---------------------------------------- -------------------------------- ,illustration3 ,,dr4 ,,william ,,konrad ,,roentgen4 pp4 #fi to #he4 ,born in ,holland1 #ahde4 ,from a photograph by ,hanfstaengl1 ,frankfort-on-the-,main4 ---------------------------------------- -------------------------------- ,,roentgen ,,rays ,,and ,,phenomena ,,of ,,the ,,anode ,,and ,,cathode4 ,,principles1 ,,applications ,,and ,,theories ,,by ,,edward ,p4 ,,thompson1 ,m4,e41 ,e4,e4 ,mem4 ,amer4 ,inst4 ,elec4 ,eng4 ,mem4 ,amer4 ,soc4 ,mech4 ,eng4 ,author of 8,inventing as a ,science and an ,art40 ,,concluding ,,chapter ,,by ,,prof4 ,,william ,a4 ,,anthony1 ,formerly of ,cornell ,university4 ,past ,president ,amer4 ,inst4 ,elec4 ,eng4 ,author1 with ,prof4 ,brackett of ,princeton1 of 8,text-,book of ,physics40 #fj ,diagrams4 #de ,half-,tones4 ,,new ,,york3 ,d4 ,,van ,,nostrand ,,company1 #bc ,,murray ,,and #bg ,,warren ,,street4 ---------------------------------------- -------------------------------- ,copyright1 #ahif1 ,,by ,,edward ,p4 ,,thompson1 ,temple ,court ,building1 ,new ,york4 ---------------------------------------- -------------------------------- ,,preface4 ------- ,,in addition to the illustrated feature for exhibiting the nature and practical application of ,x-rays1 and for simplifying the descriptions1 the book involves the disclosure of the facts and principles relating to the phenomena occurring between and around charged electrodes1 separated by different gaseous media at various pressures4 ,the specific aim is the treatment of the radiant energy developed within and from a discharge tube1 the only source of ,x-rays4 ,having always admired the plan adopted by ,german investigators in publishing accounts of their experiments by means of numbered paragraphs containing cross-references and sketches1 the author has likewise treated the investigations of a large number of physicists4 ,the cross-references are indicated by the section sign 774 ,by reference1 the analogy1 contrast1 or suggestiveness may be meditated upon4 ,all knowledge of modern physics is based upon experiments as the original source4 ,inasmuch as many years may be expected to elapse before the innumerable peculiarities of the electrical discharge will be reduced to a pure science1 and also in order that the contents of the book may be of value in the future as well as at present1 the characteristic experiments of electricians and scientists are described1 in general1 by reference to their object1 the apparatus used1 the result1 the inferences of the experimenter1 and the observations of cotemporaneous or later physicists1 together with a presentation here and there of theoretical matters and allusion to practical applications4 ,the classes of reader to which the book is adapted may best be known1 of course1 after perusal1 but some advance intimation of the kind that the author had in view may be desired4 ,let it be known that1 first1 the student and those generally interested in science ought to be able to comprehend the subject-matter1 because experiments are described1 which are always the simplest means 7e4g41 in a popular lecture7 for explaining the wonders of any given scientific principles or facts4 ,thus did ,crookes1 ,tyndall1 ,thomson 7both ,kelvin and ,j4 ,j471 ,hertz1 etc41 disseminate knowledge--by describing their researches and reasoning thereon4 ,in view of the tremendous amount of experimenting which has been carried on during the past few years in connection with the electric discharge1 it was difficult to determine just how far back to begin 7without starting at the very beginning71 so that the student and general reader1 whose object is to become acquainted especially with the properties of cathode and ,x-rays1 might better understand them4 ,the author realized that it was necessary to go back further and further in this department of science1 and he could not easily stop until he had reached certain investigations of ,faraday1 ,davy1 ,page1 and others1 which are briefly noticed in an introductory sense4 ,take1 for example1 the inaction of the magnet upon ,x-rays in open air4 #gi4 ,of course1 it would be of interest for the student to know about ,lenard's investigations relating to the action of the magnet upon cathode rays inside of the observing tube4 #gb;a4 ,it would follow1 further1 that he would desire to know about ,crookes' experiment relating to the attraction of the magnet upon cathode rays within the tube4 #ei4 ,in order that he might not infer that ,crookes was the first to investigate the action of the magnet upon the discharge1 it was evident that the book could be made of greater value by relating the experiments of ,prof4 ,j4 ,j4 ,thomson as to the discharge across and along the lines of magnetic force1 #ca1 and ,plcker's experiment on the action of the magnet upon the cathode column of light4 #cj4 ,the interest became increased1 instead of diminished1 by noting ,de la ,rive's experiment on the rotation of the luminous effect of the discharge by means of the magnet4 #bi4 ,being now quite impossible to stop1 ,davy's electric arc and magnetic action upon the same had to be alluded to1 at least briefly4 #bh4 ,on the other hand1 the very earliest experiments with the discharge in rarefied air are not described--occurring as remotely as the eighteenth century--so ably treated of in ,park ,benjamin's work4 ,those facts that have some mutual bearing are brought forward to serve as stepping-stones to the investigation of cathode and ,x-rays4 ,secondly1 the author often imagined that he was writing in behalf of the surgeon and physician and those who intend to experiment1 especially when he found in his investigations of recent publications descriptions in detail of the electrical apparatus employed in experimenting with ,x-rays4 ,he improved the opportunity of repeating the statements of the difficulties1 and how they were overcome2 also1 the precautions necessary to be taken1 and1 besides1 the kind of discharge tubes and apparatus best adapted for particular kinds of experiments4 ,the chapter on applications in diagnosis and anatomy1 etc41 is of especial interest to physicians4 ,thirdly1 as the discovery of the ,roentgen rays has established a new department of photography1 those who are interested in this art may be benefited by the results and suggestions disclosed in connection with photographic plates1 time of exposure1 adjuncts for best results1 precautions for obtaining sharp shadows1 and steps of the process1 from beginning to end1 for carrying on the operation4 ,fourthly1 expert physicists and electricians1 professors1 etc41 need something that the above classes do not1 and this is the reason why the author has not assumed the burden of carrying any line of thought or theory from the beginning to the end of the treatise1 nor has he made the book in any way a personal matter by criticising experiments1 nor even by favoring the views of one over the other1 unless it is in an exceptional case here and there2 but in each instance the investigator's name is given1 and that of the publication in which the account may be found1 so that the scientist may refer thereto to test the correctness of the author's version of the matter1 or to learn the nature of the minute details and circumstances4 ,the author suggests that the study of the phenomena of the discharge tube would not be amiss in scientific schools and colleges4 ,he argues that in view of all experimenters in this line having been made enthusiastic and fascinated by reason of 7#a7 the beautiful effects1 7#b7 the field being always open to new discoveries1 7#c7 the direct practical and theoretical bearing of the peculiar actions upon other departments of electricity1 light1 heat1 and magnetism1 7#d7 the pleasure in attempting to obtain results reported by others1 and especially the large amount of valuable theoretical and practical instruction resulting therefrom1 by repeating the experiments or studying them1 and 7#e7 the possible applications of the discharge tube in connection with electric lighting and in the new department of sciagraphy by ,x-rays1 and for other good and valuable considerations--it follows that students who have been through or who are studying a text-book of physics and electricity would be greatly benefited by a course in the discharge-tube phenomena4 ,in view of the large amount of dictation necessary in order to complete the work in such a short period1 and in order that the subject-matter might involve the treatment of the latest work of the ,french and ,german as well as of the ,english and ,american1 and inasmuch as the journals of the latter did not always contain complete translations and1 for better service in behalf of the readers1 the authorship was shared with others1 and1 therefore1 much credit is due to ,prof4 ,anthony for final chapter1 to ,mr4 ,louis ,m4 ,pignolet for assistance in connection with ,french periodicals and academy papers 7 #fc;a1 #hd1 #ii1 #aja;a1 #ajc;a1 #aab;a1 #abd;a1 #abh1 at end1 #aci;a1 #aed1 #aee1 #aef1 #aeg1 #aeh1 and #aei72 to ,mr4 ,n4 ,d4 ,c4 ,hodges1 formerly editor and proprietor of ,science1 who obtained some pertinent accounts1 7 #ig;a1 #ig;b1 #ii;,a1 ,b1 ,c1 ,d1 to #ii,t1 inclusive7 by investigations of recent literature at the ,astor ,library1 ,new ,york2 and also to ,mr4 ,ludwig ,gutmann 7,member ,american ,institute of ,electrical ,engineers7 for a few translations from the ,german4 ,credit is given in each instance to all societies and publications by naming them in the respective paragraphs herein4 ,in nearly every case the author prepared his material from original articles and papers contributed by the investigators to the societies or periodicals4 ,the author has prepared himself to withstand1 with about half as much patience as he expects will be required1 all criticisms based upon disappointments which may be experienced by the true1 or the alleged true1 first discoverer of any particular property of the electric discharge not duly credited4 ,he has been particular in presenting knowledge as to physical facts and principles1 but not equally1 perhaps1 as to the originator of the experiment1 or as to the actual first discoverer1 for the simple reason that the book is in no sense a history not a biography4 ,where the paragraph has been headed1 for example1 8,swinton's ,experiment10 it means that that party 7according to the article purporting to be written by him7 made that experiment4 ,some one else may have made exactly the same experiment previously1 yet the instruction is equally as valuable as though the researches of the first discoverer had been related4 ,on the other hand1 the author has never had any intention of giving credit to the wrong party4 ,the dates in the captions indicate the general chronological order in behalf of those thus interested4 ,with this explanation1 it is thought that the claimants will be much more lenient in their criticisms concerning priority of discovery4 ,while the developments have generally followed each other historically1 as well as appropriately for the purpose of instruction1 yet now and then it was preferable to place the description of a comparatively recent experiment in conjunction with some description of an experiment made at a much earlier date4 ,for this reason1 also1 the book is not of a chronological nature4 ,the subject-matter1 as usual1 is divided into chapters1 but the sections are to be considered as subordinate chapters1 having different shades of meaning1 and the one not necessarily bearing a direct relation to the contents of its neighbor1 but as1 in a novel or a treatise on geometry1 having its important part to play in conjunction with some later or preceding section4 ,,edward ,p4 ,,thompson4 ,,temple ,,court ,,building1 ,,new ,,york1 ,august1 #ahif4 ---------------------------------------- -------------------------------- ,,contents4 ------- ,,chapter ,i4 #a4 ,secondary ,current by ,induction4 ,no ,,faraday ,increased ,e4 ,m4 ,f4 #b4 ,electric ,spark and ,increased ,e4 ,m4 ,f4 ,,page by ,induced ,current4 #c4 ,spark in ,secondary ,increased by ,,fizeau ,condenser in ,primary4 #d4 ,atmosphere around an ,incandescent ,live ,,vincintini ,wire4 #e4 ,magnetizing ,radiations from an ,electric ,,henry ,spark4 #f4 ,arcing ,metals at ,low ,voltage4 ,,faraday #g4 ,non-arcing ,metals at ,high ,voltage4 ,,wurts ,practical ,application4 #h4 ,duration of ,spark ,measured4 ,,wheatstone #h;a4 ,discharge--,intermittent1 ,constant1 and ,,feddersen ,oscillatory--by ,variation of ,resistance4 #i4 ,musical ,note by ,discharge with ,small ,,faraday ,ball ,electrodes4 ,invisible ,discharge4 #i;a4 ,pitch of ,sound ,changed by ,approach of ,,faraday and ,conductor ,connected to ,earth4 ,,mayer #aj4 ,brush ,discharge4 ,color4 ,stri4 ,nitrogen ,,faraday ,best ,transmitter of a ,spark1 and its ,practical ,bearing in ,atmospheric ,lightning4 ,cathode ,brushes in ,different ,gases4 #aa4 ,glow by ,discharge4 ,glow ,changed to ,,faraday ,spark4 ,motion of ,air4 ,apparent ,continuous ,discharge during ,glow4 #ab4 ,spark4 ,solids ,perforated4 ,,lullin #ac4 ,spark4 ,glass ,perforated4 ,holes ,close ,,fage ,together4 ,practical ,application for ,porous ,glass4 #ad and ,spark4 ,penetrating ,power4 ,conducting ,,knochenhaurer1 #ad;a4 ,power of ,gas4 ,relation of ,e4 ,m4 ,f4 to ,,boltzmann1 ,pressure of ,gases4 ,discharge through ,,thomson ,hydrogen ,vacuum ,continued with ,less 7,,kelvin71 ,current than that ,required to ,start ,,maxwell1 it4 ,,varley1 ,,harris1 and ,,masson #ae4 ,dust ,particles or ,rust on the ,,gordon ,electrodes ,hasten ,discharge4 #af4 ,where the ,distance is ,greater1 the ,,thomson ,dielectric ,strength is ,smaller1 ,both 7,,kelvin7 ,distances ,being ,minute4 #ag4 ,discharge through ,gases under ,very ,high ,,cailletet ,pressures4 ,increased ,dielectric ,strength4 #ah4 ,discharges in ,different ,chemical ,gases ,,faraday ,variably ,resisted4 #ai4 ,gas as a ,conductor4 ,molecule for ,,thomson1 ,j4 ,j4 ,molecule1 its ,conductivity ,greater than that for ,gases4 #bj4 ,relation of ,light to ,electricity4 ,the ,,boltzmann1 ,square ,root of the ,dielectric ,,gibson1 ,capacity ,equal to the ,refractive ,,barclay1 ,index4 ,,hopkinson1 and ,,gladstone #ba4 ,hermetically ,sealed ,discharge ,tubes ,,pl,,cker and with ,platinum ,leading-in ,wires4 ,,geissler #bb4 ,luminosity of ,discharge ,tubes ,produced ,,geissler by ,rubbing4 ,increased by ,low ,temperature4 #bc4 ,different ,vacua ,needed for ,luminosity ,,alvergniat by ,friction and by ,discharge4 #bd4 ,phenomena of ,discharge around the ,edges ,,steinmetz of an ,insulating ,sheet4 #be4 ,highest ,possible ,vacuum ,considered as a ,,morgan ,non-conductor4 #bf4 ,constant ,potential at the ,terminals of ,,de ,,la ,,rue and a ,discharge ,tube4 ,m,,ller #bf;a4 ,polarity of ,discharge-tube ,terminals in ,,klingenberg ,secondary of ,ruhmkorff ,coil4 ,mathematical ,deductions4 #bg4 ,pressure in ,discharge ,tube ,produced by ,,kinnersley1 a ,spark4 ,,harris1 and ,,riess ,,chapter ,,ii4 #bh4 ,actions of ,magnetism upon the ,arc and ,,davy1 ,flame4 ,,bancalari1 and ,,quet #bi4 ,rotation of ,luminous ,discharge by a ,,de ,,la ,,rive ,magnet4 ,application in ,explaining ,aurora ,borealis4 #cj4 ,action of ,magnet on the ,cathode ,light4 ,,pl,,cker and ,relations ,different according to the ,,hittorf ,position ,relatively to the ,magnetic ,lines of ,force4 #ca4 ,discharge ,retarded ,across1 and ,,thomson1 ,j4 ,j4 ,accelerated ,along1 the ,lines of ,magnetic ,force4 #cb4 ,resistance of ,luminosity of the ,,thomson1 ,j4 ,j4 ,discharge ,afforded by a ,thin ,diaphragm4 #cc4 ,forcing ,effect of the ,stri at a ,,solomons ,perforated ,diaphragm4 ,,chapter ,,iii4 #cd4 ,electric ,images4 ,,riess #ce4 ,electrographs on ,photographic ,plate by ,,sanford and ,discharge4 ,,mckay #cf4 ,positive and ,negative ,dust ,pictures ,,lichtenberg upon ,lines ,drawn by ,electrodes4 #cf;a4 ,photo-electric ,dust ,figures4 ,,hammer #cf;b4 ,dust ,portrait4 ,,hammer #cg4 ,electrical ,images by ,discharge ,,karsten ,developed by ,condensed ,moisture4 #cg;a4 ,,magnetographs4 ,,mckay #ch4 ,bas-relief ,facsimiles by ,electric ,,piltchikoff ,discharge4 #ci4 ,distillation of ,liquids by ,discharge4 ,,gernez #dj4 ,stri4 ,black ,prints on ,walls of ,tube4 ,,de ,,la ,,rue and ,m,,ller ,,chapter ,,iv4 #da4 ,discharge ,tube in ,primary ,current4 ,,gassiot ,stri4 ,least ,e4 ,m4 ,f4 ,required4 #db4 ,current ,interrupted ,inside of ,discharge ,,poggendorff ,tube instead of ,outside4 #dc4 ,source of ,stri at the ,anode4 ,color ,,de ,,la ,,rue and ,changed by ,change of ,current4 ,m,,ller #dd4 ,dark ,bands by ,small ,discharges ,,solomons ,disappear on ,increase of ,current1 and ,appear ,again by ,further ,increase4 #de4 ,motion of ,stri4 ,method of ,obtaining ,,spottiswoode ,motion when ,desired and of ,stopping the ,same4 #df4 ,motion of ,stri ,checked at the ,cathode4 ,,thomson1 ,j4 ,j4 ,tube1 #ej ft4 ,long4 ,the ,anode the ,starting-point4 #dg4 ,electrolysis in ,discharge ,tube4 ,,thomson1 ,j4 ,j4 #dh4 ,heat ,stri without ,luminous ,stri4 ,,de ,,la ,,rue and ,m,,ller #di4 ,sensitive ,state4 ,method of ,obtaining4 ,,spottiswoode ,telephone ,used to ,prove and ,,moulton ,intermissions4 #di;a4 ,cause of ,sensitive ,state ,detected by ,,spottiswoode ,telephone4 and ,,moulton #ej4 ,sensitive ,state ,illustrated by a ,,reitlinger and ,flexible ,conductor within the ,,urbanitzky ,discharge ,tube4 #ea4 ,system of ,operating ,discharge ,tubes4 ,,tesla ,excessively ,high ,potential and ,enormous ,frequency4 #eb4 ,discharge-tube ,phenomena by ,,moore ,self-induced ,currents4 ,,chapter ,v4 #ec4 ,dark ,space around the ,cathode4 ,,crookes #ed4 ,relation of ,vacuum to ,phosphorescence4 ,,crookes #ee4 ,phosphorescence of ,objects within ,,crookes ,discharge ,tube4 #ef4 ,darkness and ,luminosity in the ,arms of ,,crookes a ,v ,tube4 #eg4 ,cathode ,rays ,rectilinear within the ,,crookes ,discharge ,tube4 #eh4 ,shadow ,cast within the ,discharge ,tube4 ,,crookes #eh;a4 ,mechanical ,force of ,cathode ,rays4 ,wheel ,,crookes ,caused to ,rotate4 #ei4 ,action of ,magnet upon ,cathode ,rays in ,,crookes ,discharge ,tube4 #fj4 ,mutual ,repulsion of ,cathode ,rays in ,,crookes ,discharge ,tube4 #fa4 ,heat of ,phosphorescent ,spot4 ,,crookes #fa;a4 ,theoretical ,considerations of ,thomson 7,kelvin74 #fa;b1 ,velocity of ,cathode ,rays4 ,,thomson1 ,j4 ,j4 page #df4 #fa;b1 ,cathode ,rays ,charged with ,negative ,,perrin page ,electricity4 #dg4 #fa;c1 ,zeugen's ,photograph of ,mt4 ,blanc ,not ,due to ,cathode ,rays4 #fb4 ,phosphorescence of ,particular ,chemicals ,,goldstein by ,cathode ,rays4 #fc4 ,spectrum of ,post-phosphorescence of ,,kirn ,discharge ,tube ,compared with that of ,red-hot ,metals4 #fc;a4 ,chemical ,action on ,photographic ,plate ,,de ,,metz by ,cathode ,rays ,inside of ,discharge ,tube4 #fc;b4 ,the ,passage of ,cathode ,rays through ,,hertz ,thin ,metal ,plates within the ,discharge ,tube 7no4 #fd74 ,,chapter ,,vi #fe1 ,cathode ,rays ,outside of the ,discharge ,,lenard top of ,tube whose ,exit is an ,aluminum page ,window4 ,a ,glow ,outside of the ,window4 #ec4 #fe41 ,properties of ,cathode ,rays in ,open ,air4 ,,lenard end of page #ec4 #ff4 ,phosphorescence by ,cathode ,rays ,outside ,,lenard of the ,discharge ,tube4 #ff;a4 ,transmission ,tested by ,phosphorescence4 #fg4 ,the ,aluminum ,window a ,diffuser of ,,lenard ,cathode ,rays4 #fh4 ,transmission of ,external ,cathode ,rays ,,lenard through ,aluminum and ,thinly ,blown ,glass4 #fi4 ,propagation of ,external ,cathode ,rays4 ,,lenard ,turbidity of ,air4 #gj4 ,photographic ,action by ,external ,cathode ,,lenard ,rays and at ,points beyond the ,glow4 ,no ,other ,chemical ,power ,probable4 ,shadows of ,objects by ,light and by ,external ,cathode ,rays ,compared4 ,no ,heat ,produced by ,external ,cathode ,rays4 #ga4 ,external ,cathode ,rays and the ,electric ,,lenard ,spark ,distinguished4 ,aluminum ,window ,not a ,secondary ,cathode4 #gb4 ,cathode ,rays ,propagated1 but ,not ,,lenard ,generated1 in the ,highest ,possible ,vacuum4 ,air ,less ,turbid when ,rarefied4 #gb;a4 ,cathode ,rays1 while ,traversing the ,,lenard ,exhausted ,observing ,tube1 ,deflected by a ,magnet4 ,no ,turbidity in a ,very ,high ,vacuum4 #gb;b4 ,an ,observing ,tube for ,receiving the ,,lenard ,rays and ,adapted to be ,exhausted4 #gc4 ,phenomena of ,cathode ,rays in an ,,lenard ,observing ,tube ,containing ,successively ,different ,gases at ,different ,pressures4 ,phosphorescent ,screen ,employed for ,making the ,test4 #gd4 ,cause of the ,glow ,outside of the ,,lenard ,aluminum ,window4 ,glow ,not ,caused by ,external ,cathode ,rays4 ,sparks ,drawn from the ,aluminum ,window4 ,transmission of ,external ,cathode ,rays ,dependent ,alone upon the ,density of the ,medium4 #ge4 ,external ,cathode ,rays of ,different ,,lenard ,kinds ,variably ,diffused4 ,theoretical ,observations4 #gf4 ,law of ,propagation of ,external ,cathode ,,lenard ,rays4 #gg4 ,charged ,bodies ,discharged by ,external ,,lenard ,cathode ,rays4 ,discharge at ,greater ,distances than ,phosphorescence4 ,not ,certain as to the ,discharge ,being ,directly ,due to ,intermediate ,air4 #gh4 ,source1 ,propagation1 and ,direction of ,,de ,,kowalskie ,cathode ,rays4 ,general ,conclusions4 ,,chapter ,,vii4 #gi4 ,x-rays ,uninfluenced by a ,magnet4 ,source ,,roentgen of ,x-rays ,determined by ,magnetic ,transposition of ,phosphorescent ,spot4 #hj4 ,source of ,x-rays may be at ,points ,,roentgen within the ,vacuum ,space4 ,different ,materials ,radiate ,different ,quantities of ,x-rays4 #ha4 ,reflection of ,x-rays4 ,,roentgen #hb4 ,examples of ,penetrating ,power of ,,roentgen ,x-rays4 #hc4 ,permeability of ,solids to ,x-rays ,,roentgen ,increases ,much ,more ,rapidly than the ,thickness ,decreases4 #hd4 ,x-rays ,characterized4 ,fluorescence and ,,roentgen ,chemical ,action4 #he4 ,non-refraction of ,x-rays ,determined by ,,roentgen ,opaque and ,other ,prisms4 ,refraction1 if ,any1 ,exceedingly ,slight4 #hf4 ,velocity of ,x-rays ,inferred to be the ,,roentgen ,same in ,all ,bodies4 #hg4 ,non-double ,refraction ,proved by ,iceland ,,roentgen and ,spar and ,other ,materials4 ,,mayer #hh4 ,rectilinear ,propagation of ,x-rays ,,roentgen ,indicated by ,pin-hole ,camera and ,sharpness of ,sciagraphs4 #hi4 ,interference ,uncertain ,because ,x-rays ,,roentgen ,tested were ,weak4 #ij4 ,electrified ,bodies1 whether ,conductors ,,roentgen or ,insulators1 or ,positive or ,negative1 ,discharged by ,x-rays4 ,hydrogen1 etc41 as the ,intermediate ,agency4 #ij;a4 ,application of ,principle of ,discharge ,,roentgen by ,x-rays4 #ij;,a1 ,supplementary ,experiments on ,charge and ,,minchin1 b1 ,discharge by ,x-rays4 ,,righi1 c1 ,,benoist1 d4 ,,hurmuzescu1 and ,,borgmann #ia4 ,focus ,tube4 ,,roentgen1 ,,shallenberger1 et al4 #ia;a4 ,tribute to the ,tesla ,apparatus4 ,,roentgen #ib4 ,x-rays and ,longitudinal ,vibrations4 ,,roentgen #ic4 ,longitudinal ,waves in ,luminiferous ,,thomson ,ether by ,electrical ,means ,early 7,,kelvin7 ,predicted by #id4 ,theory as to ,x-rays ,being of a ,,schuster ,different ,order of ,magnitude from those so far ,known4 #ie4 ,longitudinal ,waves ,exist in a ,medium ,,thomson1 ,j4 ,j4 ,containing ,charged ,ions4 ,theoretical4 #if4 ,practical ,application of ,x-rays ,,boltzmann ,foreshadowed4 #ig4 ,the ,sciascope4 ,,magie1 ,,salvioni1 et al4 ,,chapter ,,viii4 #ig;a4 ,electrified ,bodies ,discharged by ,light ,,hertz of a ,spark1 and the ,establishment of a ,radical ,discovery4 #ig;b4 ,above ,results ,confirmed and ,more ,,wiedemann and ,specific ,tests4 ,,ebert #ih4 ,negatively ,charged ,bodies ,discharged by ,,elster and ,light4 ,discharge from ,earth's ,surface ,,geitel ,explained by ,inference and ,experiment4 #ii4 ,relation between ,light and ,electricity4 ,,elster and ,cathode of ,discharge ,tube ,acted upon ,,geitel by ,polarized ,light and ,apparently ,made a ,conductor ,because of the ,discharging ,effect4 #ii;,a ,briefs ,regarding ,action between ,,schuster1 to ,electric ,charge and ,light4 ,,righi1 #ii,t4 ,,stolstow1 ,,branly1 ,,borgmann1 ,,mebius1 et al4 ,,chapter ,,ix4 #ajj4 ,stereoscopic ,sciagraphs4 ,,thomson1 ,e4 #aja4 ,obtaining ,manifold ,sciagraphs ,,thomson1 ,e4 ,simultaneously upon ,superposed ,photographic ,films and through ,opaque ,materials1 and thus ,indicating ,relative ,sensitiveness of ,different ,films to ,x-rays4 ,intensifying ,process ,applicable in ,sciagraphy4 ,thick ,films ,appropriate4 #aja;a4 ,sciagraph ,produced through #aej ,sheets ,,lumi,,re4 of ,photographic ,paper4 #ajb4 ,discharge ,tube ,adapted for ,both ,,thomson1 ,e41 ,unidirectional and ,alternating and ,,swinton ,currents4 #ajc4 ,x-rays4 ,opalescence and ,diffusion4 ,,thomson1 ,e41 ,,pupin1 and ,,lafay #ajc;a4 ,diffusion and ,reflection in ,relation to ,,imbert1 et ,polish4 al4 #ajd4 ,fluorometer4 ,fluorescing ,power of ,,thomson1 ,e4 ,different ,discharge ,tubes ,compared4 #aje4 ,modified ,sciascope for ,locating the ,,thomson1 ,e4 ,source and ,direction of ,x-rays4 ,phosphorescence ,not an ,essential ,accompaniment