated according to its specific gravity by an arbitrary measure1 known as ,baume's hydrometer scale4 ,this designation is in degrees1 the most common gasolene ranging between #fe degrees and #he degrees1 and the average being #gj degrees1 the usual density used in engines4 ,you will find it somewhat difficult at first to start up your engine when you wish to1 so ,i will give you a few hints to show how this difficulty may often be overcome4 ,there is always a reason why a gas engine refuses to obey the behest of its driver4 ,in the first place1 see that the compression is right and the admission valve so tight that it will admit only enough of the mixture 7gasolene and air7 to make a charge that will take fire from the sparker and move the piston forward4 ,next see that the sparker is clean1 that it will make a bright spark at white heat when the contact is broken1 and at the right time4 ',in time' means to go if everything else is right1 and 'out of time' means not to go even when everything else is right4 ,the valve of the engine must be kept well ground down with emery and oil so as to preclude the possibility of a leak1 as one would very seriously weaken the power of the engine even after it had started4 ,the spark must be made when the connecting rod of the engine is on the 'up stroke1' with the crank shaft about three inches below the horizontal line of the centre of the index1 and herein lies the whole secret of the greatest efficiency from the least amount of gasolene4 ,as there is an interval of time after the spark is made until it ignites the charge1 it is very evident that the movement of the machinery continues and the moment of ignition should take place when the compression is greatest4 ,this will be when the piston is on its farthest 'in stroke1' i4 e41 in perfect line with the centre of the cylinder4 ,but if the charge be ignited at this point the engine will not develop the greatest power1 as the interval spoken of will elapse and the piston will have started on its 'out stroke'1 thereby not getting its full force of the expansive gases liberated by combustion of the air and gasolene4 ,so you will readily see that you must allow for the interval spoken of1 if you would get full returns for the energy used in propelling the motor4 ,i have tried to make this plain1 and ,i hope my efforts will help you out with your engine1 either in starting or developing the power at which it is rated4 ,it was not yet late1 so the boys took down from the book shelf a code of yacht flag signals1 and found the following3 ,there are no hard and fast rules regarding shapes and colours of yacht bunting1 but the following are generally accepted by the prominent clubs in the ,united ,states and in foreign countries4 #a4 ,the pennant 7a triangular shaped flag7 is used for the club burgee4 #b4 ,the shallow tail is adopted for the private signal4 #c4 ,the rectangular flag is chiefly used for a flag officer's signal4 #d4 ,the shape1 consequently1 at once denotes whether a flag is that of a club1 a flag officer1 or a member4 #e4 ,the majority of flag officers' signals are coloured3 ,blue for commodore1 red for vice-commodore1 and white for rear-commodore4 #f4 ,the international code of signals enables yachts to communicate with each other1 and is also used for dressing ship4 ,the ensign should be flown from the peak of the main-sail on a sailing yacht1 when under way1 and from a stern flag pole when moored4 ,on a yawl1 it should be hoisted at the mizzen truck4 ,on a steamer1 launch1 or dinghy1 it should be flown from a stern flag pole1 when under way or at anchor4 ,club ,burgee4--,the burgee should measure in length about one-half inch for each foot of height of truck from the water2 width to be two-thirds of the length4 ,private signals may be smaller4 ,the burgee should be flown from the mast-head or truck of a cutter1 sloop1 or cat-rigged yacht1 the main truck of a yawl1 the fore truck of a schooner and steamer1 and from the bow pole of a launch or dinghy4 ,flag officers' and private signals should be flown from the truck of a cutter1 sloop1 or cat-rigged yacht1 the main truck of a schooner1 yawl1 or steamer1 and from the bow pole of a launch or dinghy4 ,the following flags are not considered as colours3 ,night ,pennant 7blue74--,is hoisted at the main truck from sundown to #h ,a4 ,m42 also occasionally used as a tell-tale when racing or sailing4 ,owner's ,absent ,flag 7blue rectangular74--,is flown from the main starboard spreader when yacht is at anchor only4 ,it denotes owner is not on board1 but should never be flown when under way4 ,owner's ,meal ,flag 7white rectangular74--,is flown from the main starboard spreader1 and denotes the owner is at meals--boarding a yacht when this flag is flying is considered bad form4 ,crew ,meal ,flag 7red triangular74--,is flown from the foreport spreader on schooners and main-port spreader on single-masted yachts4 ,this denotes that the crew is at meals4 ,the ,ensign4--,displayed on a vessel indicates distress and want of assistance4 ,flag ,b1 of the ,international ,code of ,signals1 is used for a protest flag1 and is conspicuously displayed in the rigging of a yacht protesting during a race4 ,a yacht1 on withdrawing from any race1 should at once lower its racing colours1 and allow yachts still competing the right of way4 ,this code was studied by the boys until both of them thoroughly understood its full meaning1 and ,george became so enthusiastic over it that he exclaimed3 ,fred1 ,i am going to be an admiral of the navy6 ,v ,a ,,talk ,,about ,,engines ,mr4 ,watts was early at the ,gregg residence next day1 and busied himself preparing the engine to start up4 ,a big tub was taken to the boat house filled with water by a hose attached to the suction pipe1 and dropped into the water4 ,this was a mystery to ,george1 who inquired about the use of the water and the other attachments4 ,it was explained to him1 that outside the cylinder there was a hollow space1 called the water jacket1 extending over the top of the cylinder1 and this had to be kept full of cold water by continual circulation4 ,it was pumped in by the engine and forced out by the same means1 a simple contrivance being arranged for the purpose4 ,this circulation of water is necessary to keep the inside of the cylinder cool1 otherwise the walls would soon become red hot1 on account of the rapid explosions of gas and air employed in the cylinder to keep the piston moving to and fro4 ,george seemed to grasp the idea thoroughly4 ,mr4 ,watts also explained the use of the carburetor1 the spark coil1 the battery1 and the method of contact to produce a spark at the proper moment4 ,after some screwing of bolts1 adjusting the piston1 and trying the valves1 the tank in the carburetor was supplied with gasolene and ,mr4 ,watts tried the engine for a few revolutions1 as gently as it could be done4 ,it was a little stiff at first1 some of the connections fitting too tight1 and the piston1 being new and harsh1 did not work smoothly4 ,by the judicious use of good lubricating oil and a few turns of some of the nuts on the bolts1 a little more freedom was given to the machine and the starting was easy and smooth4 ,george and ,jessie were delighted with the rapid movement of the machine1 the buzz of the propeller1 and particularly interested in the movement of the water in the tub4 ,mr4 ,watts allowed the engine to run quite a little while1 and arranged the exhaust so as to beat regularly and to pop6 pop6 as little as possible4 ,he then called ,fred into the boat and taught him how to run the machine1 arrange the contact breaker1 and regulate the feeding of fuel4 ,the engine was stopped to cool and to be examined again by ,mr4 ,watts1 who pronounced it all right4 ,mr4 ,gregg1 who had arrived just before the engine was stopped1 examined all its parts and watched it work for a minute or so4 ,fred arranged his pots and brushes1 and he and ,george went to work varnishing1 so that before sunset the ,caroline looked quite smart and trim4 ,the boys were very careful in applying the varnish to put it on light and thin so as not to let the coats lap over one another as they went along4 ,they finished each streak from end to end1 before starting on the next1 and following this method they obtained a nice1 even surface4 ,the varnish did not look blotchy or patched1 as it would have done had the ends of the varnish lapped4 ,to avoid lapping is one of the most essential operations in varnishing1 when a nice piece of work is desired4 ,illustration3 ,copyright1 #aiaa1 by ,underwood ,underwood1 ,n4 ,y4 ,,finishing ,,the ,,motor ,,launch ,to ,avoid ',lapping' is ,one of the ,most ,essential ,operations in ,varnishing ,it was decided to give the little craft two more coats of shellac varnish before launching her1 and the following spring to give her a good coat of marine varnish4 ,mr4 ,gregg thought that in another week1 say the following ,wednesday1 the ,caroline might be launched with safety1 as the varnish would get dry and hard1 and the inside paint would also be hard enough4 ,jessie and the boys were given permission to invite a few friends each to the boat launching1 and were promised suitable refreshments to be served on the new grounds1 if the weather was favourable4 ,fred asked his father if he could not build up some temporary picnic tables and seats for the occasion1 as there was plenty of material still left unused from the old barn stuff4 ,permission was granted1 and after counting up the number that would probably be present1 it was found that three tables1 each about fifteen feet long1 with necessary seats1 would give ample room for the accommodation of the proposed guests1 with a good allowance for overflow4 ,just then the whistle of a small steam tug1 that often plied on the river1 gave warning of her approach2 and all went down to the river edge to watch her pass and to see what effect her wash would have on the new pier and the boat house skid or slides4 ,she came up stream rapidly against the tide--which was on the ebb--and there was a considerable wash from her wheel1 but it struck the bank1 the pier1 and the skids without doing the least harm or giving any evidence that trouble would result from any reasonable wash4 ,the little steamer's exhaust1 as she passed1 made quite a noise and ,jessie was somewhat puzzled at this1 as the exhaust from the gas engine of the ,caroline only made a plaintive puff in comparison4 ,her father promised to explain the reason after tea4 ,returning to the boat house1 ,george suggested that the name of the boat be painted on both sides of the bow1 in large letters1 but ,mr4 ,gregg and ,fred1 thought it better to have ,caroline placed on the second streaks of sheathing1 in gold1 the letters to be not more than two inches over all4 ,this was agreed upon1 and a young artist1 who was a near neighbour1 was suggested as the person to do the work4 ,illustration3 ,fig4 #cj4 ,hero's steam engine ,after tea1 ,jessie and the boys followed their father into the den1 where ,mr4 ,gregg gave the children a brief history of the steam engine1 as far back as known1 commencing with the ,colipyle1 the invention of ,hero of ,alexandria about #acj ,b4,c4 ,an illustration of this is shown in ,fig4 #cj4 ,it was simply a pot or boiler1 partly filled with water1 the lid or cover being fastened down tightly4 ,on the top of this was attached a hollow bent tube having a tap fitted to it1 which supported and communicated with a hollow metal ball hung on another tube or bearing on the other side in such a manner that the ball could revolve easily4 ,attached to this hollow ball or sphere were four other hollow tubes1 so fastened as to project from the surface two or three inches1 and these were bent at their outer end1 as shown in the illustration4 ,these tubes were of course attached and bent in a direction at right angles to the axis of rotation4 ,the tap leading to the hollow ball1 when turned open1 allowed the steam from the boiler to rush into the ball and fill it up4 ,if it was closed entirely1 the ball would remain still1 but the steam exerting an equal pressure on all points of the inner surface1 and finding the openings1 escaped through with a rush and noise as it condensed in the air1 which it pressed against1 causing the ball to revolve in an opposite direction to the outflow of steam4 ,this ,hero engine or ,colipyle1 was doubtless the beginning of steam motors1 but during the #b1jjj or more years since ,hero's toy engine was invented1 great strides have been made toward bringing the steam engine to its present efficiency4 ,but ,i do not intend1 said ,mr4 ,gregg1 to give a history of the growth and development of the machine1 at this time4 ,there are numerous works on the subject1 obtainable in any fairly-equipped library4 ,illustration3 ,fig4 #ca4 ,steam cylinder and piston ,steam1 as everybody knows1 is generated by heat being applied to a closed metal kettle or boiler containing water4 ,this boiler must be strong and properly arranged so as to admit more water--which is usually injected with a force pump--and it must have an outlet for the release of the steam to the cylinder of the engine4 ,generally1 there is a small dome on the top of the boiler1 called the steam dome1 and to this the steam outflow pipe is attached4 ,the actual use of this dome is to hold a volume of steam that will remain unmixed with water1 as it is placed considerably above water level4 ,on the top of the dome there is an automatic arrangement called a safety valve1 so that when there is too much pressure of steam in the boiler1 it will open and allow the over-pressure to escape1 and thus prevent the boiler from exploding or being over strained4 ,this valve is controlled by a simple device1 somewhat similar to a steelyard4 ,a movable weight is arranged to slide on a long arm which is loosely fixed to the valve flange by a bolt and nut1 and extends some distance past the seat of the valve4 ,the arm or lever has an iron pin attached to it directly over the valve seat1 which holds down the valve and keeps the steam from escaping4 ,the movable weight on the arm is adjusted so as to regulate the pressure on the valve4 ,when there is too great a pressure1 the valve forces up the lever1 and at the same time opens a passage for the extra pressure of steam to escape4 ,there are several other contrivances for relieving the boiler of over stress1 but the one described1 or rather the principle on which it is built1 is most in use on this country4 ,there are many kinds of boilers1 or steam generators1 but the best1 and very likely the strongest1 are those employed on our first-class railway locomotives4 ,these are frequently under a pressure of #bjj or more pounds to the square inch1 which seems an enormous load for a hollow shell to carry1 yet1 so near perfection are they1 we rarely hear of a locomotive boiler explosion4 ,as there are many kinds of boilers1 so also are there many kinds of steam engines1 but all of these latter1 with very few exceptions1 have a cylinder and piston for converting the force of the steam into useful and effective motion4 ,the manner of using this force and keeping it under proper control is somewhat complex and difficult to describe briefly1 without elaborate diagrams1 but ,mr4 ,gregg explained1 in his own way1 how the great force was converted into motion4 ,on the blackboard he drew a rough diagram of a cylinder and valve or steam-chest1 with piston and slide-valve1 about as shown in ,fig4 #ca1 which gives a longitudinal section of the whole arrangement4 ,here we see near each end1 the opening of a double conduit aa1 made in the thickness of the side2 these are the openings by which the steam comes alternately to work on one end1 then on the other1 of the piston4 ,these are called the steam-ports4 ,these two open outward on a well-polished surface1 and between the two a third opening1 ,e1 is seen1 which serves to let the steam escape when it has done its work1 and is called for that reason the exhaust port4 ,c is the pipe by which the steam gains access to the open air or to the condenser1 where it parts with its elastic force4 ,here is shown by what contrivance the distribution is effected1 consisting1 as it does1 of two partial operations2 the admission of the steam and its escape1 which must be repeated twice to obtain a complete phase of the to-and-fro movement of the slide-valve4 ,there are various methods employed according to different engines--but the first described is the one represented by the illustration4 ,in the valve chest1 ,,bb1 is seen a prismatic box1 open on one side1 called the slide-valve1 and this is applied by its open face to the well-polished plane on which1 as mentioned before1 the three ports open4 ,the space ,,bb1 is called the valve or steam chest4 ,the steam coming from the boiler by the pipe ,c spreads out freely in it1 but the inside of the slide-valve1 on the contrary1 is always closed to the entering steam1 though constantly in communication with the escape pipe and also with first one then the other of the entrances to the cylinder4 ,lastly1 the movement of the slide-valve is produced by the engine itself1 aided by a rod and an eccentric fixed to the shaft of the fly-wheel4 ,illustration3 ,fig4 #cb4 ,steam valves--different positions ,by following the successive and alternating motions of the slide-valve1 as represented in ,fig4 #cb1 we can easily comprehend the different phases of the distribution of the steam4 ,this is the machinery for the distribution of steam generally4 ,there are other engines1 such as rotary and oscillating1 that are supplied by other contrivances1 but most of these have fallen1 or are fast falling into disuse1 as they are not so satisfactory as the ordinary slide-valve4 ,it will be seen upon examination of the sketch1 shown in ,fig4 #cb1 how the steam enters and leaves the cylinder and the position of the piston under the various positions of the valves4 ,the arrows show the direction of the slide1 also the direction of the piston and its position when the slide covers the ports ,x1 or leaves them open1 or partly so4 ,the ports for egress or ingress are shown at ,x1 the slide-valve at ,v1 and the cylinder at ,c4 ,when the piston is near one end of the cylinder1 the steam is admitted and forces the piston in the opposite direction1 while the valve is so arranged that when the piston starts in that other direction1 it begins to open the port at the other end of the cylinder through which the exhausted steam escapes4 ,this makes the noise ,jessie asked her father about4 ,there are some engines so devised that the exhaust is made to assist in driving another engine4 ,of course1 there are many kinds of steam engines1 but all are run on the same principle1 or nearly so4 ,as you know1 steam is generated in boilers by fire being applied to the outside and the water made hot enough to raise steam4 ,a steam engine is said to be externally heated1 while gas1 oil1 and other similar engines are internally heated1 because instead of the steam driving the piston1 the gas1 oil1 or other explosive matter is admitted into the clearance or space between the piston and the end of the cylinder1 where it is exploded by an electric spark from a battery provided for the purpose1 and this is called the ignition4 ,the explosion causes the gas and air in the cylinder to expand1 bringing a great pressure on the piston1 forcing it to move toward the other end of the cylinder1 and making the whole machine move4 ,one great advantage of employing a gas engine is that no boiler is required1 a very important matter1 as boilers take up a great deal of space4 ,the coal or wood necessary to keep up steam also takes space that could be used for other purposes1 all of which make the use of steam objectionable when it is possible to employ suitable gas engines4 ,besides1 the make-up of a steam engine is of such a character that it is very expensive1 while the first cost of gas engines is much lower4 ,all gas1 oil1 or other explosive engines are internal heaters1 because the heat is generated in the cylinder at each explosion1 and this is one of the main features that distinguishes the gas from the steam engine4 ,of course1 there are many attachments and connections to steam and gas engines that would take too long to describe1 and in a great measure be unnecessary4 ,a few items may prove both useful and profitable and it is well to know firstly3 ,how to estimate the horse-power of an engine4 ,when steam engines were first introduced they were largely used to take the place of the horses previously employed for raising water from mines4 ,naturally people inquired1 when buying an engine1 what amount of work it would perform as compared with horses4 ,the earliest engine builders found themselves very much at a loss to answer this question so they had to ascertain how much a horse could do4 ,the most powerful draught horses and the best of any then known were the ,london brewers' horses4 ,these1 it was ascertained1 were able to travel at the rate of two and a half miles per hour and work eight hours per day4 ,the duty1 in this case1 was hoisting a load of #aej pounds out of a mine shaft by means of a cable4 ,when a horse moves two and a half miles per hour1 he travels #bbj feet in a minute1 and1 of course1 at the speed named1 the #aej-pound load would be raised vertically that distance4 ,that is equal to #cjj pounds lifted #aaj feet per minute1 or1 #c1jjj pounds lifted #aa feet or #cc1jjj pounds lifted one foot high in one minute4 ,that is the standard of horse-power1 as we all know4 ,it is much more1 however1 than the average horse can do1 and therefore the builders were confident that the engines would take the place of fully as many horses as the horse-power would indicate that they should4 ,of course1 #cc1jjj pounds lifted #a foot per minute is much more convenient for calculation than #aej pounds lifted #bbj feet1 and therefore the former rate has been adopted4 ,the amount of work1 or number of foot-pounds1 is the same in either case4 ,a foot-pound represents the amount of power required to lift one pound one foot high4 ,to find the number of horse-power in any engine1 we multiply the area of the piston by the average pressure per square inch upon it2 multiply this result by the distance which the piston travels per minute in feet and the result is the number of foot-pounds per minute which the engine can raise4 ,divide by #cc1jjj and the result will be the number of horse-power4 ,the number of feet per minute travelled by the piston is twice the number of strokes per minute multiplied by the length of the stroke4 ,this gives the amount of horse-power sufficiently accurate for all practical purposes4 ,it necessarily takes time to do work1 but the amount of work done has nothing whatever to do with the time taken to do it4 ,if a man1 weighing #aej pounds1 walks up the #ijj steps leading to the highest attainable level in the ,washington ,monument1 #ejj feet high1 he does work against gravity equal to #ge1jjj foot-pounds1 irrespective of the time taken in the ascent4 ,then the work done in a given time1 divided by the time1 is called the power of activity4 ,power is the time rate of doing work4 ,in the ,english gravitational system1 the unit of power is the horse-power 7,h4,p472 it is the rate of doing work equal to #cc1jjj foot-pounds a minute1 or #eej foot-pounds a second4 ,in the centimetre-gramme-second 7,c4,g4,s47 system 7in which the unit is #a gramme moving at the rate of #a cm4 a second71 the unit of power is the watt4 ,it equals work done at the rate of one joule 7#aj1jjj1jjj ergs7 a second4 ,one horse-power is equivalent to #gdf watts4 ,a kilowatt 7,k4,w47 is #a1jjj watts4 ,it is therefore nearly #a-a_/c horse-power4 ,to convert kilowatts into horse-power add one-third2 to convert horse-power into kilowatts1 subtract one-fourth4 ,for example1 #fj ,k4,w4 equals #hj ,h4,p4 and #ajj ,h4,p4 equals #ge ,k4,w4 ,the expression foot-pound is in general use among ,english-speaking engineers1 and as explained it is the unit of work done by a force of one pound working through a distance of one foot4 ,it is not a fixed standard of measurement1 since the weight of a pound is not the same in all heights above sea level1 and on this ground it is open to objection4 ,it is the nearest constant1 however1 we have yet discovered1 hence its general adoption4 ,dry steam is the steam in which no condensation is visible1 and it may generally be obtained at a #aj-pound pressure per inch1 but no exact dividing line of pressure can be defined between dry steam and wet4 ,if care is taken in covering pipes and cylinders1 to prevent condensation1 a pressure of #aj pounds should make steam as dry as gas1 and if the steam pipe is carried through a good1 hot fire at some point1 the fire will superheat the steam and render it more dry4 ,wet steam1 of course1 is steam that can be seen1 through having been more or less condensed by contact with air or cold4 ,there can be no steam without heat1 but steam does not require as much heat as is generally supposed4 ,suppose we take one pound of water at #cb degrees ,fahrenheit and apply a fixed and known quantity of heat until it boils2 we will assume that it takes #bj minutes1 and we have supplied the water #ahj heat units1 which1 added to the #cb contained in the water at the start1 makes #bab degrees ,fahrenheit or heat units1 and is the sensible heat of steam at atmospheric pressure4 ,now let us continue the same quantity of heat per minute until all the water has evaporated into steam1 and we will then find that it has taken five and one-third times as long1 or #ajg minutes to do this work4 ,consequently we have used five and one-third times #ahj or #ifj heat units2 or1 to be exact1 #iff heat units4 ,now the temperature of the steam is the same as the water from which it has evaporated1 or #bab degrees ,fahrenheit1 and this #iff heat units is the latent heat of steam at atmospheric pressure4 ,all steam has a sensible heat corresponding with the temperature of the water it has evaporated from4 ,if you boil water under a pressure of five atmospheres1 or #ge pounds pressure1 the sensible heat is #cjf degrees ,fahrenheit1 the boiling point at that pressure1 but the latent heat has decreased by the same number of heat units that the boiling point increased1 so the total is the same in all cases4 ,in the first instance we have #bab degrees minus #cb1 plus #iff1 or #a1adf2 and in the second #cjf degrees minus #cb1 plus #hgb or #a1adf heat units4 ,this may be considered a fair description of latent heat4 ,the most useful quality of steam yet discovered is its power of expansion4 ,it follows what is known as ,marriott's ,law of ,expanding ,gases1 which means one-half the pressure double the volume4 ,so if we let steam into an engine cylinder1 at #hj pounds' pressure1 and cut it off at one-fourth stroke1 it is at #hj pounds up to the point of cut-off4 ,at one-half stroke1 because it has doubled its volume1 it is reduced to one-half pressure1 or #dj pounds2 while at three-fourths stroke the volume has trebled and the pressure has dropped to nearly #bg pounds1 and this is why it is economical to run engines that use steam expansively4 ,steam at #bg pounds' pressure is very much cooler than steam at #hj pounds1 and this difference in temperature has been converted into mechanical work by our steam 7heat7 engine4 ,there are many other peculiarities about steam and steam engines that a young boy should know1 and the information can readily be obtained from books in any good library4 ,the steam turbine1 of which so much has been heard lately1 is not constructed like an ordinary steam engine with cylinder1 slide-valve and other attachments2 but more like the ,hero engine1 with this difference that the steam jet or jets act on a wheel having vanes or blades1 the expansion producing a velocity which rotates the wheel containing the vanes4 ,a modern turbine1 of the ,parsons type1 such as are employed on the great ,atlantic steamers1 is a tremendously high speed engine4 ,it does not derive its power from the static force of steam expanding behind a piston1 as in a reciprocating engine4 ,in this case the expanding steam produces kinetic energy of the steam particles1 which receive a high velocity by virtue of the expansion1 and1 acting upon the vanes of a wheel1 force it around at a high speed of rotation in the same manner as a stream of water rotates a water-wheel4 ,the expansion produces velocity in a jet of steam1 and this is the main difference between the ordinary engine and the modern steam turbine4 ,among gas and internal explosion engines there exist some differences1 both in construction and in the manner of supplying fuel4 ,the gas-producing engine may be considered the better class1 though it has not as yet gained the popularity of the gasolene one4 ,the gas by which this style of engine is operated is produced by a special process1 namely1 by passing air and steam through a fire of hot coals4 ,after generation the gas passes over a flash-boiler and a portion of its great heat is withdrawn1 thus permitting it to enter a scrubber--a cylinder filled with coke and sawdust--while fairly cool4 ,in passing over the flash-boiler the great heat raises all the steam necessary for the production of gas required in the operation of the engine and plant4 ,in passing through the scrubber the gas is not only cooled1 but is freed from particles of suspended matter1 the coke removing the heavier particles1 and the sawdust1 the tar1 or any other volatile matter that may be left4 ,one of the most important requirements in a gas-producer is that it shall be adapted to the work it has to do4 ,its construction should be compact and simple1 so as to permit the easy removal of worn out parts4 ,the feeding device should be such as to secure a uniform distribution of fuel4 ,the blast should be so introduced as to burn out all the carbon in the ash zone1 and yet not produce localized combustion along the walls4 ,the construction should permit the easy removal of ashes1 and render the machine safe1 while the entire process of gasification should be clean4 ,the radiation loss should be low1 and the producer must be made efficient to insure satisfaction4 ,it should be borne in mind that because of the presence of carbon monoxide1 producer gas will always be more or less poisonous4 ,the carbon monoxide has a specific toxic effect on the human system1 and when inhaled enters into direct combination with the blood1 and brings about very dangerous effects4 ,as water is always required for cooling purposes when running a gasolene engine1 it is well to know about how much will be required4 ,one authority says3 ,the quantity of water required at the ordinary temperature of #fj degrees ,f4 inlet and #aej degrees outlet1 to keep the cylinder of gas engines cool is #d4e to #e gallons per indicated horse-power-hour4 ,the jacket pipe should be from #a to #b inches diameter for engines up to #bj horse-power1 while for larger engines the sizes are generally #b to #c inches for the inlet and #b4e to #c4e inches for the outlet4 ,tanks for circulating the water are generally made with a capacity for furnishing #bj to #cj gallons per indicated horse-power4 ,this rule may be taken as about correct1 but1 if anything1 it is rather an over-estimation of quantity necessary4 ,all the foregoing was made as clear as possible to the listeners by ,mr4 ,gregg before the children went to bed4 ,next morning ,fred called up his artist friend1 and got him to come down to gild the name ,caroline on the boat before the next coat of varnish should be applied4 ,the artist made an outline of the name while ,george and ,jessie stood by and watched the process with considerable interest4 ,they saw him measure off each letter1 outline it with a pencil lightly1 and then paint inside the lines with a substance known as gold size1 obtained from any store dealing in painters' supplies4 ,while the size was still sticky the artist applied gold leaf1 which he had brought in a little book along with him4 ,jessie was surprised to see him cut the gold with a thin pallette knife1 having a blunt but smooth edge4 ,she watched him pick up the small pieces of gold with a camel's hair brush1 which he rubbed in his own hair now and again whenever it would not pick up the gold4 ,the metal was applied bit by bit over and beyond the lines of the letters1 and a light puff of breath forced it down to the size4 ,when one side of the boat was finished1 so far as laying on the coat of gold was concerned1 ,jessie was very much disappointed1 as the name seemed merely a smudge4 ,she could not make out the letters1 but the artist told her to wait until to-morrow and he would show her how well they could be seen4 ,next day with a flat camel's hair brush he dusted away the surplus gold1 and the letters showed up in good style1 much to the gratification of ,jessie and ,george4 ,this part of the work being done1 the boys took down their varnish pots1 and gave the little craft another coat1 to make her quite spruce and gay4 ,fred1 and ,nick1 who was still in the employ of ,mr4 ,gregg1 laid off a space on the ground for tables and seats to accommodate the young folks who were coming to the launch on the following ,wednesday4 ,nick found a number of old cedar posts1 and with a saw cut off #ah pieces about two feet long and as many more twice that length4 ,the first were intended to place the seats on2 the second lot were to sustain the tables4 ,the spots for the tables were chosen1 measured off1 and small stakes driven into the ground to show where the posts were to be placed4 ,five posts were intended for each table--two at each end1 two feet apart1 and nine feet apart in the length of the table4 ,the single post was placed in the centre of the table both ways4 ,when the stakes were all in place1 ,nick made holes deep enough to take in the posts so that their tops measured just two feet and two inches above the level of the ground4 ,the tables were to be two feet and six inches high when finished1 as that is the regulation height4 ,it was attained1 in this case1 as follows--,first by the height of the posts from the ground1 two feet two inches2 then by a plank two inches thick laid across the two posts1 making the height two feet four inches1 and the table top1 two inches thick1 laid on these cross planks1 which brought it up to the required height4 ,a piece of plank the same thickness was nailed on the centre post across1 so that it would support the table top4 ,planks that had been used in the loft of the old barn did service for the table tops1 bearing pieces1 and the bench seats4 ,the last were constructed in the same manner as the tables1 the short posts being let into the ground--three under each seat--and fourteen inches above ground so that when the plank seat was nailed on top of them1 the seats were just sixteen inches1 the regulation height of stools1 benches1 and chairs1 though it is sometimes varied to suit conditions4 ,the benches were placed about four inches out from the edge of the table and were found to be just the thing4 ,when ,nick had planted the first post for the tables and got it the right height1 he took that one for his guide and by the aid of a long parallel straight edge which he laid on the guide post and the one he was setting1 and also a spirit-level on the straight edge1 he managed to get all the posts alike in height and this made the tops of the three tables nice and level4 ,it was quite an achievement to have three large tables and six long seats placed in picnic style at so small a cost and with so little effort4 ,in order to have the tables and seats neat and clean1 ,george turned on the garden hose and gave them a good wash off1 and when they were dry again the place was as inviting as a country hotel dining-room4 ,when ,mrs4 ,gregg1 ,jessie1 and ,grace ,scott had the tables set and garnished for the launch1 the lay out was charming1 none the less so because it was a little rustic4 ,another coat of varnish1 the third1 was given the boat the day before she was to be launched1 and ,fred had a strong rope attached to the winch1 with a heavy iron hook fastened to the end of it4 ,a stout iron ring was bolted to the stern of the boat and made secure4 ,mr4 ,gregg had purchased a number of small flags and burgees and had one made with the name ,caroline in large letters wrought on it1 ready to be unfurled when the launch was made1 and ,walter ,scott1 his mother and sister ,grace1 and others had been invited to attend4 ,a number of temporary swings were fixed up by ,nick and ,fred to the trees1 some for the large folks1 others for the smaller ones1 and everything was at last ready for the great event1 which was to take place the next day at two o'clock4 ,,vi ,,propeller ,,and ,,other ,,screws ,wednesday morning was light and sunny and the boys were up and dressed somewhat earlier than usual1 so1 while waiting for breakfast1 they took a stroll down to the river1 where they found their father looking over the grounds and examining tables1 benches1 swings1 and particularly the foot-bridge2 for1 as he told ,fred1 it was very likely all the guests might be on the bridge at one time and the combined weight would be rather trying if it had not been securely put together4 ,he satisfied himself1 however1 that the bridge was strong enough to support three times the weight it would be called upon to sustain4 ,everything else seemed to be sufficiently strong1 to apprehend little danger1 no matter how much the children romped4 ,nick had the grounds nicely raked off2 the decayed branches and shrubs he moved1 and made everything about the place as clean and as neat as possible4 ,flags and other decorations were hung or placed about the grounds1 on the trees and buildings1 but particularly about the tables and the boat house4 ,newspapers were spread over the tables1 linen covers above them1 and the whole surroundings took on a most festive appearance4 ,it was just #aa o'clock when ,the ,mocking-,bird arrived and tied up to the new dock4 ,on board were ,mrs4 ,scott1 ,grace1 and the maid1 who came to help1 besides several of the invited guests whom ,walter had brought down with him4 ,all were welcomed by ,fred1 ,jessie1 and ,george and then the women visitors went to the house to assist ,mrs4 ,gregg4 ,mr4 ,gregg came home from his office earlier than usual and took a half holiday in honour of the occasion4 ,the guests1 in little groups1 arrived on time1 and before the clock struck two ,nick had everything prepared for the launch4 ,he and ,fred and ,george had the ,caroline nicely placed on the skid1 ready to let go the winch1 and a flag pole was fixed up on the bow of the boat4 ,to this the flag with the name on it was lightly tied1 in such a manner that when a string was pulled it would unfurl1 and show the name4 ,the string looping up the flag was left long enough to enable ,mr4 ,gregg1 standing on the dock1 to hold the end in his hand1 and by pulling it to loosen the flag as soon as the boat touched the water4 ,everything being ready1 ,walter ,scott invited as many of the young people to get into the ,mocking-,bird as could crowd on board with comfort1 and each was provided with a whistle or a horn1 as he ran his boat half way across the river4 ,the children on shore were also given horns and whistles1 and all were told to blow as loud as they pleased when the boat touched the water4 ,mr4 ,gregg1 having ,mrs4 ,gregg and ,mrs4 ,scott standing beside him1 gave the word1 ,ready6 ,nick and ,fred answered1 ,aye1 aye1 sir6 and the master of ceremonies called out in a loud voice3 ,let her go6 ,nick freed the winch1 ,fred and ,george gave a little push1 and the ,caroline slid down the skids1 into the water1 without the least hitch4 ,the horns and whistles made a great din1 and when the flag was let free to open up and show the name ,caroline there was another blast of noise by horns and whistles1 mingled with voices of the younger people1 who cried out with all their might1 ,hurrah for the ,caroline6 ,the launch being over1 and everything having gone all right1 the young people were called to lunch4 ,they all sat at the tables which were nicely garnished and well supplied1 and there was plenty of small talk1 and much laughter and jollity4 ,after lunch1 ,fred1 ,walter and ,george boarded the ,caroline1 supplied her with gasolene1 and tried to run her4 ,they found a little difficulty in starting1 but after the engine was warmed up a little1 she went off beautifully1 and answered her tiller in fine style4 ,the boys ran her up and down the river for a while1 then tied her to the dock1 and ,walter and ,fred invited all the girls to ,come and have a sail4 ,the boys were promised one when the two boats returned1 which they did in the course of half an hour4 ,the swings were put in use1 dancing and romping began1 and the afternoon was passed in fun and frolic4 ,in the evening1 ,mr4 ,gregg1 ,jessie1 and the boys took a trip1 and ,mr4 ,gregg was well pleased with the boat's performance1 particularly with the working of the screw4 ,in mentioning this1 he awakened the curiosity of ,george1 who reminded his father that he had not yet explained to them about the screw as a mechanical power4 ,illustration3 ,fig4 #cc4 ,theory of screw ,that evening ,george was told to bring his blackboard and equipment into the den1 and the father at once began explaining the mechanical qualities of the screw4 ,he told of its great usefulness in the industrial arts4 ,as one of the mechanical powers1 it may be considered an inclined plane1 wrapped spirally round a solid cylinder4 ,the advantage gained by it depends on the slowness of its forward or backward progress1 that is1 on the number of turns or threads1 as they are called1 in a given distance4 ,it is always used in combination with a lever of some sort4 ,when employed as a lifting machine it has great power1 and is used to produce compression or to raise or move heavy weights4 ,if a screw is formed on the inside surface of a hollow cylinder1 it is called a nut1 and used to overcome a resistance2 either the screw or the nut may be fixed and the other movable4 ,the acting force is generally applied at the end of a lever or wrench or rim of a wheel4 ,fig4 #cc represents a screw and nut operated by a lever or length of radius r2 p is the pitch of the screw or height of the inclined plane for one revolution of the screw4 ,w is the resistance at the nut and ,p is the force at the end of the lever r4 ,remembering that1 while the resistance ,w is raised the distance p the force ,p revolves around a complete circle and moves a distance #bpinu4 ,let us now apply the condition sum work #j and we have ,p#bpinu - ,wp #j or -- ,p#bpinu_/p 7#f74 ,illustration3 ,fig4 #cd4 ,worm wheel and screw ,the worm gear 7,fig4 #cd7 is a special case of screw and nut1 where the latter is replaced by a toothed wheel called a worm wheel4 ,the teeth work in with the thread of the screw or worm1 and thus1 as the worm revolves1 the worm wheel revolves about its axis4 ,p is the force acting on the worm at a radius r4 r is the pitch radius of the teeth in the worm wheel and r is the radius of the drum on which ,w acts4 ,let ,k1 corresponding to ,w in equation ,w ,p 7#f71 be the force at the pitch circle and worm threads due to the force ,p2 then ,k ,p#b,w_/p 7#g74 ,now apply summ #j to the worm wheel and we have ,kr ,wr or ,k wr 7#h74 ,substituting the value of ,k in 7#g7 in equation 7#h7 we have ,p#bpinu ,wr or ,p#bpinu ,wrp 7#i74 ,now it is evident that the distance p moved by ,w while ,k moves through the distance p is to p as r is to r or p 3p 33 r 3 r or p pr_/r 7#aj74 ,substituting this value of pr_/r in equation 7#i7 we have ,p#bpinu ,wp or the condition sum work #j1 since #bpinu is the distance moved by 7,p7 while ,w moves the distance p4 ,no provision for friction has been made in any of the examples given1 so that allowance must be made for this propensity whenever any of the foregoing rules are applied to practice4 ,the amount of allowance required will vary and must be made to suit conditions4 ,an endless screw is sometimes used as a component part of graduating machines1 counting machines1 etc4 ,it is also employed in conjunction with a wheel and axle to raise heavy weights4 ,the distance between the threads of the screw is called the pitch or step4 ,these threads are sometimes square1 sometimes acutely