in ,production of ,x-rays4 #ajf4 ,x-rays from ,discharge ,tube ,excited by ,,rice1 ,,pupin1 ,wimshurst ,machine4 ,full ,details ,given and ,,morton of the ,electrical ,features4 #ajg4 ,source of ,x-rays ,determined by ,,rice ,projection through a ,small ,hole upon ,fluorescent ,screen ,adjustable to ,different ,positions4 #ajg;a4 ,use of ,stops in ,sciagraphy4 ,,leeds and ,,stokes #ajg;b4 ,x-rays from ,two ,phosphorescent ,spots4 ,,macfarlane1 ,,klink1 ,,webb1 ,,clark1 ,,jones1 and ,,morton #ajh4 ,source of ,x-rays ,determined by ,shadows ,,stine of ,short ,tubes4 #aji4 ,instructions ,concerning ,electrical ,,stine ,apparatus for ,generating ,x-rays4 #aaj4 ,apparent ,diffraction ,really ,due to ,,stine ,penumbral ,shadows4 #aaj;a4 ,non-diffraction4 ,,perrin #aei;a4 ,non-,refraction #aaa4 ,source of ,x-rays ,tested by ,,scribner and ,interceptance of ,assumed ,rectilinear ,m',,berty ,rays from the ,cathode4 #aab4 ,source of ,x-rays on the ,inner ,surface ,,scribner and of the ,glass ,tube ,determined by ,m',,berty1 ,pin-hole ,images4 ,,perrin #aab;a4 ,anode ,thought to be the ,source4 ,cause ,,de ,,heen of ,error ,suggested4 #aac4 ,pin-hole ,pictures by ,x-rays ,compared ,,lodge with ,pin-hole ,images by ,light to ,determine the ,source4 ,x-rays ,most ,powerful when the ,anode is the ,part ,struck by the ,cathode ,rays4 #aad4 ,valuable ,points ,concerning ,electrical ,,lodge ,apparatus ,employed4 #aae4 ,x-rays ,equally ,strong during ,fatigue of ,,lodge ,glass by ,phosphorescence4 #aaf4 ,area ,struck by ,cathode ,rays ,only an ,,rowland1 ,efficient ,source when ,positively ,,carmichael1 ,electrified4 and ,,briggs #aag4 ,transposition of ,phosphorescent ,spot ,,salvioni1 and of ,cathode ,rays without a ,magnet4 ,,elster1 ,,geitel1 and ,,tesla #aag;a4 ,molecular ,sciagraphs in a ,vacuum ,tube4 ,,hammer and ,,fleming ,,chapter ,x4 #aah4 ,x-rays ,begin before ,stri ,end4 ,,edison and ,,thomson1 ,e4 #aai4 ,reason why ,thin ,walls are ,better than ,,edison ,thick4 #abj4 ,to ,prevent ,puncture of ,discharge ,tube ,,edison by ,spark4 #aba4 ,variation of ,vacuum by ,discharge and by ,,edison ,rest4 #abb4 ,external ,electrodes ,cause ,discharge ,,edison through a ,higher ,vacuum than ,internal4 #abc4 ,profuse ,invisible ,deposit from ,aluminum ,,edison and ,cathode4 ,,miller #abd4 ,possible ,application of ,x-rays4 ,,edison and ,fluorescent ,lamp4 ,,ferranti #abd;a4 ,greater 787 ,emission of ,x-rays by ,,piltchikoff ,easily ,phosphorescent ,materials4 #abe4 ,electrodes of ,carborundum4 ,,edison #abf4 ,chemical ,decomposition of the ,glass of ,,edison the ,discharge ,tube ,detected by the ,spectroscope4 #abg4 ,sciagraphs4 ,duration of ,exposure ,,edison ,dependent upon ,distances4 #abh4 ,differences between ,x-rays and ,light ,,edison1 ,,frost1 ,illustrated by ,different ,photographic ,,chappin1 ,plates4 ,times of ,exposure4 ,,imbert1 ,,bertin-,,sans1 and ,,meslin #abh;a4 ,,georges ,,meslins ,,insured ,a ,,reduction ,,of ,,time ,,for ,,taking ,,sciagraphs ,,by ,,the ,,deflection ,,of ,,the ,,cathode ,,rays ,,by ,,means ,,of ,a ,,magnetic ,,field #abi4 ,size of ,discharge ,tube to ,employ for ,,edison ,given ,apparatus4 #acj4 ,preventing ,puncture at the ,,edison ,phosphorescent ,spot4 #aca4 ,instruction ,regarding the ,electrical ,,edison and ,apparatus4 ,,pupin #acb4 ,salts ,fluorescent by ,x-rays4 #ahjj ,,edison ,chemicals ,tested4 #acc4 ,x-rays ,apparently ,passed around a ,,edison1 ,,elihu ,corner4 ,theoretical ,consideration by ,,thomson1 ,himself and ,others4 ,,anthony1 et al4 #acd4 ,permeability of ,different ,substances to ,,edison and ,x-rays4 ,a ,list of a ,variety of ,,terry ,materials4 #acd;a4 ,illustration of ,penetrating ,power of ,,hodges ,light4 #ace4 ,penetrating ,power of ,x-rays ,increased ,,edison by ,reduction of ,temperature4 ,tube ,immersed in ,oil1 and the ,oil ,vessel in ,ice4 ,x-rays ,transmitted through ,steel #a_/h in4 ,thick4 #acf4 ,x-rays ,not ,obtainable from ,other ,,edison1 ,,rowland1 ,sources than ,discharge ,tube4 et al4 ,,chapter ,,xi4 #acg4 ,kind of ,electrical ,apparatus for ,,tesla and ,operating ,discharge ,tube for ,powerful ,,shallenberger ,x-rays4 #ach4 ,how to ,maintain the ,phosphorescent ,spot ,,tesla ,cool4 #aci4 ,expulsion of ,material ,particles through ,,tesla the ,walls of a ,discharge ,tube4 #aci;a4 ,giving to ,x-rays the ,property of ,being ,,lafay and ,deflected by a ,magnet4 ,,lodge #aci;b4 ,penetration of ,molecules into the ,glass ,,gouy of the ,discharge ,tube4 #adj4 ,vacuum ,tubes ,surrounded by a ,violet ,,tesla and ,halo4 ,,hammer #ada4 ,ansthetic ,properties of ,x-rays4 ,,tesla and ,,edison #adb4 ,sciagraphs of ,hair1 ,fur1 etc41 by ,,tesla1 ,,morton1 and ,x-rays4 ,pulsation of ,heat detected4 and ,,norton #adb;a4 #adc4 ,propagation of ,x-rays through ,air to ,,tesla ,distances of #fj ft4 #add4 ,x-rays with ,moderate ,vacuum and ,high ,,tesla ,potential4 #ade4 ,detailed ,construction and ,use of ,single ,,tesla ,electrode ,discharge ,tubes for ,generating ,x-rays4 #adf4 ,percentage of ,reflection4 ,,tesla and ,,rood #adf;a4 ,reflected and ,transmitted ,rays ,,tesla ,compared4 ,practical ,application of ,reflection in ,sciagraphy4 ,analogy between ,reflecting ,power of ,metals and their ,position in the ,electro-positive ,series4 #adg4 ,discharge ,tube ,immersed in ,oil4 ,rays ,,tesla ,transmitted through ,iron1 ,copper1 and ,brass1 #a_/d in4 ,thick4 #adh4 ,bodies ,not ,made ,conductors when ,struck ,,tesla by ,x-rays4 #adi4 ,non-conductors ,made ,conductors by a ,,appleyard ,current4 #adi;a4 ,appleyard's ,experiment4 ,non-conductors ,made ,conductors by ,current4 #aej4 ,electrical ,resistance of ,bodies ,lowered ,,minchin by the ,action of ,electro-magnetic ,waves4 ,,chapter ,,xii4 #aea4 ,sciagraphic ,plates ,combined with ,,pupin1 ,fluorescent ,salts4 ,,swinton1 and ,,henry4 #aeb4 ,penetrating ,power of ,x-rays ,varies with ,,thompson1 ,s4 the ,vacuum4 ,p4 #aec4 ,reduction of ,contact ,potential of ,,murray ,metals by ,x-rays4 #aed4 ,transparencies of ,objects to ,x-rays ,not ,,nodon1 ,influenced by the ,color4 ,detected by ,,lumi,,re1 ,simultaneous ,photographic ,,bleunard1 and ,impressions4 ,,labesse #aee4 ,chlorine1 ,iodine1 ,sulphur1 and ,,meslans1 ,phosphorus ,combined with ,organic ,,bleunard1 and ,materials ,increase ,opacity4 ,,labesse #aef4 ,application of ,x-rays to ,distinguish ,,buquet1 ,diamonds and ,jet from ,imitations4 ,,gascard1 and ,,thompson1 ,s4 ,p4 #aeg4 ,inactive ,discharge ,tubes ,made ,luminous ,,dufour by ,x-rays4 #aeh4 ,non-refraction in a ,vacuum4 ,,beaulard #aei4 ,bas-relief ,sciagraphs by ,x-rays4 ,,carpentier and ,,miller #afj4 ,transparency of ,eye ,determined by ,,wuillomenet ,sciagraph of ,bullet ,therein4 #afa4 ,mineral ,substances ,detected in ,,ranwez ,vegetable and ,animal ,products4 #afb4 ,hertz ,waves and ,roentgen ,rays ,not ,,errera ,identical4 #afc4 ,non-mechanical ,action by ,x-rays ,,gossart ,determined by the ,radiometer4 #afd4 ,x-rays within ,discharge ,tube4 ,,battelli #afe4 ,combined ,camera and ,sciascope4 ,,bleyer #aff4 ,non-polarization of ,x-rays4 ,,thompson1 ,s4 ,p41 ,,macintyre #afg4 ,diffuse ,reflection4 ,dust ,figures ,,thompson1 ,s4 ,indirectly by ,x-rays4 ,p4 #afh4 ,continuation of ,experiments in #aac4 ,,lodge #afi4 ,thermopile ,inert to ,x-rays4 ,,porter #agj4 ,non-diffraction of ,x-rays4 ,,magie #aga4 ,resistance of ,selenium ,reduced by ,,giltay and ,x-rays4 ,,haga ,total number of sections to this place1 #aii4 ,,chapter ,,xiii4 #bjj4 ,needle ,located by ,x-rays and then ,,hogarth ,removed4 #bja4 ,needle ,located at ,scalpel by ,x-rays and ,,savary then ,removed4 #bjb4 ,diagnosis with ,fluorescent ,screen4 ,,renton and ,,somerville #bjc4 ,bullet ,located by ,five ,sciagraphs4 ,,miller #bjd4 ,bones in ,apposition ,discovered by ,,miller ,x-rays and afterward ,remedied by ,operation4 ,other ,cases4 #bjd;a4 ,necrosis4 ,,miller #bje4 ,application of ,x-rays in ,dentistry4 ,,morton #bjf4 ,elements of the ,thorax4 ,,morton #bjg4 ,a ,colles' ,fracture ,detected by ,x-rays4 ,,morton #bjh4 ,motions of ,liver1 ,outlines of ,spleen1 ,,morton and and ,tuberculosis ,indicated4 ,,williams #bji4 ,osteomyelitis distinguished from ,,lannelongue1 ,periostitis4 ,,barthelemy1 and ,,oudin4 #baj4 ,concluding ,miscellaneous ,experiments ,,ashhurst1 ,relating to ,similar ,applications of ,,packard1 ,x-rays4 ,m,,ller1 ,,keen1 and ,,morton1 ,t4 ,g4 ,,chapter ,,xiv4 ,theoretical ,considerations1 ,arguments1 and ,kindred ,,anthony ,radiations4 ---------------------------------------- -------------------------------- ,,introduction4 ------- ,the new form of energy1 for which there are two names--to wit1 the ,roentgen ray and the ,x-ray--is radiated from a highly exhausted discharge tube1 which may be energized by an induction coil or other suitable electrical apparatus1 such as a ,holtz or a ,wimshurst electrical machine4 #ajf4 ,the principle underlying the construction of the usual induction 7or ,ruhmkorff7 coil is disclosed in the subject-matter of #a1 #b1 and #c1 and is represented in diagram in ,figs4 #a and #b on page #ag4 ,it would be well for the amateur or general scientific reader to study these sections carefully1 for then he will have all the knowledge that is necessary for understanding the apparatus by which the discharge tube is energized4 ,of course1 he will not comprehend the various mechanical details1 nor the many electrical and mathematical relations existing in connection with an induction coil1 but he will gain sufficient knowledge to appreciate what is intended when such a device is referred to here and there throughout the book4 ,since the time of ,faraday1 ,page1 and ,fizeau induction coils of very large dimensions have been constructed1 but none of them probably ever exceeded that built by ,spottiswoode1 during or about #ahge1 which was so powerful as to produce between the two electric terminals1 in open air1 a spark of #db in4 in the secondary current with only #cj small galvanic cells of the ,grove type in the primary circuit4 ,the cells are seldom used in this connection at the present time1 the same being replaced by the dynamo1 and the current being conveniently obtained from the regular incandescent-lamp circuit which may be found in almost any city4 ,those1 therefore1 who intend to become better acquainted with the details of the electrical apparatus should study in conjunction with this book some elementary treatise relating particularly to dynamos and electric currents4 ,the essential element in connection with the generation of ,x-rays is not the coil nor the dynamo1 but the electric discharge1 especially when occurring within a rarefied atmosphere1 provided within a glass bulb1 called the discharge tube throughout the book1 but which has usually been called by different names1 for example1 the receiver of an air pump1 or a ,geissler tube1 when the air is not very highly exhausted1 or a ,crookes tube 7see picture at #abc7 when the vacuum is definitely much higher by way of contrast4 ,it has also been called a ,hittorff tube1 the ,lenard tube1 and by several other names1 according to its peculiar characteristics4 ,illustration3 ,,fig4 #a4--;,,head4 ,illustration3 ,,fig4 #b4--;,,broken ,,arm1 ,,overlapping4 7,due to defective setting47 ,illustration3 ,,fig4 #c4--,,ribs4 ,illustration3 ,,fig4 #d4--,,knee1 ,,knickerbocker ,,buttons1 ,,bullet ,,in ,,femur4 ,,from ,,sciagraphs ,,by ,,prof4 ,,dayton ,c4 ,,miller4 #bjd4 ,for those who are not acquainted with the nature of the electric charge and discharge1 nor with the peculiar and exceedingly interesting phenomena which various investigators have discovered from time to time1 nor with the variety of effects according to the nature and the pressure of the atmosphere within the glass bulb1 it is exceedingly difficult to understand with any degree of satisfaction the properties1 principles1 laws1 theories1 and manner of application of cathode and ,x-rays4 ,consequently1 the greater part of the book treats of the electric charge and discharge in conjunction with certain kindred phenomena4 ,primarily1 the meaning of the electric discharge may be derived by referring to ,fig4 #b1 page #ag1 where there is shown an electric spark1 indicated by radial lines between the terminals of a fine wire forming the long and fine coil or secondary circuit4 ,imagine that the wires are at great distances apart4 ,let them be brought closer and closer together4 ,by suitable tests it will be found1 for example1 that no current passes through the wire1 but when the points are brought sufficiently close together a spark will occur between the two terminals4 #b4 ,sometimes instead of what is understood as a spark1 a brush or glow takes place 7 #aj and #aa71 and in fact a numerous variety of effects occur1 a general name for all being conveniently termed an electric discharge4 ,even if no sudden discharge takes place1 yet1 as when the terminals are far apart1 there may be a charge or a tendency1 or1 as it is technically called1 a difference of potential1 between the two electrodes1 one of which is the cathode and the other the anode4 ,this is comparable to a weight upon one's hand1 tending continually to fall1 and always exerting a pressure1 and it will fall when the hand is suddenly removed4 ,this is in the nature more of an analogy than of an exact correspondence4 ,a discharge through open air1 while adapted to produce a great many curious as well as useful effects1 does not act as a generator of ,x-rays4 #acf4 ,another class of phenomena is obtainable by exhausting the air to a certain extent from a discharge tube1 thereby obtaining what is usually called a low vacuum4 ,such bulbs have been called ,geissler tubes4 ,neither can ,x-rays be generated therefrom to any practicable extent1 but only feebly if at all4 #aah4 ,hittorff1 ,varley 7 #fa;a71 ,crookes 7 #ec to #fa1 inclusive71 were the first to discover and study the different phenomena that are obtained by diminishing the pressure within the discharge tube to a decrement of several thousand millionths of an atmosphere4 ,this will explain why so many allusions have been made to the ,crookes tube1 for when the electric discharge is caused to take place in such a high vacuum ,x-rays are propagated in full strength4 ,upon the first announcement of the discovery1 electricians1 eminent and otherwise1 were of one mind in assuming the possibility of obtaining ,roentgen rays from other sources than that of the highly evacuated discharge tube4 ,instead of speculating and theorizing1 hosts of crucial tests were instituted1 resulting negatively1 and it is now safe to conclude that the electric discharge is the only primary source1 and it is reasonably safe to assert that the discharge must take place within a highly evacuated enclosure4 ,the next stage of exhaustion1 of no advantage to be considered1 is that at which no discharge takes place 7 #be71 and neither are any ,roentgen rays propagated therefrom4 ---------------------------------------- -------------------------------- ,,chapter ,i ------- #a4 ,,faraday',s ,,experiment1 #ahca4 ,,secondary ,,current ,,by ,,induction4 ,experimental ,researches1 ,proc4 ,royal4 ,so4 #ahda4--;,in brief1 the experiment involved the elements illustrated in the accompanying diagram1 ,fig4 #a1 p4 #ag2 a ring made of iron2 upon the ring1 two coils of copper wire1 suitably insulated from each other and from the iron2 a galvanometer included in circuit with one coil1 and an electric battery of ten cells placed in circuit with the other coil4 ,he found that upon breaking or completing connection with the battery1 the needle was powerfully deflected4 ,without entering into further detail1 it is important1 however1 to notice that he did not perform any experiments tending to establish the principle of increase of ,e4 ,m4 ,f4 by making the very slight change now known to be necessary4 #b4 #b4 ,,page',s ,,experiment1 #ahch4 ,,electric ,,spark ,,by ,,induced ,,current4 ,pynchon1 p4 #dbg4 ,dr4 ,page performed an experiment in which the primary coil was but a few feet in length1 while the secondary coil was #cbj ft4 ,he included1 in the primary circuit1 only a few cells of battery4 ,the manner in which he first caused rapid interruptions of the circuit of the primary coil was by the use of what may be called a coarse file1 ,fig4 #b1 p4 #ag4 ,he discovered that the ,e4 ,m4 ,f4 during the rapid interruption was so much increased over that of the small battery1 that an electric spark would pass between the secondary terminals without first bringing them into contact with each other4 #f4 ,the result of these experiments was not only the generation of a current of high ,e4 ,m4 ,f4 from a generator of low ,e4 ,m4 ,f41 but also a current of great quantity as compared with currents obtained from frictional and influence machines1 whose complete history is found in ,mascart's work on ,electricity4 #c4 ,,fizeau',s ,,experiment4 ,,spark ,,in ,,secondary ,,increased ,,by ,,condenser ,,in ,,primary1 #ahec4 ,pynchon1 p4 #def4--;,he connected the plates of a condenser respectively to the terminals of an automatic circuit breaker in the primary circuit1 and noticed that the sparks between the two terminals of the interrupter produced by the self-induced current were greatly diminished1 while those of the secondary coil were about double in length4 ,since that time it has been universally customary to equip induction coils with condensers in like manner4 #d4 ,,vincentini',s ,,experiment4 ,,condition ,,of ,a ,,gas ,,around ,a ,,live ,,wire4 ,nuovo ,cimento1 ,vol4 ,,xxxvi41 ,no4 #c4 ,nature1 ,lon41 ,march #bh1 '#ie1 p4 #ead4 ,the ,elect41 ,lon41 ,feb4 #h1 '#ie1 p4 #dcc4 ,g4 ,vincentini and ,m4 ,cinelli found that the molecules of a gas at and near the surface of a platinum wire1 rendered incandescent by a current1 are electrified1 and that with hydrogen their potential is about 4#jbe volt above the mean potential of the wire4 ,with air and carbonic acid gas the increment is about #a volt4 ,the apparatus1 ,fig4 ,,ii41 consists essentially of means for passing a current along a platinum wire1 a bulb for preventing draughts1 and an electrometer having a platinum disc electrode that could be adjusted to different positions4 ,it was noticeable that the electrification did not reach a maximum instantaneously upon closing the current through the wire1 but the time was less at points below the wire than above4 ,illustration3 ,,ii #e4 ,,henry',s ,,experiment4 ,,magnetizing ,,radiations ,,from ,,an ,,electric ,,spark4 ,proc4 ,inter4 ,elect4 ,cong41 #ahic1 p4 #aai4 ,preece alluded to ,prof4 ,henry's original experiment illustrating the action of an electric discharge #b at a distance4 ,he placed a needle in the cellar4 ,disruptive discharges of a ,leyden jar at #cj ft4 distant1 in an upper room1 produced a magnetic effect upon the needle4 #f4 ,,faraday',s ,,experiment4 ,,arc ,,maintained ,,by ,,certain ,,metallic ,,electrodes ,,at ,,low ,,voltage4 ,experimental ,researches4 ,phil4 ,trans41 ,se4 ,,ix41 ,dec41 #ahid4 #ajg4 to #ajgh4 ,the generator employed in this experiment consisted of a few cells of a chemical battery1 and he obtained1 what he called1 a voltaic spark4 ,he observed that when the two terminals touched each other1 a burning took place and an appearance as if the spark were passing on making the contact1 the terminals being pointed and formed of metal4 ,when mercury was the terminal1 the luminosity of the spark was much greater than with platinum or gold1 although the same quantity of current passed in both cases4 ,he attributed the difference to a greater amount of combustion in the case of mercury1 than in those of gold and platinum4 ,he obtained almost a continuous spark by bringing down a pointed copper wire to the surface of mercury and withdrawing it slightly4 ,wheatstone1 in #ahce1 analysed the light of sparks1 and found them to be so characteristic that by means of the prism and the spectra formed1 the metal could be known4 ,illustration3 ,,iii #g4 ,,wurts',s ,,experiment4 ,,non-,,arcing ,,metals ,,at ,,high ,,voltage4 ,trans4 ,amer4 ,inst4 ,elect4 ,eng4 ,march #ae1 #ahib4 ,ann4 ,chem4 ,phar4 ,sup4 ,,vii1 #ced and ,,viii1 #acc4 ,chem4 ,news1 ,,vii1 #gj2 ,x1 #ei1 and ,,xxxii1 #ba1 #abi4--,mendelejeff and ,meyer discovered that chemical elements occur in natural groups by a principle which they termed the periodic law4 ,one of these groups includes zinc1 cadmium1 mercury and magnesium2 and another group1 antimony1 bismuth1 phosphorus and arsenic4 ,alex4 ,j4 ,wurts1 of the ,westinghouse ,electric ,co4 found that the metals of these groups are non-arcing1 by which he means that with an alternating current dynamo of a thousand or more volts1 and with the said metals as electrodes in the air only just escaping each other1 it is impossible to maintain an arc as in the case of an ordinary arc lamp having carbon electrodes or in a lightning arrester usually having copper electrodes4 ,he suggested and theorized that certain chemical reactions served to explain the phenomena4 ,with low voltage--as #ejj1 the arc was maintained between all metals4 #f4 ,a two pole lightning arrester is shown in ,fig4 ,,iii ,the arc formed1 ceased instantly4 ,one of the best metals for practical use is an alloy of #a_/b zinc and #a_/b antimony1 or any metal electroplated with a non-arcing metal4 ,freedman observed a critical point with electrodes of brass4 ,the current was gradually reduced until the arc became like the discharge of a ,holtz machine whose condensers have been disconnected4 ,see ,elect4 ,power1 ,n4,y41 ,feb4 #ahif1 p4 #aai4 #h4 ,,wheatstone',s ,,experiment4 ,,duration ,,of ,,spark4 ,phil4 ,tran4 #ahcd4--,the short duration of an electric spark produced by a single disruptive discharge is easily made apparent by a rapidly rotating disc1 having radial sectional areas of different colors4 ,with reflected sunlight1 the colors seem to blend into one tint upon the principle of the persistence of vision2 7,see ,swain's experiment4 ,trans4 ,r4 ,so4 ,edin4 '#di and '#fa472 but when viewed by the flash of a spark1 the colors are seen as distinctly separated as if the disc were at rest4 ,by calculation1 based directly upon a series of experiments1 he found the duration of the spark to be about 4#jjjjdb sec4 ,it was discovered also1 by the rotating mirror1 that the apparently single spark was composed of several following each other in quick succession1 and he concluded that the current during the discharge was intermittent4 ,he considered each of the divisions of the spark as an electric discharge4 ,prof4 ,nichols1 of ,cornell ,university1 and ,mc,kittrick obtained curves indicating the variation of ,e4 ,m4 ,f4 during the existence of a spark4 ,trans4 ,amer4 ,inst4 ,elect4 ,eng4 ,may #bj1 '#if4 #h;a4 ,feddersen1 who used a ,leyden jar1 modified the experiment by having high resistances in the circuit through which the charge was effected4 ,the duration of the spark was found to be increased4 ,in one experiment1 he employed a slender column of water as the resistance1 #i mm4 in length4 ,the spark endured 4#jjad second4 ,with a tube of water #ahj mm4 the duration was 4#jahc second4 ,he noticed also that the duration increases directly with the striking distance and with the electrical dimensions of the electrical generator4 ,by varying the resistance of the circuit1 he found as it became less1 the discharge was intermittent1 when further reduced1 continuous1 7difficult to obtain7 #aa and when very small1 oscillatory--i4e41 alternately in opposite directions4 #i4 ,,faraday',s ,,experiment4 ,,brush ,,discharge ,,sound4 ,phil4 ,trans4 ,jan4 #ahcg4 ,se4 ,,xii4--,the brush discharge was caused to occur1 in his experiments1 generally from a small ball about 4#g of an inch in diameter1 at the end of a long brass rod1 acting as the anode4 ,with smaller balls he noticed that the pitch of the sound produced was so much higher as to produce a distinct musical note1 and he suggested that the note could be employed as a means of counting the number of intermissions per second4 ,see ,mayer's book on 8,sound0 #gg1 on measuring number of vibrations in a musical note4 #i;a4 ,upon bringing the hand toward the brush the pitch increased4 #di4 ,with still smaller balls and points1 in which case the brush could hardly be distinguishable1 the sound was not heard4 ,he alluded to the rotating mirror of ,wheatstone as becoming not only useful but necessary at this stage4 ,he considered the brush as the form of discharge between the contact and the air or else some other non or semi-conductor1 but generally between the conductor and the walls of the room or other objects which are nearest the electrodes1 the air acting as the dielectric4 ,one experiment1 he performed with hydrochloric acid led him to believe that that particular gas permitted of a dark or invisible discharge4 ,sometimes the air was electrically charged #d to a less distance than the length of the brush or light4 #aj4 ,,brush ,,in ,,different ,,gases4 ,,striae ,,cathode ,,brushes4 ,in the air1 at the ordinary pressure