pointed or edged1 sometimes rounded off on the edges4 ,power is often applied by means of a lever or other contrivance attached to the end of the screw1 or by a long handled wrench 7a monkey wrench for instance71 which1 when turned1 moves forward in the direction of its axis1 overcoming resistance4 ,in the case of the screw-jack1 it may be used to raise a heavy weight4 ,the relation between the force applied and the resistance to be overcome is important to note1 for every time the screw performs one revolution it moves forward through a distance equal to the space between one thread and the next4 ,illustration3 ,fig4 #ce4 ,archimedian screw ,the ,archimedian screw we have read and heard so much about is simply a hollow pipe wound around a cylinder4 ,it was often used in olden times for raising water1 but is now only occasionally applied4 ,the lower end of the spiral pipe is1 of course1 left open and immersed in water1 as shown in the illustration 7,fig4 #ce71 a device for raising water1 the supply stream being the motive power4 ,the oblique shaft of the wheel has extending through it a spiral passage1 the lower end of which is immersed in water2 and the stream1 acting upon the wheel at its lower end1 produces its revolution1 by which the water is conveyed upward continuously through the spiral passage and discharged at the top4 ,an arrangement like this could easily be constructed at the edge of most rivers to raise water to irrigate the grounds1 if so desired1 and the little flutter wheel at the bottom of the inclined shaft would be powerful enough to lift all the water required4 ,fred thought that would be a great scheme1 and determined to try his hand at it one of these days1 but he was told that a wheel of that kind could only work at intervals1 as the river's flow was often running in opposite directions owing to the inflow of the tidal water4 ,illustration3 ,fig4 #cf4 ,spiral conveyor ,these ,archimedian water raisers are often fitted with a crank handle on top1 and a man1 standing on a platform1 turns the crank and thus lifts up all the water the machine will carry4 ,the ,archimedian screw is used for many other purposes than raising water4 ,with wide1 thin wings1 similar to the construction shown at ,fig4 #cf1 and enclosed in a case or jacket1 it is employed by millers to convey grain and other mill requirements1 and it is also good for moving coal1 ore1 gravel1 and like material1 but when used for these coarser purposes the propelling blades are made of steel1 riveted or bolted to a strong iron shaft4 ,the case or jacket containing the revolving blades1 if horizontal1 need not be covered on top1 as the blades will propel the material without jamming or clogging1 if the jacket is smooth inside1 and fits fairly close to the blades4 ,this style of a screw may be used as a sort of turbine water wheel1 if cased in a cylindrical penstock or tube1 and a body of water allowed to fall into the upper end of the tube4 ,the force of the water will give a rotary motion to the blades and shaft1 and1 the latter having a geared wheel or pulley attached to its top1 motion is imparted to other shafts and wheels4 ,illustration3 ,fig4 #cg4 ,theory of screw and gear ,another application of the screw is shown at ,fig4 #cg1 where one is arranged on a shaft or axle to give a rotary motion4 ,this device is called a worm and wheel1 and is frequently used in the make-up of machine engines and mathematical instruments4 ,the illustration shows how the power or force of a screw may be conceived4 ,for instance1 suppose the wheel ,c has a screw on its axis working in the teeth of the wheel ,d1 having #dh teeth4 ,it is plain that for every time the wheel ,c and screw are turned round by the handle or crank ,a1 the wheel ,d will be turned once round4 ,then1 as the circumference of a circle1 described by the crank ,a1 is equal to the circumference of a groove round the wheel ,d1 the velocity of the crank will be #dh times as great as the velocity of any given point in the groove4 ,consequently1 if a line ,c goes round the groove1 and has a weight of #dh pounds hung to it1 a power equal to one pound at the handle will balance and support the weight4 ,to prove this by experiment1 let the circumference on the grooves of the wheels ,c and ,d be equal to one another2 and then if a weight ,h1 of one pound1 is suspended by a line going round the groove of the wheel ,c1 it will balance a weight of #dh pounds hanging by the line ,g2 and a small addition to the weight ,h will cause it to descend1 and to raise the other weight4 ,if a line ,c1 instead of going round the groove of the wheel ,d1 goes round its axle ,i1 the power of the machine will be as much increased as the circumference of the groove exceeds the circumference of the axle1 supposing which to be six times #h1 then one pound at ,h will balance #bhh pounds1 hung to the line on the axle2 thus showing the advantage of this machine as being #bhh to #a4 ,a man who can lift by his natural strength alone1 #ajj pounds1 by making use of this combination1 will be able to raise #bh1hjj pounds alone1 and if a system of pulleys were applied to the cord ,h1 the power would be further increased to an amazing degree4 ,when a screw and wheel are attached1 as shown1 the screw is sometimes called a worm and sometimes an endless screw4 ,the propeller wheel 7,fig4 #ch7 is a screw having a large helical dimension4 ,the example shown has four blades1 each of which1 when rotated1 may be said to make one quarter of a revolution and when at work in the water has the same effect as the working of a nut1 producing motion in direction of the axis and so propelling the boat or vessel4 ,the action of the wheel pressing backward against the water tends to push the craft forward4 ,illustration3 ,fig4 #ch4 ,complete screw propeller ,this figure shows a propeller with four blades1 but two and three bladed ones1 particularly for small craft1 are mostly used4 ,the ,caroline carries a two bladed screw and her performances will be entirely satisfactory4 ,the blades1 of course1 are exactly in line with each other on the shaft1 and equally balanced1 or of equal weight4 ,a three-bladed propeller should have its extreme points in a horizontal plane1 so that they will form an equilateral triangle4 ,the principal features of a propeller may be described as3 diameter1 pitch1 area1 speed of revolution1 and slip4 ,the diameter is that of the circle described by the tips of the blades4 ,the pitch1 considering the propeller to be a portion of a screw1 is the amount which it advances in one turn1 supposing it to travel in a solid medium4 ,the blade area is the actual area of all the blades4 ,the speed of the revolution is customarily reckoned in turns per minute4 ,the slip is the difference between the amount which the propeller actually advances per turn and the amount which it would advance if turning in a solid medium4 ,for example1 if the pitch of a screw is #cj in4 it would advance #cj in4 at each turn if there were no slip4 ,suppose that it only advances #bj in4 per turn1 then the slip is #aj in4 per turn1 or as usually figured1 #cc-a_/c per cent4 ,as a further example1 suppose a propeller of #cj in4 pitch1 turning #cjj turns per minute1 drives a boat at the rate of #f miles per hour4 ,the advance of the propeller in feet per minute is #cj_/ab #cjj #gej while the advance of the boat is #f #e1bhj_/fj #ebh ft4 per minute4 ,the slip is then #gej - #ebh #bbb1 or as a percentage1 #bbb_/gej #bi4f per cent4 ,it might seem at first sight1 that a perfect screw propeller should have no slip2 but this is a practical and theoretical impossibility4 ,the most important dimension1 from the standpoint of the absorption of power1 is the blade area4 ,a certain blade area may be obtained by a relatively wide blade on a small diameter1 or by a narrow blade on a relatively large diameter4 ,in the former case the area of the blades bears a greater proportion to the area of the circle through the tips than in the latter case4 ,there are certain limits for this proportion of blade to disc area for well-designed wheels1 beyond which it is not well to go4 ,these are as follows3 ,for two blades 4#bj to 4#be4 ,for three blades 4#cj to 4#dj4 ,for four blades 4#ce to 4#de4 ,this means that for a #bd in4 diameter propeller1 whose disc area is #deb sq4 in4 the blade area should not1 for ordinary use1 be made greater than these proportions1 as the blades then become so wide as to interfere one with another4 ,of course where a propeller1 for shallow draft1 must be unusually small in diameter1 the proportion of blade area can be increased1 but with some loss in economy4 ,strictly speaking1 for a well balanced propeller1 the blade area fixes the amount of power which the propeller can deliver1 while the pitch1 combined with the turns per minute1 governs the speed4 ,as a matter of fact1 for the average propeller the two are closely related1 each having a certain influence upon the other4 ,to illustrate1 a propeller may have a small blade area and so great a pitch that the blades act somewhat like fans and simply churn the water1 offering great resistance and absorbing the power of the engine1 but doing little effective work toward driving the boat4 ,to get the measurements for a wheel required to perform a given service1 say a three-bladed propeller for a small boat or tug of #bj nominal or #ge indicated horse-power3-- assume that the size determined on is #d ft4 #f in4 in diameter and #g ft4 #f in4 pitch1 the diameter of loss may be assumed to be #h in4 swelled to be #aa in4 in the middle1 and #aa in4 long4 ,the tug would be1 say1 #fj ft4 long1 #ab ft4 beam1 and #g ft4 deep4 ,first delineate the path of the point and root of one blade through half a revolution as in ,fig4 #ci4 ,this should be drawn to a scale of not less than #a-a_/b in4 to #a ft4 by the ordinary method of projecting a screw thread4 ,the semicircle shows the half plan with twelve equal divisions1 and the half elevation is divided into the same number of equal parts4 ,the helix or thread is then obtained by drawing the curves through the intersections of similar divisions4 ,then a b will be the helix for point of the blade1 and c d the helix for the root of the blade4 ,these will be found to be practically straight lines which might have been obtained in a simpler manner if intended for a working drawing only2 but it is useful to have demonstrated the proper nature of the full curve4 ,illustration3 ,fig4 #ci4 ,diagram screw lines ,the practical way of setting off the blade follows3 ,first for dimensions3 as #bj-;in4 7pitch7 is to #aa in4 7length of boss and therefore virtual length of propeller71 so is #afi4f in4 7circumference due to outer diameter7 to the length of circumference occupied by the blade1 #afi4f #aa_/i #bj4gc1 say #bj-c_/d in4 ,in ,fig4 #dj describe a circle equal to the diameter of the propeller1 and on each side of the centre line step off #bj-c_/d in4 to half the scale1 making the whole length of arc to scale #bj-c_/d in4 ,draw vertical lines from the ends of the arc1 and from the arc on the centre line set up a height of #aa in4 and draw horizontal lines4 ,join a b1 and this will be the angle of the end of the blade4 ,on the elevation of the propeller circle describe a small circle equal in diameter to the faces of the boss2 draw radial lines from the ends of the arc first found1 and from the intersection with the boss circle draw vertical lines to cut the horizontal lines of the plan of boss4 ,join c d1 and this will be the angle of the blade at the root4 ,illustration3 ,fig4 #dj4 ,part of screw blade ,now describe an arc at every three inches from the circumference within the radical lines2 or for large propellers every #f in4 ,draw vertical lines from the intersections of the arcs with the radical lines to meet a c and b d1 as shown1 and joining the points thus found1 the diagonal lines will represent the plan or angle of the blade to each #c in4 difference of radius--in other words1 its real width at the different points1 supposing it to be a plain geometrical portion of a screw thread4 ,as a matter of fact1 the blades are always more complex than this1 the edge being curved to enter the water more easily1 to avoid vibration1 and also to lessen the risk of fracture in the event of striking any object in the water4 ,sometimes the blades are curved in the opposite direction1 as if the points were being left behind while the blade is advancing4 ,illustration3 ,fig4 #da4 ,plan of screw blade ,the next step is to draw a flattened elevation or development of one of the blades1 in order to give the actual curves of its outline1 and afterward its thickness at various points4 ,draw a horizontal line from c and f 7,fig4 #da71 and through this a centre line4 ,this will give the length of the blade from the boss1 and the centre line of the propeller shaft may be added below4 ,then take the lengths a b and c d from ,fig4 #dj1 and set them off on ,fig4 #dc1 as shown1 joining all four points4 ,this figure would be the true outline of the blade if there were no curves4 ,the actual outline is found by drawing the curves according to the dimensions4 ,illustration3 ,fig4 #db4 ,propeller lines complete ,lay out the propeller1 as shown in ,fig4 #db1 which will give the elevation of the blades1 all being alike4 ,to find the area of a propeller blade1 mark it off in parallel lines1 say #c in4 apart1 and note the width at the centre of each portion4 ,add the widths together1 and divide by the number of widths4 ,this will give the mean width1 which must then be multiplied by the length of blade to obtain the area4 ,if the measurements are all in inches1 the result should be divided by #add to give the area in square feet1 and then be multiplied by the number of blades to give the total area4 ,illustration3 ,fig4 #dc4 ,angle of propeller blade ,to measure the pitch of a propeller1 lay it down on a level surface1 hold a straight edge level across centre of blade with a square up from the lower edge1 as in ,fig4 #dc4 ,measure the distance ,b and ,h and the radius ,r from the centre to the part where the measurement is taken2 then ,b 3 #bw,r 33 ,h to pitch1 ,p or ,p #bw,r,h_/,b4 ,the measurements may be made in more than one place and the average taken1 as the blades are sometimes twisted slightly4 ,scaling only from the drawing1 ,p #bw,r,h_/,b #b #c4adaf #a4f #a_/a4bg #g4gd1 say #g ft4 #i in4 pitch1 whereas the intended pitch was #g ft4 #f in4 ,a good illustration of the use of the screw may be seen in the carpenter's auger1 used for making or boring holes in wood4 ,these tools are provided with a small tapered screw on their points1 and this is followed by cutting edges and a larger spiral4 ,the larger spiral is for the purpose of drawing up the chips or shavings4 ,another tool is made having two blades attached to the bottom of an iron bar formed like the blades of a propeller1 which is sometimes employed for boring or digging post holes in clayey or soft soil4 ,the machine is turned by a cross handle on top1 and is frequently drawn up to bring out the soil until the hole is deep enough4 ,the ordinary wood screw is one of the most useful of contrivances for fastening wood together1 and for attaching to surfaces1 hardware1 ornaments1 or other materials4 ,the adhesive strength of nails is already shown1 and the adhesive strength of wood screws1 according to ,bevan1 is set down as follows3 ,,wood ,,screws ,the following are the thicknesses or diameters corresponding to the list numbers4 ,other thicknesses can be interpolated1 each size varying in succession #a_/fd in4-- ,no4 #jj #j #a #e #aj #ad #ah #bb #bg #cb #dj ---------------------------------------- ---------------- ,thicknesses in parts of inches #a_/cbc_/fda_/af #a_/hc_/af #a_/de_/af #c_/hg_/af #a_/b #e_/h ---------------------------------------- ---------------- ,an ordinary #b-;in4 wood screw1 driven through a #a_/b-;in4 board into hard wood1 was found to be #gij lbs41 and a force of about #cie lbs4 was required to extract it from soft wood4 ,when screws are hard to drive or screw in place1 a long screw-driver should be used1 as screw-drivers with long handles seem to have a much greater leverage than short handled ones in driving screws home4 ,screws1 however1 are often split at the head1 if care is not taken when using a long driver4 ,if a screw is rusted1 hard to move or withdraw1 it can be loosened by applying a hot iron to the head and making it hot4 ,the heat expands the screw and1 of course1 makes the hole larger1 and when the screw cools it contracts a trifle so that it may be withdrawn quite easily4 ,,vii ,,aeroplanes ,george and ,fred were so much interested in the ,caroline that they neglected to do some work ,mr4 ,gregg had suggested1 but a hint or two from him reminded them that sailing the new boat every day would get so monotonous it would cease to be a pleasure4 ,fred1 therefore1 set to work to put the new property in apple-pie order1 by cleaning up the grounds1 burning the rubbish1 and tidying the place generally4 ,nick1 not being needed longer1 was allowed to go1 with the promise that whenever a man was required about the place1 he would be chosen4 ,his departure left all the work to ,fred and ,george1 both of whom gladly accepted the duty4 ,the first thing was to set up three or four long benches on the river bank4 ,these were built exactly in the same manner as the seats alongside the tables4 ,three short posts were let into the ground for each seat1 and a good1 sound plank spiked solid to their tops4 ,one of the seats was made four or five inches lower than those at the tables1 so as to accommodate the smaller children4 ,the two boys did the work well1 though they found it a little hard to dig the holes in the ground and saw off the posts4 ,george's hands became a little blistered and sore1 but his mother soon cured them1 though she warned him against working too hard or too long at a kind of labour to which he was not accustomed4 ,after tea was over1 it being a fine1 warm1 spring evening1 the whole family went down to the river's edge to sit on the new seats and enjoy the view4 ,noticing the current of the river1 ,jessie questioned her father about its going one way sometimes1 and then turning in the other direction4 ,her father explained that it was the movement of the tide that made the water flow against the stream at times1 and that when there was no tide1 the current took its natural course4 ,this explanation did not seem to satisfy ,jessie1 and she asked why there were any tides4 ,so ,mr4 ,gregg promised to explain all that was known about tides to her in the near future4 ,i wish you would1 said ,george1 and tell us about kites1 balloons1 and flying machines4 ,oh1 yes1 said the father1 ,i'll try to do that to-morrow night4 ,i'm glad1 father1 said ,fred1 as ,i want to try and make a model for ,george before the ,fourth if ,i can1 so he can have one to fly across the river that day1 instead of fooling with fire-crackers and other dangerous fireworks4 ,that's a good idea1 ,fred1 said the father4 ,a model aeroplane1 decorated with silk flags would give a great deal more real pleasure than firing off all the fire crackers in the state4 ,it would be quite easy1 now you have a boat1 for one of you to be on this side of the river1 the other on the opposite side1 and to keep a number of little machines going to and fro across the water4 ,george seemed delighted at the prospect4 ,walter ,scott had also been stricken with the aeroplane fever1 and was busy making models1 though1 as yet1 he had not finished any4 ,both ,fred and ,george were anxious to hear all their father had to say concerning these machines1 as they knew he would be thorough1 and make it all plain4 ,mr4 ,gregg told the boys that to explain fully the theory and practice of building an aeroplane of any kind would take some time1 but he would willingly give it for their benefit1 and would discuss the subject of aeronautics at length so as to give them some pointers about the design and practical making of flying machines4 ,illustration3 ,copyright1 #aiaa1 by ,underwood ,underwood1 ,n4 ,y4 ,,the ,,monoplane ,,model ,,complete ,a ,model ,aeroplane1 ,decorated with ,silk ,flags ,would ,give a ,great ,deal ,more ,pleasure ,than ,firing off ,all the ,fire ,crackers in the ,state ,on the following evening1 ,jessie did not forget to remind her father of his promise to tell them all about air-ships and things1 as she put it4 ,all right1 my dear1 said ,mr4 ,gregg1 ,i'll take you all into the 'lion's den' shortly after tea4 ,but tell me1 why is it you are so anxious to know all about 'air-ships and things'8 ,oh6 that's all right1 papa2 ,fred is going to build a great big ship1 as soon as he knows how1 and he has promised to take me up to the clouds in it for a ride4 ,well1 my dear1 it will take some time to tell you all about these things but ,i will make an attempt4 ,for ages man has wanted to fly1 and the ,greeks tell us of a mythical personage named ,icarius1 and another named ,ddalus1 who flew to the sun4 ,there have been many attempts to fly1 both with and without mechanical aid1 but history gives us nothing definite on the subject until about the year #aghe1 when two ,frenchmen1 named ,montgolfiers1 built a balloon sixty feet high and forty-three feet in diameter1 and filled it with heated air4 ,attached to the bottom was a light cage made of wicker-work1 into which were placed a lamb1 a duck1 and a rooster4 ,the balloon was cut from its moorings and rose to a height of over #a1djj feet so that these animals were the first that ever went up in a machine made by hands4 ,the ,montgolfiers attained considerable notoriety1 and out of their experiments grew the present dirigible ,zeppelin1 which measures #ddf feet in length1 over #db feet in diameter1 and is capable of carrying eight able-bodied men a distance of over #ijj miles4 ,this great machine is charged with gas1 and driven by four three-bladed propellers1 which are run by two gas engines of #aaj horse-power4 ,this is simply a monster balloon1 suspended in the air by #ebi to #gjj cubic feet of hydrogen1 or coal gas1 which is much lighter than ordinary air4 ,it may be said there are four distinct kinds of flying machines1 each unlike the other in construction and in principle4 ,the first is the old-fashioned balloon which has an envelope or covering of some air-tight fabric1 and is inflated with a light gas4 ,to it is attached a framework of some kind called a ,nacelle1 that carries the aviator1 the steering gear1 and the necessary engines to operate the propeller or propellers4 ,the second kind of flier is the aeroplane1 which1 as its name indicates1 is supplied with 'air planes1' that give it the power of rising and falling at the will of the operator when the machine is in motion4 ,these planes play a very important part in the successful operation of the machine1 as ,i will explain later4 ,the first type of machine is classed as a 'lighter-than-air' machine or a balloon1 while the planes of all kinds are classed as 'heavier-than-air' machines4 ,among other types of 'fliers1' there is the helicoptere1 which is raised by screws or propellers on vertical shafts4 ,these revolve rapidly1 and drive the machine upward1 just as the propeller on the ,caroline drives her forward when in rapid motion4 ,another type1 nearly abandoned1 is called the ornithoptere1 or 'wing flyer4' ,these machines are built to operate like the wings of a bird1 and are provided with the necessary contrivances to work the wings1 both vertically and horizontally4 ,this type1 like the helicoptere1 is not considered practicable1 and is virtually abandoned1 so that the field is now left altogether to the 'lighter-than-air1' and the aeroplane machines4 ,i do not intend giving you any instruction regarding balloons1 or dirigibles1 as ,i think such is unnecessary1 but will confine myself altogether to the discussion of aeroplanes4 ,illustration3 ,fig4 #dd4 ,aero-curves ,it must not be supposed because of the name aeroplane1 that the so-called plane is a real plane2 it is not4 ,the front edge of an air-ship plane must always be curved1 as shown in ,fig4 #dd1 so that the air strikes the under surface and is forced under the plane1 to buoy up the machine as it moves forward2 or1 to put it another way1 there must be a current of air either natural or artificial on which the machine must float1 or it will be drawn by gravitation to the earth4 ,while we cannot see air or wind1 we know from experience that it has great power1 and for thousands of years ships have been propelled across the seas by this force1 acting on sails of some kind4 ,we know how difficult it is to travel against a high wind1 and it is this quality in the air that makes it possible to travel through it4 ,the resistance of the atmosphere makes it possible for the aviator to hold his machine suspended in opposition to the laws of gravity1 and to drive it forward and upward by means of the revolving propeller acting against this resistance1 the motor acting on the same principle and manner as the wheel or propeller of a boat when it is urged forward4 ,if1 as ,i have seen ,george do1 we take a flat stone1 a piece of slate1 or flat metal1 and throw it along the face of the river1 in such a manner that its flat surface strikes the surface of the water1 it will skim along1 striking the water at intervals in its course1 until the force given by the hand that threw it is exhausted1 when it will drop and sink4 ,the water1 though lighter in equal bulk than the stone1 is aided by the force given by the hand to buoy up the stone until the force is expended4 ,the curve on the front edge of the planes1 when the machine is in motion1 really takes in more air than the space allowed for it under normal conditions1 and it may be said to be compressed to some extent4 ,if the wind be blowing in the 'teeth' of the machine1 the resistance of the air will be greater1 and the buoyancy of the machine increased4 ,so1 also1 if the machine is travelling rapidly1 the motion will increase the resistance and the buoyancy at the same time4 ,the moment the propellers stop1 gravitation grasps the machine1 and if the planes are kept evenly balanced it will quietly and gently descend to the earth4 ,you must particularly bear in mind that wind blowing in the face of a machine tends to hold it up1 and that a machine flying rapidly makes its own wind1 so that the results are the same4 ,the curve on the front of the planes may be called an 'aero-curve1' and much of the success of the machine depends on this curvature of the planes1 which gives to the inside of the plane a concave shape of a peculiar character1 and to the outside a convex form4 ,illustration3 ,fig4 #dd;a4 ,maxim's aero-curve ,if you examine the rough drawing ,i made for you on the blackboard 7,fig4 #dd7 you will notice that the upper or convex curve is different from the under or concave one1 and it is upon this difference in curvatures that many of the flying qualities of the machine depend4 ,this little section showing the different curves is the one used by many of the successful aviators1 though some prefer the form invented by ,sir ,hiram ,maxim1 shown in ,fig4 #dd;a1 which does not differ very materially from the previous section shown4 ,in all cases1 however1 the accepted plane is one of a curved vertical section in which the convex side is uppermost and the upper surface more curved than the lower4 ,although different authorities disagree as to why this shape of plane is best1 all agree that it is so4 ,sir ,hiram ,maxim's theory is that the air follows both the upper and lower surfaces of the plane1 as shown in ,fig4 #dd;a1 while ,phillips holds that the air follows the lower surface of the plane1 and1 striking the hump1 shown at ,a1 ,fig4 #dd1 is reflected off the upper surface of the plane1 thus forming a partial vacuum on the upper surface1 which gives an additional upward pull to the plane4 ,there is1 however1 little doubt that most of the work is done by the force exerted on the lower surface of the plane4 ,another consideration that enters into the design of the plane is the aspect ratio1 or the ratio between the depth of the plane fore and aft1 and the width or span4 ,authorities do not agree about this latter consideration4 ,a practical aspect ratio1 one states1 is #f to #a1 as1 for instance1 a plane #ci feet spread by #f feet #f inches in depth4 ,in ,santos ,dumont's ,demoiselle the aspect ratio is only #c to #a4 ,the ideal plane1 however1 would be a plane of great length and little depth1 but this is impossible in the practical machine1 as a plane of excessive length would greatly weaken the construction of the machine4 ,again1 the different authorities do not agree as to the shape of the ends of the planes4 ,lanchester says that an efficient plane must be of rectangular form1 and the ,voisin and ,curtiss planes are rectangular1 whereas the wings of the ,blriot and the ,wright planes are decidedly curved at the tips4 ,i will show in other illustrations the method of placing the planes on such machines1 as made by ,curtiss and some other noted aviators4 ,i think ,i have said sufficient to give you a fair idea of the reason why an aeroplane can be made to navigate the air1 but ,i have not told you how its direction can be controlled4 ,no doubt1 if the air were always still and not subject to change1 there would be but little difficulty in controlling the direction of the machine1 but1 unfortunately1 this is not the case1 so provision has to be made to meet various changes as they occur4 ,a downward current of air causes the plane to change its inclination to the horizontal1 so that it will not support the weight1 and the machine falls to the ground4 ,to overcome this unsatisfactory state of things1 small auxiliary planes are used to counteract the effect of varying air currents4 ,they control the movements of the main planes so that they always bear the same inclination to the horizontal1 and they are also used to elevate the machines so as to clear small obstacles4 ,if any great increase in altitude is desired1 the speed of the engine must be increased and the planes driven more rapidly through the air1 thus giving them more lifting power4 ,it may be that in a short time1 additional balancing planes will not be necessary1 as some other scheme may be invented that will regulate the balance of the aeroplane4 ,already an ,australian inventor1 called ,roberts1 has applied the gyroscope to the aeroplane in order to solve the problem of making it balance automatically4 ,it exerts a balancing force equal to #cjj pounds1 placed #ah inches on either side of the centre of gravity4 ,the gyroscope is driven by electricity1 and controlled by a pendulum which swings right or left1 according to the tilt of the aeroplane4 ,mr4 ,roberts is also working on a small aeroplane which is to be controlled by wireless telegraphy4 ,his inventions are being tested by the ,british ,war ,office4 ,there are many other inventors on three continents busily employed in trying to solve the balance problem4 ,a very important matter in the construction of the aeroplane is the position of the screw propeller4 ,sir ,hiram ,maxim advocates placing it at the rear of the planes1 and this construction is carried out in the ,wright1 ,curtiss1 ,voisin and ,baldwin-,mc,curdy machines1 while the tractor screw is used on the ,blriot1 ,antoinette1 and ,roe fliers4 ,sir ,hiram's theory is that if the screw is placed in front1 the backwash strikes the machine1 which offers a good deal of resistance to the passage of the air1 and retards action2 but if the propeller is placed in the rear1 the resistance of the machine imparts a forward motion to the air with which it comes in contact1 and the screw1 running in air that is moving forward1 has less slip1 and is1 therefore1 more efficient than the tractor screw4 ,while the construction of the aeroplane is yet in an experimental stage1 it is progressing quite rapidly1 and though no definite rules covering the whole ground of construction and management can yet be laid down1 the following points may be well considered before any steps are taken in making or using any make of aeroplane3 7#a7 ,that it is useless to construct the planes of flat vertical section1 as much lift is lost in doing so1 and they are best constructed after the manner shown in ,figs4 #dd and #dd;a4 7#b7 ,that the most practical aspect ratio is about #f to #a4 7#c7 ,that the angle of incidence of the inclined planes ought to be somewhere between #a in #aj1 and #a in #bj 7i4 e41 the angle by which they are inclined to the horizontal1 the forward or entering edge of the plane of course being the higher74 7#d7 ,that a reliable motor1 one that is immune from involuntary stoppages1 is absolutely essential to prevent accidents4 7#e7 ,that automatic stability of the machine is the theory of aeronautics that all inventors should study most carefully4 ,illustration3 ,fig4 #de4 ,blriot monoplane ,the illustration ,i show here 7,fig4 #de7 represents the monoplane in which the ,frenchman1 ,blriot1 crossed over the sea from ,france to ,england4 ,the thick curved lines1 shown at ,a1 exhibit the main plane which gives the machine its name of monoplane--one plane--and ,b shows the rear auxiliary plane1 which is also of curved section and curved ends4 ,the plane ,a has an area of #aej square feet1 and ,b has an area of #ag square feet1 while the rudder ,c has an area of #d-a_/b square feet4 ,the total length of the machine is #be feet1 the sweep of the rudder #f feet #f inches4 ,the rudder is a plane1 pure and simple1 and may be constructed of any light material that is strong enough to stand a reasonable wind pressure4 ,the planes must be covered on both sides with some light fabric1 silk preferred1 and all the framework made as light as possible1 consistent with safety4 ,illustration3 ,fig4 #df4 ,plan of ,blriot machine ,the plan ,i show at ,fig4 #df will give you a good idea of the form of this machine1 if you were looking from above at it4 ,e is the point where the aviator sits1 and where the #cj horse-power engine is placed4 ,the ends of the planes are rounded off1 and the ends of the rear plane at ,,dd1 are made adjustable so that the machine may be made easier to manage when in motion4 ,all engines used in aeroplanes are of the internal combustion type1 made purposely for aerial flight1 and are as strong and as light as it is possible to make them4 ,illustration3 ,fig4 #dg4 ,biplane ,illustration3 ,fig4 #dh4 ,voisin biplane ,the biplane1 or two plane machine1 is fitted up on somewhat the same lines as the monoplane1 having two planes one above the other1 as ,i show you in ,fig4 #dg4 ,the dark portion ,a ,a1 shows the positions and curvature of the planes4 ,the plane ,b is called the elevator because it keeps up the head of the machine4 ,c shows the tail with a single plane4 ,d is the part containing the mechanism and the aviator's seat4 ,e shows the vertical planes1 made of some light fabric stretched over a bamboo frame4 ,the propeller is shown at ,f1 and it is about six feet in diameter4 ,the two carrying wheels1 shown at ,g ,g1 are simply light bicycle wheels which tend to ease the landing of the machine when it comes to the earth4 ,it will be seen that machines may differ in the style of construction and yet1 so long as they contain the principles ,i have described1 they will fly with more or less success4 ,the illustration1 7,fig4 #dh71 shows the plan of the biplane1 which is somewhat different in arrangement from the monoplane4 ,this sketch is of the ,voisin biplane and shows the tail-piece1 something not used in machines of the ,wright type4 ,the ,voisin machine is quite popular in ,europe1 particularly in ,france4 ,it is not very difficult to construct or easy to control2 at least1 it has that reputation4 ,illustration3 ,fig4 #di4 ,the ,santos-,dumont monoplane ,the ,santos ,dumont monoplane1 ,demoiselle1 shown in ,fig4 #di1 is said to be the smallest and lightest known practical machine1 and there are no patents on it1 the inventor having published sketches and drawings of all its details4 ,contrary to the usual plan1 the aviator1 in this machine1 sits below the motor1 so that the propeller blades cut across the line of sight2 but as it revolves very rapidly the vision is not affected4 ,the whole machine1 when complete1 weighs only about #bej pounds4 ,its length is about #bj feet and its total width over the planes #ah feet1 and it is about #g feet #f inches high4 ,it is quite easy to build1 as the framework1 or chassis1 is fixed to a bent piece of ash or elm--like a sleigh runner--which answers very well1 because when the machine begins to move the rear end rises first4 ,if desired1 the frame can be made so that the whole thing can be taken apart4 ,sockets1 like those used on finishing rods1 may be attached at the joints and junctions to hold the structure together4 ,the two spars that constitute the main support of the planes are formed of ash1 this having been found the best material for the purpose1 as it is also for the making of the propeller blades4 ,one of the spars should be fixed about nine inches from the front edge1 and the other about twelve inches from the back4 ,bamboo cross pieces are fastened about nine or ten inches apart between the two main spars4 ,all is covered with oiled silk1 applied in two thicknesses4 ,the area of the main plane is some #aae square feet1 and that of the tail-piece about #ej square feet4 ,to cover all this would require about #djj square feet of silk4 ,i have heard it said that aeroplanes are hard to manage1 difficult to drive1 and extremely dangerous4 ,this is not true entirely1 but there is some truth in it4 ,an amateur has to go through a 'course of sprouts' and must learn all about his machine before beginning to use it practically4 ,once he becomes master of it and can keep it well under control1 he need not fear accidents1 if he does not lose his head1 nor venture out in half a gale4 ,when we consider the number of experiments that have been made from time to time with imperfect machines1 we find that fatal accidents have been very few1 less1 indeed1 than the number recorded in the early stages of automobile history4 ,i have been compelled to draw a number of the points ,i have given you from many sources1 particularly from the writings of ,messrs4 ,fetherstonhaugh and ,lanchester1 which does not detract from what ,i have told you1 but rather guarantees its correctness4 ,well1 children--it is getting late1 but1 before bidding you good-night1 ,i think ,i should finish my talk on aeroplanes by showing you how to make a small model of a flying machine1 if you are not too tired to listen further8 ,illustration3 ,fig4 #ej4 ,a model aeroplane ,please1 father1 said ,fred1 do keep on4 ,george1 also1 wanted to hear more1 so ,mr4 ,gregg decided to continue4 ,illustration3 ,fig4 #ea4 ,section model aeroplane ,i have given you an outline of the reason why an aeroplane can be made to rise from the ground and navigate the air2 but ,i have not told you of all the kinds of machines that can be made to fly1 for there are many others than those ,i have spoken of4 ,one is the glider1 which does not carry an engine1 but1 as its name indicates1 glides along in the air at a distance not far from the earth4 ,these are not capable of travelling very far and1 therefore1 are not likely to come into general use4 ,they have to be started either by gliding off a high tower1 by sliding down a hill or by being propelled by hand or towed by some rapidly moving machine4 ,some day1 perhaps1 a machine will be evolved on the same or similar lines as the glider1 that can be propelled by natural forces1 but the time is not yet4 ,beside the monoplane and the biplane1 there is the triplane1 constructed on the same lines as the other flying planes1 that is to say1 the three planes used on the machine are made the same as the planes on the others1 each having a convex and concave side of different curvatures4 ,illustration3 ,fig4 #eb4 ,blade of propeller ,the monoplane which ,i am about to describe and illustrate1 and which ,i show in ,figs4 #ej-ea-eb1 can be easily and cheaply made1 and can be guaranteed to fly1 after a little experimenting to get the correct balance and angle of the planes4 ,the frame ,a will first be treated4 ,get two pieces of yellow or white pine 7the lightest and most easily procured wood71 cut them to the shape shown1 #a foot #f inches long1 #a_/b inch by #a-c_/af inches in the middle1 and thickened at the ends to take the screws from the end bars ,b and ,c 7,fig4 #ej74 ,take great care to make them exactly alike4 ,the end pieces ,b and ,c1 which are #b-a_/b inches by #g_/af inch by #a_/d inch can then be screwed to the side pieces ,a1 and a rectangular frame is the result4 ,should the screws split the wood in the slightest degree1 new pieces must be made1 as the plane is sure to get rough usage in falling on the ground a few times4 ,illustration3 ,photograph by ,brown ,brothers ,,making ,,an ,,aeroplane ,,model ,if the ,screws ,split the ,wood in the ,slightest ,degree1 ,new ,pieces ,must be ,made ,the planes are also made of yellow pine4 ,they must be exactly equal to one another in weight1 one being right handed and the other left4 ,the wood must not be more than #a_/bb inch thick1 and1 if possible1 even thinner4 ,a large circular chip box will be the best thing from which to make these4 ,gum a piece of tracing cloth on top of the planes1 and allow about #b inches to overlap at the large ends1 to twist and glue round the main frame when fixing4 ,the cloth will fulfil two useful and necessary purposes4 ,it will strengthen the planes and curve them to a very large extent4 ,this curvature is essential to the flight of the machine4 ,a wooden block curved to suit1 and inclined at about #e degrees1 is fixed between the back planes and the frame4 ,the front or small plane is #h inches by #c inches1 and made in the same way as the others4 ,it must be adjustable1 and is1 therefore1 mounted on two wooden blocks1 #b inches by #a_/d inch by #a_/b inch and fastened by means of copper wire which acts as a hinge4 ,four silk cords are fixed to the movable end of the plane1 two being fastened to nails at the rear end of the frame and two to the front1 to hold the plane at any desired angle4 ,illustration3 ,fig4 #ec4 ,connections of propeller blade ,the propeller blades 7,fig4 #eb7 are made of thin aluminum4 ,two sheets are cut out the same size and shape1 and placed with their ends overlapping 7see ,fig4 #ec74 ,a piece of steel wire #a_/af inch in diameter is bent and placed between them to form the shaft4 ,the whole is then fixed in a piece of light copper tube1 which is slotted by means of a hack saw or fret saw to receive them4 ,the blades are bound crosswise to the tube by means of thin wire or strong thread2 then twisted to a pitch of about #f inches4 ,it is also advisable to place a washer between the copper tube and the end bar of the frame4 ,this method of fixing the propeller blades is not the same as that shown in ,fig4 #ej but it is the better way4 ,the drive for the propeller is elastic 7a rubber band71 which1 when twisted and released1 will rapidly revolve the shaft for a short time4 ,the best kind to use is the gray variety1 and when in the form of bands1 say #c_/h inch by #a_/af inch by #f inches1 is ready for use without jointing4 ,the wire carrying the elastic should be made so that the elastic is just in tension when untwisted4 ,the monoplane1 when complete1 should be tested without the propeller until it will glide perfectly4 ,the front of the plane will need weight added if there is a tendency to somersault2 but if the back rises ahead of the forward end1 more weight is necessary there4 ,the best glide to be expected is about a #a in #f slope4 ,the propeller should then be tried1 and a flight of #ej or #ajj feet1 or more1 should result4 ,if there is a tendency to twist1 owing to the side pull of the propeller1 a screw should be fixed to the end of the plane to counteract it4 ,a much longer flight can be given the model1 if the spring is made so that the tension may continue a longer period4 ,sometimes a rubber attachment can be applied and twisted so that the propeller can be kept running long enough to carry the machine a much greater distance than here stated4 ,the dimensions of all the parts of the machine are marked on the illustrations1 so that you will find no difficulty whatever in making a model monoplane that will fly from the start4 ,in the making of little models of this kind1 you will encounter many things that will tax your skill and ingenuity1 as amateur workmen4 ,now1 children1 ,i have told you all about aeroplanes that ,i intended1 though ,i may take up the subject again1 when ,i try to explain the recognized theory of flight1 and the making and flying of kites4 ,,viii ,,kites1 ,,sundials1 ,,patents ,the next day1 just as ,mr4 ,gregg returned from his office1 ,fred1 ,jessie1 and ,george landed on their new dock from the ,caroline4 ,they had been for a sail on the river1 and ,jessie was quite enthusiastic over the trip4 ,fred was a real good captain4 ,why1 papa1 he let me steer the boat all by myself1 and taught me so well ,i didn't have any collisions4 ,an hour or so later the boys1 ,jessie1 and ,mr4 ,gregg1 retired to the den4 ,after questioning the boys regarding the previous talk1 to discover if they remembered the main points1 ,mr4 ,gregg said he would now tell them something of kites and kite flying4 ,the highest kite ascent yet recorded was made at the aeronautical observatory at ,lindenburg1 7,prussia7 on ,november #be1 #aije1 #ba1ajj feet being attained4 ,six kites were attached to one another with a wire line of nearly #af1jjj yards in length4 ,the minimum temperature recorded was #ac degrees1 ,f42 at starting the reading was #da degrees4 ,the wind velocity at the surface of the earth was eighteen miles an hour1 and the maximum altitude it reached was fifty-six miles an hour4 ,the previous height record by a kite was nearly #a1ajj feet lower1 and it had been reached from a ,danish gunboat in the ,baltic4 ,these ascents were wonderful1 for it is not an easy matter to train a kite higher than a given altitude1 for several reasons4 ,the higher a kite rises the more string it will require1 and this tends to weight down the plane or kite4 ,the wind1 too1 acting on the string1 tends to retard the upward flight and to cut short further ascent4 ,when an ordinary kite reaches a height of #a1bjj or #a1ejj feet1 it is doing very well2 and few exceed this height4 ,when ,benjamin ,franklin angled in the clouds for lightning1 his kite did not attain an altitude of more than #a1jjj feet1 which was quite sufficient for the purpose he had in view4 ,when ,franklin flew his kite1 he was so afraid of ridicule that he took a small boy with him to carry the kite and string1 in order to prevent his neighbours from thinking he was going 'kite flying4' ,in these days when a man is seen flying a kite1 people very naturally imagine him to be an aeronaut1 studying the science for the purpose of improving or inventing a flying machine of some kind--for which there seems to be ample room4 ,illustration3 ,fig4 #ed4 ,science of kite-flying ,the first thing a beginner in the science of aeronautics will want to know is1 ',why does the kite or machine lift itself off the ground8' ,if you take a kite and hold it in an inclined position1 the wind on the lower side will have a tendency to blow it backward2 but as it is held by the kite string1 this movement is impossible1 and so it is inclined to rise in the air 7see ,fig4 #ed74 ,if we construct a large plane and equip it with a motor operating a screw which pushes or pulls the plane along through the air1 the result is the same as if the plane were anchored1 and the wind hits the lower surface of the inclined plane1 thus forcing it up4 ,also1 we find1 within certain limits1 the more you incline a plane the more lift or upward thrust will it give2 but it will take more power to drive it through the air1 and the faster the plane is driven through the air the less surface is required to support the weight4 ,a matter of great importance in the construction is the shape of the plane1 and the shape of the vertical section through the same4 ,the shape of these planes has been explained in ,figs4 #dc and #dd1 and the reasons were given why these shapes were considered the proper ones for the purpose4 ,it does not follow1 said ,mr4 ,gregg1 that all kites should have the same kind of a surface or plane1 though the flat planes of the toys of our school days were all of the flat surface kind2 these being of various shapes and sizes from the lozenge to the square1 bow top1 octagon1 and many others1 according to the whim or skill of the maker4 ,one of the conditions of these planes or flat kites1 was that each one must have at least one tail attached to the bottom of it4 ,this tail was flexible1 simply a piece of string having paper similar to 'curl papers' tied to it at intervals4 ,the tail was a necessity1 for without it the equipoise would be impossible4 ,in ,china and ,japan1 where the natives have been kite-flying for more than twenty centuries1 they make kites that fly and maintain the aerial equipoise without having tails hung to them1 no matter whether the shape be that of a dragon1 a lion1 or an eagle4 ,illustration3 ,fig4 #ee4 ,box kite ,a kite is simply an aeroplane on a small scale1 and should be considered as such1 as it has a fixed fulcrum in the belly band1 a constant pressure when flying1 and an angle which is varied in proportion to the load it may have to carry4 ,the common kite is easily made1 but it does not always fly as desired2 for it seems almost impossible to make two kites that will fly in the same manner under similar conditions4 ,box kites are the most reliable1 and not so very difficult to make1 as you will discover by examining ,figs4 #ee1 #ef1 and #eg and following the directions ,i give you4 ,first1 procure four straight strips of light wood1 preferably spruce1 #b ft4 #f in4 by #c_/h in4 by #a_/h in42 these dimensions should be full 7see ,fig4 #ee47 ,obtain also four other pieces1 each #a ft4 #g-a_/b in4 long1 but #a_/af in4 wider and thicker than the foregoing1 and halve their ends to a depth of #a_/h in4 by #a_/d in41 in order that when the false end ,a 7,fig4 #ef7 is tightly bound on1 these cross sticks will firmly grip the long pieces edgewise1 the sides of the cells being indicated by the dotted lines4 ,the long sticks should be notched at a distance of #d in4 from their ends to receive the forks of the cross sticks4 ,illustration3 ,fig4 #ef4 ,making a kite ,the width of the cloth or paper cells should be #h in41 and they should be separated by a distance of #a ft4 #a in4 or #a ft4 #b in41 their edges being bound with fine twine4 ,the easiest way to make the cells is to cut two strips of the material1 #aj in4 wide and #d ft4 #h-a_/b in4 long4 ,turn over the edges #a_/b in4 along each side1 and insert fine strong twine6 ,if paper is used1 glue the fold2 if cloth1 stitch the hem4 ,when completed1 either glue or stitch the ends of the strip with a #c_/d in4 lap1 so as to form a continuous band4 ,by folding1 divide this accurately into four equal parts and at each of the creases glue one of the long sticks edgewise 7see ,fig4 #ef74 ,when dry1 the whole can be put together and the flying line attached1 without a bridle1 as in ,fig4 #ee4 ,for additional clearness an enlarged detail of one end of the kite is shown at ,fig4 #eg4 ,illustration3 ,fig4 #eg4 ,single box kite ,illustration3 ,photograph by ,brown ,bros ,,making ,,kites ,box ,kites ,are the ,most ,reliable1 ,and ,not so ,very ,difficult to ,make ,it is advisable in all cases to make the cross pieces a trifle too long1 to insure their straining the band tightly4 ,they may also be shortened by cutting away the shoulder formed by the halving4 ,these kites are easy to fly4 ,avoid an enclosed space1 where the wind whirls in invisible eddies2 having let out #bj yds4 or #cj yds4 of line1 get some one to throw up the kite in the usual fashion4 ,if several large kites are sent up in tandem1 steel wire should be used4 ,illustration3 ,fig4 #eh4 ,square cellular kite ,another kind of a kite1 known as the cellular kite is shown in ,fig4 #eh4 ,this is made by forming two square frames ,n4 ,o41 divided into nine compartments each and connected together by a light rod at r1 the fulcrum or string being at ,p1 the air pressure at ,t4 ,the whole forms a good1 strong kite1 but it is not able to carry much weight1 on account of the equipoise being self adjusted in accordance with the constant pressure and surface4 ,the equipoise is due to the current being cut by the edges a a1 and diverted into the cellular divisions of each area4 ,this being the case1 any upward or downward tendency of a a1 would be counterbalanced by the effect on the other side and the kite would naturally adjust itself on the opposite side4 ,we are not dependent upon any particular shape for obtaining a good serviceable kite--like the plane made kite1 the cellular one may be of any shape4 ,i show you one here1 at ,fig4 #ei1 having a circular rim1 with thin tubes inserted in such a manner that the current of wind will rush through when the machine is in the air4 ,the two portions1 ,a and ,b1 are held together by a rod in a similar manner to the square kites1 and the cord or fulcrum is fastened to the rod at ,r4 ,illustration3 ,fig4 #ei4 ,circular cellular kite ,a number of kites may be sent up at once1 all attached to the same string1 if properly adjusted4 ,here are six square cellular kites looped together1 shown at ,fig4 #fj4 ,they may be made of any suitable size1 but need not be all of one size1 though each pair would be better if made the same size4 ,they may be looped up1 as shown1 and the point ,s may be loaded lightly2 it will help to steady the kite and keep it from swaying4 ,illustration3 ,fig4 #fj4 ,group of kites ,a peculiar kite1 called 'a war kite1' is very popular in some parts of ,europe1 and in some parts of our country also4 ,it is easily made and gives good results4 ,it is on the principle of the 'cellular' or 'box' kite1 being cubical or box-shaped1 and1 when used for carrying weights1 usually has several cells built together1 or several kites may be coupled when a heavy load1 such as that of a man1 is to be raised4 ,these kites are made of light wood or cane covered with nainsook or fine cotton1 and strengthened with cross pieces which hold the frames tight and keep the kite in shape4 ,they can be taken to pieces and the covering material rolled up so that they occupy very little space4 ,two forms of box kites are shown in ,figs4 #fa and #fb1 and it will be seen that an attachment is made each side of the frame4 ,this is fine steel wire1 very light compared with its strength1 wound on a drum by means of a small engine4 ,large kites of the ordinary form can be used for the same purpose1 but their lifting power is not equal to that of the box kite4 ,a small box kite is used for taking photographs1 a camera being carried by a separate wire connection to the attachment wire1 and the shutter released at the proper time by an ingenious arrangement1 similar to the pieces of paper called 'messengers' which boys used to send up on the cords of ordinary kites4 ,this kite is a little more expensive to make than most of those shown1 but it gives an excellent result when properly handled4 ,illustration3 ,fig4 #fa4 ,sextuple kite ,illustration3 ,fig4 #fb4 ,war kite ,in making kites of any kind1 the lightest materials consistent with sufficient strength1 should be employed4 ,the frames should be split bamboo or cane4 ,the joints may be lashed together with fine wire or silk thread1 and the envelope in each case should be fine silk or similar material that would be close1 light1 and strong4 ,these qualities1 in all sorts of kites and aeroplanes1 are absolutely essential to accomplish the best results4 ,before leaving the subject of aeronautics1 ,i think it would not be amiss to tell you something of bird flight4 ,there are different modes of flying1 just as men have different gaits in walking or running4 ,rapid wing movement does not always imply speed in flight1 any more than does rapid leg movement imply speed in walking or running4 ,with us it is the length of the stride that tells ultimately4 ,what tells1 correspondingly1 in the flight of the bird is not known4 ,speaking broadly1 long-winged birds are strong and swift fliers2 short-winged birds are feeble in flight4 ,when we consider that a cumbrous1 slow-moving bird like the heron moves its wings twice per second when in flight1 it is evident that many birds have a very rapid wing movement4 ,most small birds have it1 combined with feeble powers of flight4 ,the common wren and the chipping sparrow1 for instance1 have a flight like that of a young bird4 ,what can give one more exquisite pleasure than to watch seagulls swooping round the edge of a cliff1 to see them drift down wind with wings motionless1 then suddenly dart downward1 turn to meet the breeze1 and beat up against it with all their ingenuity and skill8 ,the beauty of a ship depends on the way it glides through the water4 ,watch a liner1 and you can see that it is being driven by its screws1 but look at a racing yacht3 there is no sense of effort whatever4 ,she seems to move like a bird1 by natural means4 ,here is the secret of the beauty of the aeroplane4 ,it seems to be completely master of the element in which it moves4 ,it flies with no visible effort and at a little distance one could imagine it endowed with magic power1 moving by natural force1 like a bird4 ,all the early attempts at flying were made on the theory of wing motion1 and the failures resulting were doubtless due to careless study of what nature could teach4 ,there was a great deal more to be learned from nature than from mathematics4 ,an examination of the different types of birds testifies1 among other things1 to their rigid backs1 and to the fact that nearly all their bones are hollow and have air cavities4 ,an erroneous deduction had been drawn from this that the hollows were purely for the sake of lightness1 and that the cavities were for hot air to make the bird light when it wanted to fly4 ,the amount of lightness so obtained1 however1 was so small as not to be worth consideration4 ,the passages are simply reservoirs for air1 and they allow the bird more energy than a less freely breathing animal4 ,the wing of the bird does a double duty3 it is an aeroplane and a propeller combined4 ,the valvular action has nothing at all to do with the flight4 ,some explanation of how a sparrow can rise from the gutter to the eaves may be seen by the difference in the construction of its wings from those of the swallow1 which cannot rise from the ground like a sparrow1 but has to get initial velocity4 ,the swallow1 however1 has much more mastery over its movements in the air than the sparrow has4 ,these1 and many other things in connection with bird flight1 under proper methods of scientific investigation1 may show us the whole theory of aviation4 ,i am inclined to think that scientific men will soon be able to solve the problem1 and to give us better control of the coming aeroplanes1 or even direct their flight by the aid of electric waves or other natural forces4 ,in kite-flying1 it is well to know something of the wind and its pressure1 and1 in this connection1 the following short table will give some idea of the force exercised on objects in its path3 ,a light air current presses #j4jjd lbs4 per square foot4 ,light wind has a pressure of #j4abe lbs4 per sq4 foot ,light breeze #j4bdf lbs4 per sq4 foot ,moderate breeze #j4djf lbs4 per sq4 foot ,strong breeze #b4jj lbs4 per sq4 foot ,moderate gale #b4ih lbs4 per sq4 foot ,this last should be the limit1 as a kite or aeroplane of any kind will find it hard to manoeuvre in a breeze stronger than a moderate gale4 ,of course1 there are winds sometimes that have a velocity of #fj to #ge miles an hour1 and a pressure of over #dj pounds to the square foot1 but these would prove disastrous to any kind of a flying machine1 if it was in action4 ,father1 asked ,fred1 how can one tell the velocity of the wind1 without one of those expensive machines ,i see at the weather office1 an anemometer1 ,i think it is called8 ,i am glad1 said the father1 that you have noticed those and other instruments for gauging and foretelling weather conditions4 ,it is an indication that you keep your eyes open when you visit such places1 and to learn by observation is almost as effectual as to obtain knowledge by experience4 ,i have in mind a very simple contrivance you can make yourself1 for measuring wind pressure from a couple of ounces to four pounds to the foot4 ,i will make a sketch of it1 which ,i am sure you will understand4 ,illustration3 ,fig4 #fc4 ,wind gauge ,it consists of a light pine or cedar wood frame on a strong stand1 supporting on a centre two bent wires1 carrying at one end a #c-;in4 square of thin wood1 ,a1 and on the other a thin bar of wood1 to the centre of which is attached a fine string tied to a spring balance scaled to #a_/h of an ounce and up to #d ounces 7,fig #fc74 ,as the square of #c inches is the #afth of a foot1 each ounce on the spring is equal to #a lb4 pressure on the square foot4 ,the latter balance slides in the ,v-frame at the back so as always to keep the square parallel to the face of the frame1 whether the wind is strong or light1 and the balance must be slidden in or out until the face of the square is so placed before registering the force of the wind4 ,by attention to this it will register very truly up to #d lbs41 which is the extent of an ordinary spring balance4 ,there is also a front view1 a side view1 and a bird's-eye view1 also one of the bent wires and the #c-;inch square4 ,i think this requires no further explanation4 ,fred was satisfied with the description of the register and promised to make one at an early date4 ,the following evening when they were all sitting on the river bank1 ,fred suddenly asked his father if it was difficult1 or costly1 to secure patents4 ,he wanted to know1 because he had been thinking of making a kite on a new principle--that of a funnel1 and he was so sure it would prove a success that he would like to have it patented4 ,mr4 ,gregg thought the scheme rather an ambitious one1 but1 while he could not see it as ,fred did1 he determined not to say anything that would be likely to discourage the boy4 ,so he explained1 as well as he could1 the patent laws3 ,in order to apply for a patent it is necessary to file in the ,patent ,office at ,washington1 ,d4 ,c41 a petition1 affidavit of invention1 drawings1 and specifications1 all of which must be prepared in legal form and in accordance with official rules and practice of the office4 ,this can best be done by a reliable attorney but an applicant should understand some of the requirements as well4 ,the ,patent ,office does not require a model to be furnished in order to apply for a patent1 but if the attorney is not near enough to see the one made by the inventor1 then one should be sent him1 unless good photographs and drawings can be supplied4 ,since the drawing attached to the specifications and claims is to be on a sheet of a special size1 no attention need be paid to having the original sketches of a uniform size4 ,when ready to apply for a patent1 secure as much evidence as possible of the reliability of some attorney you have heard of and consult him about the matter1 explaining as much as is necessary for him to prepare an outline that will suffice for a preliminary search through the records in the ,patent ,office to see that no interference will take place should the application be made4 ,this usually costs #e4jj1 and an attorney often supplies copies of existing patents that look the most like the one in question4 ,if it is thought that there will be no interference1 the case is then prepared for the examiners1 and the application duly made4 ,the drawings should be made and lettered1 so that the specifications can be written up1 including the proper reference to the different parts4 ,the drawings should be made upon paper stiff enough to stand in a portfolio1 the surface of which must be calendered and smooth4 ,the best kind is patent office bristol1 though there is a style on the market printed with margin and headings all ready for use1 but the surface is not of the best4 ,the size of the sheet on which a drawing is made should be exactly #aj #ae inches with margin lines one inch from all the edges1 leaving a clear space of #h #ac inches4 ,one of the smaller sides is regarded as its top1 and measuring downward from the margin1 or border line1 a space of not less than #a-a_/d inches is to be left blank for the insertion of title1 name1 number and date1 to be put in by the patent officials4 ,all drawings must be made with the pen only1 using the blackest ,india ink4 ,every line and letter1 including the signature must be absolutely black4 ,this applies to all lines1 however fine1 to shading and to lines representing cut surfaces in sectional views4 ,all lines must be clean1 sharp1 and solid1 and they must not be too fine or crowded4 ,surface shading1 when used1 should be left very open4 ,sectional shading should be by oblique parallel lines1 which may be about one-twentieth of an inch apart4 ,drawings should be made with the fewest lines possible consistent with clearness1 for the drawings are subjected to photographic reduction1 which decreases the space between the lines4 ,shading 7except on special views7 should be used only on convex and concave surfaces1 and there sparingly1 or it may be dispensed with if the drawing is otherwise well made4 ,the plane on which a sectional view is taken should be indicated on the general view by a broken or dotted line4 ,heavy lines on the shade sides of objects should be used1 except where they tend to thicken the work and obscure the reference letters4 ,the light is always supposed to come from the upper left hand corner1 at an angle of forty-five degrees4 ,imitations of wood or surface graining should not be attempted4 ,the scale to which a drawing is made ought to be large enough to show the mechanism without crowding1 and two or more sheets should be used if one does not give sufficient room to accomplish this end2 but the number of sheets must never be increased unless it is absolutely necessary4 ,sometimes the invention1 although constituting but a small part of a machine1 has to be represented in connection with other and much larger parts4 ,in a case of this kind1 a general view on a small scale is recommended1 with one or more of the invention itself on a much larger scale4 ,letters or figures may be used for reference1 but they should be well made1 and when at all possible should not be less than one eighth of an inch in height1 that they may bear reduction to one twenty-fourth of an inch2 or they may be much larger when there is sufficient space4 ,reference letters must be so placed in the close and complex parts of a drawing as not to interfere with a thorough understanding of the same1 and to this end should rarely cross or mingle with the lines4 ,the illustrations on pages of current topics under the head of new patents show the manner of putting in the reference lines from the letters to the part indicated4 ,these are carried out some distance1 but if placed on the face of the object where sectioned1 a blank space should be left in the shading for the letter4 ,if the same part of the invention appears in more than one view1 it should always be represented by the same letter4 ,great care should be exercised in the matter of drawings1 or they will be returned to the applicant1 but1 at his suggestion and cost1 the officials will make the necessary corrections4 ,the time required to procure an allowance of a patent averages from six weeks to two months4 ,united ,states patents are granted for a term of seventeen years1 and cannot be extended4 ,the patent remains good whether the invention is worked or not1 and no additional payments are required beyond the cost of first taking out the patent4 ,patents are not subject to taxation4 ,reissues of patents are granted whenever one is inoperative or invalid1 by reason of a defective or insufficient specification1 or by reason of the patentee claiming more than he had a right to claim as new1 provided the error arose by inadvertence1 accident1 or mistake1 without fraudulent intent4 ,a fee of #cj4ej must be forwarded upon application for patent4 ,as stated before1 a patent is obtained by a petition to the ,commissioner of ,patents accompanied by a description1 including drawings and a model1 when the invention will admit of these4 ,a fee of #ae is required when the application is made1 and a further fee of #bj when the patent is issued4 ,postage on model is at the rate of #a cent per ounce4 ,a patent for a design is granted to any person who has invented or produced any new and original design for the printing of woollen1 silk1 cotton1 or other fabrics2 any new and original impression1 ornament1 pattern-print1 or picture to be printed1 painted1 cast1 or otherwise placed on or worked into any article of manufacture2 or any new1 useful1 and original shape or configuration of any article of manufacture1 the same not being known or used by others before this invention or production thereof1 or patented or described in any printed publication1 upon payment of the duty required by law1 and other required proceedings the same as in cases of inventions or discoveries4 ,these are granted for three and one-half years1 seven years or fourteen years1 for which the respective fees of #aj1 #ae1 and #cj are paid the government4 ,a caveat is a provisional protection to any person who has thought of an invention and desires the time to complete or perfect the same4 ,it is procured at an expense of #aj1 and runs for one year with the permission of renewal from year to year4 ,in ,canada the patent office is a branch of the ,department of ,agriculture1 and the ,minister of ,agriculture for the time being is the ,commissioner of ,patents4 ,any intending applicant for a patent who has not yet perfected his invention1 and is in fear of being despoiled of his idea1 may file in the patent office a description of his invention so far1 with1 or without plans1 of his own will1 and the ,commissioner1 on payment of the prescribed fee1 shall cause the said document1 which shall be called a caveat1 to be preserved in secrecy1 and1 if application is made by any other person for a patent interfering in any way therewith1 the ,commissioner shall forthwith give notice1 by mail1 of such application to the person filing such caveat1 who shall1 within three months thereafter1 if he wishes to avail himself of the caveat1 file his petition1 and take the other steps necessary on application for a patent4 ,the application for the patent must be made within one year from the filing of caveat1 otherwise the ,commissioner is relieved from the obligation of giving notice4 ,the following fees are payable3 ,full fee on patent for #ah years1 #fj4jj2 partial fee for #ab years1 #dj4jj2 partial fee for #f years1 #bj4jj2 on filing caveat1 #e4jj2 on registering assignment patent1 #b4jj2 for copy of patent1 with specification1 #d4jj4 ,the disbursements for filing an application in ,great ,britain are #be4jj2 ,france1 #bj4jj2 ,germany1 #e4jj1 and #g4ej before issuing patent2 ,australia1 #bj4jj2 ,russia1 #ge4jj2 ,british ,india1 #bj4jj4 ,the ,german and ,french patents cover not only ,germany and ,france but their colonies also4 ,the ,russian patent extends to all of the ,russian possessions4 ,the disbursements for filing an application in the ,australian states1 namely1 ,queensland1 ,victoria1 ,new ,south ,wales1 ,south ,australia1 ,western ,australia and ,tasmania are #e4jj on filing the application1 #aj4jj on allowance of same1 and #be4jj for preparation of the sealing of patent2 ,new ,zealand1 #bj4jj2 ,mexico1 #ge4jj2 ,natal1 #ej4jj2 ,japan1 #ge4jj2 ,jamaica1 #aej4jj4 ,this talk on patents was quite interesting to ,fred1 and very instructive to ,george1 and they thanked their father for it4 ,illustration3 ,photographs by ,c4 ,m4 ,d',enville ,a ,,sun ,,dial ,,made ,,of ,,concrete ,an excellent illustration of the possibility which concrete offers in ornamental as well as practical construction4 ,this sun dial1 complete1 cost approximately ten dollars1 and may be duplicated by any clever boy4 ,see formula for concrete on page #bj4 ,boys1 he said to them next morning1 why not try your hands on a sundial8 ,you will find it easy to make1 and if properly set up it will keep accurate time4 ,there is a nice place for one near the bridge on the new grounds1 as there is a stump there1 the top of which can be cut off smooth1 and it stands out full in the sun4 ,illustration3 ,fig4 #fd4 ,sundial ,go to our jeweller in the city and get him to give you an old tin clock-dial1 like the one shown in ,fig4 #fd4 ,if you cannot get one1 make a dial out of cardboard yourself1 printing the hours in ink4 ,slit the dial from the centre to a point directly underneath the number #ab1 if you have ,arabic numerals on your dial4 ,then cut out a triangular blade or gnomon1 like the one shown4 ,if your dial is of tin1 make the blade of tin1 or cardboard if your dial is of cardboard4 ,insert the blade in the slit of the dial and secure it to the top of the stand you have selected--with tacks if your dial is cardboard1 with small nails if it is tin4 ,then your sundial will be completed and ready for business4 ,at #ab o'clock1 there will be only the shadow of the thin edge of the blade over the dial1 but as the sun moves1 so will the shadow1 so as to tell always the correct time of day4 ,you will find this not only a useful but a quaint and artistic addition to the grounds1 and not at all expensive4 ,papa1 said ,george1 mamma wants a flower bed made in the front garden1 and she would like to have it an oval or elliptical shape4 ,i have promised to make it for her1 but ,i do not know how to make the shape1 and ,i wish you would tell me4 ,certainly1 my boy1 ,i will show you4 ,it can be done easily with a string and two wooden pegs4 ,follow the lines ,i make on the blackboard4 ,first we must decide on the length and width of the oval or rather ellipse required4 ,then draw two straight lines1 ,a ,b and ,c ,d1 ,fig4 #fe1 equal to the two axes1 and bisect or halve each at right angles4 ,set off from ,c half the length of the great axis at ,e and ,f1 which are the two foci of the ellipse4 ,take an endless string1 as long as the three sides of the triangle1 ,c ,e ,f1 fix two pins or nails in the two foci1 one at ,e and one at ,f4 ,lay the string around ,e and ,f1 stretch it with a marker ,g1 and it then will describe the desired ellipse4 ,illustration3 ,fig4 #fe4 ,drawing an ellipse ,this is not at all difficult1 and will answer for any kind of an ellipse1 short or long1 narrow or wide4 ,this is called the gardener's method4 ,the main thing is to get the two points1 ,e and ,f4 ,this distance is always half of the long diameter ,a ,b1 no matter what that may be1 and this distance is then transferred by taking ,c as the starting point1 measuring from there until the other point of measurement cuts the long diameter1 as at ,e and ,f4 ,the ellipse has many peculiar and useful qualities1 which you will doubtless discover before long4 ,,ix ,,tides ,now1 papa6 said ,jessie the following evening1 after ,mr4 ,gregg and the family had strolled down to the river bank to enjoy the cool air1 you promised to tell me about the tides and the moon--when you could spare time4 ,haven't you got time now8 ,i may as well say all ,i intended now1 my dear1 and leave some other matters for future consideration4 ,as this subject may tax your patience1 ,i hope you1 ,fred1 and ,george1 will give me your earnest attention4 ,in order to have a clear understanding of the movements of the tides and their supposed causes1 you must know something of the moon's influence over them2 as this knowledge will aid you very much in remembering what ,i am about to say4 ,the earth is a globular body4 ,one reason for this belief1 among many others1 is that sailors or others who go to sea soon observe that as they sail from shore1 the lower portions of mountains1 steeples or other high objects1 are gradually lost sight of while the higher parts do not so soon disappear4 ,persons on shore first notice the upper portions of masts1 and the smoke-stacks of approaching vessels1 which would not be the case1 if the earth were a plane1 but is very easily accounted for1 on the supposition of its being a sphere1 as you can readily understand by looking at ,fig4 #ff4 ,several navigators have sailed completely round the earth by continuing in the same direction1 and coming at last to the same place from which they started4 ,the earth1 however1 is not a perfect sphere but a spheroid like an orange2 having its equatorial longer than its polar diameter or axis4 ,it is flattened at the poles1 and more protuberant at the equator4 ,the diameter at the equator is #g1igg miles1 and at the poles #g1idj1 a difference of #cg miles4 ,illustration3 ,fig4 #ff4 ,proof of earth's rotundity ,you know that the cause of day and night is the rotation of the earth on its own axis4 ,it shows a large portion of its surface to the sun continually1 or in other words1 the sun is always shining on some portion of the earth's surface4 ,you are also aware of the earth and its satellite1 the moon1 both being held in their orbits by the sun's attraction1 the moon being further kept in her orbit by the attraction of the earth4 ,now the earth is composed of three main elements1 air1 water1 and land1 and if you consider1 for a moment1 that the daily rotatory movement of the earth is something like #a1jjj miles an hour1 this rapid speeding through space must have some effect on air and water in assisting or retarding their flow4 ,illustration3 ,fig4 #fg4 ,phases of the moon ,nature has divided time1 and man has named and subdivided it into years1 months1 and days4 ,the natural month1 however1 does not consist of four weeks1 nor is the natural year made up of the twelve calendar months given us by the almanac4 ,a natural1 or lunar1 month is the time the moon takes to perform her journey round the earth1 which is #bg days #g hours1 and #dc minutes2 this is called the periodical month1 while the average calendar or synodical month consists of #bi days #ab hours and #dd minutes4 ,the light of the moon is borrowed from the sun1 for if it were her own light1 she would shine all the time and not be subject to her present phases4 ,the moon is seen by means of the light which comes to it from the sun being reflected from it4 ,its changes1 or phases1 depend upon its relative position to the earth and the sun4 ,when the moon is in opposition to the sun at ,a 7,fig4 #fg7 the lighted side is turned toward the earth1 as ,a1 and it appears full4 ,when the moon is in conjunction at ,e with the sun1 its dark side is turned toward us1 and it is invisible1 as at e4 ,as it proceeds in its orbit1 as at ,f1 a small part of the light side is seen1 and then we have what is called a new moon2 and we continue to see more and more of the light side1 as the moon approaches at ,g and ,h1 to the state of opposition or full moon4 ,the waning or decreasing of the moon takes place in the same manner1 but in a contrary order4 ,the earth must perform the same office to the moon that the moon does to us2 and it will appear to the inhabitants of the moon 7if there be any71 like a very magnificent moon1 being to them about thirteen times as large as the moon is to us and it will also have the same changes or phases4 ,hence it is evident1 that one half of the moon is never in darkness1 the earth constantly affording it a strong light1 during the absence of the sun2 but the other half has a fortnight's light and darkness by turns4 ,the moon's orbit is elliptical1 and she also rotates on her axis and takes the same time to circle the earth1 consequently every part of the moon is successively presented to the sun1 yet the same hemisphere is always turned to the earth4 ,this has been discovered by observation with good telescopes4 ,the length of a day and night in the moon is more than twenty-nine and a half days of ours2 and while her year is the same length as ours1 being measured by her journey around the sun with us1 so she has but twelve days and a third in a year4 ,another remarkable circumstance is that the moon's hemisphere next the earth is never in darkness1 for when it is turned from the sun1 it is illuminated by light reflected from the earth in the same manner as we are lighted by a full moon4 ,the other hemisphere of the moon however1 has a fortnight's light and darkness by turns4 ,if there are inhabitants in the moon1 which is doubtful1 the satellite will appear to them to be about thirteen times as large as the moon does to us1 and when it is new moon to the earth1 it is full earth to the moon4 ,there are many things regarding our relationship to the moon that would be of interest1 if ,i had time to explain them1 such as eclipses1 the moon's surface as seen through telescopes1 its supposed influence on the weather1 etc41 but ,i fear too much moon might prove tiresome4 ,beside ,i have shown you sufficient to enable you to understand the relationship existing between the moon and the tides1 generally accepted as the true theory4 ,if we agree that the tides are occasioned by the attraction of sun and moon1 more particularly the latter1 we can readily understand their dependence on some known and determinate laws4 ,our almanacs published long in advance give the exact time of high water at any prominent port in the ,united ,states on the morning and afternoon for every day in the year2 and seafaring men can tell you when the tide will be high or low1 notwithstanding the fact that these movements are not fixed4 ,they know from experience that the time of ebb and flow varies about three quarters of an hour each day4 ,the first person who clearly pointed out the accepted cause of the tides and showed its agreement with the effects1 was ,sir ,isaac ,newton4 ,he discovered a relationship between the moon and the tides1 and by the application of his new principles of geometry1 the attraction was made clear4 ,the ocean1 it is well known1 covers more than one half the globe2 and this large body of water is found to be in continual motion1 ebbing and flowing alternately1 without the least intermission4 ,for instance1 if the tide is now at high water mark1 in any port or harbour which lies open to the ocean1 it will presently subside1 and flow regularly back for about six hours1 when it will be found at low water mark4 ,after this it will again gradually advance for six hours2 and then recede in the same time to its former situation1 rising and falling alternately twice a day1 or in the space of about twenty-four hours4 ,the interval between its ebb and flow is not precisely six hours1 for there is a little difference in each tide2 so that the time of high water does not always happen at the same hour1 but is about three quarters of an hour later each day1 for about thirty days1 when it again recurs as before4 ,for example1 it is high water to-day at noon1 it will be low water at eleven minutes after six in the evening2 and1 consequently1 after two changes more1 the time of high water the next day will be at about three quarters of an hour after noon2 the day following it will be at about half an hour after one1 the day following that at a quarter past two1 and so on for thirty days2 when it will again be found to be high water at noon1 as on the day the observation was first made4 ,this exactly answers to the motion of the moon which rises every day about three quarters of an hour later than upon the preceding one1 and by moving in this manner round the earth1 completes her revolution in about thirty days1 and then begins to rise again at the same time as before4 ,to make the matter still plainer2 suppose1 at a certain place1 it is high water at three o'clock in the afternoon1 upon the day of the new moon2 the following day it will be high water at three quarters of an hour after three2 the day after that at half an hour past four2 and so on till the next new moon1 when it will again be high water exactly at three o'clock1 as before4 ,by observing the tides continually at the same place1 they will always be found to follow the same rule2 the time of high water1 upon the day of every new moon1 being exactly at the same hour1 and three-quarters of an hour later every succeeding day4 ,the change of the tides is in such exact conformity with the motion of the moon that1 independently of mathematical calculations1 a thoughtful person would certainly be induced to look to her as their cause4 ,illustration3 ,fig4 #fh4 ,theory of the tides ,the waters at ,z1 on the side of the earth1 ,a1 ,b1 ,c1 ,d1 ,e1 ,f1 ,g1 ,h1 next the moon ,m1 7,fig4 #fh7 are more attracted by the moon than the central parts of the earth1 ,o1 and the central parts are more attracted by her than the waters on the opposite side of the earth at n2 and therefore the distance between the earth's centre and the waters on its surface under and opposite to the moon will be increased4 ,let there be three bodies at ,h1 ,o1 and ,d2 if they are all equally attracted by the body ,m1 they will all move equally fast toward it1 their mutual distance from each other continuing the same4 ,if the attraction of ,m is unequal1 then that body which is most strongly attracted will move most quickly and will increase its distance from the other body4 ,m will attract ,h more strongly than does ,o1 by which the distance between ,h and ,o will be increased1 and a spectator on ,o will perceive ,h rising higher toward ,z4 ,in like manner1 ,o being more strongly attracted than ,d1 it will move farther toward ,m than ,d does2 consequently the distance between ,o and ,d will be increased2 and a spectator on ,o1 not perceiving his own motion1 will see ,d receding farther from him towards ,n2 all effects and appearances being the same1 whether ,d recedes from ,o1 or ,o from ,d4 ,suppose now there is a number of bodies1 as ,a1 ,b1 ,c1 ,e1 ,f1 ,g1 ,h1 placed round ,o1 so as to form a flexible or fluid ring2 then1 as the whole is attracted toward ,m1 the parts at ,h and ,d will have their distance from ,o increased2 whilst the parts at ,b and ,f being nearly at the same distance from ,m as ,o is1 these parts will not recede from one another2 but rather by the oblique attraction of ,m1 they will approach near to ,o4 ,hence1 the fluid ring will form itself into an ellipse ,z1 n1 ,l1 ,n1 whose longer axis n1 ,o1 ,z1 produced will pass through ,m1 and its shorter axis ,b1 ,o1 ,f1 will terminate in ,b and ,f4 ,let the ring be filled with fluid particles1 so as to form a sphere round ,o2 then1 as the whole moves toward ,m1 the fluid sphere being lengthened at ,z and n will assume an oblong or oval form4 ,if ,m is the moon1 ,o the earth's centre1 ,a1 ,b1 ,c1 ,d1 ,e1 ,f1 ,g1 ,h1 the sea covering the earth's surface1 it is evident1 by the above reasoning1 that whilst the earth by its gravity falls toward the moon1 the water directly below at ,b will swell and rise gradually toward her2 also the water at ,d will recede from the centre1 7strictly speaking1 the centre recedes from ,d7 and rise on the opposite side of the earth2 whilst the water at ,b and ,f is depressed1 and falls below the former level4 ,hence as the earth turns round its axis from the moon to the moon again in #bd-c_/d hours1 there will be two tides of flood and two of ebb in that time1 as we find by experience4 ,that this doctrine may be still more clearly understood1 let it be considered that1 although the earth's diameter bears a considerable proportion to the distance of the earth from the moon1 yet this diameter is almost nothing when compared to the distance of the earth from the sun4 ,the difference of the sun's attraction1 therefore1 on the sides of the earth under and opposite to him1 will be much less than the difference of the moon's attraction on the sides of the earth under and opposite to her2 and1 for this reason1 the moon must raise the tides much higher than they can be raised by the sun4 ,the effect of the sun's influence1 in this case1 is nearly three times less than that of the moon4 ,the action of the sun alone would1 therefore1 be sufficient to produce a flow and ebb of the sea2 but the elevations and depressions caused by this means would be about three times less than those produced by the moon4 ,the tides1 then1 are not the sole production of the moon1 but of the joint forces of the sun and moon together4 ,or1 properly speaking1 there are two tides1 a solar one and a lunar one1 which have a joint or opposite effect1 according to the situation of the bodies which produce them4 ,when the actions of the sun and moon conspire together1 as at the time of new and full moon1 the flow and ebb become more considerable2 and these are then called the spring tides4 ,but when one tends to elevate the waters while the other depresses them1 as at the moon's first and third quarters1 the effect will be exactly the contrary3 the flow and ebb1 instead of being augmented1 as before1 will now be diminished2 and these are called the neap tides4 ,to explain this more completely1 let ,fig4 #fi represent the sun1 ,z1 ,h1 ,r1 the earth1 and ,f and ,c the moon at her full and change4 ,then1 because the sun ,s1 and the new moon ,c1 are nearly in the same right line with the centre of the earth ,o1 their actions will conspire together1 and raise the water above the zenith ,z1 or the point immediately under them1 to a greater height than if only one of these forces acted alone4 ,but it has been shown that when the ocean is elevated to the zenith ,z1 it is also elevated to the opposite point1 or nadir1 at the same time2 and therefore in this situation of the sun and moon1 the tides will be augmented4 ,and again1 whilst the full moon ,f raises the waters at ,n and ,z1 directly under and opposite to her1 the sun ,s1 acting in the same right line1 will also raise the waters at the same point ,z and ,n1 directly under and opposite to him4 ,therefore1 in this situation also1 the tides will be augmented2 their joint effect being nearly the same at the change as at the full2 and in both cases they occasion what are called the spring tides4 ,illustration3 ,fig4 #fi4 ,attractions of the moon ,on this theory1 the tides ought to be highest directly under and opposite to the moon2 that is1 when the moon is due north and south2 but we find that in open seas1 where the water flows freely1 the moon is generally past the north and south meridian of the place where it is high water4 ,the reason is obvious2 for though the moon's attraction were to cease altogether when she was past the meridian1 the motion of ascent communicated to the water before that time would make it continue to rise for some time after2 much more must it do so when the attraction is only diminished4 ,a little impulse given to a moving ball will cause it still to move farther than otherwise it could have done2 and experience shows that the day is hotter about three in the afternoon than when the sun is on the meridian1 because of the increase made to the heat already imparted4 ,tides do not always answer to the same distance of the moon from the meridian at the same place1 but are variously affected by the action of the sun1 which brings them on sooner when the moon is in her first and second quarters1 and keeps them back later when she is in her third and fourth2 because1 in the former case1 the tide raised by the sun alone would be earlier than the tides raised by the moon2 and in the latter case1 later4 ,the sea1 being put in motion1 would continue to ebb and flow for several times1 even though the sun and moon were annihilated1 and their influences at an end1 on the same principle that if a basin of water is once agitated1 the water will continue to move for some time after the basin is left to stand still4 ,a pendulum1 put in motion by the hand1 continues to make several vibrations without any new impulse4 ,when the moon is at the equator1 the tides are equally high in both parts of the lunar day1 or time of the moon's revolving from the meridian to the meridian again1 which is #bd hours #ej minutes4 ,but as the moon declines from the equator toward either pole1 the tides are alternately higher and lower at places having north or south latitude4 ,one of the highest elevations1 which is that under the moon1 follows her toward the pole to which she is nearest1 and the other declines toward the opposite pole2 each elevation describing parallels as far distant from the equator1 on opposite sides1 as the moon declines from it to either side2 and consequently the parallels described by those elevations of the water are twice as many degrees from one another as the moon is from the equator2 then increase their distance as the moon increases her declination1 till it is at the greatest1 when these parallels are1 at a mean state1 #dg degrees from one another2 and on that day the tides are most unequal in their heights4 ,as the moon returns toward the equator1 the parallels described by the opposite elevations approach toward each other1 until the moon comes to the equator1 and then they coincide4 ,as the moon declines toward the opposite pole1 at equal distances1 each elevation describes the same parallel in the other part of the lunar day which its opposite elevation described before4 ,whilst the moon has north declination1 the great tides in the northern hemisphere are when she is above the horizon2 and the reverse whilst her declination is south4 ,in open seas1 the tides rise to very small heights in proportion to what they do in wide-mouthed rivers1 opening in the direction of the stream of tide4 ,in channels growing narrower gradually1 the water is accumulated by the opposition of the contracting bank--like a gentle wind1 little felt on an open plain1 but stronger and brisk in a street2 especially if the wider end of the street is next the plain1 and in the way of the wind4 ,the tides are so retarded in their passage through different shoals and channels1 and otherwise so variously affected by striking against capes and headlands1 that in different places they happen at all distances of the moon from the meridian1 consequently at all hours of the lunar day4 ,there are no tides in lakes because they are generally so small that when the moon is vertical she attracts every part of them alike2 and1 therefore1 by rendering all the waters equally light1 no part of them can be raised higher than another4 ,the ,mediterranean and ,baltic ,seas suffer very small elevations1 because the inlets by which they communicate with the ocean are so narrow that they cannot1 in so short a time1 receive or discharge enough to raise or sink their surface sensibly4 ,air being lighter than water and the surface of the atmosphere being nearer to the moon than the surface of the sea1 it cannot be doubted that the moon raises much higher tides in the air than in the sea4 ,therefore many have wondered why the mercury does not sink in the barometer when the moon's action on the particles of air makes them lighter as she passes over the meridian4 ,but we must consider1 that as these particles are rendered lighter1 a greater number of them are accumulated1 until the deficiency of gravity is made up by the height of the column2 and then there is an equilibrium1 consequently an equal pressure upon the mercury as before2 so that it cannot be affected by the aerial tides4 ,it is probable1 however1 that stars seen through an aerial tide of this kind will have their light more refracted than those which are seen through the common depth of the atmosphere2 and this may account for the supposed refractions of the lunar atmosphere that have been sometimes observed4 ,you see now how the tides are caused2 while there may be some influences at work other than those exerted by the sun and moon1 the latter are the chief ones1 so ,i will not attempt to explain any other4 ,here1 on the ,passaic ,river1 we do not have excessive tides1 as the highest on the coast near us seldom rise over ten or twelve feet4 ,as a rule1 tides rise highest and strongest in those places that are narrowest4 ,in the ,black ,sea and the ,mediterranean1 the tides are scarcely perceptible1 while at the mouth of the ,indus1 in the ,bay of ,fundy1 and other places1 they rise thirty or more feet at times4 ,the general rise1 however1 in mid-ocean1 is from eleven to twelve feet4 ,the diameter of our moon is nearly #b1bjj miles1 and her distance from the earth is about #bdj1jjj miles2 so you see it is not her size1 but her proximity to the earth that gives her so much influence over the tides2 for the sun1 which is many times larger than the earth and moon combined1 because of its being some ninety-three millions of miles away1 exerts only one sixth of the attraction on the earth that the moon does4 ,these facts1 children1 should be remembered1 as you may often be called upon to make use of them4 ,oh1 papa6 said ,jessie how many wonderful things there are in this world4 ,but ,i have not told you all1 my dear4 ,there is much more to learn1 but ,i hope the knowledge you have now acquired will act as an incentive1 and cause you to pursue this study further4 ,next morning ,fred asked his father to enlighten himself and ,george regarding the making of a few simple meters1 such as barometer1 hygrometer1 and a thermometer4 ,he also wished to know if it would be possible for him to make a boomerang4 ,mr4 ,gregg told him he would be pleased to help him1 and that there would be no difficulty in making a boomerang if he went to work at it earnestly4 ,on the arrival of his father that evening1 the subject was again introduced1 and ,mr4 ,gregg using the blackboard1 laid out the following drawing and wrote the accompanying instructions4 ,the best hygrometer of absorption is 7according to ,deschanel7 that of ,de ,saussure1 consisting of a hair deprived of grease1 which by its contractions moves a needle4 ,when the hair relaxes1 the needle is caused to move in the opposite direction by a weight which serves to keep the hair always tight as seen in the illustration1 ,fig4 #gj4 ,the hair contracts as the humidity increases4 ,in the accompanying illustration ,a ,a and ,b ,b represent the frame2 e f1 the scale2 a1 screw for tightening the hair2 b1 the hair2 ,o1 weight2 ,h1 thermometer4 ,illustration3 ,fig4 #gj4 ,hygrometer ,illustration3 ,fig4 #ga4 ,index of ,hygrometer ,a neater hygrometer1 and one on the same principle1 may be made by taking an old tooth powder box 7as deep a one as possible1 since the longer the string1 the more sensitive it is71 and boring a hole through the centre of the top and bottom4 ,paste a kind of dial in paper on the top of the box2 take a piece of catgut1 or small fiddle string1 and push it up through the hole in the bottom and out at the one in the lid4 ,glue the bottom end immovably1 and let the top end move freely3 make a small index of a strip of whalebone 7,fig4 #ga72 bore a hole in the centre1 and fix it on the catgut with glue4 ,wet the catgut1 see which way it turns1 and mark 'wet' and 'dry'1 accordingly on the dial4 ,so much for the hygrometer4 ,now about that curious thing1 the boomerang4 ,if the following directions are closely adhered to1 and the proper shape followed1 a regular ,australian boomerang will result4 ,it is not difficult to make4 ,take a piece of hard wood1 the natural shape of one of the segments of an ordinary wheel felloe1 or bend in the wood2 let it be #a_/d inch thick1 shaped as at ,fig4 #gb1 to be held in the right hand at ,a1 which shows the way the edges of the side facing the left hand must be bevelled off4 ,it requires a slight curve on the flat side2 so that1 if on a table1 each end would turn about #a_/h inch4 ,it is then a part of a very fine pitch screw1 in motion similar to a piece of slate jerked into the air1 the sole difference being due to the slight curve in the back1 which gives the screw motion1 in conjunction with the forward and rotatory motion given by the hand4 ,sheet-iron would not do1 as there would not be thickness to show the bevelled edge4 ,the boomerang was made in the form of a cross1 with four legs of equal length1 bevelled1 but it does not work as well as the regular form4 ,you must be careful in throwing it as it may strike you on return4 ,illustration3 ,fig4 #gb4 ,boomerang ,george asked his father to describe one and to explain its uses4 ,mr4 ,gregg told the boys that a boomerang1 as used by the aborigines of ,australia for a weapon or missile of war or in the chase1 consisted of a flat piece of hard wood bent or curved in its own plane1 and from #af inches to #b feet long4 ,generally1 but not always1 it is flatter on one side than on the other4 ,in some cases the curve from end to end is nearly an arc of a circle2 in others it is rather an obtuse angle than a curve1 and in a few specimens there is a reverse curve toward each end4 ,in the hand of a skilful thrower1 the boomerang can be projected to a great distance1 and made to ricochet almost at will4 ,it can be thrown in a curved path1 somewhat as a ball can be screwed or twisted1 and it can be made to return to the thrower1 striking the ground behind him4 ,it is capable of inflicting serious wounds4 ,it is very good of you1 father1 said ,fred1 to tell and show us all these things2 ,i'd like very much to have a very common1 every-day matter explained3 the theory of the pump4 ,the following questions also were asked by one or another on the same line3 ,what is the greatest distance or height a pump of any type can be placed away from the water8 ,is there any limit to the length of the delivery pipe to the tank8 ,what is the difference between a lift and a plunger or force pump8 ,is it the sucker of the pump that draws the water up1 or does it flow because the air being drawn out of the pump barrel and forced on the water outside1 causes it to flow into the pump8 ,mr4 ,gregg started in at once to give them the facts desired3 ,theoretically1 the greatest height a pump can be fixed above the water level depends on certain conditions3 the atmospheric temperature1 and the altitude the pump is to be fixed above the sea-water level4 ,the higher the temperature1 and the greater the altitude1 the less distance the height of the pump can be above the water4 ,the height to which water can be drawn from the source to the top of the bucket1 or under side of a piston or plunger1 when at the top of the stroke1 or what is termed the 'height of suction1' cannot reach more than about #cc feet when the pump is at the sea level4 ,if a tube about #cd feet long is immersed in a well1 and the air is extracted by means of an air pump at the upper so that a vacuum is formed1 the water will not rise in the tube until the air is expelled1 when it will not rise more than #cc feet1 even though there is a complete vacuum formed in the upper end of the tube4 ,the reason why the water will not rise in the tube higher than this1 is that the height of the water counterbalances the pressure of the atmosphere4 ,this height is the theoretically greatest height that water will rise in a suction pipe4 ,for the pump to discharge water1 it is necessary for the water to be in motion1 and to set and keep it in motion a portion of the water will rise1 due to the atmospheric pressure4 ,the shorter the suction pipe1 the more certain the pump is of being completely filled at every stroke of the pump handle4 ,the action of the pump is as follows3 ,the bucket on moving upward attracts the air1 so that the atmospheric pressure on the surface of the water in the well causes the water to follow the bucket up the suction pipe1 through the suction valve1 into the working barrel4 ,on the return stroke1 the suction valve will close1 the valve in the bucket will open1 and the water which before was under the bucket will pass through it to the top side4 ,when the bucket is again raised1 the water will be lifted through the delivery valve into the delivery pipe4 ,there is practically no limit to the height of lift1 which may be any height consistent with the strength of the pump and the available power4 ,the ordinary pump used for raising water to the level of the top of the bucket1 is termed a lift pump2 for raising water above this1 a force pump or a plunger pump must be used1 when the water is displaced by a solid plunger on its downward stroke1 when the quantity of water raised will be equal to the volume of the plunger4 ,this system may be repeated when water is to be lifted more than ordinary heights4 ,x ,,wall ,,making ,,and ,,plumbing ,a few evenings later1 ,mr4 ,gregg and his little family were gathered together on the river's bank1 watching the movements of a number of pleasure boats and launches1 when a good-sized tugboat came along and made quite a wash as she steamed past the ,gregg domain4 ,mr4 ,gregg noticed that this had actually carried down a portion of the bank near the new pier1 and he called ,fred's attention to it4 ,the two1 followed by ,george1 walked to the pier1 and1 to their alarm1 found that quite a piece of the bank had been carried away by the current1 the tides1 and the frequent wash of passing steamers4 ,this will never do1 said ,mr4 ,gregg4 ,we must protect the bank at this point1 or the water will soon undermine and demolish our pier1 for you see it is only near the landing where the bank shows signs of injury1 and it is as badly damaged on one side as the other4 ,this is caused by projection of the pier into the river1 which prevents the water from flowing in its regular course1 and causes it to rush into the angle formed by the junction of the pier with the bank1 thus cutting away the latter4 ,perhaps it will be best to build a sort of retaining wall against the bank for ten or twelve feet each side of the pier to prevent this rush of water from cutting away the earth4 ,if we had field stones enough on the ground1 it would be cheaper to use them1 though they would not make as good a 'job' as either cut stones or concrete2 since we haven't the stones1 we'll build it of concrete1 as you have some knowledge of that material1 and ,i will engage ,nick to help you4 ,illustration3 ,fig4 #gb;a4 ,retaining wall ,the next day ,mr4 ,gregg ordered ,portland cement and all the other materials required to build the wall1 and engaged ,nick1 who promised to come the following morning4 ,in the evening1 ,mr4 ,gregg had the boys in his den1 and explained to them how to go about constructing the wall4 ,he decided to have it built of concrete blocks about #ab #bd #ab inches1 to be faced with good1 strong1 cement mortar on the face and ends1 which would give the exposed wall a nice1 smooth appearance4 ,mr4 ,gregg explained that there must be a foundation of stone under the concrete1 formed by large bowlders or fielders1 laid as closely together as possible1 the joints filled in with smaller stones and1 when possible1 cement mortar1 to bind the whole into a solid mass--as shown by dotted lines in the illustration which he made on the blackboard4 ,the blocks for the work were to be cast in wooden moulds or forms1 which ,fred and ,george could easily make out of boards taken from the dismantled barn4 ,at the points where the wall was wanted1 the bank was about #h feet high from the bottom of the river1 and it was determined to make the wall #h feet high1 #b feet wide at the top and #c feet at the bottom1 with the batter on the water side1 the weight of the wall being #adj pounds per cubic foot4 ,it is always best to have the inclined surface on the side of the wall where the water will be4 ,the water at high tide rises to a level of #f feet above the base ,c ,d4 ,in designing such a retaining wall1 said the father1 for water one side1 and earth the other1 or determining its stability1 the principles generally followed may easily be worked out by ,fred1 or even by ,george4 ,taking the earth side first1 as shown in diagram ,fig4 #gb;a1 ,w ,c ,x1 angle of repose of earth to be retained--#cj degrees2 ,g ,c1 the line of rupture2 ,g ,c ,a1 the wedge of earth at #aab pounds per cubic foot to be accounted for1 the weight of which equals-- 7,,ga ,,ac7_/#b #aab lb4 7#d' #g #h'7_/b #aab lb4 #b1jec lb4 ,this will act at a point one-third the height of the wall ,h4 ,from ,h erect a perpendicular ,h ,i equal to #b1jec lb4 ,set out the angle ,h ,i ,j equal to angle of repose1 #cj degrees4 ,from ,h erect a perpendicular to ,a ,c1 cutting ,i ,j in ,j4 ,then ,j ,h equals the direction and magnitude of the weight of the earth acting on the wall4 ,produce ,j ,h through the wall toward the water side4 ,find centre of gravity of wall in ,k and the weight of the wall1 which in this illustration equals-- 7,,ab ,,cd7_/#b ,,ac #adj lb4 7#b #c7_/b #h_/a #adj lb4 #b1hjj lb4 ,from where ,j ,h produced meets a vertical line drawn through the centre of gravity1 ,k1 in ,l set of ,l ,n equal to #b1hjj lb42 make ,l ,m equal to ,j ,h2 complete parallelogram ,l ,m ,o ,n1 when ,l ,o equals resultant of earth and wall4 ,the magnitude and direction of ,p ,r can be found as in the first part of this article4 ,produce ,r ,p through the wall1 and from where it cuts the resultant ,l ,o in ,s make ,s ,t equal ,r ,p4 ,let the diagonal ,l ,o now be produced so as to make ,s ,v equal to ,l ,o4 ,complete the parallelogram ,s ,t ,u ,v1 when the resultant ,s ,u equals the combined resultant of earth1 water1 and wall1 and as it passes within the middle third it can be considered safe4 ,now1 boys1 said ,mr4 ,gregg1 ,i have not only told you how to build a retaining wall1 ,i have also told you how to make all the necessary calculations for designing it1 as the same figuring and diagraming1 on this principle1 will answer for any sea wall requiring like conditions4 ,i know you both understand figures and geometry enough to make such calculations1 if you are ever called upon to do so4 ,the next morning1 before the boys had finished their breakfast1 ,nick was on hand ready to go to work1 equipped with a pair of hip rubber boots which would enable him to wade in water two feet deep and remain dry4 ,fred and ,george were soon ready and ,mr4 ,gregg went out to tell them the proper way to commence4 ,the foundation was the first consideration1 so an examination of the site and was made1 the length of the proposed walls measured off4 ,while waiting for the tide to ebb to its lowest point1 ,nick and the boys busied themselves gathering up stones for the foundation and wheeling them to the point nearest where they were to be used4 ,after gathering all the stones thought necessary1 the question of making the moulds for the concrete blocks was considered1 and1 as the greatest bulk of the blocks would be simply blocks with square ends and square faces1 the moulds for these would be a box having inside dimensions of #ab inches deep1 #ab inches wide1 and #bd inches long4 ,these dimensions would then allow of blocks being made in the moulds that will contain exactly #b cubic feet4 ,the mixed concrete was dropped gently in the mould and lightly tamped so as to make it solid4 ,the mixture consisted of not less than #c of cement1 #e of sand1 and #g of very fine gravel or broken stone1 no piece being larger than a white bean4 ,it was mixed in the same manner and in accordance with the rules given for making concrete for the sidewalk in ,chapter ,i4 ,the mould should rest on a smooth block of stone1 wood1 or other suitable material1 while being filled and tamped1 and when full the surplus should be levelled off1 by a straight-edge--wood or iron--drawn over the top of the mould1 until all the surplus is removed4 ,the mould is then allowed to stand a little while until the concrete sets fairly hard1 when the mould may be removed4 ,to make it easy to take the block out of the mould1 the inside should be well sprinkled with neat cement before the concrete is put in1 and the box itself might be made slightly tapering to permit the block to move out easy4 ,this method1 however1 is not to be recommended1 as the blocks do not fit so well in a wall as when left perfectly square4 ,there are a number of devices for making moulds so that delivery of blocks may be easy4 ,one of the best is to hinge one corner of the mould with heavy hinges1 while the opposite diagonal corner is left loose but held in place by a strong hasp and staple4 ,when the box or mould is full and the block ready to remove1 the hasp is loosened1 the mould opens across at the two corners and frees the block4 ,should there be any holes or defects on the face of the blocks1 they can be filled with cement mortar made with #b of cement and #c of clean sand4 ,blocks of this size should season not less than #d or #e days1 to set hard before being used4 ,a portion of these blocks must have a bevel face on them to form the batter on the front of the wall4 ,there must also be a proper proportion of them having their ends bevelled to the batter of the wall1 to use as headers4 ,a header in brick1 stone1 or concrete1 is a unit1 or piece1 that is laid in the wall with its ends showing through on the face1 while a stretcher shows its whole length on the face of the wall4 ,other portions of brick or stone1 when built in a wall1 are called closers4 ,the batter on the blocks is formed by making one side of the mould lower than the other4 ,in this case1 the difference in the width of the sides of the mould would be #a-a_/b inches2 because the height of the wall being #h feet1 the blocks #a foot thick1 and the batter #a foot1 there would be a falling off on each block of #a-a_/b inches in order to have the top front of the wall #ab inches back from the bottom front4 ,the ends of the header blocks may be battered by placing in the ends of the mould a piece of wood #ab inches wide1 and the lower edge #a-a_/b inches thick1 and the top edge planed to a thin wire edge4 ,the end or section of the plank will then have the appearance of a wedge #ab inches long1 #a-a_/b inches thick on one end1 and tapered to nothing at the other end4 ,when the block is taken from the mould1 and the wedge piece removed1 the block will show the same batter on its end as the stretchers do on their face1 and they can be built in together without showing any difference in the slope1 if the work is carefully done4 ,nick1 who had had some experience in this kind of work1 found no difficulty in understanding the whole process4 ,at low tide he set to work to make a solid bed for the foundation1 while the boys handed him the stone and the prepared mortar as he required it1 so that before the tide rose one side of the stone foundation was ready to receive the concrete blocks4 ,during the interim between tides1 ,nick and the boys made the moulds1 prepared for mixing the concrete1 and got old timbers and lumber for a temporary scaffolding4 ,after the moulds were made and some concrete mixed1 ,nick began on the blocks4 ,it was not long before he had a sample1 which seemed all right1 and before he stopped quite a number of them were ranged on boards setting4 ,on the sixth day after it had been commenced1 the job was entirely finished4 ,the joints in the wall had been nicely pointed up with cement mortar by aid of a fine-pointed trowel4 ,the back1 or ground side of the wall was filled in with earth1 and danger to the pier was entirely removed4 ,that night ,mr4 ,gregg told the boys and ,jessie--who had watched closely the growth of the wall--quite a lot about ,portland cement and concrete1 which interested them very much4 ,portland cement as we have it now was unknown a hundred years ago1 but an ,englishman invented the method of making it and properly proportioning the various materials used4 ,fifty years ago there was scarcely any made in this country1 the little that was used being imported from ,england1 and later from ,belgium2 but now more of it is made and used in the ,united ,states than anywhere else in the world4 ,he pointed out that the building of the ,panama ,canal was made much easier and less costly because of cement1 and that the largest dam ever built had just been suggested1 to dam the ,mississippi near ,keokuk1 ,iowa4 ,this would be over #e1hjj feet long and nearly #dj feet high and from #be to #ce feet thick4 ,he told of the various big storage dams being built and contemplated by the ,united ,states1 in ,montana1 ,arkansas1 ,nebraska1 ,wyoming1 ,new ,mexico1 ,dakota1 ,texas1 and many other places1 at a cost of hundreds of millions of dollars--which never would have been attempted if concrete had not been available4 ,he also made mention of the great wall that now protects ,galveston from the ravages of the sea4 ,it is not many years since ,galveston was almost destroyed by tidal waves that caused an enormous loss of life1 and destruction of property amounting to over #ag1jjj1jjj4 ,the wall was built to prevent a recurrence of similar disasters4 ,it is #ag1ejc feet long1 #ag feet high1 and #af feet thick at the base4 ,another recent work is the enormous dam built by ,english engineers across the river ,nile at ,assiout1 about #bej miles above ,cairo in ,egypt1 which increases the area of good land some #cjj1jjj acres4 ,ancient ,babylon is again to blossom and become a beautiful country to live in1 for ,british engineers are laying out plans for building storage dams and irrigating canals in these now sandy and barren lands4 ,all1 or nearly all1 of these works and proposed works would never have been thought of1 if ,portland cement had not been in existence4 ,mr4 ,gregg1 after finishing his talk on concrete1 noticed that ,george had two fingers on his right hand tied up1 and on inquiry was told that ,george had his fingers hurt by a concrete block falling on them just as the retaining wall was being finished4 ,the father insisted on seeing the bruised fingers and found they were not badly hurt1 though the skin in one place was broken4 ,george explained that his mother had washed his hand1 dressed the wound1 and applied an antiseptic to it1 so that it was all right now and did not pain him4 ,you were wise to go to your mother and have your bruise attended to immediately1 otherwise you might have had something serious happen to you1 as lockjaw frequently comes from wounds of that kind1 if deep enough and not attended to immediately4 ,it is often said that lockjaw or tetanus is caused by a wound made by a rusty nail4 ,it is certainly bad to be wounded with a rusty nail--or any other rusty iron--and tetanus may follow2 but it does not follow because the nail is rusty1 but because the tetanus microbe that may be on the nail1 or on the skin when the wound is made1 is carried into a favourable place for development4 ,this tetanus microbe1 which has a long name1 is very plentiful and is scattered broadcast by every gust of wind4 ,it is a microbe of dirt1 and the ground and street abound with it4 ,its first home and breeding place is in the intestines of horses and other domestic animals1 but its greatest danger to the human family is when it gets into the blood by way of a wound4 ,cleanliness1 in this as in many other cases1 is both a preventive and a cure4 ,father1 said ,jessie1 ,i saw a very funny thing to-day while watching ,nick and the boys finish the wall4 ,the train across the river came to a standstill for some reason or other1 and1 as ,i was watching it1 ,i saw three puffs of steam go out of its boiler1 and a short time after ,i heard three loud whistles4 ,this seemed to me quite curious1 but while ,i was thinking over it1 there were three more jets of steam1 followed by three more 'toots4' ,how was it that ,i saw the toots before ,i heard them8 ,this is a question1 my dear1 that will require some little time and thought to answer properly4 ,in the first place1 you must understand that light travels very much faster than sound and that sounds do not reach you until some time has elapsed1 if you are a little distance away4 ,you see a flash of lightning1 and a little while after you hear the thunder2 and if you count #a1 #b1 #c1 in the ordinary way1 between seeing the flash and hearing the thunder1 you may be fairly satisfied the source of the thunder is well on to three miles away4 ,this1 of course1 is not exactly correct1 but approximately so4 ,every time you count one1 it stands for a mile4 ,according to science1 light travels #ahf1jjj miles a second1 while sound only travels at the rate of #a1jij feet per second at a temperature of #cb degrees ,fahrenheit1 or freezing1 its velocity being increased at the rate of one and one tenth feet per second for every degree above this temperature4 ,so you see light travels nearly a million times faster than sound1 and this accounts for your seeing the puffs quite a little while before you heard the 'toots'1 as you call them4 ,there are many curious and interesting things about light and sound which ,i'd like to describe to you sometime4 ,sound travels in dry air at #cb degrees1 #a1jij feet per second1 or about #agj miles per hour2 in water1 #d1ijj feet per second2 in iron1 #ag1ejj feet2 in copper1 #aj1cgh feet2 and in wood1 from #ab1jjj to #af1jjj feet per second4 ,in water1 a bell heard at #de1jjj feet1 could be heard in the air out of the water but #fef feet4 ,in a balloon1 the barking of dogs can be heard on the ground at an elevation of four miles4 ,divers on the wreck of the ,hussar frigate1 #ajj feet under the water1 at ,hell ,gate1 near ,new ,york1 heard the paddle wheel of distant steamers hours before they hove in sight4 ,the report of a rifle on a still day may be heard at #e1cjj yards2 a military band at #e1bjj yards4 ,the fire of the ,english1 on landing in ,egypt1 was distinctly heard #acj miles4 ,dr4 ,jamieson says he heard1 during calm weather1 every word of a sermon at a distance of two miles4 ,the length of the sound waves in the air is sometimes many feet1 while the length of the longest light wave is not more than 4#jjjjbff of an inch2 it is no longer a mystery why we can hear1 but cannot see1 around a corner4 ,the children were greatly interested by these familiar marvels and made their father promise that he would resume the talk some other evening and tell them about thermometers and barometers4 ,the late afternoon next day was taken up with an excursion on the ,caroline down the river to ,newark1 where ,fred induced his father to purchase a full soldering outfit1 as the boys wanted to try some plumbing and soldering work4 ,there had been a plumber at the ,gregg home nearly all that day doing repair work of various kinds1 and ,fred1 who had watched the workman1 concluded he could have made the repairs himself if he had had the proper tools4 ,an hour or two in the city1 then a pleasant sail home1 proved a fine ending for a day's labour4 ,the next day1 after school1 ,george and ,jessie assisted their mother making garden1 planting flowers1 trimming bushes1 and destroying weeds1 while ,fred gave the ,caroline another coat of varnish1 and finished painting his little workshop1 which now looked very snug and tidy4 ,he soldered up all the leaks in every kitchen utensil he found defective1 much to the delight of his mother and the maid4 ,fred found many things about the house wanting more or less attention1 so he determined to try to put them in order4 ,he discovered that to make a good job of soldering1 he must first make the metal to be fastened together1 perfectly clean and free from rust1 dirt1 or grease1 the parts around the leak being scraped bright and smooth4 ,he found some little difficulty in getting the solder to the exact place he wanted4 ,in the outfit his father bought him1 was not only a soldering iron1--which is not iron but copper--but a scraper1 a lump of solder1 a box of rosin1 a piece of chamois leather1 a bottle of muriatic acid1 and a piece of sal-ammoniac1 to be crushed fine and dusted over any surface that is to be finished bright4 ,fred had no trouble in soldering holes of small size in teakettles1 tins1 or such things as he could handle easily1 for the impaired portions could be placed in a horizontal position before him and the solder applied readily4 ,a leak in an upright water pipe in the shed1 however1 gave him a hard time1 for he could not get the solder either to run up hill or to stay on the place where it was put4 ,he got over this difficulty1 however1 by making a clay dam1 a tinker's dam--mixing clay until it was soft1 then winding a strip of it around the pipe just below the leak and applying the solder until the hole or crack was entirely covered1 when a good solid job resulted4 ,of course1 before applying any solder1 all the water was drained from the pipe1 and the defective part was thoroughly scraped4 ,when the work was done1 there was an edge of solder left projecting from the pipe1 which ,fred rasped away with a course rasp1 leaving just enough solder to cover the leak properly4 ,he then sandpapered the work and it looked almost as good as new4 ,it is easy enough to solder across the work when level1 even if the article being soldered is round1 because the metal can be worked across the top and down the sides2 but on the under side1 it may be necessary to make use of a clay dam4 ,a plumber's work covers a lot of things1 among which may be mentioned metal roofing1 wall flashings1 water-pipes of all kinds1 drain connections1 hot water and steam fittings1 hot-air and ventilation fittings1 stove and range settings1 and many other things connected in some way or another with the foregoing4 ,many times an offensive odour is noticeable in the cellar1 or near the line of drainage1 and it is often difficult to locate the source1 so that expensive excavations are made before the trouble is remedied4 ,plumbers and drainage men often use what is termed the peppermint test1 to find where the leakage exists1 and this is particularly suitable for the examination of existing soil pipes and drainage fittings4 ,this test consists in pouring a small quantity of oil of peppermint or other substance possessing a pungent1 penetrating1 and distinctive odour1 into the pipe or drain4 ,the defective pipe or joint is then located by the escaping odour4 ,it is very important that defects of this kind should be located and repaired immediately1 for odours emanating from drains or soil pipes carry with them germs of the kind most dangerous to human health and life4 ,some taps in the bath room and over the kitchen sink were not working freely1 and others were dropping a little4 ,fred1 after cutting off the water from the main1 unscrewed these and put new rubber washers in some1 wound cotton twine around the plugs of others1 and made the tight ones work easy by removing worn out washers and cut strings4 ,he also fixed the hydrants on the lawn in the same manner1 and made all the taps in and about the house work tightly and smoothly4 ,when ,mr4 ,gregg arrived home1 ,fred told him all he had done1 showing the tin pans and the leaky pipe he had soldered1 and he straightened up with pride at being told that he was already quite a plumber4 ,after tea1 the family went down to the river's bank and chatted awhile on home matters2 then shortly after the sun went down1 they adjourned to the lion's den4 ,now1 said ,george1 father will tell us about barometers and thermometers1 as he promised4 ,well1 said ,mr4 ,gregg1 ,i'm pleased to know you are so ready to listen to my talks1 and ,i hope you'll remember some of the facts ,i've been telling you4 ,there are many kinds of barometers1 but all are constructed about on the same principle1 and on the old theory that 'nature abhors a vacuum'4 ,there may have been some kind of an instrument that did service as a barometer in the early ages1 but we have no knowledge of it4 ,the instrument as we now know it had its beginning with ,galileo1 ,torricelli1 and ,pascal1 but was not perfected until about #afej4 ,good barometers require the greatest possible care in their construction1 and there ought to be two or more standing together as checks on one another in order to obtain correct results4 ,the mercury used must be pure and good1 free from all other substances and from air bubbles or films of air on the sides of the bulb4 ,simple barometers1 suitable for ordinary purposes1 can be easily made4 ,i will describe one1 and make a sketch of it on the blackboard4 ,illustration3 ,fig4 #gc4 ,simple barometer ,this simply consists of a wide-mouthed glass bottle filled with ordinary drinking water up to the point indicated by the letter ,a 7,fig4 #gc72 in this is dipped an inverted glass flask1 or an incandescent light bulb1 the extremity of the neck being allowed to dip just below the surface of the water4 ,the flask should be inverted quite empty during wet weather1 and as long as the atmosphere remains in a stormy condition1 no change in the water takes place2 but immediately the weather becomes finer1 the water will rise in the neck of the inverted flask1 and1 if a continuance of fine weather be probable1 will rise to the point indicated by letter ,b4 ,i have found this simple contrivance to give sure and early warning of the approach of rain1 and ,i need hardly remark that the principle upon which this little weather glass acts is exactly similar to that of the ordinary mercury barometer1 for the rise and fall of the water is due to the respective increase or decrease of atmospheric pressure4 ,by dividing the neck ,a ,b into six or eight divisions1 with the aid of a diamond or piece of flint1 and then marking the lines so cut1 with ink1 an approximate graduation of degrees of pressure may easily be obtained4 ,i show you a water barometer here1 7,fig4 #gd7 that is somewhat less hard to construct than the one ,i have already described1 as the parts are easier to obtain4 ,illustration3 ,fig4 #gd4 ,barometer ,it consists of a bottle1 containing water1 inverted and suspended with its mouth in the jar of the same fluid4 ,it is capable of roughly indicating atmospheric changes in a similar way to the mercurial barometer4 ,when the atmosphere becomes denser1 the greater pressure on the surface of the water in the jar causes it to rise in the bottle2 while with a lesser density it falls4 ,as with the mercurial barometer1 temperature makes a slight difference1 which1 strictly speaking1 should be allowed for2 but1 as the arrangement is of such a simple character1 this may be ignored4 ,water1 also1 is more subject to evaporation than mercury1 besides going stagnant1 and will require occasional changing and replenishing4 ,a barometer of a more scientific character1 and more presentable1 is1 ,i think1 within your range of skill1 and it may be made as follows3 ,obtain a glass tube1 closed at one end1 about two feet ten inches long and three eighths of an inch thick1 with a bore of about three sixteenth inch4 ,a circular turned wood box1 one and one half inches in diameter and one and one fourth inches deep1 is required for the cistern4 ,cut out the bottom and glue on instead a piece of leather1 sagging loosely4 ,then cut the lid in two1 and make an opening in the centre to receive the tube4 ,illustration3 ,fig4 #ge4 ,thermometer ,the mahogany base1 shown in two halves by ,a and ,b 7,fig4 #ge71 is #c feet #a inch long1 #c-c_/d inches at its greatest width1 #b inches at its least width1 and #c_/d inch thick4 ,make a groove down the centre to admit the tube1 and cut an opening #b inches square right through the wood at the round end4 ,glue at the back of this a circular piece of pine or cedar1 #c inches in diameter and #a_/b inch thick1 and screw a semicircular piece of the same thickness at the other end1 with a ring for hanging4 ,fill the tube by degrees with pure mercury1 boiling each portion1 as introduced1 by holding the tube in a nearly horizontal position over a spirit lamp1 taking care not to crack it by too sudden heating4 ,half fill the wooden cistern with mercury1 and when the tube is full1 place a finger over the end1 carefully raise it to a vertical position1 and lower the open end below the surface of the mercury in the cistern4 ,while some one holds the tube1 glue on the two halves of the box lid and seal up the opening round the tube with wax or cement4 ,then fasten the tube to the base with brass clips and screws1 and secure the cistern from shifting by gluing in wedges of wood4 ,a thumb screw1 with washer1 for regulating the height of the mercury1 is fixed at the bottom2 this presses on a cork washer glued to the leather of the cistern4 ,a hollowed hardwood boss is screwed over the top end of the tube1 and a hollowed circular turned boss of mahogany1 ,c1 is glued over the bottom4 ,the ivory or cardboard scale ,d1 is of inches and tenths1 from twenty-six and one half inches to thirty-one inches1 the distance being measured approximately from the surface of the mercury in the cistern4 ,a vernier having a scale of eleven-tenths of an inch1 divided into ten parts1 works in a slot on the scale and should be attached as shown at ,d4 ,before screwing on the scale1 fix its correct position by comparison with the standard barometer4 ,it is usual to place a small thermometer