he found the color to be 8purple20 when rarefied still more purple1 and then approaching to rose2 in oxygen1 at the ordinary pressure1 a dull white2 when rarefied1 8purple20 and with nitrogen1 the color was particularly easily obtained at the anode1 and when nitrogen was rarefied the effect was magnificent4 ,the quantity of light was greater than with any other gas that he tried4 ,hydrogen1 as to its effect1 fell between nitrogen and oxygen4 ,the color was greenish grey at the ordinary pressure and also at great rarity4 ,the striae were very fine in form and distinctness1 pale in color and velvety in appearance1 but not as beautiful as those in hydrogen4 ,with coal gas1 the brushes were not easily produced4 ,they were short and strong and generally green1 and more like an ordinary spark4 ,the light was poor and rather grey4 ,also in carbonic acid gas the brush was crudely formed at the ordinary pressure as to the size1 light and color4 ,the tendency of the discharge in this case was always towards the formation of the spark as distinguished from the brush4 ,when rarefied1 the light was weak1 but the brush was better in form and greenish to purple1 varying with the pressure and other circumstances4 ,as to hydrochloric acid1 it was difficult to obtain a brush at the ordinary pressure4 ,he tried all kinds of rods1 balls and points1 and while carrying on all these experiments he kept two other electrodes out in the air for comparison1 and while he could not obtain any satisfactory brush in the hydrochloric acid gas1 there were simultaneously beautiful brushes in the air4 ,in the rarefied gas1 he obtained striae of a blue color4 ,he compared the appearances also of the anode and cathode brushes in different gases at different pressures4 ,he noticed that in air1 the superiority of the anode brush was not very marked 7 #da at end47 ,in nitrogen1 this superiority was greater yet4 ,a line of theory ran through ,faraday's mind in connection with all these experiments1 whereby he held that there is 8,a direct relation of the electric forces with the molecules of the matter concerned in the action40 #dg4 ,he made a practical application of the principles in the explanation of lightning1 because nitrogen gas forms #d_/e of the atmosphere1 and as the discharge takes place therein so easily4 ,illustration3 ,,from ,,magnetographs ,,by ,,prof4 ,,mckay4 p4 #be4 #a4 ,platinum wire4 #b4 ,copper gauze4 #c4 ,iron gauze4 #d4 ,tinfoil4 #e4 ,gold-foil4 #f4 ,brass protractor4 #g4 ,silver coin4 #h4 ,platinum-foil4 #i4 ,brass4 #aj4 ,lead-foil4 #aa4 ,aluminum4 #ab4 ,magnesium ribbon4 #ac4 ,copper objects4 ,illustration3 ,,from ,,sciagraph ,,of ,,various ,,objects4 p4 #acj4 ,by ,prof4 ,terry1 ,u4 ,s4 ,naval ,academy4 #aa4 ,,glow ,,by ,,discharge4 ,,glow ,,changed ,,to ,,spark4 ,,motion ,,of ,,air4 ,,continuous ,,discharge ,,during ,,glow4 ,the glow was most easily obtained in rarefied air4 ,the electrodes were of metal rods about 4#b of an inch in diameter4 ,he also obtained a glow in the open air by means of one or both of the small rods4 ,he noticed some peculiarities of the glow4 ,in the first place1 it occurred in all gases and slightly in oil of turpentine4 ,it was accompanied by a motion of the gas1 either directly from the light or towards it4 ,he was unable to analyze the glow into visible elementary intermittent discharges1 nor could he obtain any evidence of such an intermittent action1 #h;a4 ,no sound was produced even in open air4 #i4 ,he was able to change the brush into a glow by aiding the formation of a current of air at the extremity of the rod4 ,he also changed the glow into a brush by a current of air1 or by influencing the inductive action near the glow4 ,the presentation of a sharp point assisted in sustaining or sometimes even in producing the glow2 so also did rarefaction of the air4 ,the condensation of the air1 or the approach of a large surface tended to change the glow into a brush1 and sometimes into a spark4 ,greasing the end of the wire caused the glow to change into a brush4 #ab4 ,,lullin',s ,,experiment4 ,,spark4 ,,penetrating ,,power4 ,,passage ,,through ,,solids4 ,encyclo4 ,brit4 ,article ,electricity4 ,he placed a piece of cardboard between two electrodes and discovered that a spark penetrated the material and left a hole with burnt edges4 ,when the electrodes were not exactly opposite each other1 the perforation occurred in the neighborhood of the negative pole4 ,later experiments have shown that a glass plate1 #e or #f cm4 in thickness1 can be punctured by the spark of a large induction coil4 ,the plate should be large enough to prevent the spark from going around the edges4 ,the spark is inclined1 also1 to spread over the surface of the glass instead of piercing it1 #bd4 ,glass has been cracked by the spark in some experiments4 #ac4 ,,fage',s ,,experiment4 ,,spark4 ,,penetrating ,,glass4 ,,holes ,,close ,,together4 ,,practical ,,application4 ,la ,nature1 #ahgi4 ,nature1 ,dec4 #bf1 #ahgi1 p4 #ahi4 ,the length of the spark from the secondary coil in air was #ab cm4 ,one terminal of the secondary passed through an ebonite plate 7#ah cm4 #ab7 and touched the glass4 ,olive oil was spread around said terminal 7 #aa at end71 and served to insulate the same4 ,oil dielectric in this connection originally employed at least prior to #ahgj4 ,remembered by ,prof4 ,anthony as far back as #ahgb1 who often performed the experiment according to instructions contained in a publication4 ,the other terminal of the secondary coil was brought against the glass opposite the first terminal4 ,the spark was then passed and the glass perforated1 #ab4 ,by pushing the glass along to successive positions and passing the spark at each movement1 holes could be made very close together4 ,in ,nature1 of #ahif1 the author noticed that certain manufacturers were introducing glass perforated with invisible holes to be used for windows as a means of ventilation without strong draughts4 ,perhaps the fine holes were made by means of the electric spark4 #ad4 ,,knochenhaurer',s ,,experiments4 ,,conducting ,,power ,,of ,,gas4 ,,spark4 ,,penetrating ,,power4 ,,relation ,,of ,e4 ,m4 ,f4 ,,to ,,pressure ,,of ,,gas4 #ahcd4 ,pogg4 ,ann41 ,vol4 ,,lvii41 and ,gordon1 ,vol4 ,,ii4 ,boltzmann's experiment 7,pogg4 ,ann41 ,,clv41 '#ge71 and calculation indicated that a gas at ordinary pressure and temperature must have a specific resistance at least #ajbf times that of copper4 ,pogg4 ,ann41 ,,clv41 '#ge4 ,sir ,william ,thomson 7,kelvin7 confirmed this limit for steam1 and ,maxwell the same for mercury and sodium vapor1 steam and air4 ,from ,maxwell's ,,mss4 ,herwig was not sure but that the ,bunsen burner flame and mercury vapor conducted4 ,he allowed for the conductivity of the walls of the glass container4 ,braun treated of the conductivity of flames4 ,pogg4 ,ann41 '#ge4 #ad;a4 ,varley found that #cbc ,daniel cells only just initiated a current through a hydrogen ,geissler tube1 and only #cjh cells continued the current after once started4 ,knochenhaurer found that ,harris' 7,phil4 ,trans41 #ahcd7 law did not hold exactly true1 and that the ratio between the ,e4 ,m4 ,f4 and the air pressure becomes greater and greater as the pressure becomes less and less4 ,harris thought the ratio was constant4 ,the limits of his pressures were from #c to #bg4jd inches of mercury4 ,stated in other words1 his results were the same as those of ,harris and ,masson 7,ann4 de ,chimie1 ,,xxx41 #crd ,se471 except that a small constant quantity should be added4 #af4 #ae4 ,,gordon',s ,,experiment4 ,,dust ,,particles ,,hasten ,,discharge4 ,gordon1 ,vol4 ,,ii4 ,other experimenters had investigated the phenomena of the electric spark with different densities of the dielectric by a spark produced by a frictional or an influence machine1 or1 in a few cases1 by powerful batteries without coils1 while ,gordon claims to be the first to carry out these experiments with an induction coil4 ,he observed that when the discharging limit was nearly reached1 small circumstances1 such as a grain of dust or a rusting of the terminal by a former discharge1 would cause the discharge to take place at a lower ,e4 ,m4 ,f41 which should be allowed for4 #af4 ,,kelvin',s ,,experiment4 ,proc4 ,r4 ,so41 #ahfj4 ,encyclo4 ,brit41 ,art4 ,elect4 ,he used as the terminals1 two plates4 ,one of them was perfectly plane1 while the other had a curvature of a very long radius4 ,the object of this arrangement was to obtain a definite length of spark for each discharge4 ,the plates were gradually moved away until the spark would no longer pass1 and the reading of the distance was noted4 ,the law which he found cannot well be expressed in the form of a rule or principle1 because it is of a rather intricate nature1 but a discovery resulted1 namely in the case where the distance was greater1 the dielectric strength was smaller for respective distances of 4#jjbed and 4#ece cm4 ,many theoretical considerations in reference to this matter have been presented1 notably that of ,maxwell in his treatise on ,electricity and ,magnetism1 ,vol4 ,i4 #ag4 ,,cailletet',s ,,experiment4 ,,spark4 ,,penetrating ,,power4 ,,high ,,pressures4 ,,increased ,,dielectric ,,strength4 ,mascart1 ,vol4 ,i4 ,he experimented with dry gas up as high as pressures of #gjj lbs4 per sq4 inch4 ,he found that the dielectric strength continues to increase with increase of pressure4 ,he used about #ae volts in the primary and a powerful induction coil4 ,the dielectric strength was so great that at the maximum pressure named above1 the spark would not pass between the electrodes when only 4#je mm4 apart4 #be and #aa1 near end4 #ah4 ,,faraday',s ,,experiment4 ,,discharges ,,in ,,different ,,chemical ,,gases ,,variably ,,resisted4 ,exper4 ,res4 ,phil4 ,trans41 ,se4 ,,xii41 ,jan4 '#cf4 ,faraday passed on from the consideration of the effect of pressure1 temperature1 etc41 and wondered whether there would be any difference in the law according to what gas was used4 ,he arranged apparatus so that he could know1 with air as a standard1 whether another gas had a greater or less dielectric power4 7,cavendish before him had noticed a difference47 ,he tabulated the results4 ,they exhibited the following facts1 namely that gas1 when employed as dielectrics1 depend for their power upon their chemical nature4 #aj4 ,hydrochloric acid gas was found to have three times the dielectric strength of hydrogen1 and more than twice that of oxygen1 nitrogen or air2 therefore the law did not follow that of specific gravities nor atomic weights4 ,see also ,de la ,rue1 ,proc4 ,royal ,so41 ,,xxvi41 p4 #bbg4 #ai4 ,,thomson',s ,,experiments4 ,,gas ,,as ,a ,,conductor4 ,,visible ,,indication ,,by ,,discharge4 ,nature1 ,lon41 ,aug4 #bc1 '#id1 p4 #dji2 ,jan4 #ca1 '#ie1 p4 #ccb1 and other references cited below4 ,lec4 ,royal ,inst4 ,proc4 ,brit4 ,asso41 ,aug4 #af1 '#id4 ,in making comparisons1 things of like nature should be considered4 ,take1 for example1 gas at 4#ja m4 ,the number of molecules in such a rarefied atmosphere is comparatively small1 while in an electrolyte there are molecules sufficient in number to produce #ae1jjj lbs4 of pressure1 if imagined in the gaseous state within the same space4 ,by an experiment and rough calculation1 ,prof4 ,j4 ,j4 ,thomson1 ,f4,r4,s41 calculated that the conductivity of a gas estimated per molecule is about #aj million times that of an electrolyte1 for example1 sulphuric acid4 #ad4 ,this is greater than the molecular conductivity of the best conducting metals4 ,the experiment which is illustrated in ,fig4 ,,iv4 was a second experiment which did not serve as a basis for calculation1 but exhibited very strikingly to the eye that gases having different pressures have different conductivities4 ,for this apparatus he had two concentric bulbs1 as indicated1 one being contained within the other4 ,the inner one had air rarefied to the luminous point4 ,the outer one had a vacuum as high as it was practical to make it1 and contained in a projection a drop of mercury1 which1 when heated1 would gradually increase the pressure4 ,two ,leyden jars were employed1 and their outer coatings were connected to the coil which is seen surrounding the outer bulb1 and the inner coatings were connected to the coils of a ,wimshurst machine4 ,the operation was as follows3 ,when the mercury was cold1 that is1 with a high vacuum in the outer compartment1 a bright discharge passed through the inner bulb1 while the outer bulb was dark4 ,when the mercury was heated1 the outer bulb was