on the other side4 ,with regard to the thermometers1 it would be quite out of place here to discuss them at length1 or to offer you a scientific explanation of the principles governing their construction4 ,i may say however1 that1 as the barometer is intended to measure the different degrees of density of the atmosphere1 so the thermometer is designed to mark the changes in its temperature1 with regard to heat and cold4 ,the first thermometers1 so far as we know1 were made less than three hundred years ago1 and water1 spirits of wine1 or alcohol1 and oil were used to fill the bulbs1 in the order given4 ,it was the great ,halley1 of ',halley's ,comet' fame1 who first made use of mercury or quicksilver in these instruments1 because of its being highly susceptible to expansion and contraction1 and capable of showing a more extensive scale of heat4 ,it is owing to this quality of expansion and contraction that the degrees of heat and cold can be measured4 ,if you put your thumb on the bulb1 you will notice the quicksilver in the little tube gradually rise until it reaches the limit of the thumb's heat4 ,thermometers1 in this and nearly all ,english-speaking countries1 make use of the ,fahrenheit scale1 which is different from those used in some other places2 and this often causes trouble and annoyance4 ,the scale of ,reamur prevails in ,germany4 ,he divides the space between the freezing and boiling points into #hj degrees4 ,france uses that of ,celsius1 who graduated his scale on the decimal system4 ,the most peculiar scale of all1 however1 is that of ,fahrenheit1 the renowned ,german physicist1 who1 in #agad or #agae1 composed his scale1 having ascertained that water could be cooled under the freezing point without congealing4 ,he1 therefore1 did not take the congealing point of water1 which is uncertain1 but composed a mixture of equal parts of snow and sal-ammoniac1 about fourteen degrees ,r4 ,this scale is preferable to both those of ,reamur and ,celsius1 or1 as it is called1 ,centigrade1 because3 7#a7 ,the regular temperature of the moderate zone moves within its two zeros and can1 therefore1 be written without or -4 7#b7 ,the scale is divided so finely that it is not necessary to use fractions whenever careful observations are to be made4 ,these advantages1 although questioned by some1 have been considered so weighty that both ,great ,britain and ,america have retained this scale1 while nations on the ,continent of ,europe use the other two4 ,the conversion of any one of these scales into another is very simple4 7#a7 ,to change a ,fahrenheit temperature into the same given by the ,centigrade scale1 subtract #cb degrees from ,fahrenheit's degrees and multiply the remainder by #e_/i4 ,the product will be the temperature in ,centigrade degree4 7#b7 ,to change from ,fahrenheit to ,reamur's scale1 subtract #cb degrees from ,fahrenheit's degrees and multiply the remainder by #d_/i4 ,the product will be the temperature in ,reamur's degrees4 7#c7 ,to change a temperature given by the ,centigrade scale into the same given by ,fahrenheit1 multiply the ,centigrade degrees by #i_/e and add #cb degrees to the product4 ,the sum will be the temperature by ,fahrenheit's scale4 7#d7 ,to change from ,reamur's to ,fahrenheit's scale1 multiply the degree on ,reamur's scale by #i_/d and add #cb degrees to the product4 ,the sum will be the temperature by ,fahrenheit's scale4 ,a handy table can easily be figured out from the data given4 ,mr4 ,gregg concluded his conversation for the night at this point1 but promised to take it up again the first available evening4 ,two or three nights afterward it was very wet and dreary4 ,the boys and ,jessie were called into the den by ,mr4 ,gregg1 where a brisk fire1 made of limbs and branches gathered by the boys1 was burning in the little fireplace1 and the room looked bright and cheerful4 ,the young folks all drew up around the fire to listen4 ,i have so many things to talk to you about1 said he1 that ,i scarcely know where to begin2 however1 ,i promised to tell you something concerning springs1 so ,i will make these useful contrivances my theme to-night4 ,illustration3 ,fig4 #gf4 ,car-spring ,there are many kinds of springs1 but ,i will only talk of steel or other metal springs2 and even then must limit myself to a few4 ,the carriage or laminated spring is probably the most in use1 as it is an important factor in the construction of all classes of railway trucks and carriages1 locomotives1 automobiles1 road carriages and light wagons of all kinds4 ,these are also much used in the manufacture of invalids' chairs1 children's perambulators1 and many other things4 ,the springs used in the construction of the largest locomotives are big affairs and often weigh over #ejj pounds4 ,these are bearing springs and carry the whole weight of engine and boiler4 ,there are1 of course1 a number of these springs to each engine4 ,springs on the coaches and carriages are somewhat lighter and more flexible than those on the heavier trucks4 ,the double spring1 shown at ,fig4 #gf1 is known in railroad parlance as a 'draw-spring4' ,one of these is secured at each end of the car1 and used to attach or couple the cars together1 or to attach the engine to the train1 the object being to lessen the bump or impact of the blow when the engine and cars come together4 ,the effect is the same when the engine starts a train2 the springs in the first car draw out1 then the springs on the second car do likewise1 and this causes the load of the whole train to fall on the engine gradually1 a matter of great importance in railway economy4 ,if it were not for bearing springs on the trucks and carriages1 it would be almost impossible to use railroads for passenger traffic or for carrying fine goods1 as the jolting and pounding on the iron rails would shake things to pieces1 destroy the carriages1 and pound the roadbed and bridges to bits in a very short time4 ,now1 by the aid of steel springs1 you ride in a ,pullman as smoothly almost as in a boat1 so you see how useful springs are to mankind4 ,illustration3 ,fig4 #gg4 ,cross-bow spring ,there are many kinds of bearing springs1 but all are built in the same manner1 of steel leaves1 made of different dimensions to suit conditions4 ,as you will see in the diagram1 the sheets of steel are laid over each other1 like the scales of a fish1 and made shorter as they approach the top4 ,all the leaves are fastened together by having an iron buckle driven onto the middle1 as shown1 while hot1 and when this cools1 it shrinks and clasps the whole so tight it cannot be taken off until heated or cut4 ,i could tell you of many other kinds of springs--watch springs1 gun springs1 trap springs1 spiral springs--used for various purposes1 but ,i will end this subject by describing to you something you can make for yourself1 if you wish2 namely1 a cross-bow1 which is very simple4 ,i make on the blackboard a diagram1 7,fig4 #gg71 with ,a representing the stock1 #e feet long2 ,b1 the bender1 #f feet long1 which should be made in four pieces4 ,the front piece should be #c_/d inch thick1 the three inner pieces #a_/b inch thick4 ,c are brass ferrules to keep the leaves of the bender from shifting2 ,d the string1 which should be very strong4 ,the bender should be cut out of straight well-seasoned ash1 rock elm1 or hickory4 ,instead of brass ferrules1 strong brass or copper wire can be used1 properly twisted at the joints4 ,illustration3 ,fig4 #gh4 ,gyroscope ,the gyroscope has become quite famous of late1 because of its having been employed as a steadier for the monorail car1 and proposed as a regulator or governor for aeroplanes1 so that ,i think it will not be amiss to tell you that a study of this toy is well worth any time and labour you may spend on it4 ,there are great possibilities within this little instrument and its applications4 ,i do not intend dealing with its principles1 or with rotation problems generally1 as they would1 ,i fear1 be beyond your present comprehension1 but ,i will confine myself to describing the toy and showing you how it can be made1 though it would be much cheaper to buy one from a dealer4 ,the instrument consists of a ring of brass or other metal1 like a curtain ring1 and a smaller brass ring attached to a thick disc of white metal1 or a metal disc with a thickened rim1 as shown in ,fig4 #gh4 ,this disc is securely fixed to a metal pin1 which is passed through two holes in the outer brass ring1 and at one side a small rounded nut or ball of brass is screwed on the outer ring4 ,the metal disc is at right angles to the outer ring4 ,if a cord is wound several times round the metal pin1 the outer ring held in the left hand1 the pin and metal disc will revolve at a very high speed1 while the outer ring remains stationary4 ,the gyroscope can be placed on the knob1 and while the disc is revolving the outer ring can be placed at any angle1 and will remain stationary4 ,it is also possible to balance it at any angle on the top of a support1 such as the tip of a stick4 ,,part ,,ii ,,everyday ,,machines ,i ,,some ,,practical ,,advice ,some of our inventions and some of our discoveries are of comparatively recent date1 but most of them had their beginnings centuries before historical times1 as many of our greatest inventions are the result of gradual growth and development4 ,the early discovery1 by some unknown persons or persons1 of the making of bronze and the hardening of it1 led up to stone and woodcutting1 perhaps to the breaking-up and smelting of iron ore1 and the extraction of the metals4 ,this again opened the way for the making of steel1 a discovery that placed in the hands of man a source of power which enabled him to overcome many natural difficulties4 ,one improvement led the way to another1 and made other improvements possible4 ,take locomotives and steamboats for instance4 ,the making of a raft1 no doubt1 suggested the canoe1 and this led to the built-up boat1 and the ship4 ,the paddle and the oar doubtless led up to the sidewheeler1 and the scull to the propeller4 ,the crude steam engine of ,hero very likely suggested the steam engines now in use1 and this new power rendered it easy for ,stephenson and ,fulton to perform their work2 but1 if either of these inventors were to come back to the earth and examine the great steamers of to-day1 or the perfect and powerful locomotives now in use1 they would be surprised to think that the present tractable monsters1 were the outgrowth of their early efforts4 ,in the same manner may be traced the same gradual growth in all the arts and sciences2 for step by step1 in every department of life1 have completeness and perfection come to us4 ,it is not yet one hundred years since ,congreve invented or rather completed the invention of the ,parlor match1 called in his day1 the ,lucifer match4 ,this grand achievement was accomplished after many failures in the efforts of chemists for ages4 ,the perfection of the match was a great blessing to humanity1 as the old methods of making a light or fire were tiresome and very uncertain4 ,so it is with many of the blessings we enjoy to-day3 they are simply the results of the struggles of many unknown minds1 the threads of which were gathered up and pieced together by one master mind1 so as to be made useful and profitable to mankind4 ,in the early and middle ages1 the inventor was looked upon as a wizard1 a sort of inferior demon1 or1 at best1 an uncanny kind of man1 and a proper subject for the stake4 ,when1 by superior wisdom and skill1 he invented some machine or device1 or discovered some new and better method of accomplishing a useful end1 he was at once looked upon as a necromancer in league with his ,satanic majesty1 and1 therefore1 unfit to associate with or be recognized as a ,christian4 ,history records many instances of inventors and progressive men being persecuted--and executed--because of their having discovered or invented something which would interfere with some vested or imaginary rights4 ,the new inventions must be destroyed or put away out of sight and hearing1 and the most powerful influences were employed to bring about this result4 ,the stories told of ,friar ,bacon1 ,papin1 ,crompton1 and hundreds of other inventors1 give us a few of the reasons why so little progress was made in the arts and sciences previous to the sixteenth century4 ,down to a period within the past few years the term invention has been considered almost synonymous with the word chance4 ,an inventor1 was a lucky individual1 who had happened to hit upon some new idea1 not so much by his own great ability as by good fortune1 similar to that which brings success to the purchaser of a lottery ticket4 ,in many cases this was really the true state of affairs4 ,men who experimented in various mechanical pursuits often stumbled upon results1 which they perceived to be useful and valuable1 and1 if they protected the invention by patent1 they often became wealthy4 ,at the present time this meaning of the word invention must be greatly modified1 if not altogether abandoned4 ,the law which controls the action of the forces of nature is becoming so well understood among all classes of mechanics that chance invention1 in the early sense of the term1 has almost become an impossibility4 ,success can be assured only to the man who has tried to win it by the acquirement of the necessary knowledge1 to be obtained by steady application and hard study4 ,in the pursuit of discovery1 the old saying1 knowledge is power1 never has had more force than when applied to unravelling the tangled web of nature's mysteries4 ,science1 says ,lord ,brougham1 is knowledge reduced to a system4 ,a man may have a lifetime of practical experience and amass a fund of knowledge of great use to himself1 but entirely unavailable for others4 ,but if his experience be combined with that of other men and systematized into a regular order1 it becomes part of the science of that branch of industry1 and although the person himself may have a profound contempt for science and theory his work may be quite scientific4 ,ignorance1 in the past centuries1 was another great factor in preventing mechanical progress4 ,new machines and labour-saving devices were looked upon by the great mass of workers as contrivances designed to deprive them of the means of making an honest livelihood1 and this point of view caused the people to smash and burn many machines that had cost great labour and expense to the unfortunate inventor4 ,but1 as public schools became more numerous and learning increased1 the way of the inventor became smoother4 ,the more enlightened nations encouraged inventors and inventions1 and now our country has on its statute books laws for this purpose1 the most liberal in the world4 ,the opportunities for obtaining mechanical and scientific knowledge and technical instruction are now so many and so easy of access that inventors have but little trouble in acquiring the data and facts essential to their purposes4 ,the earliest students had nothing but their own observations and experiences to build on1 and even as late as the eighteenth century1 men had to grope in the dark for the data required to carry out their ideas4 ,a brief examination of the early treatises on mechanics and the rude illustrations in the works of ,leopold1 ,amoutons1 and ,desaguliers will reveal the germs of many modern machines4 ,the inventor of to-day1 however1 must proceed by a different path from his predecessor1 if he expects to succeed in the present advanced state of mechanical arts4 ,the demonstration of the mechanical equivalent of heat1 the discovery of the correlation of the physical forces1 and the development of the sciences of thermo-dynamics have furnished powerful weapons for the advancement of mechanical science1 and he who does not use them is at a woeful disadvantage in the fight4 ,there is no royal road to success for the inventor1 and ,i hope you will always bear this in mind when attending to your studies1 for you must remember that it is nearly always necessary to use formul and symbols to express relations1 which are hardly within the range of words1 and often a combination of data obtained from different sources may be used to derive entirely new relations4 ,it is here that invention1 in the modern sense of the term1 comes in to hold a place midway between theory and practice1 and may be properly called a science4 ,,the ,,laws ,,of ,,gravitation ,suppose a one-pound weight is suspended by a string3 there is a tensile stress in the string1 varying slightly at different parts of the earth1 but always the same at the same place1 say1 ,newark1 for the variation is very slight within a pretty wide area4 ,if we take a spring balance and graduate it in pounds at ,newark1 such a balance will accurately indicate forces in pounds wherever it may be used4 ,the stress produced in a string carrying a one-pound weight at ,newark is the unit of force4 ,if the string with its weight is hung from a nail1 the nail is pressed on its upper side with a force of one pound4 ,the same pressure may be produced by pushing the nail downwards from above1 using a short piece of stick2 in such circumstances1 the stick bears a compression stress of one pound4 ,this is a good1 common-sense definition of force1 though it does not by any means cover the whole subject4 ,the word force is used in a different sense by persons who speak of the force of gravity4 ,when a one-pound weight is suspended by a string1 as stated in the foregoing1 the attraction between the mass of the weight and the mass of the earth is balanced by the stress in the string4 ,we can double the stress by doubling the weight1 and in this way1 by adding weights1 we can make the force of gravity very great4 ,but the force of gravity is spoken of as an invariable thing1 and it is said to be equal to #cb 7roughly74 ,if any weight whatever be allowed to fall freely 7for reasonable heights and neglecting the effect of the resistance of the air7 it will be found that at the end of the first second it will have a velocity of #cb feet per second2 at the end of the second second it will have a velocity of #fd feet per second2 and generally at the end of any number of seconds its velocity will be #cb1 and the rate of increase of velocity 7acceleration7 is #cb feet per second1 all of which has been previously explained4 ,it is found convenient to call this acceleration gravity--it is inaccurately called the force of gravity1 it varies at different places on the earth4 ,it is usual to designate the acceleration by the letter g1 and we speak of the g1 or gravity1 of the place4 ,this seems to cover the point of inquiry completely4 ,the subject of specific gravity is a far-reaching one1 and includes the testing of liquors for revenue purposes and many other things of a scientific nature2 but when we speak of specific gravity in an ordinary way we mean the comparative weight1 bulk for bulk1 of water at a certain temperature4 ,the specific gravity of a substance like coal can be ascertained experimentally4 ,by means of a specially adapted and delicate balance1 the sample of coal is first weighed in the ordinary way1 after which it must be weighed suspended in a vessel of water4 ,weighed in water1 it will be found the coal does not weigh so much4 ,if the loss of weight1 or the difference between the first and second weighings be taken1 and the first weighing divided by this loss of weight1 we obtain the specific gravity of coal4 ,for example1 suppose a sample of coal weighs in the ordinary way #bj ounces1 and in the water only four ounces1 showing a loss of weight of #af ounces4 ,divide #bj by #af1 and we get the specific gravity of the sample of coal1 viz41 #a4be4 ,the use of specific gravity is of great importance in mining1 with regard to analysis of the minerals worked1 for with a class of coal having the same relative composition1 qualities1 and calorific power per ton of coal employed for different purposes1 yet having a higher specific gravity1 the room required for storage or transport will be less4 ,this is an important factor1 where there is limited space1 as in depots and naval vessels4 ,it is also employed in the arts and industries for many purposes1 and is particularly useful to workers in precious metals1 as the amount of alloy or baser metal may be determined by it that have been used in the manufacture of jewellery1 plate1 and similar articles4 ,to put it briefly3 ,specific gravity is the ratio of the heaviness of any substance to that of water4 ,the specific gravity of water is taken as unity1 and that of any other substance is expressed as a decimal4 ,tables of the weight and specific gravity of substances can be found in any good hand-book of engineering4 ,,how ,,to ,,adjust ,,sewing ,,machines4 ,sewing machines often get out of order1 and it is not always that an expert is at hand to adjust them1 so a few general observations on the subject of these household machines may prove useful and interesting to every one who is at all mechanically inclined4 ,there are several distinct types of machines1 but we shall confine our remarks to the ,singer vibrating shuttle1 the hook shuttle types1 and one or two others4 ,to secure a perfect stitch in the vibrating shuttle machine1 and to keep it from puckering thin goods1 such as ,japanese silks1 muslins1 and voiles1 though possible1 is difficult4 ,success depends entirely on the careful fitting of parts and the skilful adjustment of the machine to the particular fabric4 ,in the first place1 it is essential that a machine should work quite freely1 a point not of such great importance if it is used for rougher classes of work4 ,machines used for domestic purposes1 like the ,v4 ,s4 7vibrating shuttle71 often stand unused for weeks together1 so that the oil thickens and makes a machine run somewhat heavily and unevenly4 ,this may indirectly affect the regularity of the tension1 especially with thin goods4 ,therefore1 it is important to keep a machine clean and regularly oiled4 ,important parts are often overlooked during the operation2 in fact1 many users of machines do not know how nor where to oil one properly4 ,therefore ,figs4 #gi and #hj will be helpful1 as they show the location of oil holes and parts to be oiled1 and the illustrations will serve as a guide to other machines4 ,in these figures1 it will be seen that there are a number of parts to oil which could very easily be overlooked4 ,when a machine has been unworked for a length of time1 the application of a little paraffin will cleanse the parts which should afterwards be oiled thoroughly with a good quality of machine oil4 ,the shuttle raceway1 where the shuttle works1 should be wiped out with an oily rag4 ,any lint or dirt which has accumulated inside the shuttle at the nose end should be withdrawn1 as such might retard the unwinding of the bobbin4 ,it is imperative that the cotton should pull evenly1 that is1 free from jerks2 this refers to the upper as well as to the lower tension4 ,illustration3 ,fig4 #gi4 ,section showing oil holes ,for silk and similar materials1 best results can be obtained if fine cottons are used4 ,numbers #fj1 #gj1 or #hj would be preferable to ,no4 #dj4 ,a good quality of fine silk is even better4 ,it must be remembered that when working on thin silk1 say two thicknesses1 a coarse cotton cannot be locked centrally4 ,fine cotton will need a fine needle1 which necessitates a fine hole needle plate4 ,illustration3 ,fig4 #hj4 ,action of shuttle in the race ,if1 after the foregoing points have been attended to1 the machine runs easily1 the parts fit properly1 there is no end play to the upper shaft and the cottons pull evenly1 yet the tensions are erratic1 attention should be given to the loop as it draws off the shuttle heel4 ,in machines of the ,c4 ,b41 ,o4 ,s41 and especially the ,v4 ,s4 class1 there is a tendency for the loop to hang on the heel of the carrier1 or to become trapped between the shuttle and the carrier heel4 ,in the two former types of machines1 the heel of the carrier should be rounded so as to induce the cotton to pass off as freely as possible4 ,sometimes it is necessary to time the shuttle a little later1 that is1 put the carrier back a little to allow the loop to draw off more in a line with the hole in the needle plate4 ,in ,v4 ,s4 machines the carrier is already rounded off at the heel4 ,by referring to ,fig4 #hj1 the action of the shuttle in the raceway can be seen1 which is from ,a to ,b4 ,the shuttle1 having just entered the loop1 is about to move to ,b4 ,this movement can be regulated by an eccentric screw and nut 7,fig4 #hj74 ,when a machine has been taken to pieces and cleaned1 this screw is not always replaced to the best advantage4 ,if the shuttle moves too much toward ,b1 the loop is carried by the heel of the carrier1 and1 at the same time1 the shuttle cotton1 by bearing tightly on the needle plate1 pulls the shuttle toward the carrier heel1 thus making it difficult for the loop to release itself4 ,more tension is applied1 perhaps more pressure is put on the take-up spring1 yet the uneven tension is not overcome1 and owing to the softness of the fabric1 it is drawn up or puckered4 ,the remedy is to turn the screw ,c 7,fig4 #hj71 until the carrier is in a position to allow the loop a free exit4 ,for such soft materials as mentioned it may be necessary to slacken both tensions4 ,it should be remembered that the upper tension is generally somewhat tighter than the under one1 and this should be a guide to the adjustment of the latter1 according to the fabrics to be stitched4 ,to prevent puckering when the tensions are correct1 reduce the pressure of the foot by loosening the thumbscrew ,d 7,fig4 #gi74 ,use a small size stitch--set the feed so that the teeth are just above the needle plate4 ,do not have the teeth too sharp1 and if necessary1 rub off the knife edge with ,f emery-cloth4 ,make the foot to bear squarely on the needle plate1 and the feed square to the presser foot4 ,round off all sharp edges from the under side of the foot1 especially the back edge4 ,special feeders are made for silk goods in machines used for factory work1 which overcome the difficulty of puckering4 ,by attention to the foregoing instructions1 a machine should work easily1 especially if the fabric is slightly pulled from behind the pressure foot4 ,in ,c4 ,b4 machines1 attention should also be given to the loop as it passes over the bobbin case and off the stop pin1 it being necessary sometimes to round off the latter4 ,if the tension spring screw projects too high or is rough1 it may occasionally catch the cotton4 ,the machine shown at ,fig4 #ha is of the ,rotary ,hook--zigzag type4 ,its uses are similar to that of the oscillating shuttle type1 but its construction is rather more complicated4 ,illustration3 ,fig4 #ha4 ,rotary hook--,zigzag type ,illustration3 ,fig4 #hb4 ,rocking frame ,the machine may be said to consist chiefly of an upper and a lower shaft1 each having two cranks4 ,in the vertical portion of the arm are two links which connect the shafts1 causing them to work in unison with each other4 ,the upper shaft gives motion by means of a cam and link to the needle bar and take-up lever2 while the lower shaft1 by means of three gear wheels1 gives the rotary movement to the hook or shuttle1 and by an eccentric cam and segment lever the necessary motion is given to the feed or stitch mechanism4 ,figure #hb shows the rocking frame into which the needle bar is fitted at ,a and ,b1 while1 at ,c and ,d1 it is recessed to receive the taper ends of two screws1 which pass through the face plate end of the machine arm4 ,these screws are held secure by lock nuts1 so screwed in as to allow the frame to rock freely4 ,a ball-headed screw is fitted at ,e1 to which is fastened a connection rod extending to a switch lever situated about the centre of the arm4 ,this lever1 by means of a cam movement1 gives the vibrating motion to the needle bar1 which can be regulated according to the relative position of the connection rod and lever4 ,when the rod is at the bottom of the lever1 a wide throw is obtained4 ,by raising the rod a narrower throw is given1 and if raised to the position shown in ,fig4 #ha no vibration will be given to the needle bar4 ,the needle bar can be raised or lowered by loosening the screw that secures it to its link collar1 which will be better seen by removing the face plate4 ,most needle bars have two marks upon them1 and they should be set as follows3 ,remove the face plate1 and turn the hand wheel ,f 7,fig4 #ha7 toward you until the needle bar link has reached its lowest point of travel4 ,loosen the set screw of the needle bar collar1 and set the needle bar so that its highest mark will be just level with the bottom of the rocking frame 7,fig4 #hb74 ,then tighten the set screw1 give the hand wheel a spin round1 and again examine the position of the mark when the needle bar has reached its lowest point of travel1 to make sure that no mistake has been made4 ,of course1 it is necessary when parts are badly worn to set the needle bar a trifle lower1 but this can be done after the foregoing rule has been adopted and proved a failure4 ,in case of any unnecessary looseness in the middle bar or any of its connecting parts1 they should be taken out and new parts fitted4 ,the position of the needle may be altered to the right or left by loosening the screws ,g and ,h 7,fig4 #ha71 and adjusting the connection rod4 ,care should be taken not to set the connection rod too low down1 or the needle may strike on the needle plate and cause trouble4 ,illustration3 ,fig4 #hc4 ,section showing face plate removed from machine ,fig4 #hc shows the face plate removed from the machine arm1 ,a being a tension release lever4 ,when the presser foot is lifted to its highest position1 the end of the lever goes between the tension disc1 thus releasing all tension1 so that materials can be taken from the machine without drawing slack cotton1 or putting any unnecessary strain on the needle4 ,when the presser foot is lowered1 this lever should withdraw itself from the disc1 thus allowing the proper tension to be put on the cotton4 ,in some machines the withdrawal of this lever depends on a stud screw1 fastened to the needle bar and projecting through the face plate4 ,in the downward course of the needle bar this stud screw touches a spring1 and causes the lever to trip backward4 ,should the spring become strained1 or the stud screw become raised up a little1 the release lever may remain between the disc and cause trouble4 ,sometimes it is necessary to bend the lever forward or backward to ensure its proper action4 ,illustration3 ,fig4 #hd4 ,hook ring ,illustration3 ,fig4 #he4 ,hook guide ,illustration3 ,fig4 #hf4 ,hook driver ,the hook or shuttle is rotary in motion4 ,the hook 7,fig4 #hd71 is fitted to a ring1 which is fixed to the hook guide 7,fig4 #he7 by means of three small pins1 and it is prevented from falling out by a steel cap secured with two screws and springs4 ,the hook is carried round by a driver 7,fig4 #hf74 ,much depends on the hook1 driver1 and hook guide1 so that a little detailed information is necessary4 ,the hook driver must be a perfect fit in its bearings and free from sharp places where it comes in contact with the hook4 ,the body of this driver is generally hardened1 but the prong ,j 7,fig4 #hf7 is left soft so that it can be bent to meet requirements4 ,when a machine is stitching1 the hook driver rotates1 and the prong ,j draws a given amount of slack cotton from the bobbin case4 ,the farther this prong stands out1 the more slack cotton it draws off the bobbin4 ,the prong may be bent inward1 as shown by the dotted lines1 but care must be taken not to drive it in so far as to allow the needle when descending1 to strike on it1 or to deviate from its true vertical position4 ,points ,k and ,l fit between the nose and neck of the hook1 while ,m comes against the heel4 ,the hook is driven alternately by points ,k and ,m4 ,when the hook is just entering the loop formed by the needle1 it 7the hook7 is being driven by the driver wheel or ,m1 and an opening is being made between point ,k and the hook nose for the free passage of the cotton4 ,when the loop is being drawn off the hook by the take-up lever1 the hook is driven by point ,k1 and an opening is made between ,m and the heel of the hook for the exit of the cotton4 ,there must always be sufficient clearance at points ,k1 ,l1 and ,m for the cotton or thread being used4 ,as the heel of the driver ,m wears1 the space at ,k will be reduced4 ,sometimes this can be remedied by bending the driver in at ,m1 by giving it a blow with a hammer1 placing a brass punch at ,m1 but this should not be attempted if the driver is very hard4 ,there is a means of adjustment provided in the hook guide 7,fig4 #he74 ,this part is held in position by two set screws ,n and ,o4 ,at the left of ,o is a small adjusting screw ,p4 ,supposing there is not sufficient space at point ,k 7,fig4 #hf71 for the cotton to pass1 loosen the screw ,o 7,fig4 #he71 and slightly tighten the screw ,p4 ,this will tilt the hook guide and give more space4 ,should the screw ,p be turned in too far1 the point ,l 7,fig4 #hf71 will be brought in contact with the narrow part of the hook near the neck1 and this will impede its freedom1 so that if allowed to run at much speed1 the probable result will be the breaking of the hook off at the neck4 ,this should be noticed in fitting a new hook1 as the adjusting screw ,p 7,fig4 #he7 will in all probability require loosening4 ,the screws at ,n and ,o1 however1 must be kept quite tight4 ,at each side of ,n is a small screw hole4 ,the screws which fit here are for adjusting the hook closer to or farther from the needle4 ,as an example1 supposing a very fine needle has been used in the machine1 and it is now required to take a very coarse one on account of the thick material to be stitched1 the hook in all probability would strike the needle1 indicating that the hook guide requires moving back a little4 ,to do this1 loosen the two small adjusting screws and tighten the set screw in ,n4 ,afterward try the set screw in ,o to ascertain if it is secure4 ,in this way1 the hook is thrown farther from the needle4 ,loosening the screw at ,n1 and tightening the adjusting screws1 will bring the hook forward4 ,if the hook stands too far from the needle1 it is likely to miss the loop4 ,the hook nose must be well pointed and perfectly smooth1 roughness or sharpness removed from any part of the hook over which the cotton passes during the formation of a stitch4 ,hook rings are made in three sizes1 numbers #a1 #b1 and #c4 ,number #a is for a new hook1 numbers #b and #c are for fitting as the hook wears4 ,no matter what size of ring is used the hook must have perfect freedom4 ,sometimes the three pins in the guide draw the ring1 and cause the hook to bind4 ,it is best1 therefore1 to fix the ring to the guide1 and then test the hook4 ,if it is at all tight1 grind it on the rim by means of an emery wheel or a grindstone4 ,if neither is available1 use number #a or number #a-a_/b emery cloth first1 finishing with number #jj emery cloth4 ,it is better to have the hook a little loose1 even sluggish1 than too tight4 ,the timing of the hook will be dealt with later on4 ,illustration3 ,fig4 #hg4 ,bobbin case ,illustration3 ,fig4 #hh4 ,bobbin case in position ,illustration3 ,fig4 #hi4 ,bobbin in position in bobbin case--,method of threading ,the bobbin case 7,fig4 #hg71 fixes to a stud in the centre of the hook4 ,it is held in position1 that is1 kept from revolving with the hook1 by means of a stop pin1 ,q1 fitting between a holder4 ,the tension is obtained by a spring1 ,r1 which is regulated by turning a small screw1 ,s1 to the right to tighten and to the left to loosen4 ,fig4 #hh shows the bobbin case in position1 with the holder raised ready for taking it out of the machine4 ,fig4 #hi shows the bobbin in position in the bobbin case and method of threading1 and ,fig4 #ia1 the direction the cotton should draw off the bobbin when it is in the machine4 ,it will be noticed that the cotton pulls in the opposite direction to which the hook travels1 as shown by an arrow in ,fig4 #hh4 ,the bobbin case holder 7,fig4 #ia71 should prevent the bobbin case from revolving with the hook4 ,as parts wear1 the bobbin case is liable to slip past the holder1 causing the cotton to be stranded and broken4 ,when such is the case the holder should be bent as shown by 7,fig4 #ib71 but it must not fit so tightly against the bobbin case as to cause the cotton to become trapped4 ,the holder is held rigid by means of a catch and spring ,t 7,fig4 #hh74 ,should the catch or holder become worn1 fit new parts by driving out the pins ,u and ,v4 ,any sharpness or roughness on the forked part of the holder should be removed4 ,should the stop pin ,q 7,fig4 #hg7 become loose1 it should be soldered and well cleaned with an emery cloth4 ,the centre tube of the bobbin case should also be kept quite firm4 ,should it become loose1 place it over some hard substance1 rivet it until tight1 and thoroughly smooth with very fine emery cloth4 ,illustration3 ,fig4 #ij4 ,direction cotton should draw off ,illustration3 ,figs4 #ia and #ib4 ,bobbin case holders ,illustration3 ,fig4 #ic4 ,take-up spring ,the take-up spring 7,fig4 #ic7 is attached to the face plate1 and is shown in position in ,fig4 #hc4 ,replace a new one as follows3 ,first take out the set screw ,w 7,fig4 #ic71 and remove the complete thread controller from the face plate4 ,then take out the screw and withdraw the old spring4 ,place the ring part of the new spring in the recess between plate ,y and back plate ,z1 and replace the screw ,x1 being careful not to get the spring fastened under the screw head4 ,this done1 fix the spring and other parts on the face plate4 ,a small barrel with a slot in it receives the coiled portion of the spring4 ,see that the part of the spring that is turned in enters the slot in the barrel1 then replace the screw ,w1 but before tightening this screw1 see that the hooked part of the spring ,a rests on the regulator ,b1 which determines the amount of action given to the take-up spring4 ,by raising it1 less action is given4 ,the amount of pressure on the spring is regulated by adjusting the barrel in the face plate4 ,take off the face plate1 loosen the screw ,c 7,fig4 #hc71 fix a screw-driver in the rear of the barrel 7seen inside the face plate71 turn it toward you for more pressure1 and backward for less and tighten the set screw ,c4 ,illustration3 ,figs4 #id1 #ie1 #if4 ,presser foot with details ,presser feet are made solid for ordinary purposes1 although alternating feet can be fitted when desired4 ,figs4 #id1 #ie1 and #if show a pressure foot1 collar1 and spring4 ,to fix this foot1 remove the ordinary presser foot1 turn the foot bar round by loosening the set screw1 so that the groove made for the reception of the presser foot is directly behind the needle4 ,put on the collar 7,fig4 #ie71 then turn the foot 7,fig4 #id71 and screw it in position4 ,next place the spring each side at the points ,d 7,fig4 #id71 press down the collar 7,fig4 #ie71 and secure it by its set screw4 ,the springs will act on each half of the foot1 and keep them firm1 though the material be uneven4 ,the foot is particularly useful when overseaming a hem or the top band of a lady's boot1 etc4 ,to time the hook and needle1 raise the connection rod so as to produce no throw1 and tighten the screw as in ,fig4 #ha4 ,then take off the needle plate and remove the slide ,e 7,fig4 #ha7 under which will be seen a crank and screws4 ,now turn the machine back as at ,fig4 #hh1 lift up the bobbin case holder by pressing the catch ,t1 and remove the bobbin case4 ,take off the hook guide cap by removing the two screws4 ,turn the hand wheel ,f 7,fig4 #ha71 toward you1 until the needle bar has descended to its lowest point of travel1 and loosen the crank screw farthest from you4 ,having done this1 continue turning the hand wheel until the needle bar has risen4 ,with the lowest mark level with the rocking frame casting1 at this point1 examine the hook1 the point of which should be just up to the needle4 ,if otherwise1 loosen the other screw in the crank under the plate ,e 7,fig4 #ha74 ,be sure the needle bar mark is level with the rocking frame1 place the hook with its point just up to the needle1 and tighten the crank set screw1 being careful to have no end play to the short shaft4 ,again examine the needle bar and hook and if in proper time finally secure crank set screws and replace the fittings previously removed4 ,thread the machine as indicated 7,fig4 #ha74 ,set the needle as high in the bar as it will go1 with the long groove facing the operator1 and thread the needle from the long groove side4 ,the stitch regulator will be found at ,f 7,fig4 #ha74 ,the raising of it will shorten and the lowering of it will lengthen the stitch4 ,the feed should be set about one thirty-second of an inch above the needle plate when at its highest point4 ,to raise the feed1 turn the machine back as in ,fig4 #hh4 ,near to the part ,g 7,fig4 #hh7 will be found a large set screw4 ,loosen it and press the lever ,h 7,fig4 #hh7 upward raising the feed bar ,j as high as required1 and tighten the set screw at ,g firmly4 ,to remove the feed for cleaning and sharpening1 take off the needle plate1 under which will be seen two feed set screws4 ,by unscrewing these1 the feed can be lifted out4 ,one of the modern machines on the market is the ,wheeler and ,wilson1 known as the ,number #fa1 which is of rotary hook principle4 ,the hook forms part of the under shaft1 somewhat similar to that known as the ,d#i ,w and ,w4 ,this hook and shaft revolves in two long bearings1 and is held in position by a fluted wheel1 which forms a collar at the right-hand end2 thus when set properly no end play is permitted4 ,this is an advantage over the boat-shaped shuttle machine4 ,in the latter1 the shuttle rocks about1 becomes worn on the surface1 often blunt pointed by striking the needle4 ,as it wears1 it becomes loose in the carrier1 thus giving it freedom to roll away from or toward the needle1 as well as making its action with relation to the needle very uncertain2 and on account of the number of little loosenesses in fittings that this uncontrolled shuttle produces1 missed stitches are frequent1 and difficult to remedy1 unless a number of new fittings are obtained or old ones repaired4 ,if there is any alteration required in the time of the rotary hook referred to1 it can be made to the smallest fractional part of an inch very quickly and easily1 and the movement can be relied on4 ,the shaft to which it is secured is positive in its action 7no variable motion71 and at every stitch will meet the needle at exactly the same spot4 ,this is an improvement over the boat-shaped shuttle1 which has to have a certain amount of play or slackness to allow the loop to extricate itself2 and this slackness increases as the machine is worked1 so that the shuttle action often becomes very erratic4 ,sometimes a carrier becomes sprained at one end1 thus allowing the shuttle too much freedom4 ,if at the heel end1 the carrier should be removed and placed in a vise 7heel uppermost74 ,the heel should be given a light blow with a hammer1 thus bending it into correct position1 but it must never be allowed to incline toward the shuttle2 it should stand perfectly square1 and have the upper corners rounded off4 ,if inclined toward the shuttle1 the loop may occasionally hang on the heel1 and cause an irregular tension4 ,in some machines the bobbin case holder 7,fig4 #ig7 rests on the casting seen in ,fig4 #ha4 ,it is secured by a large set screw1 ,d 7,fig4 #ig74 ,for general use1 this screw should be adjusted to allow number #dj cotton to pass freely over the bobbin case4 ,the holder should not be removed1 except when adjustment or repair is needed4 ,the vertical portion is hinged to the base1 and is kept upright by a lock spring and stud4 ,if the spring is pressed from the stud1 the vertical or ring part can be drawn back for placing in or taking out the bobbin case4 ,the face of this portion must be perfectly square with the bottom of the base1 otherwise it may cause considerable trouble4 ,a slight adjustment can be made by loosening the two screws and moving the lock spring4 ,a set square1 ,e1 should be used for testing the accuracy of this part as shown 7,fig4 #ih71 ,f representing the bobbin case holder4 ,illustration3 ,fig4 #ig4 ,bobbin case holder ,illustration3 ,fig4 #ih4 ,set square ,the thread controller is similar in design to several others1 but its movement is regulated by a small lever 7,fig4 #ii7 which receives its motion from a link attached to the foot bar bracket set screw1 and this may be seen through a hole in the face plate4 ,at ,g 7,fig4 #ii71 this lever engages with a stop washer located behind the thread controller plate4 ,the washer is recessed to form a stop1 at the same time to give sufficient clearance for the action of the spring2 thus as the foot bar rises and falls1 so does the thread controller spring4 ,it is a common practice when cleaning a machine to remove the face plate1 thus detaching the link referred to1 and not connecting it again when replacing the face plate4 ,from this1 trouble arises4 ,the tension pulley should be placed on its stud1 the large boss being toward the face plate4 ,illustration3 ,fig4 #ii4 ,lever ,thread a machine as follows3 ,from the reel pin to nipper ,f 7,fig4 #ha71 round tension pulley ,g as the arrow indicates1 down and into thread controller ,h up to take-up lever1 threading over the roll and through the slot from the top of lever1 then down the thread guide ,j1 into guide ,k1 and through the needle-eye from right to left4 ,in the ordinary boat-shaped shuttle1 the looping up of the thread is not difficult4 ,the needle1 as it descends1 enters an opening or cavity in the carrier1 one side of which forms a support for the needle and guards it from contact with the shuttle point4 ,now1 it is important that there be clearance for the needle4 ,if the carrier stands so prominent as to spring the needle out of its true vertical line it will carry it away from the shuttle1 and give the latter a chance to miss the loop4 ,illustration3 ,fig4 #ajj ,a1 ,b1 ,c1 ,d4 ,carriers and drivers ,then there are carriers and drivers of varying heights4 ,those of the raised kind are preferable1 if properly fitted4 ,by raised is meant that they are higher1 so as to form a better guard for the needle1 as previously referred to 7,fig4 #ajj ,a1 in which ,e indicates the portion of raised carrier1 ,f the shuttle point1 and ,g the needle74 ,but sometimes they are too high1 and permit the needle-eye to be buried in the carrier1 thus preventing the proper formation of the loop4 ,this can be so bad as to cause very frequent missing2 or it may be of such a slight character as to cause a miss-stitch only now and then4 ,occasionally1 a needle bar has to be lowered1 and that is sufficient to cause the same fault4 ,the eye of the needle should always be about one thirty-second of an inch above the upper edge of the carrier1 and the latter should be shaped so as to allow that amount of clearance the whole of the time the needle is rising to form the loop1 until the shuttle point has well entered the same4 ,fig4 #ajj ,b shows how a carrier is hollowed to give the necessary clearance to the needle eye4 ,illustration3 ,fig4 #aja4 ,sewing machine items ,when a machine is reasonably tight in all parts1 gauges and setting marks may be adhered to for the preliminary adjustments2 and then if the machine works erratically1 other adjustments must be made4 ,where no marks or gauges are furnished for the adjustment of the needle bar1 it should be so set as to allow the shuttle or hook to enter the bold part of the loop formed from the needle4 ,a good rule is to set the needle bar so that the needle-eye is about #a_/cb inch below the point of the shuttle ,m 7,fig4 #ajj ,c7 when the latter is up to the centre of the needle groove4 ,but this may have to be varied from #a_/fd-;inch to #c_/cb-;inch4 ,in boat-shaped and similar shuttle machines1 a good rule is to set the needle so that the eye ,n will pass just below the lower side of the shuttle ,o as the latter is passing through the loop as in ,fig4 #ajj ,d1 ,p1 indicating the level of the bed plate4 ,,ii ,,mechanical ,,movements ,what is meant by this term is that these devices are intended for the transmission of motion4 ,motion in mechanics may be simple or compound4 ,simple motions are those of straight translation1 which if of indefinite duration must be reciprocating1 or what is called oscillating or helical4 ,compound motions consist of combinations of any of the simple motions4 ,perpetual motion is an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without1 or which has within itself the means1 when once set in motion1 of continuing its motion perpetually1 or until worn out1 without any new application of external force4 ,the machine by means of which it has been attempted1 or supposed possible to produce such motion1 is an invention much sought after1 but physically impossible4 ,illustration3 ,fig4 #ajb4 ,coffee mill and details ,the illustrations herewith exhibit a number of devices of various kinds1 well known to the practical mechanician and professional engineer1 and usually called mechanical movements4 ,it is estimated there are no less than #a1ejj of these movements doing service at the present day2 but many of them are1 of course1 quite complex1 and difficult to master4 ,in this book1 ,i show about one hundred of the simplest sort1 or those in common use4 ,their usefulness will at once be appreciated if we refer to ,fig4 #ajb1 which shows a machine for grinding or breaking up substances within its capacity4 ,it contains within itself the true principle of the little mill used to grind coffee4 ,the word grind in this connection is scarcely the right one1 as the mill rather crushes or breaks up1 than grinds4 ,you will notice coffee1 ready for use1 is coarse and unlike flour in texture1 the latter being ground fine and smooth4 ,in grinding1 the abrading surfaces are brought very much closer together than in the breaking or crushing processes4 ,in a coffee mill1 the berries or grains drop into a vacancy1 left between the revolving cone and the walls of the mill4 ,the vacancy between the walls and the cone is a little less at the bottom where the crushed coffee is discharged1 and this enables the small and large grounds to fall into the drawer4 ,the detailed plan in illustration 7,fig4 #ajb7 shows a mill complete1 as well as the various parts4 ,it will be noticed that the cone 7,fig4 #e71 is corrugated or grooved as shown 7,fig4 #d74 ,figs4 #f and #g show sections of lining at ,b and ,c 7,fig4 #c74 ,a shows the hopper into which the coffee berries are placed before grinding4 ,figure #i shows the crank detached1 and ,figs4 #h and #aj show the remaining parts of the machine1 while ,figs4 #a and #b show the handle and drawer4 ,the latter is to receive the ground or crushed coffee after it has gone through the mill4 ,further description is unnecessary if we take for example the movement represented at ,fig4 #aej1 which is a sort of ball-bearing motion1 only instead of small balls wheels are used4 ,besides being made use of in bicycles in small balls1 it is used as depicted for hanging grindstones1 and for many other similar purposes4 ,the device also shown at ,fig4 #aci1 is one in common use4 ,it is a modification of the sprocket wheel on the bicycle4 ,many of the devices shown herewith are rarely noticed because of our familiarity with them4 ,the action of pumps1 the working of pistons1 the changing of motion1 and many other things are shown and explained in the little illustrations given in these descriptions1 which do not pretend to be exhaustive1 or even full4 ,fig4 #ajc4 ,in this the lower pulley is movable4 ,one end of the rope being fixed1 the other has to move twice as fast as the weight1 and a corresponding gain of power is consequently effected4 ,fig4 #ajd is a simple pulley used for lifting weights4 ,in this the power must be equal to the weight to obtain equilibrium4 ,fig4 #aje4 ,blocks and tackle4 ,the power obtained by this contrivance is calculated as follows3 ,divide the weight by double the number of pulleys in the lower block2 the quotient is the power required to balance the weight4 ,fig4 #ajf represents what are known as ,white's pulleys1 which can be made with separate loose pulley2 or a series of grooves can be cut in a solid block1 the diameters being made in proportion to the speed of the rope2 that is1 #a1 #c1 and #e for one block1 and #b1 #d1 and #f for the other4 ,power as #a to #g4 ,illustration3 ,figs4 #ajc1 #ajd1 #aje1 #ajf1 #ajg4 ,various phases of block and tackle ,figs4 #ajg-ajh are what are known as ,spanish bartons4 ,fig4 #ajh is a combination of two fixed and one movable pulley4 ,figs4 #aaa-aac are different arrangements of pulleys4 ,the following rule applies to these3 ,in a system of pulleys where each is embraced by a cord attached to one end of a fixed point1 and at the other to the centre of the movable pulley1 the effect of the whole will be the number #b multiplied by itself as many times as there are movable pulleys in the system4 ,illustration3 ,figs4 #ajh1 #aji1 #aaj1 #aaa1 #aab4 ,other combinations of blocks and pulleys ,fig4 #aad4 ,endless chain for maintaining power on going barrel1 to keep a clock going while winding1 as during that operation the action of the weight or mainspring is taken off the barrel4 ,the wheel to the right is the going wheel1 and that to the left the striking wheel4 ,p is a pulley fixed to the great wheel of the going part1 and roughened to prevent a rope or chain hung over it from slipping4 ,a similar pulley rides on another arbour1 p1 which may be the arbour of the great wheel of the striking part1 attached by a ratchet and click to that wheel1 or to the clock frame if there is no striking part4 ,the weights are hung as may be seen1 the small one being only large enough to keep the rope or chain on the pulleys4 ,if the part b of the rope or chain is pulled down1 the ratchet-pulley runs under the click1 and the great weight is pulled up by c1 without taking its pressure off the going wheel at all4 ,fig4 #aae4 ,triangular eccentric1 giving an intermittent reciprocating rectilinear motion1 often used for the valve motion of steam-engines4 ,fig4 #aaf4 ,ordinary crank-motion4 ,illustration3 ,figs4 #aac1 #aad1 #aae4 ,blocks and rocker ,fig4 #aag4 ,in this1 rotary motion is imparted to the wheel by the rotation of the screw1 or rectilinear motion of the slide by the rotation of the wheel4 ,used in screw cutting and slide lathes4 ,illustration3 ,figs4 #aaf1 #aag4 ,crank and rotary motion ,fig4 #aah4 ,uniform circular into uniform rectilinear motion2 used in spooling frames for leading or guiding the thread on to the spools4 ,the roller is divided into two parts1 each having a fine screw-thread cut upon it1 one a right and the other a left-handed screw4 ,the spindle1 parallel with the roller1 has arms which carry two half nuts1 fitting to the screw1 one over the other under the roller4 ,when one half nut is in1 the other is out of gear4 ,by pressing the lever to the right or left the rod is made to traverse in either direction4 ,fig4 #aai4 ,a system of crossed levers1 termed lazy tongs4 ,a short1 alternating rectilinear motion of rod at the right will give a similar1 but much greater motion to the rod at the left4 ,it is frequently used in children's toys4 ,it has been applied to machines for raising sunken vessels2 also applied to ship pumps three quarters of a century ago4 ,illustration3 ,figs4 #aah1 #aai4 ,rectilinear motion ,fig4 #abj4 ,centrifugal governor for steam engines4 ,the central spindle and attached arms and balls are driven from the engine by the bevel gears at the top1 and the balls fly out from the centre by centrifugal force4 ,if the speed of the engine increases1 the balls fly out from the centre1 raise the slide at the bottom1 and thereby reduce the opening of the regulating valve1 which is connected with the slide4 ,a diminution of speed produces an opposite effect4 ,fig4 #aba4 ,water-wheel governor acting on the same principle as ,fig4 #abj1 but by different means4 ,the governor is driven by the top horizontal shaft and bevel gears1 and the lower gears control the rise and fall of the shuttle or gate over or through which the water flows to the wheel4 ,the action is as follows3 ,the two bevel gears on the lower part of the centre spindle1 which are furnished with studs1 are fitted loosely to the spindle1 and remain at rest so long as the governor has a proper velocity2 but immediately the velocity increases1 the balls flying farther out1 draw up the pin1 which is attached to a loose sleeve which slides up and down the spindle1 and this pin1 coming in contact with the stud on the upper bevel gear1 causes that gear to rotate with the spindle1 and to give motion to the lower horizontal shaft in such a direction as to make it raise the shuttle or gate1 and so reduce the quantity of water passing to the wheel4 ,on the contrary1 if the speed of the governor decreases below that required1 the pin falls and gives motion to the lower bevel gear1 which drives the horizontal shaft in the opposite direction1 and produces a contrary effect4 ,fig4 #abb4 ,another arrangement for a water-wheel governor4 ,in this the governor controls the shuttle or gate by means of the cranked lever1 which acts on the strap or belt in the following manner3 ,the belt runs on one of three pulleys1 the middle one of which is loose on the governor spindle1 and the upper and lower ones fast4 ,when the governor is running at the proper speed the belt is on the loose pulley1 as shown2 but when the speed increases1 the belt is thrown on the lower pulley1 and thereby caused to act upon suitable gearing for raising the gate or shuttle and decreasing the supply of water4 ,a reduction of the speed of the governor brings the belt on the upper pulley1 which acts upon the gearing for producing an opposite effect on the shuttle or gate4 ,fig4 #abc4 ,another form of steam-engine governor4 ,instead of the arms being connected with a slide working on a spindle1 they cross each other1 are elongated upward beyond the top1 and connected with the valve-rod by two short links4 ,figs4 #abd1 #abe4 ,diagonal catch and hand-gear used in large blowing and pumping engines4 ,in ,fig4 #abd the lower steam valve and upper eduction valves are open1 while the upper steam valve and lower eduction valve are shut2 consequently the piston is ascending4 ,in the ascent of the piston rod the lower handle will be struck by the projecting tappet1 and being raised will become engaged by the catch1 so as to shut the upper eduction and lower steam valves2 at the same time the upper handle will be disengaged from the catch1 the back weight will pull the handle up and open the upper steam and lower eduction valves1 when the piston will consequently descend4 ,fig4 #abe represents the position of the catches and handles when the piston is at the top of the cylinder4 ,in going down1 the tappet of the piston rod strikes the upper handle1 and throws the catches and handles to the position shown in ,fig4 #abd4 ,illustration3 ,figs4 #abj1 #aba1 #abb1 #abc4 ,governors for steam-engines ,fig4 #abf4 ,a mode of driving a pair of feed rolls1 the opposite surface of which require to move in the same direction4 ,the two wheels are precisely similar1 and both gear into the endless screw1 which is arranged between them4 ,the teeth of one wheel only are visible1 those of the other being on the back or side which is concealed from view4 ,illustration3 ,figs4 #abd1 #abe1 #abf4 ,valve ,regulation and ,feed ,rolls ,fig4 #abg4 ,link-motion valve gear of a locomotive2 two eccentrics are used for one valve1 one for the forward and the other for the backward movement of the engine4 ,the extremities of the eccentric rods are jointed to a curved slotted bar1 or1 as it is termed1 a link1 which can be raised or lowered by an arrangement of levers terminating in a handle1 as shown4 ,in the slot of the link is a slide and pin connected with an arrangement of levers terminating in the valve stem4 ,the link1 in moving with the action of the eccentrics1 carries with it the slide1 and thence motion is communicated to the valve4 ,suppose the link raised so that the slide is in the middle1 then the link will oscillate on the pin of the slide1 and consequently the valve will be at rest4 ,if the link is moved so that the slide is at one of the extremities1 the whole throw of the eccentric connected with that extremity will be given to it1 the valve and steam ports will be opened to the full1 and it will only be toward the end of the stroke that they will be totally shut2 consequently the steam will have been admitted to the cylinder during almost the entire length of each stroke4 ,but if the slide is between the middle and the extremity of the slot1 as shown in the figure1 it receives only a part of the throw of the eccentric and the steam ports will only be partially opened1 and quickly closed again1 so that the admission of steam ceases some time before the termination of the stroke1 and the steam is worked expansively4 ,the nearer the slide is to the middle of the slot the greater will be the expansion1 and vice versa4 ,illustration3 ,figs4 #abg1 #abh4 ,link and other motions ,fig4 #abh represents a mode of obtaining motion from rolling contact4 ,the teeth are for making the motion continuous1 or it would cease at the point of contact shown in the figure4 ,the fork catch is to guide the teeth into proper contact4 ,fig4 #abi4 ,what is called the ,geneva-stop1 used in ,swiss watches to limit the number of revolutions in winding-up2 the convex curved part of the wheel serving as the stop4 ,fig4 #acj4 ,a continuous rotary motion of the large wheel gives an intermittent rotary motion to the pinion-shaft4 ,the part of the pinion shown next the wheel is cut of the same curve as the plain portion of the circumference of the wheel1 and therefore serves as a lock while the wheel makes a part of a revolution1 and until the pin upon the wheel strikes the guide-piece upon the pinion1 when the pinion-shaft commences another revolution4 ,illustration3 ,figs4 #abi1 #acj4 ,stop and rotary motions ,fig4 #aca4 ,the two crank-shafts are parallel in direction1 but not in line with each other4 ,the revolution of either will communicate motion to the other with a varying velocity1 for the wrist of one crank working in the slot of the other is continually changing its distance from the shaft of the latter4 ,illustration3 ,figs4 #aca1 #acb1 #acc4 ,irregular ,motions ,figs4 #acb and #acc4 ,these are parts of the same movement1 which has been used for giving the roller motion in wool-combing machines4 ,the roller to which the wheel ,f1 7,fig4 #acb7 is secured1 is required to make #a_/c revolution backward1 then #b_/c revolution forward1 when it must stop until another length of combed fibre is ready for delivery4 ,this is accomplished by the grooved heart-cam ,c1 ,d1 ,b1 e1 7,fig4 #acc7 the stud working in the said groove2 from ,c to ,d it moves the roller backward1 and from ,d to e it moves it forward1 the motion being transmitted through the catch ,g1 to the notch wheel ,f1 on the roller-shaft ,h4 ,when the stud ,a arrives at the point e in the cam1 a projection at the back of the wheel1 which carries the cam1 strikes the projecting piece on the catch ,g1 and raises it out of the notch in the wheel ,f1 so that while the stud is travelling in the cam from e to ,c1 the catch is passing over the plain surface between the two notches in the wheel ,f1 without imparting any motion2 but when stud ,a arrives at the part ,c1 the catch has dropped in another notch and is again ready to move wheel ,f and roller as required4 ,fig4 #acd4 ,an arrangement for obtaining variable circular motion4 ,the sectors are arranged on different planes1 and the relative velocity changes according to the respective diameters of the sectors4 ,fig4 #ace4 ,intermittent circular motion of the ratchet-wheel from vibratory motion of the arm carrying a pawl4 ,illustration3 ,figs4 #ace1 #acd1 #acg1 #acf4 ,movements of various kinds ,fig4 #acf4 ,this represents an expanding pulley4 ,on turning pinion d to the right or left1 a similar motion is imparted to wheel c1 by means of curved slots cut therein1 which thrust the studs fastened to arms of pulley outward or inward1 thus augmenting or diminishing the size of the pulley4 ,fig4 #acg represents a chain and chain pulley4 ,the links being in different planes1 spaces are left between them for the teeth of the pulley to enter4 ,fig4 #ach4 ,another kind of chain and pulley4 ,fig4 #aci4 ,another variety4 ,fig4 #adj shows two different kinds of stops for a lantern-wheel4 ,illustration3 ,figs4 #adj1 #ach1 #aci4 ,chain pulleys and lantern-wheel ,fig4 #ada4 ,intermittent circular motion is imparted to the toothed wheel by vibrating the arm ,b4 ,when the arm ,b is lifted1 the pawl ,c is raised from between the teeth of the wheel1 and travelling backward over the circumference again drops between two teeth on lowering the arm1 and draws with it the wheel4 ,fig4 #adb4 ,the oscillating of the tappet-arm produces an intermittent rotary motion of the ratchet-wheel4 ,the small spring at the bottom of the tappet-arm keeps the tappet in the position shown in the drawing1 as the arm rises1 yet allows it to pass the teeth on the return motion4 ,fig4 #adc4 ,a nearly continuous circular motion is imparted to the ratchet-wheel on vibrating the lever a to which the two pawls b and c are attached4 ,illustration3 ,figs4 #ada1 #adb1 #adc4 ,intermittent circular motion ,fig4 #add4 ,an arrangement of stops for a spur-gear4 ,fig4 #ade4 ,a reciprocating circular motion of the top arm makes its attached pawl produce an intermittent circular motion of the crown-ratchet1 or ray-wheel4 ,illustration3 ,figs4 #add1 #ade4 ,intermittent circular motion ,fig4 #adf represents varieties of stops for ratchet-wheel4 ,fig4 #adg4 ,intermittent circular motion is imparted to the wheel ,a by the continuous circular motion of the smaller wheel with one tooth4 ,illustration3 ,figs4 #adf1 #adg4 ,ratchet motion ,fig4 #adh4 ,a dynamometer1 or instrument used for ascertaining the amount of useful effect given out by any motive power4 ,it is used as follows3 ,a is a smoothly turned pulley1 secured on a shaft as near as possible to the motive power4 ,two blocks of wood are fitted to this pulley1 or one block of wood and a series of straps fastened to a band or chain1 as in the drawing1 instead of a common block4 ,the blocks1 or block and straps1 are so arranged that they may be made to bite or press upon the pulley by means of the screws and nuts on the top of the lever ,d4 ,to estimate the amount of power transmitted through the shaft1 it is only necessary to ascertain the amount of friction of the drum ,a when it is in motion1 and the number of revolutions made4 ,at the end of the lever ,d is hung a scale ,b1 in which weights are placed4 ,the two stops ,c ,c are to maintain the lever as nearly as possible in a horizontal position4 ,now1 suppose the shaft to be in motion1 the screws are to be tightened and weights added in ,b1 until the lever takes the position shown in the drawing1 at the required number of revolutions4 ,therefore the useful effect would be equal to the product of the weights1 multiplied by the velocity at which the point or suspension of the weights would revolve if the lever were attached to the shaft4 ,illustration3 ,figs4 #adh1 #adi4 ,dynamometer--,pantagraph ,fig4 #adi represents a pantagraph for copying1 enlarging and reducing plans4 ,one arm is attached to and turns on the fixed point ,c4 ,b is an ivory tracing point1 and ,a the pencil4 ,arranged as shown1 if we trace the lines of a plan with the point ,b1 the pencil will produce it double the size4 ,by shifting the slide attached to the fixed point ,c and the slide carrying the pencil along their respective arms1 the proportions to which the plan is traced will be varied4 ,fig4 #aej4 ,anti-friction bearing4 ,instead of a shaft revolving in an ordinary bearing1 it is sometimes supported on the circumference of wheels4 ,the friction is thus reduced to the least amount4 ,fig4 #aea4 ,releasing hook used in pile-driving machines4 ,when the weight ,w is sufficiently raised1 the upper ends of the hooks ,a1 by which it is suspended1 are pressed inward by the side of the slot ,b1 in the top of the frame2 the weight is thus suddenly released1 and falls with accumulating force on to the pile-head4 ,fig4 #aeb4 ,a and ,b are two rollers which require to be equally moved to and fro in the slot ,c4 ,this is accomplished by moving the piece ,d1 with oblique slotted arms1 up and down4 ,illustration3 ,figs4 #aej1 #aea1 #aeb4 ,anti-friction--,drop hook--,regular motion ,fig4 #aec4 ,centrifugal check-hooks1 for preventing accidents in case of the breakage of machinery which raises and lowers workmen1 or ores1 in mines4 ,a is a framework fixed to the side of the shaft of the mine1 and having fixed studs ,d1 attached4 ,the drum on which the rope is wound is provided with a flange ,b1 to which the check-hooks are attached4 ,if the drum acquires a dangerously rapid motion1 the hooks fly out by centrifugal force1 and one or other1 or all of them1 catch hold of the studs ,d1 arrest the drum1 and stop the descent of whatever is attached to the rope4 ,the drum ought besides this1 to have a spring applied to it1 otherwise the jerk arising from the sudden stoppage of the rope might produce a worse effect than its rapid motion4 ,fig4 #aed4 ,a sprocket-wheel to drive or to be driven by a chain4 ,fig4 #aee4 ,a combination movement1 in which the weight ,w moves with a reciprocating movement1 the down-stroke being shorter than the up-stroke4 ,b is a revolving disc1 carrying a drum which winds around itself the cord ,d4 ,an arm ,c is jointed to the disc and to the upper arm ,a1 so that when the disc revolves1 the arm ,a moves up and down1 vibrating on the point ,g4 ,this arm carries with it the pulley ,e4 ,suppose we detach the cord from the drum1 tie it to the fixed point1 and then move the arm ,a up and down4 ,the weight ,w will move the same distance1 and in addition the movement given it by the cord1 that is to say1 the movement will be doubled4 ,now1 let us attach the cord to the drum1 and revolve the disc ,b1 and the weight will move vertically with the reciprocating motion1 in which the down-stroke will be shorter than the up-stroke1 because the drum is continually taking up the cord4 ,illustration3 ,figs4 #aec1 #aed1 #aee4 ,hooks--,sprocket--,combination movement ,figs4 #aef1 #aeg4 ,the first of these figures is an end view1 and the second is a side view of an arrangement or mechanism for obtaining a series of changes in velocity and direction4 ,d is a screw on which is placed eccentrically the cone ,b1 and ,c is a friction roller1 which is pressed against the cone by a spring or weight4 ,continuous rotary motion1 at a uniform velocity of the screw ,d carrying the eccentric cone1 gives a series of changes of velocity and direction to the roller ,c4 ,it will be understood that during every revolution of the cone the roller would press against a different part of the cone1 and that it would describe thereon a spiral motion1 the movement in one direction being shorter than that in the other4 ,illustration3 ,figs4 #aef1 #aeg4 ,change of speed ,fig4 #aeh4 ,an engine governor4 ,the rise and fall of the balls ,k are guided by the parabolic curved arms ,b1 on which the anti-friction wheels ,l run4 ,the rods ,f1 connecting the wheel ,l with the sleeve1 move it up and down the spindle ,c ,d4 ,fig4 #aei4 ,toe and lifter for working poppet-valves in steam engines4 ,the curved toe on the rock-shaft operates on the lifter attached to the lifting rod to raise the valve4 ,fig4 #afj4 ,mercurial compensation pendulum4 ,a glass jar of mercury is used for the bob or weight4 ,as the pendulum-rod is expanded lengthwise by increased temperature1 the expansion of mercury in the jar carries it to a greater height therein1 and so raises its centre of gravity relatively to the rod sufficiently to compensate for downward expansion of the rod4 ,as rod is contracted by a reduction of temperature1 contraction of mercury lowers it relatively to rod4 ,in this way the centre of oscillation is always kept in the same place1 and the effective length of pendulum always the same4 ,illustration3 ,figs4 #aeh1 #aei1 #afj4 ,governor1 lifter1 and pendulum ,fig4 #afa4 ,compound bar compensation pendulum4 ,c is a compound bar of brass and iron1 or steel brazed together with brass downward4 ,as brass expands more than iron1 the bar will bend upward as it gets warmer1 and will carry the weights ,w1 ,w1 up with it1 raising the centre of the aggregate weight ,m1 to raise the centre of oscillation as much as elongation of the pendulum-rod would let it down4 ,fig4 #afb4 ,watch regulator4 ,the balance-spring is attached at its outer end to a fixed stud ,r1 and at its inner end to staff of balance4 ,a neutral point is formed in the spring at ,p1 by inserting it between two curb-pins in the lever1 which is fitted to turn on a fixed ring concentric with staff of balance1 and the spring only vibrates between this neutral point and staff of balance4 ,by moving lever to the right1 the curb-pins are made faster1 and by moving it to the left1 an opposite effect is produced4 ,illustration3 ,figs4 #afa1 #afb4 ,compound bar--,hair spring ,fig4 #afc4 ,compensation balance4 t1 a1 t is the main bar of balance1 with timing screws for regulation at the ends4 t and t are two compound bars1 of which the outside is brass and the inside steel1 carrying weights b1 b4 ,as heat increases1 these bars are bent inward1 diminishing the inertia of the balance4 ,as the heat diminishes1 an opposite effect is produced4 ,this balance compensates both for its own expansion and contraction1 and that of the balance-spring4 ,fig4 #afd4 ,parallel ruler1 consisting of a simple straight ruler ,b1 with an attached axle ,c1 and a pair of wheels ,a ,a4 ,the wheels1 which protrude but slightly through the under side of the ruler1 have their edges nicked to take hold of the paper and keep the ruler always parallel with any lines drawn upon it4 ,illustration3 ,figs4 #afc1 #afd4 ,balance--,ruler ,fig4 #afe4 ,compound parallel ruler1 composed of two simple rulers ,a1 ,a1 connected by two crossed arms pivoted together at the middle of their length1 each pivoted at one end to one of the rulers1 and connected with the other one by a slot and sliding pin1 as shown at ,b4 ,in this the ends as well as the edges are kept parallel4 ,the principle of construction of the several rulers represented is taken advantage of in the formation of some parts of machinery4 ,fig4 #aff4 ,a simple means of guiding or obtaining a parallel motion of the piston rod of an engine4 ,the slide a moves in and is guided by the vertical slot in the frame1 which has been planed to a true surface4 ,illustration3 ,figs4 #afe1 #aff4 ,ruler--,parallel motion ,fig4 #afg4 ,parallel motion for direct-action engines4 ,in this1 the end of the bar ,b ,c is connected with the piston-rod1 and the end ,b slides in a fixed slot ,d4 ,the radius bar ,f ,a is connected at ,f with a fixed pivot1 and at ,a midway between the ends of ,b ,c4 ,illustration3 ,figs4 #afg1 #afh1 #afi4 ,parallel motion methods ,fig4 #afh4 ,oscillating engine4 ,the cylinder has trunnions at the middle of its length1 working in fixed bearings1 and the piston rod is connected directly with the crank1 and no guides are used4 ,fig4 #afi4 ,inverted oscillating or pendulum engine4 ,the cylinder has trunnions at its upper end1 and swings like a pendulum4 ,the crank shaft is below1 and the piston rod connected directly with crank4 ,fig4 #agj4 ,section of disc-engine4 ,disc-piston1 seen edgewise1 has a motion substantially like a coin when it first falls after being spun in the air4 ,the cylinder heads are cones4 ,the piston rod is made with a ball to which the disc is attached1 said ball working in concentric seats in cylinder-heads1 and the left-hand end is attached to the crank arm or fly-wheel on end of shaft at left4 ,steam is admitted alternately on either side of piston4 ,fig4 #aga4 ,the gyroscope1 or rotascope1 an instrument illustrating the tendency of rotating bodies to preserve their plane of rotation4 ,the spindle of the metallic disc ,c is fitted to return easily in bearings in the ring ,a4 ,if the disc is set in rapid rotary motion on its axis1 and the pintle ,f at one side of the ring ,a is placed on the bearing in the top of the pillar ,g1 the disc and ring seem indifferent to gravity1 and instead of dropping begin to revolve about the vertical axis4 ,fig4 #agb4 ,bohnenberger's machine1 illustrating the same tendency of rotating bodies4 ,this consists of #c rings1 ,a1 ,a1 ,a#b1 placed one within the other1 and connected by pivots at right angles to each other4 ,the smallest ring1 ,a#b1 contains the bearings for the axis of a heavy ball ,b4 ,the ball being set in rapid rotation1 its axis will continue in the same direction1 no matter how the position of the rings may be altered2 and the ring ,a#b1 which supports it1 will resist a considerable pressure tending to displace it4 ,illustration3 ,figs4 #agj1 #aga1 #agb4 ,disc-engine and gyroscopes ,fig4 #agc4 ,what is called the gyroscope governor1 for steam-engines1 introduced by ,alban ,anderson in #aheh4 ,a is a heavy wheel1 the axle ,b ,b of which is made in two pieces connected together by a universal joint4 ,the wheel ,a is on one piece ,b1 and a pinion ,i on the other piece ,b4 ,the piece ,b is connected at its middle by a hinge-joint with the revolving frame ,h1 so that variations in the inclination of the wheel ,a will cause the outer end of the piece ,b to rise and fall4 ,the frame ,h is driven by bevel gearing from the engine1 and by that means the pinion #a is carried round the stationary toothed circle ,g1 and the wheel ,a is thus made to receive a rapid rotary motion on its axis4 ,when the frame ,h and wheel ,a are in motion1 the tendency of the wheel ,a is to assume a vertical position1 but this tendency is opposed by a spring ,l4 ,the greater velocity of the governor1 the stronger the tendency1 above mentioned1 and the more it overcomes the force of the spring1 and the reverse4 ,the piece ,b is connected with the valve rods by rods ,c1 ,d1 and the spring ,l is connected with the said rods by levers ,n and rod ,p4 ,illustration3 ,figs4 #agc1 #agd1 #age4 ,governor--,reverse motions ,fig4 #agd4 ,pair of edge runners or chasers for crushing or grinding4 ,the axles are connected with vertical shaft1 and the wheel or chasers run in an annular pan or trough4 ,fig4 #age4 ,rotary motion of shaft from treadle by means of an endless band running from a roller on the treadle to an eccentric on the shaft4 ,fig4 #agf4 ,tread-wheel horse-power turned by the weight of an animal attempting to walk up one side of its interior2 has been used for driving the paddle-wheels of ferry-boats and many other purposes4 ,the turn-spit dog used also to be employed in such a wheel in ancient times for turning meat while roasting on a spit4 ,fig4 #agg4 ,the treadmill1 employed in jails in some countries for exercising criminals condemned to labour1 and employed in grinding grain2 turns by weight of person stepping on tread-boards on periphery4 ,this is supposed to be a ,chinese invention1 and it is still used in ,china for raising water for irrigation4 ,illustration3 ,figs4 #agf1 #agg1 #agh4 ,by different sources of power ,fig4 #agh4 ,a4 ,b4 ,wilson's four-motion feed1 used in ,wheeler and ,wilson's1 ,sloat's1 and other sewing machines4 ,the bar ,a is forked1 and has a second bar ,b1 carrying the spur or feeder1 pivoted in the said fork4 ,the bar ,b is lifted by a radial projection on the cam ,c1 at the same time the two bars are carried forward4 ,a spring produces the return stroke1 and the bar ,b drops of its own gravity4 ,fig4 #agi4 ,mechanical means of describing parabolas1 the base1 altitude1 focus1 and directrix being given4 ,lay straight edge with near side coinciding with directrix1 and square with stock against the same1 so that the blade is parallel with the axis1 and proceed with pencil in bight of thread1 as in the preceding4 ,illustration3 ,figs4 #agi1 #ahj4 ,to describe conic sections ,fig4 #ahj4 ,mechanical means of describing hyperbolas1 their foci and vertices being given4 ,suppose the curves two opposite hyperbolas1 the points in vertical dotted centre line their foci4 ,one end of thread being looped on pin inserted at the other focus1 and other end held to other end of rule1 with just enough slack between to permit height to reach vertex when rule coincides with centre line4 ,a pencil held in bight1 and kept close to the rule1 while latter is moved from centre line1 describes one-half of parabola2 the rule is then reversed for the other half4 ,fig4 #aha4 ,cyclograph for describing circular arcs in drawings where the centre is inaccessible4 ,this is composed of three straight rules4 ,the cord and versed sine being laid down1 draw straight1 sloping line from ends of former to top of latter2 and to these lines lay two of the rules crossing at the apex4 ,fasten these rules together1 and another rule across them to serve as a brace1 and insert a pin or point at each end of chord to guide the apparatus1 which1 on being moved against these points1 will describe the arc by means of pencil in the angle of the crossing edges of the sloping rules4 ,fig4 #ahb4 ,proportional compasses used in copying drawings on a given larger or smaller scale4 ,the pivot of compasses is secured in a slide which is adjustable in the longitudinal slots of legs1 and capable of being secured by a set screw2 the dimensions are taken between one pair of points and transferred with the other pair1 and thus enlarged or diminished in proportion to the relative distances of the points from the pivot4 ,a scale is provided on one or both legs to indicate the proportions4 ,fig4 #ahc4 ,one of the many forms of rotary engine4 ,a is a cylinder having the shaft ,b pass centrally through it4 ,the piston ,c is simply an eccentric fast on the shaft1 and working in contact with the cylinder at one point4 ,the induction and eduction of steam take place as indicated by arrows1 and the pressure of the steam on one side of the piston produces its rotation and that of the shaft4 ,the sliding abutment ,d1 between the induction and eduction ports1 moves out of the way of the piston to let it pass4 ,illustration3 ,figs4 #aha1 #ahb1 #ahc4 ,for drawing curves4 ,rotary engine ,fig4 #ahd4 ,another form of rotary engine1 in which there are two stationary abutments ,d1 ,d1 within the cylinder2 and the two pistons ,a1 ,a1 in order to enable them to pass the abutments1 are made to slide radially in grooves in the hub ,c of the main shaft ,b4 ,the steam acts on both pistons at once1 to produce the rotation of the hub and shaft4 ,the induction and eduction are indicated by arrows4 ,fig4 #ahe4 ,jonval turbine4 ,the shutes are arranged on the outside of a drum1 radial to a common centre1 and stationary within the trunk or casing b4 ,the wheel c is made in nearly the same way2 the buckets exceed in number those of the shutes1 and are set at a slight tangent instead of radially1 and the curve generally used is that of the cycloid or parabola4 ,fig4 #ahf4 ,a method of obtaining a reciprocating motion from a continuous fall of water1 by means of a valve in the bottom of the bucket which opens by striking the ground1 and thereby emptying the bucket1 which is caused to rise again by the action of a counterweight on the other side of the pulley over which it is suspended4 ,illustration3 ,figs4 #ahd1 #ahe1 #ahf4 ,different forms of water movements ,fig4 #ahg4 ,overshot water-wheel4 ,fig4 #ahh4 ,undershot water-wheel4 ,fig4 #ahi4 ,breast-wheel4 ,this holds intermediate place between overshot and undershot wheels2 has float-boards like the former1 but the cavities between are converted into buckets by moving in a channel adapted to circumference and width1 into which water enters nearly at the level of axle4 ,fig4 #aij4 ,horizontal overshot water-wheel4 ,illustration3 ,figs4 #ahg1 #ahh1 #ahi1 #aij4 ,water-wheels ,fig4 #aia4 ,a plan view of the ,fourneyron turbine water-wheel4 ,in the centre are a number of fixed curved chutes1 or guides1 ,a1 which direct the water against the buckets of the outer wheel ,b1 which revolves1 and the water discharges at the circumference4 ,fig4 #aib4 ,warren's central discharge turbine1 plan view4 ,the guides ,a are outside1 and the wheel ,b revolves within them1 discharging the water at the centre4 ,fig4 #aic4 ,volate wheel1 having radial vanes ,a1 against which the water impinges and carries the wheel around4 ,the scroll or volute casing ,b confines the water in such a manner that it acts against the vanes all around the wheel4 ,by the addition of the inclined buckets c1 c1 at the bottom1 the water is made to act with additional force as it escapes through the openings of said buckets4 ,illustration3 ,figs4 #aia1 #aib1 #aic4 ,central discharge and turbine wheels ,fig4 #aid4 ,barker1 or reaction mill4 ,rotary motion of central hollow shaft is obtained by the reaction of the water escaping at the ends of its arms1 the rotation being in a direction the reverse of the escape4 ,fig4 #aie represents a trough divided transversely into equal parts1 and supported on an axis by a frame beneath4 ,the fall of water filling one side of the division1 the trough is vibrated on its axis1 and at the same time that it delivers the water the opposite side is brought under the stream and filled1 which in like manner produces the vibration of the trough back again4 ,this has been used as a water-meter4 ,fig4 #aif4 ,persian wheel1 used in ,eastern countries for irrigation4 ,it has a hollow shaft and curved floats1 at the extremities of which are suspended buckets or tubs4 ,the wheel is partly immersed in a stream acting on the convex surface of its floats2 and as it is thus caused to revolve1 a quantity of water will be elevated by each float at each revolution1 and conducted to the hollow shaft at the same time that one of the buckets carries it full of water to a higher level1 where it is emptied by coming in contact with a stationary pin placed in a convenient position for tilting it4 ,illustration3 ,figs4 #aid1 #aie1 #aif4 ,water motors ,fig4 #aig4 ,machine of ancient origin1 still employed on the river ,eisach1 in the ,tyrol1 for raising water4 ,a current keeping the wheel in motion1 the pots on its periphery are successively immersed1 filled1 and emptied into a trough above the stream4 ,fig4 #aih4 ,application of ,archimedes screw for raising water1 the supply stream being the motive power4 ,the oblique shaft of the wheel has extending through it a spiral passage1 the lower end of which is immersed in water1 and the stream acting upon the wheel at its lower end produces its revolution by which the water is conveyed upward continuously through the spiral passage and discharged at the top4 ,fig4 #aii4 ,common lift pump4 ,in the upper-stroke of piston or bucket the lower valve opens and the valve in piston shuts2 air is exhausted out of suction pipe1 and water rushes up to fill the vacuum4 ,in down stroke lower valve is shut and valve in piston opens1 and the water simply passes through the piston4 ,the water above piston is lifted up1 and runs over out of spout at each up stroke4 ,this pump cannot raise water over thirty feet high4 ,illustration3 ,figs4 #aig1 #aih1 #aii4 ,water-wheels and pumps ,fig4 #bjj4 ,ordinary force pump1 with two valves4 ,the cylinder is above water1 and is fitted with solid piston2 one valve closes outlet pipe1 and other closes suction pipe4 ,when piston is rising suction-valve is open1 and water rushes into cylinder1 outlet valve being closed4 ,on descent of piston suction valve closes1 and water is forced up through outlet valve to any distance or elevation4 ,fig4 #bja4 ,double-acting pump4 ,cylinder closed at each end1 and piston-rod passes through stuffing-box on one end1 and the cylinder has four openings covered by valves1 two for admitting water and like number for discharge4 ,a is suction pipe1 and ,b discharge pipe4 ,when piston moves down1 water rushes in at suction valve #a1 on upper end of cylinder1 and that below piston is forced through valve #c and discharge pipe ,b2 on the piston ascending again1 water is forced through discharge valve #d1 on upper end of cylinder1 and water enters lower suction valve #b4 ,illustration3 ,figs4 #bjj1 #bja1 #bjb4 ,pumps and windmill ,fig4 #bjb4 ,common windmill1 