bright1 and the inner one was almost dark4 ,by well-known principles of conductors and non-conductors1 the operation was explained by ,prof4 ,thomson1 who assumed that the gas in the outer bulb is a conductor2 then1 at each spark will the alternating current in the coil induce currents of an opposite direction in the gas1 which will become luminous1 as occurred when the mercury was heated4 ,the currents circulating in the gas act as a shield to the induction of the currents in the inner bulb4 ,however1 with the vacuum exceedingly high in the outer bulb1 the air therein being a non-conductor comparatively1 or for the given ,e4 ,m4 ,f41 does not prevent the discharge through the inner bulb1 which becomes1 therefore1 luminous4 ,he next compared the dielectric power of a gas1 a liquid and a solid4 ,he found that the ,e4 ,m4 ,f4 had to be raised1 in order to produce the discharge1--higher in the liquid than in the gas1 and higher in the solid than in the fluid4 #ab4 ,illustration3 ,,iv4 #bj4 ,,boltzmann1 ,,gibson1 ,,barclay1 ,,hopkinson ,,and ,,gladstone',s ,,experiments4 ,,square ,,root ,,of ,,the ,,dielectric ,,capacity ,,equal ,,to ,,the ,,refractive ,,index4 ,phil4 ,trans41 #ahga1 p4 #egc4 ,maxwell1 ,vol4 ,,ii41 #ghh4 ,maxwell has argued elaborately upon results of some of the above experimenters upon the theory that the luminiferous ether is the medium for transmission of electricity1 light and magnetism2 therefore he predicted that the relation stated in the title above should exist4 ,he acknowledged that the relation is sufficiently near a constant to show in connection with other results1 especially those obtained1 that his theory is probably correct4 #ba4 ,,pl,,cker',s ,,experiment4 ,,hermetically ,,sealed ,,vacuum ,,tube4 ,encycl4 ,brit41 vol4 #h1 p4 #fd4 ,pogg4 ,ann41 #aheh1 and vol4 ,,cxxxvi1 #ahfi4--;,he engaged ,geissler 7according to ,hittorf7 to make a glass tube in which the platinum wire electrodes were sealed in the glass by fusion1 as in the modern incandescent lamp4 ,after the air was exhausted by a mechanical air pump through a capillary tube1 the same was sealed with the flame of a spirit lamp4 ,he thus established means whereby a practically permanent vacuum could be maintained within a glass bulb4 ,platinum expands by heat at about the same rate as glass3 hence there is no tendency to crack and admit air4 #bb4 ,,geissler',s ,,experiment4 ,,luminosity ,,of ,,vacuum ,,tubes ,,by ,,friction4 ,,increased ,,by ,,low ,,temperature4 ,science ,record1 #ahgc4--;,by rubbing the vacuum tubes with an insulator--cat skin1 silk1 etc4--he observed that light was generated and that its color depended upon the particular gas forming the residual atmosphere4 ,at a low temperature1 the colors were more luminous4 #ace4 ,the best form of tube consisted of a spiral tube contained within another tube4 ,a modified construction involved the introduction of mercury4 ,by exhausting the air1 and shaking the tube1 the friction or motion of the mercury against the glass produced luminous effects according to the gas4 ,only chemically pure mercury would cause the light1 which endured for an instant after the rubbing ceased4 #fc4 #bc4 ,,alvergniat',s ,,experiment4 ,,luminosity ,,of ,,vacuum ,,tubes ,,by ,,friction ,,and ,,discharges4 ,,different ,,vacua ,,required4 ,sci4 ,rec41 #ahgc1 p4 #aaa4 ,comptes ,rendus1 #ahgc4--,to obtain luminosity by charging the tubes with the coil1 it was necessary to increase the degree of the vacuum--but when this was done the rubbing of the tube would not cause light4 ,the tube employed was #de cm4 in length1 and contained a small quantity of silicic bromide4 ,the atmospheric pressure within the tube for obtaining the glimmer by friction was #ae mm4 #bd4 ,,steinmetz',s ,,experiment4 ,,luminous ,,effects ,,by ,,alternating ,,current ,,and ,,solid ,,dielectrics4 ,trans4 ,amer4 ,inst4 ,elec4 ,eng41 ,feb4 #ba1 '#ic4--;,in carrying on experiments in the accurate measurement of dielectric strength1 he noticed that upon placing mica between the electrodes1 as is hereinafter set forth1 a spark did not at first form1 but that which he called a corona4 ,he attributed the appearances to a condenser phenomenon1 or at least he suggested this as an explanation4 #c4 ,as soon as the corona reached the edge of the plate1 the disruptive discharge took place1 by means of the sparks passing over the edge of the dielectric4 #ch4 ,he employed an alternating current dynamo of about #ej volts and #a h4p41 frequency of #aej complete periods per second4 ,the ,e4 ,m4 ,f4 of the alternator was varied1 by changing the exciting current1 up to #ij volts4 ,step-up transformers were employed4 ,with a difference of potential in the secondary of #hcj volts1 and a thickness of mica of #a4h mm4 and when the experiment was performed in a dark room a faint bluish glow appeared between the mica and the electrodes4 ,at #igj volts the glow was brighter1 while at #aefj volts the luminosity was visible in broad day-light1 and kept on increasing with the increase of ,e4 ,m4 ,f4 ,he modified the experiment by using mica of a thickness of #b4c mcm4 ,the difference of potential was #d4e kilo-volts4 ,in addition to the bluish glow1 violet streams or creepers broke out and increased in number and length as the ,e4 ,m4 ,f4 became greater1 forming a kind of aurora around the electrodes and on both sides of the mica sheet4 ,a loud hissing noise occurred4 #i4 ,as soon as the corona reached the edges of the mica1 the disruptive discharge occurred in the form of intensely white sparks and it was noticeable that the length of these sparks was #aj fold greater than could be obtained in the air at #ag kilo-volts4 ,these sparks were so hot as to oxidize the mica1 as apparent from the white marks remaining4 ,the electrodes also became very hot1 and the mica was contorted and finally broke down4 #be4 ,,morgan',s ,,experiment4 ,,no ,,discharge ,,in ,,high ,,vacua4 ,wiedemann1 vol4 #b4 ,phil4 ,trans41 #ahge1 vol4 #ge4--;,he was led to believe by an experiment1 that when the vacuum is sufficiently perfect1 no electromotive force could drive the spark from one terminal to the other1 however close together they may be4 #ah4 ,details of ,morgan's ,experiments were as follows1 given roughly in his own words3--,a mercurial gauge about fifteen inches long1 carefully and accurately boiled till every particle of air was expelled from the inside1 was coated with tinfoil five inches down from its sealed end1 and being inverted into mercury through a perforation in the brass cap which covered the mouth of the cistern1 the whole was cemented together and the air was exhausted from the inside of the cistern1 through a valve in the brass cap1 which1 producing a perfect vacuum in the gauge1 formed an instrument peculiarly well adapted for experiments of this kind4 ,things being thus adjusted 7a small wire having been previously fixed on the inside of the cistern1 to form a communication between the brass cap and the mercury1 into which the gauge was inverted71 the coated end was applied to the conductor of an electrical machine1 and notwithstanding every effort1 neither the smallest ray of light nor the slightest charge could ever be procured in this exhausted gauge4 #bf4 ,,de ,,la ,,rue ,,and ,m,,ller',s ,,experiment4 ,,constant ,,potential ,,at ,,the ,,terminals ,,of ,a ,,discharge ,,tube4 ,phil4 ,trans41 part #a1 vol4 #afi1 p4 #ee and #aee4--,the apparatus consisted of an exhausted bulb1 a chloride battery of #bdjj cells and a large resistance adapted to be varied between very wide limits4 ,the result was a constant potential at the electrodes of the bulb1 during all the variations of the resistance4 ,they concluded1 therefore1 that the discharge in highly rarefied gases is disruptive1 the same as in air at ordinary pressure4 ,illustration #bf;a4 ,,klingenberg',s ,,calculations4 ,,direction ,,of ,,discharge ,,tube ,,current ,,in ,,secondary ,,of ,,ruhmkorff ,,coil4 ,translated from the ,german1 by ,ludwig ,gutmann4 ,extract of paper read by ,g4 ,klingenberg before the ,electro-technischer ,verein4 ,it would naturally be inferred that an induction coil1 the primary current of which is intermitted1 and of one direction1 would produce an alternating current in the secondary coil4 ,the fact of the matter is1 however1 that a good induction coil will produce the sparking only in but one direction4 #da4 ,the reason is the following3 ,if the coil had no self-induction nor capacity1 then the current impulses would be represented by a rectangle a1 ,fig4 #a4 ,on closing1 the current would suddenly reach its maximum1 which is determined by the terminal pressure and circuit resistance1 and this current strength would be maintained as long as the circuit remained closed4 ,on the opening of the circuit1 the current would decrease just as suddenly2 if not1 the arc on opening of the circuit would oppose such sudden fall1 therefore the corner will be slightly rounded at a1 ,fig4 #b4 ,the influence of self-induction1 which we find in any coil1 is the force that will tend to oppose any change in the current strength4 ,therefore1 the self-induction will be the cause of a retardation of the minimum current4 ,on the other hand1 it increases the size of the spark on opening4 ,next a condenser is enclosed in the main circuit1 so that the spool is closed through it at the moment the current is intercepted4 ,if we assume1 for simplicity sake1 that the magnetization of the iron is proportional to the current strength1 then the primary current curve represents at the same time1 the curve of the rate of change of line of force in the magnetic field4 ,the secondary ,e4 ,m4 ,f4 is determined by e n7dw_/dt7t t2 the rise then will have a smaller ,e4 ,m4 ,f4 than at the fall1 like ,fig4 #c1 except that the curve representing the fall should be shown as more nearly perpendicular to the abscissa4 ,illustration3 ,v #bg4 ,,kinnersley1 ,,harris ,,and ,,riess',s ,,experiments4 ,,spark4 ,,pressure ,,produced ,,by4 ,ganot1 #gij1 et al4 ,encyclo4 ,brit4 ,art4 ,elect4--,these experimenters passed a spark through air contained over mercury1 so that if the pressure of the air were increased1 the mercury would move along through a capillary tube1 having a scale so that the amount could be represented to the eye1 as in the cut4 7,fig4 ,v47 ,the experiments proved that when a spark passes through the air1 the pressure is increased1 and it was concluded in view of several experiments1 that the spark being the source of an intense1 but small amount of heat1 expanded the air1 thereby causing the pressure in a secondary manner1 through the agency of heat4 ,a spark as short as #b mm4 will produce a considerable pressure of the mercury4 ,riess performed an experiment also in causing the spark to pass through cardboard1 and also through mica located within the air chamber4 #ab4 ,other things being equal1 the increase of temperature was less by using the solid material like mica or cards1 than without4 ,this illustrated that a part of the energy of the spark was converted into heat and a part into mechanical force1 and explained why sound1 #bd1 is produced by a spark and by lightning4 ---------------------------------------- -------------------------------- ,,chapter ,,ii ------- ,illustration3 ,,vi #bh4 ,,davy1 ,,bancalari ,,and ,,quet',s ,,experiments4 ,,electric ,,arc1 ,,magnetism ,,and ,,flame4 ,,sound ,,produced4 ,,practical ,,application ,,of ,,electric ,,arc4 ,phil4 ,mag41 #ahja4--,when the electric arc1 for example between two carbon electrodes1 occurs1 in a powerful magnetic field1 it is violently drawn to one side as first shown by ,sir ,humphry ,davy1 as if the wind were blowing it and sometimes it is broken into two parts4 ,fig4 ,,vi4 ,again a loud noise is produced4 #i4 ,without the magnet1 the appearance is as at the left4 ,with the energized magnet1 the arc and light1 as a whole1 are as shown at the right4 #bi4 ,,de ,,la ,,rive',s ,,experiment4 ,,rotation ,,of ,,luminous ,,effect ,,by ,,magnet4 ,,application ,,to ,,explain ,,aurora ,,borealis4 ,phil ,trans41 vol4 #acg1 #ahdg4 ,pynchon1 p4 #dga4 ,ganot1 ,sect4 #ibh4--;,an oval discharge tube was employed1 having a highly exhausted atmosphere 7for those days7 of spirits of turpentine4 ,a cylindrically shaped pole of a magnet extended into the bulb half way1 ,fig4 #d1 p4 #ag4 ,the inner end of the magnetic pole formed one electrode of the tube1 and the other electrode was a ring within the vacuum at the foot of the magnetic pole4 ,a fountain of light extended from