illustrating the production of circular motion by the direct action of the wind upon the oblique sails4 ,fig4 #bjc4 ,ordinary steering apparatus4 ,plan view4 ,on the shaft of the hand wheel1 there is a barrel on which is wound a rope1 which passes round the guide-pulleys1 and has its opposite ends attached to the tiller1 or lever1 on top of the rudder2 by turning the wheel1 one end of the rope is wound on and the other left off1 and the tiller is moved in one or the other direction1 according to the direction in which the wheel is turned4 ,fig4 #bjd4 ,capstan4 ,the cable or rope wound on the barrel of the capstan is hauled in by turning the capstan on its axis by means of handspikes or bars inserted into holes in the head4 ,the capstan is prevented from turning back by a pawl attached to its lower part and working in a circular ratchet on the base4 ,illustration3 ,fig4 #bjc4 ,cable ,illustration3 ,fig4 #bjd4 ,capstan ,fig4 #bje4 ,lewis bolt for lifting stone in building4 ,it is composed of a central taper-pin or wedge1 with two wedge-like packing pieces arranged one on each side of it4 ,the three pieces are inserted together in a hole drilled into the stone1 and when the central wedge is hoisted upon it1 it wedges the packing pieces out so tightly against the sides of the hole as to enable the stone to be lifted4 ,illustration3 ,figs4 #bje1 #bjf4 ,lewis bolts1 for lifting stones ,fig4 #bjf4 ,tongs for lifting stones4 ,the pull on the shackle which connects the two links causes the latter so to act on the upper arms of the tongs as to make their points press themselves against or into the stone4 ,the greater the weight1 the harder the tongs bite4 ,,iii ,,the ,,weather ,,and ,,indoor ,,work ,the measure of rainfall varies considerably within comparatively small areas1 and this renders it no easy matter to get correct figures1 so that the nearest records are those taken from a number of gauges within a limited district1 and generalized4 ,the more this is done1 the less will be the inaccuracy in referring to the rainfall of any particular district or country4 ,if numerous rain-gauges were established throughout the country1 and all their records sent to one central station1 what valuable information might be collected for a particular district or country in the course of years4 ,means might be found for using the superabundant water1 which falls in one part over another part1 where the rainfall is less4 ,information such as this might be of special value in the ,west and ,south4 ,it is collected now to a certain extent2 but not done so generally as it ought to be4 ,illustration3 ,fig4 #bjg4 ,rain-gauge ,illustration3 ,fig4 #bjh4 ,a made rain-gauge ,illustration3 ,fig4 #bji4 ,a more complete rain-gauge ,as the fall of rain is always measured in inches gauges are made to indicate the equivalent of a cubic inch of rain on the surface of the earth4 ,the simplest form of rain-gauge is a square or circular box or jar with a perfectly flat bottom and perpendicular sides 7see ,fig4 #bjg74 ,if the depth of water in such a gauge be measured after a fall of rain1 one can ascertain in inches1 or parts of an inch1 the amount of rain that has fallen on the surface of the earth4 ,care must be taken to have the edge of the gauge thin and free from dents1 the sides perpendicular and the bottom of the jar perfectly flat1 for though in one measurement these irregularities may not make much difference1 they would lead to a very decided error in a large number of measurements4 ,evaporation is also liable in such a gauge to give rise to errors1 and extraneous matters are easily introduced4 ,the better rain-gauges are constructed to avoid these contingencies1 as far as possible and to depend only on the area of entry for the accuracy of the measurements4 ,this area may be a square1 but is usually circular for convenience4 ,the circle must be accurate1 and its area is then easily calculated1 so that one can estimate the amount of rainfall1 however large the receiving vessel may be4 ,the edge of the circle1 which may be made of copper1 more durable than iron1 must be sharp1 with an overlapping rim to prevent raindrops from being whirled out of the receiver1 and connected by a shoulder to a funnel1 which directs the water into the receiver4 ,this may be a glass bottle fitted with a cork to hold the funnel firmly1 and prevent leakage between the outside of the funnel and the neck of the bottle 7see ,fig4 #bjh74 ,a more convenient receiver1 and one less likely to be broken1 is a round tin case of convenient size1 with a top fitting accurately under the overlapping edge of the funnel-shaped cover4 ,in this large receiver may be placed a small tin mug1 with a lip just under the funnel1 for conveniently measuring small quantities of rain1 and preventing waste by evaporation4 ,any overflow from the mug will be caught in the large receiver 7see ,fig4 #bji74 ,the circle of entry may1 of course1 be of any size2 but one whose diameter is between #d or #h inches will be most convenient4 ,make the circle determine its area by careful measurement1 using the following formula3 ,d#b 4#ghed area1 each square inch will give cubic inches for area4 ,take this amount of water and pour it into a glass1 marked at the top of the water1 and then divide the intervening space between this mark and the bottom into #ajj equal parts4 ,this graduated glass will give the rainfall in inches and #ajjths of an inch4 ,as an inch glass is somewhat cumbersome1 a half-inch glass is usually sent out with a rain-gauge4 ,it may1 however1 be sometimes convenient to use an ordinary ounce measure1 as graduated glass measures1 when broken1 are not always easily replaced2 so that it may be necessary to find the corresponding relation between the cubic inches of receiving area and ounces and drachms4 ,to do this1 we will suppose the diameter of the circular top of gauge to be #d4g inch2 this squared #bb4ji1 multiplied by 4#ghed #ag4cdidhf1 divided by #a4gcc 7an ounce avoir4 #a4gcc c4 in47 #aj4jaa oz4 avoir4 ,now if the rainfall is collected daily at a certain time in an ounce measure1 the amount may easily be recorded in inches by reference to the accompanying table3 inch inch #aj oz4 #a4jjjj #a oz4 4#ajjj #i 4#ijjj #g dr4 4#jhge #h 4#hjjj #f 4#jgej #g 4#gjjj #e 4#jfbe #f 4#fjjj #d 4#jejj #e 4#ejjj #c 4#jcge #d 4#djjj #b 4#jbej #c 4#cjjj #a 4#jabe #b 4#bjjj ,a similar calculation can be made and table prepared for any larger circle of entry by the same method4 ,the amount of rainfall in any country is a matter of great importance to that country1 and1 like the rise of the ,nile in ,egypt1 it indicates the coming state of the crops4 ,if we have too small a rainfall1 drought and withered crops follow1 and if we get too great a fall of rain1 drowned out crops1 and disastrous floods occur1 so you see how necessary it is that those people who are elected to look after the welfare of a nation1 should keep posted on matters of rainfall in all its phases4 ,in ,india1 ,china and some other parts of the world the question of rainfall is one of life and death to the people1 and most of the great famines of the past have been due to the small rainfall4 ,hundreds of thousands of people used to perish by famine and disease year after year4 ,much of this danger from shortage of rain has happily been avoided in ,india by the efforts of the ,british government1 which has inaugurated and carried out great schemes of irrigation and artificial waterways to prevent the recurrence of famine from drought4 ,our own government also is expending large sums of money on irrigation plans now being executed in ,arizona1 ,texas1 ,colorado and other states1 which will render immense territories fit for cultivation1 which would otherwise have remained barren and of no use4 ,the matter of rainfall is of the highest importance to a nation and to the men and beasts inhabiting it4 ,will it rain to-day8 is a question frequently asked1 as regards the weather1 showing how important the subject is1 and while ,i am talking on it1 it may not be amiss to make a few remarks regarding the formation and distribution of rain1 as formulated by learned meteorologists4 ,we are told that the two great causes of rain are the sun and the ocean--the latter1 of course1 includes the great lakes and rivers--and since these two factors may be taken as constant1 it follows that the rainfall over the earth as a whole will always be constant1 while the local variations will be due to local conditions4 ,the rain which falls on this continent is drawn up by the sun from the various sources1 but the conditions which cause its precipitation may be said to be local4 ,to your imagination may be left the tracing of the journey of the rain drops back to the ocean again4 ,the starting points in considering the causes of rain are1 therefore1 heat and moisture4 ,from the surface of land and water moisture is continually evaporating into the atmosphere1 and the higher the temperature of the air the more watery particles it can hold4 ,if any reduction in the temperature of this saturated air should take place1 the vapour becomes visible as fog1 mist1 or cloud1 and it is from this vapour that the rain drops are formed4 ,recent research says that these watery particles require minute dust atoms as nuclei before they can form1 and it has been estimated1 by experiment1 that there are one thousand millions of them in a cubic foot of saturated air1 though their total weight amounts to only #c grains4 ,accepting these figures1 the mathematically inclined may be told that it would require a cloud three miles thick to produce one inch of rainfall4 ,but before these watery particles can fall to the earth as rain1 they must first form into rain drops1 and the question arises1 how are rain drops formed8 ,these watery particles pass into the air by evaporation1 and there are several ways by which the reduction in temperature necessary to render them visible can be brought about4 ,it may take place through contact with a colder body of air1 by expansion1 or by a reduction of pressure owing to a rise in altitude4 ,clouds are said to be formed by this last method1 for a volume of hot air rises higher and higher until it presently reaches a point when its contained vapour condenses1 and becomes visible as a cloud4 ,meteorologists repeat one of these processes in the laboratory1 by releasing from pressure damp air placed in a convenient glass globe1 and are able to see something of the methods of cloud formation4 ,it has been customary to speak of a cloud as being composed of watery particles floating motionless in the upper air2 but although it may appear unchanged in form1 it is all movement4 ,so soon as ever a cloud is formed1 its particles of moisture commence to fall slowly1 the rate of fall being in proportion to the diameter of the particles1 and this is due to the slight resistance the air makes to such very small atoms4 ,in passing1 it may be said that one observer estimates the diameter of these particles as from 4#jjjcc inch to 4#jjjbe inch4 ,the component parts of a cloud are always in motion and recognizing this fact it becomes possible to take the first step in considering the formation of a raindrop4 ,an easy way out of the difficulty of explaining the formation of a raindrop1 is to say that1 since clouds are so often of two opposite electric potentials1 there is always a continuous bombardment of watery particles taking place1 and some of these must unite and fall as rain4 ,the meteorologist is always tempted to call in electricity as an agency whenever he is anxious to discover a cause for some particular phenomenon4 ,this often explains one mystery by another4 ,the production of rain1 snow1 and hail has for many years been explained by vaguely ascribing them to the action of electricity1 without any information being forthcoming as to the precise way in which this action takes place4 ,meteorologists are at present attempting to find a more satisfactory explanation4 ,another theory is that the particles of moisture in a cloud1 like all other objects1 radiate heat1 and1 growing cold1 condense moisture upon their surfaces1 thereby increasing in weight until they assume the proportions of a drop4 ,this seemed a reasonable explanation of the formation of a rain drop until modern research decided that whenever moisture is condensed1 latent heat is set free1 so that all moisture deposited on a watery particle only serves to raise its temperature1 and cause evaporation of the moisture thus acquired4 ,the particles of water could not by this means grow to the full estate of a rain drop1 and the theory is being gradually abandoned4 ,a rain drop is1 according to modern meteorologists1 explained in a very simple way4 ,it has been seen how the hot1 damp air is formed into a cloud1 and also how the minute particles of water at once commence to fall slightly earthwards4 ,now these little particles as they pass into a warm layer of air would soon be evaporated1 and would never reach the earth at all4 ,their downward journey1 however1 is often through a cloud many miles thick1 and the most modern and simple theory is that in this journey they overtake some of their fellows1 and the joined particles increase their rate of travel1 overtake more and more particles until they presently become heavy enough to take the final plunge to earth4 ,were it possible to be just beneath a cloud1 an observer would see rain drops coming from it of all sizes4 ,the same process goes on in drops1 which trickle down a window pane1 or in the effervescing globules in a bottle of seltzer water4 ,in the latter instance1 the process is reversed1 for the globules are seen overtaking one another in an upward direction4 ,there are many points in favour of this theory of the formation of rain drops1 and at least it gets rid of those elaborate complications1 electricity and condensation4 ,with respect to the formation of rain by the impinging of clouds upon the tops of cold mountains in the northwest1 one authority argues that moisture is in these circumstances not condensed solely because of the contact with the cold hills2 that rain there is due to a mechanical cause1 the watery particles being squeezed together by the grinding effect of the clouds on the sides of the mountains in such a way that they coalesce1 and fall as drops4 ,a rain drop's roundness is due to the action of capillarity4 ,just as a circle made by dropping a stone into water owes its shape to the fact that the force is able to act equally in all directions1 so a rain drop is spherical1 owing to similar untrammelled action on the part of capillarity4 ,these are some of the explanations of the formation of a rain drop1 but meteorologists still have the subject under consideration4 ,the periods of rainfall are divided broadly into times of drought and times of flood1 and it is in these matters that meteorology is seen in its practical aspect4 ,some people ask1 ,where does all the rain come from8 ,others are surprised that rainfall totals up to such large quantities4 ,a fall of rain to a depth of one inch over a very limited area1 represents millions of gallons1 but in spite of this vast quantity of falling water1 many times multiplied if the annual rainfall be taken into account1 there still are water famines4 ,the question has often been debated whether man can modify climate or effectively tamper with the processes which produce rain4 ,rain making has not1 so far1 been a success1 though the firing off of heavy guns has been tried1 along with the legitimate avocations of the meteorologist4 ,the afforesting or deforesting of a district has1 however1 a marked effect upon rainfall4 ,three notable instances are ,ascension ,island1 ,malta1 and the neighbourhood of the ,suez ,canal1 where the planting of trees seems to have had the result of increasing the rainfall4 ,the effect of trees is felt more in the storage of rain water1 while leaves and roots serve to retain moisture that would otherwise quickly drain away4 ,a hill may be converted into a sponge by the judicious planting of trees4 ,the question of the storage of rain water becomes more pressing each year1 and the longer the settlement is put off1 the more difficult will decision become4 ,engineers called upon to prevent floods and to conserve rain water reply1 ,save our forests1 cover the land with trees4 ,the fact that such problems arise1 serve to show how great is the amount of water formed by the continual falling of the tiny raindrops4 ,as long as this beneficent downpouring is allowed to drain away unused or uncontrolled1 so long will droughts annoy and water famines bring distress4 ,in recording weather conditions1 symbols are sometimes used in order to shorten reports and1 while not universal1 most nations adopt these3 ,the symbol for rain is o1 a small circle filled in2 for lightning o2 for thunder ,t1 while the two latter combined make ,to1 the symbol for a thunder-storm4 ,nearly every weather component has a distinctive symbol1 and since a great part of the meteorologist's work consists in going over records of observations to search for the number of times the different phenomena occur during each week or month1 the task is much simplified when observers employ the symbols1 as it is easier to pick out a symbol from a printed or written page than it is to recognize a word4 ,these symbols1 moreover1 have been agreed upon as a sort of international notation1 and make it easier for the meteorologists of different countries to understand the records of foreign meteorological services4 ,everybody does not know the ,russian word for snow1 or the ,dutch for hail1 or the ,bosnian for rain1 but all who run1 may read when snow is universally written1 and hail represented by a wedge-shaped figure with lines drawn across4 ,time and space being limited1 nearly all published records of weather merely set forth the number of days throughout the year on which the different phenomena occurred1 and should snow1 hail or thunder happen two or three times in one day1 it would still be counted only as one day4 ,the yearly totals1 therefore1 show the number of days on which these conditions have been observed4 ,it is now an almost universal custom to count 4#ja inches or more during the twenty-four hours as a day of rain4 ,accordingly1 where observers read their rain-gauge to three places of decimals1 that on which less than 4#jje inch fell would not be counted as a rainy day4 ,smaller amounts would1 however1 be included in the total4 ,dew may sometimes fall to the amount of 4#ja in4 or more2 and that is counted as a rainy day1 the rule being to consider the amount of precipitation1 irrespective of the manner in which it has fallen4 ,if you wish to make these observations comparable with published records you would do well to conform to these rules4 ,,hail ,hail1 the next weather component to be considered1 presents many difficulties when the attempt is made to explain its origin and formation4 ,those who have anything to do with scientific matters are well acquainted with the hypothesis1 which explains a given fact1 and in considering the subject of hail1 the meteorologist hears of many hypotheses which are put forward as complete explanations of this phenomenon4 ,caution is1 therefore1 to be exercised and every reported statement severely questioned4 ,remembering the aphorism3 ,the man or boy who never makes a mistake will never make anything1 meteorologists have attacked the question of hail formation1 and1 although many mistakes have probably been made1 the subject has lost a good deal of its mystery4 ,for many years1 it was customary to be content with a recognition of the fact that hail and lightning very often occur together1 and the conclusion was drawn that the one was in some way responsible for the other4 ,sufficient corroboration of this hypothesis was to some meteorologists1 found in the fact that thunder and lightning are said to be almost unknown in the ,arctic regions1 and this supposed companion1 hail1 almost unknown4 ,roughly speaking1 the assumption was that lightning1 as it flashed through a cloud laden with watery particles1 caused hail to form4 ,such an explanation only tended to make the subject more mysterious1 and the question1 ,how is hail formed8 practically remained unanswered4 ,many simpler explanations of hail have been propounded as the result of modern research1 and1 like rain and lightning1 it has been demonstrated that hail owes its origin to the movement of the minute watery particles found everywhere in the atmosphere4 ,the clouds from which hail fall are ordinarily of great height above the earth1 #dj1jjj feet or even higher4 ,these are the well-known cirrus4 ,the first condition necessary to the formation of hail is a powerful ascending current of hot1 moist air1 which may condense its moisture in the shape of the large woolly cloud1 known as cumulus4 ,such a cloud may be #ajj cubic miles in volume1 and as long as it retains its shape nothing is likely to fall from it to the earth beneath4 ,before the formation of a thunder-shower1 cirriform fibres in some instances break away from the upper portion of this cloud1 the electrical tension is lowered1 and rain falls4 ,the coalescing of the particles of moisture has a great deal to do with the changes which take place in a cloud4 ,all these changes take place in the higher clouds in a marked degree1 and the varying strata through which the watery particles pass in ascending to and descending from this great height bring about the violent change essential to the formation of hail4 ,the necessary conditions for hail are1 therefore1 a powerful1 hot1 ascending current of air and great variation in the strata of the atmosphere as regards moisture and temperature4 ,mountains assist in forcing currents of air upwards1 and one mass of air impinging on another is also thrown upwards1 so that condensation of moisture rapidly takes place4 ,a hail cloud may be described as a tower of hot air1 from the top of which1 vapor is ejected into a frosty region4 ,hot plains are accordingly the most favourable spots for the formation of hail1 and in mountainous districts1 more hail falls at a distance from the mountains than among them4 ,snow is observed in all latitudes and at all heights1 but hail is confined to middle latitudes1 and is rare in high latitudes4 ,the places most affected by hail are those in which1 the temperature and humidity of the air are high1 while above1 at a great height1 there is a cold area below the temperature of freezing point2 but1 as in the case of the rain drop1 before anything can be definitely stated1 it must be shown how the particles of moisture coalesce to form hail4 ,,snow ,snow is frozen water which falls instead of rain when the temperature is below the freezing point4 ,the ultimate constituents of snow are tiny1 six-pointed crystals of ice4 ,they assume in combination a thousand different figures 7,fig4 #baj71 all exceedingly beautiful4 ,professor ,tyndall has shown1 further1 that the ultimate particles of ice are also these six-pointed stars4 ,the white colour of snow is caused by the commingling of rays of all the prismatic colours from the minute snow crystals4 ,separately the crystals exhibit different colours4 ,illustration3 ,fig4 #baj4 ,snow crystals ,snow is usually from ten to twelve times as light as water1 bulk for bulk2 so that where the snow falls pretty evenly1 the corresponding rainfall is readily determined by merely measuring the depth of snow and taking one tenth of the result4 ,the more accurate plan1 however1 is to thrust the open end of a cylindrical vessel into the snow1 invert the cylinder1 and then melt the snow in it4 ,snow plays an important part in the economy of nature4 ,in the first place1 the mere transformation of the water particles into ice is a process during which a large amount of heat is given out2 so that we may regard the formation of snow renders the air currents warmer than they would otherwise be4 ,fallen snow serves to protect the ground1 for1 owing to its loose texture1 it is a bad conductor of heat2 so that1 while checking the radiation of heat from the earth into space1 it does not draw off the earth's heat by conduction4 ,the ground is thus often #bc degrees to #cj degrees warmer than the surface of the snow above1 and sometimes the difference of temperature has been more than #dj degrees4 ,red snow and green snow have been met with1 more commonly in ,arctic regions1 but also in other parts of the world4 ,these colours are caused by the presence of minute organisms--a species of alga called ,protococcus nivalis4 ,the snow line of mountains is on the slopes below which1 all the snow which falls in the year1 melts during the summer4 ,above the snow line1 therefore1 lies the region of perpetual snow4 ,the altitude of the snow line depends on a variety of conditions4 ,the latitude of a snow range is1 of course1 important in determining the position of the snow line1 but many other circumstances have to be considered1 as the shape and slope of the mountain1 the aspect of either side of the range1 the character of the surrounding country1 the prevalent winds1 and so on4 ,the following table shows the observed height of the snow line in feet above the sea level in different places3 ,place ,latitude ,height ,spitzbergen #gh ,n #j4 ,sulitelma1 ,sweden #fg #e #c4hce ,kamtchatka #ei #cj #e4bdj ,unalaschta #ef #cj #c4eaj ,altai #ej #g4icd ,alps #df #h4hhe ,caucasus #dc #aa4jfc ,pyrenees #db #de #h4iej ,rocky ,mountains #dc #ab4dfg ,north ,himalaya #bi #ai4efj ,south ,himalaya #bh ,n #ae4ejj ,abyssinian ,mts4 #ac #ad4jfe ,purace #b #b #ae4cha ,nevades of ,quito #j #ae4hbj ,arequipa1 ,bolivia #af ,s #ag4gag ,paachata1 ,bolivia #ah #ab4jgi ,portillo1 ,chili #cc #ad4gac ,cordilleras1 ,chili #db #cj #f4jaj ,magellan ,strait #ec #cj #c4gjg ,,designing1 ,,making1 ,,and ,,inflating ,,paper ,,balloons ,draw a rough figure of the balloon1 as shown at ,a1 7,fig4 #baa47 ,divide this into any number of parts 7the more the better7 by horizontal lines4 ,take a radius of balloon on each line1 and describe circles1 ,b4 ,illustration3 ,fig4 #baa4 ,paper balloon ,divide this into twelve parts by radius lines1 then make pattern as follows3 ,draw a perpendicular1 ,c1 with horizontal lines at distance of horizontal lines on ,a1 but measured on circumference as c d4 ,then set off on each line from perpendicular one half the distance between the radius lines1 ,b1 on the corresponding circle as e f2 draw line through points thus found1 and result will be shape of each section4 ,allow a little on one side when cutting out for pasting4 ,this will be best made with strong tissue paper of any colour desired4 ,illustration3 ,fig4 #bab4 ,an improved balloon ,another method1 giving a shape somewhat different1 is shown in ,fig4 #bab4 ,first draw an elevation of the balloon it is intended to make1 either full size1 on the floor1 or to scale4 ,the shape here illustrated differs slightly from that of balloons usually sold ready made1 being wider at the mouth4 ,this shape1 however1 is not so liable to catch fire when swayed about by the wind4 ,divide the elevation into any number of parts 7the more the better7 by horizontal lines as shown 7,no4 #a74 ,take the radius of the balloon on each line1 as ,a ,b1 describe circles 7,no4 #b71 and divide these into twelve parts by radial lines4 ,then to make a pattern1 draw a perpendicular 7,no4 #c71 with horizontal lines at the distance of the horizontal lines 7,no4 #a17 but measured on the circumference as ,c ,d4 ,then set off on each line from the perpendicular half the distance between the radius lines 7,no4 #b71 on the corresponding circle as ,e ,f1 and draw a line through the points thus found1 and the result will be the shape of each section4 ,allow a little 7say #a_/d inch71 on one side when cutting out for pasting4 ,each section will be made up of one1 two1 or three pieces1 according to the size of the balloon to be made4 ,if the pieces are cut as shown 7,no4 #d17 a great saving of paper results4 ,to paste these pieces together1 place them in a pile on the table or bench with the edges flush and a piece of waste paper under the pile4 ,now rub the top sheet with the thumb nail until each piece is moved back from the one immediately under it about one-fourth inch4 ,place a piece of waste paper about the same distance from the edge of the top sheet1 and pass the paste brush over the whole of the exposed edges4 ,no4 #e will explain what is meant4 ,now place two of the completed sections together so as to look like ,no4 #c1 with a small part projecting as shown by the dotted line ,g4 ,paste the edge of the under section--that is1 the part hatched--and turn it over on to the dotted line ,h4 ,when each two of the sections have been joined in this way1 proceed in the same manner to join these together till the whole is completed4 ,a circular piece of paper is cut out to join the sections at the top1 and a loop of string should be pasted to the top to suspend the balloon while inflating4 ,a ring of wire with two cross pieces is fitted to the bottom of the balloon1 and the inflammable material1--tow soaked in methylated spirits--is fastened to the junction of the cross pieces4 ,,magnetized ,,watches ,the owner of a good ,american watch was a little troubled concerning it1 because it had been running irregularly for some time past4 ,it came out that he had visited the electric power house and had stayed for some time examining the works and machinery1 so that parts of his watch had evidently become magnetized by the influence of the dynamos4 ,the watch had been made some time ago1 and had not the power to resist1 or neutralize electric influences1 that most watches have now4 ,to demagnetize the watch would bring it back to its original condition1 but a second visit to the lighting plant would again spoil its time-keeping qualities4 ,the watchmakers now have a way of making watches so that they are not affected by magnetism1 but comparatively few of the time pieces in use are non-magnetic1 and the average watch is subject to these seasons of fickleness4 ,the exceedingly fine and exact construction of the watch is not realized by the average possessor of the article4 ,an examination of the works of a watch shows the mechanism as now constructed1 although very small in size1 to be accurately planned and executed4 ,changes of temperature are provided for1 so that the movement is automatically adjusted4 ,the mainspring and train of gears are usually concealed1 while the balance and hair springs are in full view when the case is open4 ,upon the regularity of the movement of the balance depends the time keeping quality of the watch4 ,on looking closely at the balance1 you will observe that it is not a complete ring1 but two halves supported at one end4 ,these rings bear a number of large-headed screws1 placed at irregular distances1 which give it the exact weight and balance required4 ,these half rings will also be found1 on looking closely1 to be composed of two metals so closely joined that a difference in colour alone gives evidence of the quality4 ,this arrangement of iron and brass1 on account of their different coefficients of expansion and contraction with changes of temperature1 has been so carefully constructed that1 with changes of temperature1 the balance assumes such forms as to give it a uniform rate of motion4 ,the parts affected by magnetism are the balance and springs4 ,the balance in an ordinary watch moves five times a second1 #ah1jjj times an hour1 and #dcb1jjj times each day2 but a slight change in the forces that move it is necessary to make a difference of several minutes each day4 ,as the balance moves back and forth1 the magnetism of the mainspring is pulling or pushing it4 ,if this force were constant1 and always in the same direction1 the watch would run uniformly4 ,such1 however1 is not the case4 ,when the mainspring is tightly wound1 its magnetic poles are in a certain direction1 and in unwinding they are constantly changing1 so that the direction of this force is also constantly changed4 ,the effect on the balance is to cause the watch to run too fast sometimes1 and too slow at other times4 ,non-magnetic watches are made with these parts of a non-magnetic metal1 so that they are not influenced by electric machinery4 ,for testing watches a small compass is used4 ,when placed over the balance1 the needle will vibrate with the motion of the balance in proportion to its magnetism4 ,a ,,boy',s ,,wheel-,,barrow ,illustration3 ,fig4 #bac4 ,a boy's wheel-barrow4 ,perspective view ,illustration3 #bac ,a4 ,boy's wheel-barrow4 ,side elevation ,illustration3 #bac ,b4 ,finished plan ,illustration3 #bac ,c4 ,plan of frame ,the bottom1 sides1 and ends were about three-quarters of an inch thick4 ,good white and red pine were used for the purpose4 ,the stiles and rails of the bottom framework were mortised and tenoned together as shown at ,fig4 #bac2 these may be just stubbed together1 or the tenons of the rails can go right through the stiles4 ,the most satisfactory job is to groove the sides and ends together1 and put all together with oil paint in the joints4 ,if the joints are painted before the framework of the barrow is put together1 it will last for years2 otherwise1 being a boy's wheel-barrow1 it would likely often be forgotten and left out in the rain1 and the joints getting wet would hasten decay4 ,two coats of good oil paint1 ,indian red1 will give it a very nice appearance4 ,this barrow1 while not intended for heavy work1 is capable of carrying quite a load4 ,the wheel was cut out of a piece of plank about #a-a_/b inches thick1 hooped up with an iron tire made from heavy hoop iron4 ,the axle was made of wood with a #c_/d-;inch round iron rod running lengthwise through it and projecting about three inches through on each end4 ,the arbours or boxing1 in which ran the ends of the round rod1 were formed on the ends of the handle stiles1 as may be seen in the illustration4 ,the cost of all the materials for this really useful article was less than #a4ej1 all told4 ,,vacuum ,,cleaners ,a single hand vacuum cleaner can be made from a powerful suction pump1 as indicated in the sketch ,fig4 #bad4 ,this should be connected with a metallic box by means of a flexible armoured rubber hose1 covered at the end with a piece of fine wire gauze to prevent large particles of dust1 etc41 being drawn into the pump4 ,to another opening of the box should be fastened another flexible rubber tube1 with a bell-shaped metal attachment at the end4 ,the bell-shaped arrangement should be held closely to the carpet while the pump is in action4 ,within the box1 the pipe to which the pump is attached should be bent upward1 so that the rush of air shall not bring the dust with it2 the object being to collect the dust in the box4 ,a lid covers the box so that it can be emptied from time to time4 ,the success of this arrangement depends on the strength of the pump2 if it be a weak one1 the inrush of air through the funnel will be so slight that the dust will not be raised4 ,illustration3 ,fig4 #bad4 ,home-made vacuum cleaner ,illustration3 ,fig4 #bae4 ,metallic vacuum cleaner ,illustration3 ,fig4 #baf4 ,simple vacuum cleaner ,rotary pumps are not satisfactory for vacuum cleaners4 ,the best type for this work is a plunger1 having a large displacement1 with a comparatively short stroke in proportion to the diameter4 ,a suitable pump is shown in the accompanying illustrations4 ,fig4 #bad1 shows the section of a single barrel1 but should a greater supply be required1 two barrels may be worked and connected as shown in ,fig4 #baf4 ,the pump is easily made1 and of light construction4 ,in ,fig4 #bae1 is a brass cylinder with a flange at the bottom2 this may be made out of a length of #c-;inch brass tube with a flange cut from #a_/h-;inch sheet brass4 ,the barrel is #h inches long4 ,g is the plunger1 which may be constructed as a piston2 but in the drawing1 it is adapted to the arrangement that is shown in ,fig4 #baf4 ,with a piston will be required a guide for the rod at the top of the cylinder4 ,e is a hydraulic cup1 its leather kept soft and pliable by oiling4 ,b is the base1 which is hollow1 and may be built up in sheet metal4 ,at the centre at ,j1 the base is divided into two compartments1 one side being the inlet to the pump from the dust box1 and the other in communication with the outlet valve ,c4 ,c and ,d are two valves with guards4 ,the valves are discs of very soft and pliable leather1 well saturated with grease1 ,d being the inlet from the dust box1 and ,c the outlet to the atmosphere4 ,the drawing clearly shows the construction of the other parts4 ,fig4 #baf shows two pumps fitted to one base and worked by a rocking lever2 both pumps are in communication with the one inlet ,n4 ,this arrangement of pumps is easy to work1 portable1 and well adapted to domestic purposes in cleaning carpets4 ,illustration3 ,fig4 #bag4 ,a motor vacuum cleaner ,fig4 #bag1 which is reproduced from ,the ,scientific ,american1 exhibits an ingenious form of vacuum cleaner4 ,it has recently been patented1 and consists of a suction-fan operated by a water-motor that may be attached to the ordinary kitchen faucet4 ,a tube is connected with the chamber of the suction-fan1 and this terminates in a suitable nozzle1 or foot plate1 which may be moved over a carpet or rug to draw out the dust and dirt4 ,one of the advantages of this system is that dirt drawn up by the suction fan can be carried away with the water down the kitchen drain4 ,illustration3 ,fig4 #bah4 ,home-made power-driven vacuum cleaner ,a good power-driven cleaner may be made at home1 says ,popular ,mechanics1 by following these directions3 ,first take a good pine board1 #a inch thick1 #a foot wide1 and #c feet long1 and nail to each end a #a-;foot length of #b-;inch by #b-;inch pine1 as shown at ,a1 ,fig4 #bah4 ,next a #c_/d-;inch board1 #a foot wide and about #a foot1 #c inches long1 should be fastened near the centre1 and at right angles to the first board1 as shown at ,b4 ,procure a tin pan measuring about #aj inches in diameter and #c inches deep4 ,this pan shown at ,c1 must be fitted with two valves1 which are the most important and difficult part of the work4 ,cut1 from a smooth piece of pine1 #a inch thick1 two discs1 #e inches in diameter1 with a #c-;inch hole in the centre of each4 ,obtain a sheet of packing rubber1 #a_/h of an inch thick1 and cut from it two discs1 each #e inches in diameter1 and two #c-a_/b inches in diameter4 ,one of the discs of wood should be fastened to the back of the pan at the top1 as shown at ,d1 ,fig4 #bai1 with one of the #e-;inch diameter rubber discs placed between the tin and the wood1 and both secured to the tin by a row of small bolts around the outside edge of the wood4 ,a hole1 #c inches in diameter1 can now be cut through the tin and rubber1 using the hole in the wood as a guide4 ,two discs with a diameter of #c-a_/d inches should be cut from cigar box wood and fastened centrally on the #c-a_/b-;inch rubber disc4 ,one of the latter pieces should be fastened by its top edge to the top edge of the #e-;inch disc of wood1 as shown in ,e4 ,this forms a flap valve1 and great care should be taken to see that the rubber disc covers the opening all the way around when the valve is closed1 so that it will be air-tight4 ,a spring will be necessary to quicken the action of this valve4 ,this is best made by fastening a narrow strip of wood across the valve opening on the inside of the pan1 as shown at ,f1 and attaching a rubber band to the centre of the valve and to this stick4 ,this completes the outlet or exhaust valve4 ,another valve must now be made in the same manner1 and fastened to the bottom of the pan on the inside1 as shown4 ,this is the inlet valve1 and works in the opposite direction to the outlet valve just described4 ,illustration3 ,fig4 #bai4 ,home-made1 power-driven vacuum cleaner ,next procure a piece of leatherette about twelve inches in diameter1 or large enough to cover the opening of the pan4 ,this is to be used for the diaphragm4 ,cut a round hole about #h inches in diameter in the upright piece ,b 7,fig4 #bah71 its centre about #g inches from the top4 ,from a piece of #a_/b-;inch pine1 cut two discs #f inches in diameter4 ,also secure a piece of hardwood ,h #a inch by #a foot #b inches4 ,the discs ,g should now be placed1 one on each side of the leather diaphragm1 exactly in the centre1 and fastened to one end of the #a-;foot #b-;inch piece by means of a long screw4 ,this piece ,h should exactly be in the centre of the diaphragm4 ,the pan can now be put in place4 ,set the diaphragm over the hole in the board ,b1 the stick projecting through the hole4 ,the pan is now placed over the diaphragm1 and held by means of small bolts around the edge4 ,the diaphragm between the wood and the tin acts as a gasket1 and makes an air-tight joint4 ,secure an air-tight tin about #h inches in diameter and #ab inches high1 and fasten it to the base board1 as shown at ,j1 ,fig4 #bah4 ,the cover of a coffee tin should now be soldered over the inlet valve1 as shown at ,k1 ,fig4 #bai4 ,solder a hose connection in the centre of this cover1 also one in the side of the tin1 as shown at ,l1 ,fig4 #bah4 ,couple a short piece of hose ,m to these connections4 ,the strainer ,s should be made of very strong and closely woven unbleached drill4 ,make it in the form of bag with a #a-;inch hem at the top1 and place it in the tin1 as shown by the dotted line1 the hem fitting closely over the inside edge of the tin4 ,the cover of the tin is made from a flat pine board about one inch thick1 and is held in place by two #a_/d-;inch rods fastened in the base board4 ,these rods have thumb nuts on the top1 which allow the cover to be readily removed or tightened down4 ,it is best to place a rubber or leather gasket between the cover and the edge of the tin so as to make an air-tight joint4 ,an air-tight piece of garden hose can be used for the suction hose ,n1 one end being fastened in the centre of the cover and the other to the brush or nozzle ,r1 ,fig4 #bah4 ,it is best to buy this nozzle1 as it would be rather expensive and unsatisfactory if home-made4 ,this machine may be driven by an electric motor of about #a-a_/d horse-power1 which should be placed in the position shown in ,fig4 #bah4 ,the end of the connecting rod ,h is fastened to a crank on the motor shaft1 and allowed to have about a one and one half inch stroke4 ,the motor is wired up with a switch1 ,p1 and it would be best to connect to a rheostat1 to allow the regulation of speed best suited to the machine4 ,this can readily be determined after the machine is started4 ,if an electric motor is not available1 a small water motor will do equally well2 or it may even be run by hand1 by means of a long lever1 fulcrumed at ,p4 ,the machine is now ready for using4 ,first1 however1 test it all over for leakage1 as its success depends on its being perfectly air-tight4 ,as the motor revolves1 the rod ,h is drawn forward1 bringing with it the diaphragm4 ,this creates a partial vacuum in the pan ,c1 which opens the inlet valve1 sucking the air through the suction hose and strainer1 the air carrying with it the dust and dirt4 ,the refuse is left in the strainer bag while the air goes on through the connecting hose and pan and outlet valve into the atmosphere4 ,after the article being cleaned has been gone over thoroughly1 care being taken to hold the nozzle against the material1 the cover may be removed and the bag emptied4 ,,iv ,,motors ,,and ,,type-,,writers ,,motors1 ,,gasolene ,,and ,,steam--,,automobile ,,frames--,,the ,,modern ,,type-,,writer--,,directions ,,for ,,securing ,,copyrights4 ,there are two classes of heat engines in use2 in one class the combustion takes place on the inside of the cylinder or generator1 just as fire is applied to a tea-kettle1 and the heat is transmitted by conduction through the metal walls to the part of machine doing the work4 ,motors and machines of this kind1 are generally called external combustion engines1 of which the steam engine is a prominent example4 ,engines where the combustion takes place inside the machine itself1 and acts directly on it1 are engines of the second class1 termed internal combustion engines4 ,the gasolene engine is of this type1 and so are all gas and oil engines4 ,the principle of the motor-cycle engine1 in its action1 is similar to the regular automobile engine and the gas engine4 ,all these are internal combustion or explosion engines2 that is1 their motive power is derived from the force exerted by the explosion of a gas while under compression1 the compressed gas generally ignited by means of an electric spark4 ,in the case of gasolene motors1 the gas is obtained from the liquid gasolene1 either by allowing air to be drawn through it or by spraying the spirit through a small hole1 the latter being the method most generally used4 ,a great quantity of air has to be mixed with the vapour before it will ignite4 ,the amount that is required varies considerably1 atmospheric conditions and the height above sea level causing variations in the demand4 ,the action of the common gasolene engine is known as the four-stroke-cycle1 that is1 there are four strokes of the piston for every impulse1 one being a power stroke and the other three duty strokes1 as it were4 ,each performs a certain operation that is necessary for the correct working of the engine4 ,some engines are worked on the two-stroke-cycle principle2 in this case1 there are only two strokes for each impulse4 ,this type of engine has many disadvantages1 and there are very few two-stroke engines in use for driving motor cycles4 ,illustration3 ,fig4 #bbj4 ,suction stroke begun ,illustration3 ,fig4 #bba4 ,compression stroke begun ,illustration3 ,fig4 #bbb4 ,power stroke begun ,illustration3 ,fig4 #bbc4 ,exhaust stroke begun ,the principle of the four-stroke-cycle is shown in ,figs4 #bbj to #bbc4 ,in ,fig4 #bbj the piston ,a is just beginning the downward stroke1 and the valve ,b is opened by the pressure of the atmosphere1 or by mechanical means4 ,the piston in descending causes a partial vacuum in the cylinder head or top ,c1 which allows the atmospheric pressure on the surface of the gasolene in the carburetor to force some of the liquid through the spray hole1 thence through the inlet-valve opening ,d1 into the compression space of the engine cylinder4 ,the suction of the piston does not bring in the explosive mixture of gas and air2 it is the pressure of the atmosphere that causes the mixture of gas and air to rush into the cylinder4 ,just before the piston is at the extreme end of the downward or outward stroke1 the inlet valve ,b is closed by the spring shown1 and the piston begins the first upward or compression stroke with both the inlet valve ,b and the exhaust valve ,e closed4 ,the charge is being compressed when the piston is on its upward stroke1 as shown in ,fig4 #bba4 ,speaking generally1 soon after the piston is over what is known as the dead centre1 and is about the position shown in ,fig4 #bbb1 an electric spark is made to jump across two points of the sparking plug ,f2 this ignites the mixture of gas and air 7which is at a pressure of about #hj lb4 per sq4 in471 and the explosion causes the piston to descend on the power stroke4 ,just before the piston reaches the bottom of the power stroke1 the exhaust valve ,e1 ,fig4 #bbc1 opens1 and remains open during the upward stroke4 ,the momentum of the flywheels1 etc41 carries the piston upward1 and thus forces out the burnt gases through the exhaust opening ,g1 and from there to the silencer4 ,immediately the piston begins its next downward stroke1 the inlet valve opens1 fresh air is drawn in1 and the cycle of operations is repeated as before4 ,the illustrations show a magneto gear driven by the engine4 ,these engines when properly arranged are made to do service as marine motors1 and are then installed either horizontally or vertically4 ,a vertical engine has been shown on previous pages1 but perhaps a little further explanation may not be amiss4 ,engines for boats are made with one cylinder or with more1 and there are many considerations which make an engine of two or more cylinders particularly desirable4 ,it is a self-evident fact that when the limit of size of a single-cylinder is reached1 it is necessary to add other cylinders if greater power is desired4 ,even for moderate or small powers1 there are many advantages4 ,among these may be noted the fact that with the proper arrangement of cylinders the impulses may be made to occur at shorter intervals than with a single-cylinder engine4 ,thus with a two-cylinder engine1 the cylinder may be so arranged that the impulses will occur twice for every revolution instead of once1 as in a single-cylinder4 ,this gives a more even turning effect to the shaft1 and consequently steadier running1 and it also requires a less heavy fly-wheel4 ,the vibration is much less1 as one set of working parts may be made to travel upward while the other is travelling downward1 thus neutralizing the throw of each and lessening the vibration4 ,in case of the disablement of one cylinder1 there is the chance of getting home on the remaining ones4 ,the weight1 power for power1 of the multiple-cylinder engine is less than that of the single-cylinder engine1 as the weight of the fly-wheel and other working parts is less4 ,while for marine work1 single-cylinder engines have been built as large as eight or ten horse-power1 they are so large as to be rather cumbersome and the practice now is to build engines of more than six horse-power with two or more cylinders4 ,there are several firms who are making double-cylinder engines as small as four horse-power1 which both as to weight and reliability are much superior to those of a single-cylinder4 ,illustration3 ,fig4 #bbd4 ,two-cylinder engine ,the original method of constructing a multiple engine1 and one which is still used by some builders1 is simply to use two or more single-cylinder engines coupled together4 ,this is a cumbersome method and takes up a great amount of space4 ,the simplest method which can be recommended is that shown in ,fig4 #bbd4 ,it consists of two single-cylinders mounted on a common base of special design1 bringing the cylinders much nearer together than when a coupling is fitted to connect two separate engines--as the shaft can be made in one piece4 ,this particular engine is of the two port type1 two vaporizers ,v-,v being used4 ,the gasolene enters at ,g and branches to each vaporizer4 ,the pump is shown at ,p with the discharge at ,w1 piped with a branch to each cylinder4 ,the cooling water outlet is at ,o4 ,the exhausts are connected to a common pipe with the outlet at ,e4 ,the igniting gear for each cylinder is independent and on opposite ends4 ,by means of the lever ,l1 which is connected to both igniting gears1 the time of ignition is regulated and kept the same on both cylinders4 ,this allows multiple-cylinder engines to be built with very few extra parts1 as the cylinders1 ignition gear1 etc41 are the same as in the single-cylinder engine4 ,illustration3 ,fig4 #bbe4 ,single-cylinder engine ,a view of a representative single-cylinder engine is shown at ,fig4 #bbe4 ,the cam shaft is located at a and is driven by the gears which are shown just in the rear of the fly-wheel4 ,at c are the cam and the roller1 which actuates the exhaust valve4 ,the cam consists of a collar with a flat projection or toe upon its surface2 the roller rests just above the surface of the collar1 and is forced upward when struck by the projection4 ,the roller is inserted to lessen the friction by rolling instead of rubbing4 ,the valve stem extends upward into the valve chamber1 and is encircled by the coiled spring e2 the stem is guided by the guide at g4 ,the exhaust is at ,e2 ,i is the pipe leading from the vaporizer ,v to the inlet port in the valve chest4 ,the inlet valve is directly below the spring ,s and is inverted1 being held in place by the spring4 ,the dome-shaped cap containing the inlet valve is removable for access to both valves4 ,the complete cover is also removable4 ,it will be observed that this engine has an open frame very similar to that of a steam engine1 giving free access to the crank-pin and main bearings2 the latter are shown fitted with oil boxes b instead of the grease cups1 as there is no pressure tending to force the oil out along the shaft as in the two-cycle type4 ,this open base not only makes the bearings more accessible1 but renders it easier to lubricate them and keep them cool4 ,at ,h is the ignition gear4 ,p is the cooling water pump1 run by the eccentric e4 ,the suction is piped to d and the pump discharges through the pipe k into the cylinder4 ,the outlet for the cooling water is at ,o2 ,n is the cylinder oil cup for oiling the bore of the cylinder4 ,the compression cock ,r is for relieving the compression at starting4 ,the coupling at ,x is for attaching the propeller shaft4 ,in this engine1 the cylinder1 base and bolting flange are one casting1 the upper half of the main bearing being removable for the insertion of the shaft4 ,the cover is bolted on separately4 ,,automobile ,,frames ,the chassis for the single-cylinder1 eight horse-power motor machine shown herewith is built on the principle of most frames1 of any make and is typical of the majority of light motor car chassis at present in use4 ,illustration3 ,fig4 #bbf4 ,eight horse-power single cylinder chassis ,a diagrammatic plan of the eight horse-power1 single-cylinder chassis is shown in the accompanying illustration 7,fig4 #bbf7 in which1 ,a indicates parts enclosed1 taking the mixture of gasolene and air from the float-feed spray carburetor ,b1 which has an automatic air regulator4 ,the purpose of this last device is to dilute the mixture when the engine has a light load and is inclined to race2 generally speaking1 this regulator serves to proportion the ingredients of the explosive mixture to the requirements of the engine4 ,current ,o for the ignition of the explosive mixture 7ignition occurs once for every two revolutions of the fly-wheel71 is supplied by an accumulator and intensified by a high-tension coil4 ,the products of combustion pass through the exhaust pipe ,c to the muffler ,d1 from which they pass to the atmosphere through a series of fine holes4 ,the starting handle ,e makes a simple connection with the end of the motor shaft ,f when required4 ,g is the fly-wheel4 ,the drive from the engine is through a universal joint ,h to the change-speed gear ,j1 the latter consisting of two trains of toothed wheels1 a big wheel on the primary shaft gearing with a small one on the secondary shaft to give a high speed1 and vice versa4 ,from the change-speed gear1 the drive is through a shaft ,k1 having a universal joint ,l at each end1 to the bevel gearing above the differential gear of the live rear axle4 ,bevel gears and the differential gear are all contained in the casings ,m4 ,three brakes are fitted1 one operated by pedal1 working on a drum ,n secured to the propeller shaft1 the others operated by the side lever and working on drums ,o ,o1 secured to the rear wheels4 ,the change-speed gear gives three speeds forward and a reverse2 the frame is of pressed steel2 the rod and wheels are of the artillery type and carry #gjj mm4 by #he mm4 pneumatic tires4 ,the gasolene tank holds #d-a_/b gallons1 sufficient for #bjj miles1 and the lubricating oil tank holds #a gallon1 sufficient for #cej miles4 ,any beginner in motoring matters1 who studies the diagram1 will obtain a fair idea of the mechanism of the customary type of light car chassis4 ,illustration3 ,fig4 #bbg4 ,plan of chassis of light racing car--two-cylinder motor ,a chassis1 suitable for a #g-a_/b horse-power quick-speed1 two-cylinder motor1 is shown in ,fig4 #bbg4 ,it is not necessary to enter fully into the details of construction after describing such a typical gear-driven car as that at ,fig4 #bbf4 ,the frame ,a is of tubular steel1 there are four semi-elliptic springs1 and the artillery wheels have #bh-;inch by #c-;inch tires4 ,the two-cylinder engine ,b is one casting1 with a large waterway covered by an inspection plate ,c4 ,the bore is #c4e inches1 stroke #d-;inches1 cylinder capacity #gf4i cubic inches1 and the piston displacement is #ib4cjj cubic inches per minute4 ,a governor automatically throttles the inlet when the motor attempts to race1 but by means of a lever the governor can be cut out and the motor accelerated from its normal speed of #a1bjj revolutions per minute4 ,the balanced crank has but a single throw2 the water circulation is assured by a motor-driven pump1 and there is a belt-driven fan behind the radiator4 ,the commutator is easily accessible1 being mounted on a bevel shaft lying in a sloping position and passing through the side of the crank chamber4 ,ignition is high tension with wide contact1 the wiring being enclosed in a neat wooden casing4 ,the change-speed gear ,d gives three speeds and a reverse1 and its main bearings are fitted with ring lubricators4 ,a pressure sight feed lubricator on the dash-board has three outlets1 one to the engine1 another to the main clutch1 and a third to the driving pinion on the end of the propeller shaft4 ,the brakes are of the usual kind4 ,in ,fig4 #bbg1 ,e is the carburetor1 ,f the inlet and ,g the exhaust pipes1 ,h the exhaust muffler1 ,j the brake pedal1 ,k the clutch pedal1 ,l the band-brake on the propeller shaft1 and ,m the internal expanding brakes on the wheel hubs4 ,a shield is arranged under the front of the car to protect the mechanism from mud and dust4 ,the weight of the car unladen is about #a1dad pounds1 the wheel base is #gc-a_/b inches1 the track #df inches1 and the over-all dimensions are #aaa inches by #fj inches4 ,during a #fjj-mile trial this engine consumed #cf gallons1 #f pints of gasolene1 this being at the rate of #a gallon for every #af4i car miles2 4#jgg gallon was consumed every ten miles4 ,,the ,,modern ,,type-,,writer ,every home of importance contains a writing machine of some kind1 and these often require some little adjustment or fixing4 ,it is within the capacity of any bright boy to make these adjustments1 or to do the little fixings1 if he tries it earnestly4 ,the first marketable type-writer was introduced in the year #ahge4 ,no sooner had the type-writer acquired a commercial value1 than the fire of inventive talent was awakened in ,europe and ,america1 and type-writer after type-writer appeared on the market--a few came to stay1 but the many disappeared1 either during the chrysalis or experimental stage1 or shortly after it had been passed4 ,inventors and investors have learned that hasty innovations and untried experiments spell failure in the type-writer field1 and only patient and careful study1 backed by experience1 tireless effort1 and abundant resource1 have a chance of success4 ,by the year #ahhh1 there were six different kinds of machines in the market1 to-day there are at least twenty1 but the favourites seem to be1 ,the ,remington1 ,smith ,premier1 ,the ,underwood and ,the ,oliver4 ,modern type-writers may be defined as being tabulating1 book recording1 card indexing1 and document writing machines4 ,they are speedier and produce finer and more varied work than their predecessors4 ,the manner in which the type-writer performs its work is of the simplest4 ,the type-writer may be considered as composed of three general parts1 as follows3 ,the keyboard1 by which the operation of the machine is directed4 ,the type mechanism1 by which the desired letters are1 one after the other1 in any desired sequence1 imprinted on the paper4 ,the carriage1 which holds the paper in proper position for writing1 and which1 by its regular movements1 provides for the spacing of letters and lines4 ,the ,remington may be considered the pioneer of writing machines4 ,in appearance the ,remington ,no4 #e 7introduced in #ahhh7 is square1 and strikes a novice as being somewhat complicated4 ,it is only the multiplicity of parts1 however1 which creates this impression4 ,the machine is not complex1 the same parts being repeated over and over again4 ,the action is simplicity itself4 ,the machine is quite open on every side1 so that its entire construction can easily be seen4 ,there is a japanned iron frame enclosing and holding the working parts1 consisting of a base1 four upright posts1 and a top plate4 ,in front is a series of keys arranged in four banks1 like the keys of an organ1 each key representing the two characters1 termed upper and lower case letters4 ,these are connected with long light wooden levers1 which1 being depressed1 communicate motion by means of a rod fastened to the lever of a type bar4 ,at the end of each type bar is fixed the hard metal type representing the two characters4 ,the type bars are arranged in a circle1 therefore the point of percussion of the type on the paper is at a common centre4 ,the inking is done by a ribbon1 which travels automatically across the machine1 winding and rewinding on and from spools4 ,the paper is inserted between two rollers2 one of rubber1 called the paper cylinder1 and the other of wood1 called the feed roll4 ,the rollers are held together by two elastic india-rubber bands4 ,as one revolves so does the other4 ,the portion which holds these rollers is designated the carriage4 ,by a clever1 yet simple piece of mechanism1 this carriage is caused to travel1 simultaneously with the return of the type or spacing bar1 from right to left1 the width of a letter at each movement across the machine4 ,the carriage works on a sliding frame1 and this sliding mechanism is controlled by two keys1 which do not impress letters on the paper4 ,these change the character of the printing keys1 causing them to print capitals or small letters1 numerals or other marks at will4 ,depress the key marked upper case and all the keys will print capitals2 remove the finger and they all print small letters again4 ,moreover1 the machine can be arranged to print capitals continuously by the mere raising of a lever1 and quite independently of the upper case shift key4 ,to obtain an impression1 the required key is struck lightly1 and the type bar causes the type to strike against the ribbon1 thus leaving an imprint on the paper held round the cylinder2 the carriage moves automatically the width of the letter1 and the operation is repeated until a word is completed4 ,then the spacing bar at the front of the machine is depressed at any point1 thereby securing the requisite space between the words4 ,when the end of a line is reached1 warning is given by the ringing of a bell1 and then1 by pulling out the lever at the right-hand side of the carriage and gently pressing to the right1 the paper carriage is advanced into position to receive the next line4 ,the distance between the lines and the width of the writing can be regulated4 ,the paper carriage being hinged at the back allows of its being raised from the front by the hand1 so that the line that has just been written can be inspected4 ,the motive power is imparted by an adjustable coiled spring1 a thin leather strap being fastened to it and the carriage1 and the uniform space is governed by two clutches working on a rack4 ,this rack is fixed on a rocking shaft1 and derives a swinging motion from a universal bar fixed beneath the light wooden key levers4 ,a small lever attached to the left of the carriage holds its movements under the control of the operator4 ,two scales are fixed on the machine1 and these in conjunction with the pointer1 permit of head-lines being centred1 corrections made1 etc4 ,in some machines1 a special key and its accompanying mechanism is provided for each character or sign used--such are termed complete keyboard machines4 ,in others1 each key is made to represent the letters or signs--such are designated single-shift machines4 ,others1 again1 have two shift-keys1 and each key represents not only a lower case 7small7 and an upper case 7capital7 letter1 but a figure or other sign as well--such are known as double-shift machines4 ,the two classes of modern type-writers may be arranged into three groups1 namely3 ,blind writers1 in which the writing remains hidden until exposed by manipulative effort of the operator4 ,semi-visible writers1 which show only the last lines1 or only expose the centre of the paper1 hiding the writing at both ends of the line4 ,visible writers1 which expose a character directly in front of the operator the instant it is imprinted2 the character subsequently does not pass out of sight1 by feeding behind a scale or bar1 or other obstruction4 ,this classification and grouping is for convenience only1 and is in no way intended to denote superiority4 ,illustration3 ,fig4 #bbh4 ,remington type-writer ,no4 #g ,with regard to the ,remington1 many changes of the details of construction1 tending toward strength1 durability1 and a greater ease and convenience of operations1 have been introduced into the machine1 which have survived the severe test of time4 ,this is especially the case with ,remington ,no4#g 7see ,fig4 #bbh74 ,the most important of these valuable improvements are3 ,an entirely new form of escapement1 giving increased speed and an easy touch4 ,the carriage is stronger and lighter1 and steadier in all respects4 ,the annoying rubber bands1 which guide the paper around the platen have been discarded for a new form of paper guide1 which may be adjusted to any desired point4 ,the paper feed has been so arranged as to render it possible to write on wide or narrow paper1 and this can be fed into the machine by a simple movement of the hand without lifting the carriage1 and can be turned forward or backward at will4 ,the ribbon movement is improved and works entirely automatically1 reversing and giving a lateral movement4 ,the marginal stops also are improved1 and simple means provided for writing outside the margin whenever desired4 ,there is a keyboard lock1 locking the types at the end of the line1 and thus preventing one letter being printed over another4 ,a new variable line spacer is embodied1 which makes it easier to write at any point on the paper1 and prolongs the life of the platen for the reason that the type no longer strikes in unchanging grooves4 ,an adjustable side guide for arranging the paper to any desired marginal indentation is a recent addition4 ,a new two colour ribbon lever bearing a disc1 which signals the color which the machine is adjusted to write is another recent addition4 ,illustration3 ,fig4 #bbi4 ,smith ,premier ,no4 #d ,the ,smith-,premier type 7,fig4 #bbi7 has six models in the market and all nearly alike in their mechanism1 differing only in the carriage arrangements1 or the number of the characters4 ,the machine is particularly simple in construction1 and claims1 by means of a very long and strong adjustable bearing1 to have secured a perfect and permanent alignment4 ,the type bars work on hardened steel bearings1 #a-e_/h inches apart1 and the type bars are the shortest of any on a complete keyboard machine4 ,but the original and exclusive feature of the machine is the rocking shaft1 which replaces the usual wooden or metal key lever4 ,this consists of a circular rod1 passing from the front to the rear of the machine--one rod for each key4 ,projecting from each shaft is a small bar1 which is attached at the front end to the lower portion of the key stem4 ,a similar projection is attached to the rod communicating with the type bar1 and the result is that on the depression of the key the rocking shaft is made to revolve slightly1 and so raise the free end of the type bar to the printing point4 ,the type bar hangers are solidly riveted to the type ring4 ,it will be seen that matters are so arranged that the amount of force to imprint the character is precisely the same in every case--a uniform1 light and elastic touch4 ,a very noticeable feature is its quietness in operation1 due to the rigidity of its parts1 and the fact that the ball-bearing principle is adopted wherever it can be used to advantage4 ,it is also equipped with a circular brush1 built into the machine1 into which a handle can be immediately inserted1 when1 with a turn or two1 the whole of the type can be cleaned4 ,the most striking recent development is the adoption of a three-coloured ribbon device4 ,a simple movement of the lever in front of the machine brings the required colour into place ready for use4 ,a two-colour or single colour ribbon may be employed4 ,if desired the ribbon can be instantly shifted from the printing point for duplicating purposes4 ,the ribbon reverses automatically1 and it is attached to the spools with clamps--one on each spool1 dispensing entirely with pins and tapes4 ,illustration3 ,fig4 #bcj4 ,the ,oliver ,no4 #c ,the ,oliver1 ,fig4 #bcj1 differs in mechanical principle from other machines4 ,it has a wide ,u-shaped steel type bar1 provided with a tool-steel axle as broad as the bar is long1 and braced joints insuring the alignment without guides4 ,the connection between the type bars and the key levers is direct and perpendicular4 ,the type bars strike down on the platen in a line perpendicular to its plane1 thus transmitting the maximum power with the minimum resistance1 and further1 maintaining the alignment with several sheets as with one4 ,the type are of steel1 and lie face upward--very convenient for cleaning4 ,the keyboard is the ,universal1 having twenty-eight keys with a double shift1 giving eighty-four characters and the special model thirty-two keys1 giving ninety-six characters4 ,the tension and depression of the keys are light and uniform4 ,it may also be noted that the type blocks decrease in weight with the increase of length of type bar--necessary to secure a uniform stroke4 ,the escapement mechanism is exceedingly simple and positive1 and although very rapid is almost frictionless4 ,the writing is semi-visible4 ,the carriage is provided with three paper-feed rolls1 thus ensuring a perfect feed of the paper down to the bottom edge of the sheet4 ,it runs on anti-friction travellers on guide rails1 ensuring an easy and steady motion4 ,it is equipped with all the necessary devices4 ,the line space mechanism operates automatically as the carriage is returned from the left to the right for a new line4 ,the machine is compact and portable--weight about twenty pounds4 ,the parts of any of the machines now in the market1 may readily be disconnected1 but care must be taken by the novice in laying aside the parts so that they may be easily and correctly assembled4 ,repairs on the various parts may be made while out1 and when made may be placed in situ4 ,any or all of the parts may be cleaned when the carriage is taken off4 ,a little study of the machine when sitting before a person1 will enable him to understand its mechanism1 and when this is accomplished1 cleaning and repairing can be done intelligently4 ,the tendency of the times is to employ the type-writer whenever possible4 ,special devices are from time to time invented to meet extended uses4 ,the most important of recent applications is to office work for billing and book-keeping2 this work alone has necessitated important modifications4 ,in this direction1 the tabulator calls for review4 ,the lack of a practical method enabling tabular matter to be typed with a rapidity equal to that of the ordinary typing has long been felt to be a deficiency in type-writers4 ,the invention of the tabulator has enormously increased the scope of the machine in this direction4 ,the tabulator is a device by means of which1 figures or words can be written in columns1 with out employment of the space bar or carriage release lever1 or any adjustment whatever of the carriage by hand4 ,by its use1 the carriage may be set automatically at any point that may be required4 ,at present this device is an accessory to most machines1 but in the near future1 it must form an integral part of all machines1 and further1 enable the carriage to be automatically placed in a proper position to write numbers in correct relation to each other in columns2 that is1 units under units1 tens under tens1 and so on4 ,the built-in tabulators of to-day1 with but two exceptions1 are deficient in this respect4 ,the tabulator in either form does not interfere with the use of the machine for other work1 such as correspondence1 etc4 ,the tabulator was followed by the introduction of a bi-chrome 7two-coloured ribbon71 and quite recently the ,smith ,premier ,typewriter ,company has advanced still further in this direction by introducing a tri-chrome 7three-colour7 ribbon4 ,by a simple movement it is possible to vary the colour of the impression instantaneously1 so that credits1 marginal notes1 footnotes1 and underscoring may be indicated in red or other colour preferred4 ,one-colour ribbons can be used if desired4 ,the machine embodying the parti-coloured ribbons and tabulator devices are generally known as invoicing machines1 and by simple arrangements1 every phase--not only of correspondence1 but also of office and statistical work--can be accomplished1 with an enormous saving of time4 ,items can be made on sheets1 which may be taken from the machine with absolute certainty that when re-inserted1 the subsequent entries will fall into their proper places4 ,card ,indexing4--,for greater convenience in card indexing1 special platens are obtainable1 or the ordinary platens can be temporarily fitted with a metal clip4 ,both can be fitted to or removed from the machine in a few seconds1 and the cards can be adjusted in an instant4 ,the increasing use of the card file system for a wide variety of purposes lends special importance to the value of the type-writer for this class of work4 ,interchangeable ,carriages4--,for years the thousand and one wide forms1 statements1 and blanks common in every business office1 have been filled by the pen1 the reason being that there was no machine practicable for both wide and ordinary work4 ,the manufacturers of most of the modern type-writers now have models embodying interchangeable carriages1 which enable any one possessing a machine with this improvement to have at the same time a set of carriages from the largest to the smallest1 all of which can be used upon one machine4 ,in one or two makes this is additional to interchangeable platens4 ,illustration3 ,fig4 #bca4 ,interchangeable carriage ,duplicators4--,the value of a mechanical contrivance for the rapid and effective multiplication of copies of documents is fully recognized at the present time4 ,duplicating machines have been on the market for several years4 ,they will produce from one typescript original up to #c1jjj copies1 of any size1 from a post card to a sheet of brief1 every copy having the exact appearance of an original4 ,while there are various makes and styles of duplicators1 the main principle is the same throughout4 ,the original is prepared by the now well-known stencil process2 that is1 writing the matter required with a type-writer on a sheet of waxed paper4 ,the pressure of the type expels the wax out of the paper and leaves openings through which the ink can penetrate4 ,in the ,roneo rotary duplicator1 a metal frame supports a cylinder of thin1 perforated steel4 ,on the outer surface of the cylinder is stretched a linen ink-pad1 and over this is placed the stencil4 ,the pad is inked by a rubber roller resting in an ink receptacle suspended between the two sides of the framework4 ,by means of a simple lever this roller can be brought into contact with the cylinder1 and ink is thus supplied as required4 ,the cylinder is rotated by a handle4 ,paper fed into the machine is gripped by a rubber impression roller1 which presses it against the stencil as the cylinder revolves1 and the sheet perfectly printed1 is then automatically discharged on the other side4 ,the rotary can be fitted with three devices1 namely a feeder1 a simple contrivance1 which automatically feeds the sheet into the machine1 reducing hand labour to a minimum2 an interlever1 which automatically drops an interleaving sheet as each copy is printed--thus permitting of the use of highly glazed or very hard paper2 a cyclometer for registering the number of copies4 ,the rotary system is far superior to the hand duplicators in the matter of speed2 such a machine will print ten copies while the hand device prints one4 ,there is no lost motion1 a copy being printed and discharged at every revolution4 ,press ,copying4--,at the present time1 there are four methods of letter copying in vogue1 namely3 7#a7 ,the letter-book method1 damping sheets and screw press4 7#b7 ,roller process1 water bath and drying drum4 7#c7 ,carbon paper4 7#d7 ,the chemical letter copier4 ,the roller copies employ a water bath1 and give but little if any improvement in the regulation of the degree of moisture4 ,the copies are wound on a drying drum to prevent off-setting1 and subsequently have to be cut apart for filing purposes4 ,the carbon process enables the answers to be filed with the original letter4 ,the modern chemical letter copier offers distinct advantages over other methods4 ,it consists of a simple machine designed to carry a roll of specially prepared paper4 ,the letter to be copied is laid on the feed board1 the handle is turned1 the sheet is fed automatically into the machine4 ,it will be noticed that a water bath and brush or damping sheets1 are completely dispensed with2 there is no off-sheeting and no drying drum4 ,the copy may be either filed with the letter to which it relates1 or placed1 day by day1 in a cover having the appearance of an ordinary letter-book2 or two copies can be made of each letter--one for filing and the other for the book4 7#a74 ,a type-writer should be durable4 ,every part should be simple and strong and adapted to serve its purpose with the smallest degree of wear4 ,every mechanical movement must be definite1 and incapable of incomplete performance4 ,all wearing parts should be adjustable and interchangeable4 7#b74 ,it should possess absolutely visible writing4 ,the common-sense way to write easily and speedily is to see what you are writing while you are writing it4 ,the writing should be performed in such a part of the machine as to be most readily seen during progress4 7#c74 ,the keyboard--on type bar machines in particular--should be that known as the ,universal1 or ,standard arrangement4 ,the keys on any style of keyboard should have a light and uniform depression1 so that the machine may be operated with the minimum of fatigue4 7#d74 ,the types should present an even and regular appearance1 termed alignment4 ,a type bar made of suitable material in the right way is the keystone of typewriter construction4 ,in all machinery1 there is some part on which falls the greatest strain and wear2 consequently on the durability of that part rests the life of the machine4 ,the devices used to secure alignment are numerous and ingenious4 ,one machine depends on a wide pivoted bearing and a rigid type bar2 another has a bearing composed of a continuous steel rod1 with a type bar flexible while in motion1 and made rigid at the printing point by means of guides2 a third employs a wide pivotal bearing1 a flexible type bar and an indispensable guide plate at the printing point2 a fourth employs a compound type bar and an indispensable guide at the printing centre1 and so on4 ,some have wide and adjustable bearings1 to enable the wear to be taken up4 ,these devices1 however1 are not the only essentials4 ,the type bar hangers in machines embodying the pivotal principle need to be rigid and solidly fixed1 while the paper carriage should be perfectly rigid and present a level and even platen surface for the type to strike against4 7#e74 ,the type should be capable of being easily and quickly cleaned1 and in such a way as not to injure the type or soil the hands4 ,a device should be embodied for rendering it impossible to batter the face of the type when the type bars are accidentally struck one against the other1 and for preventing the type perforating or puncturing the platen4 7#f74 ,the mechanism controlling the movement of the carriage should act rapidly and uniformly1 and its tension should be adjustable4 ,the carriage should have a sure and regular paper feed and be capable of accommodating any smaller width of paper2 also the margin regulators and bell trip should be easily and readily altered4 7#g74 ,the platen roll should be instantly interchangeable1 thereby allowing of a soft substance platen being used for a single copy work and a hard one for manifolding4 ,if the hard platen is of reduced diameter1 more perfect alignment is secured on machines employing a complete circle of rigid type bars and a central top carriage4 7#h74 ,the line-spacing mechanism should be variable1 and effected by one movement at all times2 that is1 the same movement that accomplishes the line feed should be utilized to return the carriage for a new line4 7#i74 ,the ribbon movement should consist of a reliable feeding mechanism1 and allow of the fabric being quickly withdrawn1 replaced1 or adjusted4 ,it should bring the whole surface in contact with the type1 and also automatically reverse the endwise travel4 7#aj74 ,the machine should be as noiseless in operation as possible4 ,machines differ very much in this particular4 ,the employment of the guides to force the alignment introduces metallic contact1 and consequent friction and noise4 ,,copyrights ,directions for ,securing ,copyrights1 under the revised act of ,congress1 which took effect ,august #a1 #ahgd4 7#a74 ,a printed copy of the title of the book1 map1 chart1 dramatic or musical composition1 engraving1 cut1 print1 photograph1 or a description of the painting1 drawing1 chromo1 statue1 statuary1 or model or design for a work of the fine arts1 for which copyright is desired1 must be sent by mail or otherwise1 prepaid1 addressed3 ,librarian of ,congress1 ,washington1 ,d4 ,c4 ,this must be done before publication of the book or other article4 ,no entry can be made of a written title4 7#b74 ,a fee of fifty cents1 for recording the title of each book or other article1 must be enclosed with the title as above1 and fifty cents in addition 7or one dollar in all71 for each certificate of copyright under seal of the ,librarian of ,congress1 which will be transmitted by early mail4 7#c74 ,within ten days after publication of each book or other article1 two complete copies of the best edition issued must be sent1 to perfect the copyright1 with the address ,librarian of ,congress1 ,washington1 ,d4 ,c4 ,the postage must be prepaid1 or else the publication enclosed in parcels covered by printed ,penalty ,labels1 furnished by the ,librarian1 in which case they will come free by mail1 according to rulings of the ,postoffice ,department4 ,without the deposit of copies above required the copyright is void1 and a penalty of #be is incurred4 ,no copy is required to be deposited elsewhere4 7#d74 ,no copyright is valid unless notice is given by inserting in every copy published1 on the title page or the page following1 if it be a book2 or if a map1 chart1 musical composition1 print1 cut1 engraving1 photograph1 painting1 drawing1 chromo1 statue1 statuary1 or model or design intended to be perfected as a work of the fine arts1 by inscribing upon some portion thereof1 or on the substance on which the same is mounted1 the following words1 viz3 ,entered according to act of ,congress1 in the year----by----1 in the office of the ,librarian of ,congress1 at ,washington1 or1 at the option of the person entering the copyright1 the words3 ,copyright1 #ai--1 by----4 ,the law imposes a penalty of #ajj upon any person1 who has not obtained copyright1 who shall insert the notice ,entered according to act of ,congress1 or ,copyright1 etc41 or words of the same import1 in or upon any book or other article4 7#e74 ,any author may reserve the right to translate or to dramatize his own work4 ,in this case1 notice should be given by printing the words ,right of translation reserved1 or ,all rights reserved1 below the notice of copyright entry1 and notifying the ,librarian of ,congress of such reservation1 to be entered upon the record4 7#f74 ,each copyright secures the exclusive right of publishing the book or article entered for the term of twenty-eight years4 ,within six months before the end of that time1 the author or designer1 or his widow or children1 may secure a renewal for the further term of fourteen years1 making forty-two years in all4 ,application for renewal must be accompanied by explicit statement of ownership1 in the case of the author1 or of relationship1 in the case of heirs1 and must state definitely the date and place of entry of the original copyright4 7#g74 ,the time within which any work entered for copyright may be issued from the press is not limited by any law or regulation1 but depends upon the discretion of the proprietor4 ,a copyright may be secured for a projected work as well as for a completed one4 7#h74 ,a copyright is assignable in law by any instrument of writing1 but such assignment must be recorded in the office of the ,librarian of ,congress within sixty days from its date4 ,the fee for this record and certificate is one dollar1 and for a certified copy of any record of assignment one dollar4 7#i74 ,a copy of the record 7or duplicate certificate7 of any copyright entry will be furnished1 under seal1 at the rate of fifty cents each4 7#aj74 ,in the case of books published in more than one volume1 or of periodicals published in numbers1 or of engravings1 photographs1 or other articles published with variations1 a copyright is to be entered for each volume or part of a book1 or number of periodical1 or variety1 as to style1 title1 or inscription1 of any other article4 7#aa74 ,to secure a copyright for a painting1 statue1 or model or design intended to be perfected as a work of fine arts1 so as to prevent infringement by copying1 engraving1 or vending such design1 a definite description must accompany the application for copyright1 and a photograph of the same1 at least as large as cabinet size1 should be mailed to the ,librarian of ,congress within ten days from the completion of the work or design4 7#ab74 ,copyrights cannot be granted upon ,trade-marks1 nor upon ,labels intended to be used with any article of manufacture4 ,if protection for such prints or labels is desired1 application must be made to the ,patent ,office1 where they are registered at a fee of #f for labels and #be for trade-marks4 7#ac74 ,every applicant for a copyright must state distinctly the name and residence of the claimant1 and whether the right is claimed as author1 designer1 or proprietor4 ,no affidavit or formal application is required4 ,,office ,,of ,,the ,,librarian ,,of ,,congress4 ,transcriber's ,notes4 ,spelling appears to be evolving between ,,us_/,,uk e4g4 both color and colour1 vapor and vapours are seen4 ,corrected obvious typos3 guage - gauge decending - descending radical - radial artifical - artificial comtemplated - contemplated barometor - barometer p#dag4 namely inserted 'a feeder'1 a simple contrivance ,chapter headings in ,contents do not always match chapter headings in text4 ,,ii4 ,building a ,boathouse - ,,ii4 ,building of a ,boat ,house4 ,inconsistent hyphenation left as printed3 ,both boat house and boat-house are used several times4 ,both typewriter and type-writer are used several times4 ,both ,wheel-barrow and wheelbarrow are used several times4 ,both ,,everyday and every-day are used several times4 ,moved equations to single lines to make them clearer4 ,some maths errors were found in the text1 they have been corrected as follows3 p#abf4 find that it has taken five and one-third times as long1 or #aj minutes to do this work4 #aj should read #ajg4 p#ada4 ,the equation ,p#bpinu - ,wp #j or -- p#bpinu_/p should read3 ,p#bpinu - ,wp #j or -- ,p#bpinu_/p p#bda4 ,the equation 7,,ab ,,cd7_/#b ,,ab #adj lb4 7#b - #c7_/b #h_/a #adi lb4 #b1hjjlb4 should read 7,,ab ,,cd7_/#b ,,ac #adj lb4 7#b #c7_/b #h_/a #adj lb4 #b1hjj lb4 p#cec4 #a3gcc - #a4gcc p#ada4 and p#adb4 ,for clarity1 the numbering of the equations has been changed from a mixture of ,n and 7,n7 to 7,n7 only1 and the mix of using ,n4 and ,n have been changed so all numbering and references to the numbering have no 4 ,the maths in this sequence of equations has gone wrong somewhere probably due to a mistyped w for ,w1 r' for r'' or a missed divisor4 ,corrected incorrect figure references3 p#big4 ,d#a - ,d1 ,e#a - ,e p#bih4 ,e#a - ,e p#bii4 ,g#a - ,g1 ,h#a - ,h1 ,g#a - ,g1 ,j#a - ,j p#dja4 ,fig4 #b should be ,fig4 #bbg ,left as printed3 ,inconsistent use of italics between figures and text unless needed to make description in text unambiguous4 ,inconsistent hyphenation in measurements e4g4 #g-a_/b-;in4 and #c-a_/b in4