one end of the magnet pole to the other1 and remained stationary1 while the magnet was not energized2 but the light was condensed into an arc and travelled around the magnet pole when a current was passed through the coils of the magnet4 ,for similar action of magnet on a flexible and movable wire carrying a current1 see experiments of ,spottiswoode and ,stokes1 ,proc4 ,r4 ,so41 #ahge4 ,the aurora borealis rotates around the pole of the earth1 and therefore1 ,de ,la ,rive thought that the phenomenon in his laboratory and in nature were but one and the same thing and different only in degree4 ,he also extinguished an arc in open air by means of a powerful magnet4 ,illustration3 ,,vii #cj4 ,,pl,,cker ,,and ,,hittorf',s ,,experiments4 ,,action ,,of ,,magnet ,,on ,,cathode ,,column ,,of ,,light4 ,pogg4 ,ann41 #aheh and #ahfi4 ,plcker found that the magnet acts on the cathode light in a rarefied atmosphere in a different manner from that on the anode light4 ,in the former the light follows the magnetic curves and strike the side of the bulb1 according to position of the poles1 see ,fig4 ,,vii4 8,where the discharge is perpendicular to the line of the poles1 it is separated into two distinct parts1 which can be referred to the different action exerted by the electro-magnet on the two extra currents produced in the discharge40 ,ganot4 #ibe4 #ca4 ,,thomson',s ,,experiment4 ,a ,,discharge ,,retarded ,,across ,,and ,,accelerated ,,along ,,the ,,lines ,,of ,,magnetic ,,force4 ,nature1 ,lon41 ,jan4 #ca1 #ahie1 p4 #ccc4 ,lect4 ,royal ,inst4--,prof4 ,j4 ,j4 ,thomson1 ,f4 ,r4 ,s41 performed an experiment which illustrates that the electrical discharge is retarded in flowing across the lines of magnetic force and accelerated in flowing with or parallel to such lines4 ,as illustrated in ,fig4 #bj1 p4 #ag1 he employed a large electro-magnet adapted to be cut in and out of circuit4 ,he had two air chambers1 one a bulb1 indicated by a circle1 and the other a tube bent into a rectangle1 indicated by the dotted square4 ,between these1 was an adjustable coil having its terminals connected to the outside coatings of ,leyden jars4 ,when the discharge took place between the poles of the magnet1 that is1 in the direction of the lines of force1 the discharge was helped along by the magnetic field1 but when it took place across the bulb1 that is1 across the lines of force1 the discharge was retarded4 8,the coil can be adjusted so that when the magnet is #8off' the discharge passes through the bulb1 but not round the square tube2 when1 however1 the magnet is #8on1' the discharge passes in the square tube but not in the bulb40 ,illustration3 ,,some ,,experiments ,,prior ,,to ,,lenard',s4 #cb4 ,,thomson',s ,,experiment4 ,,resistance ,,offered ,,to ,,striae ,,by ,a ,,thin ,,diaphragm4 ,lect4 ,royal ,inst4 ,nature1 ,lon4 ,jan4 #ca1 '#ie1 p4 #ccc4--;,it has often been remarked that lightning always takes the easiest path4 ,the same has been noticed with references to the artificial electric spark4 ,prof4 ,j4 ,j4 ,thomson1 ,f4,r4,s4 performed an experiment1 which not only confirms this principle but does so in an emphatic manner1 and proves it true in reference to the electric discharge in rarefied gases4 ,he arranged a very thin platinum diaphragm so as to divide a ,geissler tube into two compartments1 ,fig4 #ai1 p4 #ag4 ,he then formed a passage way around the diaphragm1 which could be opened and closed by mercury1 by respectively lowering and raising the lower vessel of mercury along the barometer tube4 ,when the passage way is opened around the diaphragm1 the luminosity extends through the passage way in preference to going through the diaphragm4 ,when the passage way is closed by mercury1 the discharge goes through the thin metal plate4 ,the same was found to occur when the platinum leaf was replaced by a mica scale4 #cc4 ,,sir ,,david ,,solomon',s ,,experiment ,,in #ahid4 ,proc4 ,royal ,so41 ,june #ba1 '#id4 ,nature1 ,lon4 ,sept4 #ac1 '#id1 p4 #dij4--,with a tube having a perforated diaphragm1 he noticed a 8forcing effect0 at and near the hole4 ,the striae had the appearance of being pushed through from the longer part of the tube--the diaphragm not being in the centre4 ,there was no passage way around the diaphragm--only through the small puncture4 #ai4 ,illustration ---------------------------------------- -------------------------------- ,,chapter ,,iii ------- #cd4 ,,riess',s ,,experiment4 ,,electric ,,images4 ,riess's ,reibungs4 vol4 #b1 #gci4--;,he laid a coin upon a plate of glass and charged the same electrically about one-half of an hour or more4 ,upon removing the coin and sprinkling the plate with dust1 an engraving of the coin was visible upon the glass4 #ac4 ,a suitable dust is licopodium powder4 #ce4 ,,sanford ,,and ,,mckay',s ,,experiment4 ,,electrographs4 ,,original ,,contribution ,,by ,,prof4 ,,mckay ,,of ,,packer ,,inst41 ,brooklyn1 ,may1 '#if4--,the picture of the coins in ,fig4 ,,ix1 was produced by the apparatus shown in ,fig4 ,,viii1 t1 t1 tinfoil1 p1 photographic plate with coins on sensitive side1 all wrapped in black paper4 ,fig4 ,,viii represents the general arrangement for taking electrographs4 ,this particular one was made by removing the upper tinfoil and touching each coin successively with wire from one of the poles1 while the other wire was connected with tinfoil on the opposite side4 ,the condenser thus formed is charged and discharged many times by a ,holtz machine or induction coil4 ,this is not a new discovery1 it was first described by ,prof4 ,sanford1 ,i think1 of ,leland ,stanford ,university1 two or three years ago4 ,other claimants of earlier date probably exist4 #cf4 ,,lichtenberg',s ,,experiment4 ,,dust ,,figures4 ,,pictures ,,drawn ,,with ,,anode ,,and ,,cathode4 ,gttingen1 #aggh-gi4 ,,motum ,,fluidi ,,electriciti4--,he drew two independent superposed pictures upon a flat surface of an insulating material1 for example1 rosin4 ,one picture was drawn with one terminal of a charged ,leyden jar4 ,another picture was drawn with the other terminal of a charged ,leyden jar4 ,he sprinkled upon the surface over the two pictures1 a dust made of a mixture of red lead and sulphur powder4 ,the former became attracted to the picture drawn with the cathode1 and the latter to that made with the anode1 so that the two figures were clearly visible4 ,before sprinkling the powders upon the surface it is necessary to stir them together whereby they become oppositely electrified4 ,illustration3 ,,viii ,,arrangements ,,for ,,taking ,,electrographs4 #ce1 p4 #ai4 ,illustration3 ,,from ,,electrographs ,,of ,,coins4 #ce1 p4 #ai4 ,taken by ,prof4 ,mc,kay4 ,illustration3 ,x ,the sulphur arranges itself in tufts with diverging branches and the red lead in small circular patches4 ,the particular materials1 namely1 the sulphur and red lead were first used by ,villarsy4 ,in case only one powder is employed1 for example1 licopodium1 it adheres to both the positively and negatively electrified portion of the insulating plate1 but in larger quantities upon the latter portions4 ,fig4 ,x1 shows rosin disc covered with licopodium powder after touching the disc with the knob of a ,leyden jar4 #cf;a4 ,,hammer',s ,,photo-,,electric ,,dust ,,figures4 ,from personal interview4--,according to experiments of ,elster and ,geitel1 hereinafter noted1 #ih1 ,hammer's dust figures shown in the accompanying half-tone cut may possibly be accounted for on the principle of the discharge of negatively electrified bodies by light4 ,mr4 ,william ,j4 ,hammer1 ,mem4 ,amer4 ,inst4 ,elect4 ,eng41 has a historical collection of incandescent lamps 7,elect4 ,eng41 ,n4,y41 ,april #bi1 '#if1 p4 #ddf47 which were arranged on shelves in a glass case standing obliquely in the sunlight about an hour a day4 ,after the lapse of many months1 the very fine dust within the case lodged upon the inner surface of the glass in such a manner as to produce oval dust figures corresponding somewhat to the shapes of the lamps and some of them1 appear after reproduction by the half-tone process in the accompanying cut4 ,when the figures are inspected closely and the circumstances are known1 no one can doubt that the sun and lamps acted as agents in their formation4 ,as to the correct explanation1 the matter has not been sufficiently discussed by scientists 7presented here for the first time7 to enable the author to render the opinions of others1 but it is of interest in connection with ,roentgen rays and the discharge of electrified bodies by light4 ,as a matter of course1 the surfaces of the lamps would reflect the light in such a way as to make bright spots 7movable1 however1 with the sun7 upon the glass of the containing case1 and if the latter were in any sense charged by negative atmospheric electricity1 this light would cause a variable amount of dust to be attracted according to the intensity of the rays striking the glass4 ,these remarks are in the nature merely of a suggestion of a hypothesis4 ,the heavy curved black line in the cut is a part of the frame of the glass case4 ,the incandescent lamps do not show1 simply because the case was empty when the photograph was taken4 ,that the figures were not due to chemical action was shown by rubbing off some of the dust with the fingers4 ,finger marks were pictured on the figures4 ,off hand1 ,mr4 ,hammer and ,prof4 ,anthony intimate air convection by differentiation of temperature1 as a possible cause4 ,illustration3 ,,fig4 #a4--;,,hammer',s ,,dust-,,figure ,,on ,,glass4 #cf41 p4 #ba4 ,illustration3 ,,fig4 #b4--;,,hammer',s ,,historical ,,collection ,,of ,,incandescent ,,lamps1 ,,contained ,,in ,,case ,,having ,,the ,,dust ,,figures4 #cf1 p4 #ba4 #cf;b4 ,independently of the above peculiar phenomenon1 ,mr4 ,hammer recently had on exhibition at the ,electrical ,exposition of the ,national ,electric ,light ,association in ,new ,york1 #ahif1 a portrait formed of fine dust upon a pane of glass4 ,the circumstances were as follows1 as remembered by the author4 ,mr4 ,hammer happened to be in some place where an artisan was removing a photograph from an old frame4 ,the glass which protected the portrait exhibited a fac-simile in dust on the inner surface4 ,the glass had not been in contact with the photograph1 because of a thick passe-partout surrounding the picture4 ,neither was the glass an old negative photographic plate4 ,further test and inspection tended to prove that the dust picture was executed by some action of the heat or light of the sun4 ,prof4 ,benjamin ,f4 ,thomas1 of the ,university of the ,state of ,ohio1 in an interview1 scarcely thought that the result was due to convection1 because the dust print was so sharply defined4 ,the principle of the discharge of bodies by light may be applicable perhaps1 but further experiment would be necessary as a more secure foundation4 ,it is common to find the print of a picture in a book upon the opposite page1 being due merely to the pressure of the inked surface1 as in the art of printing4 ,this explanation cannot be applied to the dust portrait1 because there was no contact between the photograph and the glass4 #cg4 ,,karsten',s ,,experiment4 ,,electrical ,,images ,,developed ,,by ,,condensed ,,moisture4 ,riess's ,reibungselect41 vol4 ,,ii41 #gci4--;,he arranged the following articles in the following order3 ,first1 a metal plate suitably insulated2 secondly1 a piece of a glass plate on top of the metal plate1 and1 thirdly1 a coin or small metal object on top of the glass4 ,sparks were then allowed to pass for several minutes from a ,holtz or similar machine to the coin4 ,the image of the latter appeared by removing the glass plate and breathing upon it4 ,the bas-relief of the image on the coin also was visible in all its details1 appearing as in ,sanford's ,electrograph1 #ce4 ,theoretical considerations led others to believe that the figures of ,riess and ,karsten are due to a different cause from that involved in the figures of ,lichtenberg1 for the former are thought to be due to a molecular action of a permanent nature upon an insulating material4 ,a slight change in the color often occurs1 thereby outlining the object4 ,illustration3 ,,dust-,,portrait ,,on ,,glass1 #cf41 p4 #bc1 ,,discovered ,,by ,,william ,j4 ,,hammer4 ,lighter portions1 dust2 darker portions1 due to less or no dust4 ,finger-marks across the shoulder and at right4 ,exposure #h years4 ,portrait as sharp and clear as a daguerreotype4 ,during exposure in frame1 distance of glass from photograph1 #a_/af inch4 ,above half tone was made from a photograph of the dust-portrait only after several unsuccessful attempts by different photographers4 ,the original dust-portrait is scarcely visible4 ,let every one examine closely glass plates when taken from old frames4 #cg;a4 ,,mckay',s ,,experiment4 ,,magnetographs4 ,,from ,,personal ,,notes ,,by ,,request4 ,april1 #ahif4--;,although this experiment does not belong to that class connected with discharge tubes1 yet the phenomenon has a theoretical interest in connection with ,x-rays4 ,he obtained a photograph of different objects in the dark by means of radiations from the poles of an electro-magnet after two hours' exposure1 but it need not have been so long1 as he obtained clear images in five minutes in one experiment with frequent variations of current by means of a rheostat1 and by approach and recession of the armature4 ,the elements involved in the experiment were arranged in the following order3 ,first1 a large inverted magnet for supporting #ajj lbs41 the poles hanging downward4 ,next in order was a wooden board pressing flatwise against the ends of the poles of the magnet4 ,next1 the objects and the sensitive plates backed thereby and all enclosed in a completely opaque wrapping extending over the sides1 face1 back1 etc41 of these two elements4 ,next in order was an armature about as heavy as the magnet would support4 ,the cut herein represents the photograph that was produced of the different objects named4 ,by reading ,prof4 ,mc,kay's very detailed description in the ,scientific ,american1 ,april #ah1 #ahif1 p4 #bdi1 the reader may feel certain that the photograph was not due to light for he tried the experiments in different ways and with various precautions4 ,in a course of experiments carried on by student ,austin1 about ,feb4 #ae1 '#if1 in the ,dartmouth laboratory1 a sciagraph of what appeared to be the lines of force was obtained by means of ,x-rays1 but upon repeating the experiment the result was negative4 ,see ,elect4 ,engineer1 ,mar4 #aa1 '#if1 p4 #beg4 ,article by ,e4 ,b4 ,frost4 ,illustration3 ,,xi #ch4 ,,piltchikoff',s ,,experiment4 ,,liquid ,,bas-,,relief ,,facsimiles ,,by ,,electric ,,discharge4 ,pro4 ,acad4 ,sci41 ,paris1 ,march1 '#id4 ,the ,electr41 ,lon41 ,april #ac1 '#id1 p4 #fef4--,these shadow pictures were obtainable either with the anode or cathode1 the particular machine employed being a large ,voss4 ,to either pole was electrically connected a pointed wire which was held just above the surface of castor oil1 in a copper pan4 ,a remarkable effect was obtained of the shadow of a piece of mica1 ,fig4 ,,xi1 of whatever shape1 located between the point and the surface4 #bd4 ,let it be observed that this shadow was not one in the sense of light and darkness but it consisted of a plateau within a depression1 the former being of the same shape as though it were a shadow of the mica triangle4 ,to illustrate the experiment better1 let the mica be supposed to be removed1 then will there be a depression formed in the oil upon bringing the metallic point near to the surface4 ,now insert the insulating sheet between the point and the surface1 then will there be an elevation within the depression of the same shape that the shadow would be4 #ci4 ,,gernez',s ,,experiment4 ,,distillation ,,of ,,liquids ,,by ,,discharge4 ,phys4 ,so41 ,paris1 #ahgi4 ,nature1 ,nov4 #bj1 #ahgi1 p4 #gb4--;,in order that the apparatus with which he experimented may be understood1 imagine a tube standing vertically in another tube4 ,the two concentric tubes communicate with each other at the top only4 ,the ,holtz machine is the generator4 ,the liquids in the two tubes at the beginning stand at the same level4 ,sparks are passed through the adjacent air1 which is in contact with both liquids4 ,the liquid at the cathode rises and at the anode falls4 #ch4 ,such was the experiment performed by ,gernez4 ,he was inclined to conclude that the effect was due to 8,an electrical transport of liquids along the moistened surfaces of the tubes40 ,when the liquid was alcohol1 it actually went over as by distillation1 three times as fast as water4 ,a soluble salt in water increased the rate of distillation2 and so also did the addition of a small quantity of sulphuric acid or ammonia4 ,no distillation of bi-sulphide of carbon1 tetra chloride of carbon1 nor turpentine occurred4 ,query3 ,can alcohol be concentrated or practically distilled upon this principle8 #dj4 ,,de ,,la ,,rue ,,and ,m,,ller',s ,,experiment4 ,,striae4 ,,black ,,prints ,,on ,,walls ,,of ,,tube4 ,phil4 ,trans41 #ei1 '#gh4--,particles of the metal of the electrodes were deposited upon the inside of the glass forming permanent black striae or bands #dd1 at points corresponding to the spaces between the luminous striae4 #f4 near the end4 ---------------------------------------- -------------------------------- ,,chapter ,,iv ------- #da4 ,,gassiot',s ,,experiment4 ,,striae4 ,,tube ,,in ,,primary ,,current4 ,,current ,,vibratory4 ,phil4 ,trans41 '#ei1 p4 #acg4 ,bakerian ,lectures4 ,phil4 ,trans41 '#eh1 p4 #a4 ,proc4 ,r4 ,so41 x41 pp4 #cf1 #cic1 #djd2 xii41 p4 #cbi2 xxiii41 p4 #cef4--,the form of tube in which to obtain luminous striae to the best advantage was that of a dumbbell with the electrodes located respectively in the balls--afterwards confirmed by ,sir ,david ,solomons1 ,bart4 ,proc4 ,royal ,so41 ,june #ba1 '#id4 ,nature1 ,lon41 ,sept4 #ac1 '#id1 p4 #dij4 ,he obtained in the vacuum luminosity with #ejj ,daniell's cells1 which he found to be the least ,e4 ,m4 ,f4 that could be employed4 ,he omitted1 and apparently overlooked1 the introduction of an automatic interrupter in the circuit and the use of a very low ,e4 ,m4 ,f4 #eb4 ,in conjunction with ,spottiswoode1 #a1jhj cells of chloride of silver 7about #b1jjj volts7 were employed1 first without1 and then with condensers4 ,one of the condensers consisted of the usual tinfoil type1 and the other of a self-induction kind1 namely of about #a1jjj feet of wire4 ,the results were striae with the condensers1 and no striae without the condensers4 #h;a4 ,the results suggested to them that there was some relation in principle between the striae and vibration of the current4 ,they therefore built an ingenious apparatus to test whether this was true or not1 and they found such was the case by the following related means4 ,if a current passing directly from the primary battery through the condenser and the discharge tube is undulatory or intermittent in any sense1 then it would be able to induce a current in the secondary of the induction coil4 #h at centre4 ,they found that there was a current thus induced1 and they detected it by means of a small discharge tube which became luminous4 ,fig4 #c p4 #ag4 ,this was an independent tube near the top of the figure1 having nothing to do with the one containing striae1 which were produced by the primary current and shown at the right4 ,dr4 ,oliver ,lodge1 ,f4,r4,s41 in treating of the cathode and ,x-rays in ,the ,elect41 ,lon41 ,jan4 #ca1 '#if1 p4 #dch1 stated the following with reference to ,gassiot's experiments3 8,in the days of ,gassiot and other early workers 7 #dc7 on the discharge in rarefied air1 it was the stream from the anode that chiefly excited attention4 ,it is this which developed the well-known gorgeous effects which used to be shown at nearly every scientific conversazione40 #db4 ,,poggendorff',s ,,experiment4 ,,effects ,,of ,,interrupting ,a ,,current ,,within ,,discharge ,,tube4 ,phil4 ,mag41 #dth ,se41 vol4 x41 #ahee1 p4 #bjc-bjg4--;,imagine an electric bell vibrator and magnet within the glass receiver upon an air pump4 ,upon connecting the magnet and vibrator in series with a small electric battery1 it is evident that in the open air1 as usual in electric bells1 there will be a minute violet spark at the terminals of the circuit breaker4 #f4 ,now1 let the air be exhausted as far as possible by means of a mechanical pump as constructed in #ahee4 ,poggendorff performed such an experiment1 and he noticed that in the poor vacuum the ordinary violet spark became yellow1 while blue light like a small enveloping tube surrounded the hammer of the vibrator and wire leading to the opposite contact and a little projection extending away from the hammer4 ,his experiment was unique1 because showing for the first time that a current from a battery1 if interrupted in the vacuum1 will not only produce the usual minute spark1 but that a blue tube of light will be produced around the conductors within the vacuum4 #dc4 ,,de ,,la ,,rue ,,and ,m,,ller',s ,,experiment4 ,,source ,,of ,,the ,,striae ,,at ,,the ,,anode4 ,,number ,,of ,,striae ,,varied ,,by ,,change ,,of ,,current4 ,phil4 ,trans41 #ahgh4--;,by an arrangement of means for causing different pressures1 they made a discovery1 namely1 that as far as the eye is concerned the striae begin to have their existence at the anode4 #df4 ,imagine the internal gas pressure to become less and less4 ,first1 a violet luminosity occurs around the anode as in #db4 ,as the pressure becomes less and less1 luminous striae move toward the cathode accompanied by more and more striae1 which increase either to form a column reaching a certain distance or else extending through the whole distance between the electrodes4 #df4 ,they observed that when the ,e4 ,m4 ,f4 was constant and the current changed1 the variation in the appearance of the striae was very regular4 #da4 ,with some tubes the number of striae increased with the increase of current1 while with a decrease of current the number of striae became less and less4 #h;a4 ,with some tubes the number of striae increased while the current decreased4 #h;a4 ,with the use of a condenser1 then as the ,e4 ,m4 ,f4 decreased together with a diminution of current1 the number of striae varied4 ,the striae nearest the anode vanished first1 as they diminished in number with the fall of the ,e4 ,m4 ,f4 ,the striae on the other hand originated at the anode1 when the charge of the condenser was gradually increased from a minimum1 and then the striae continued to increase from the anode as the source4 ,as to the color of the striae1 the same was changed by an alteration of the current4 #dd4 ,,solomons' ,,experiment4 ,,dark ,,bands ,,by ,,small ,,discharges4 ,nature1 ,lon41 ,sept4 #ac1 '#id4 ,proc4 ,r4 ,so41 ,june #ba1 '#id4--,solomons found that in a very dark room1 striae 7alternate light and darkness7 appeared with very minute discharges1 and as the current was increased1 they vanished1 appearing again when the discharge was strong4 ,he could not obtain them until the luminous column extended to the glass forming the large glass tube4 #dj4 #de4 ,,spottiswoode',s ,,experiment4 ,,governing ,,the ,,motion ,,of ,,striae4 ,,effect ,,upon ,,motion ,,by ,,diameter ,,of ,,discharge ,,tube4 ,,motion ,,stopped ,,by ,,magnet4 ,proc4 ,r4 ,so41 vol4 #cc1 p4 #dee4--,spottiswoode found that he could obtain motion when he desired4 ,he introduced some constant resistances and also a rheostat of fine adjustment4 ,the least change of resistance caused some effect upon the striae4 ,the general principle that he established was that letting it be assumed that the striae are stationary then2 8,an increase of resistance produces a forward flow1 and a decrease of the resistance a backward flow10 differences of as little as #a ohm in the primary current caused the effect4 ,sometimes the velocity of the flow is fast and sometimes slow1 being so rapid in certain instances that the unaided eye cannot distinguish them1 but they are known to exist by the use of the revolving mirror4 #df4 ,with tubes of small diameter1 compared with their length1 he noticed the fact that the striae in one portion of the tube moved faster than those in another portion4 #df4 ,sometimes one group moved while the other one was stationary4 ,sometimes they moved in opposite directions4 ,this last named phenomenon occurred also in very wide tubes4 ,the points at which the charge took place he called nodes4 ,he discovered external means for stopping this action4 ,he did it by means of a magnet located opposite one end of the tube4 #ca4 ,when the magnet was energized1 all motion ceased4 #ca4 ,illustration3 ,,from ,,sciagraph ,,of ,,foot ,,deformed ,,by ,,pointed ,,shoes4 #bjd4 ,by ,prof4 ,miller4 ,illustration3 ,,from ,,hammer',s ,,molecular ,,sciagraph4 #aag41 p4 #aad4 #df4 ,,thomson',s ,,experiment4 ,,velocity ,,of ,,striae ,,checked ,,at ,,the ,,cathode4 ,nature1 ,lon4 ,jan4 #ca1 '#if1 p4 #ccj4--;,a tube #ej ft4 long was exhausted1 #h;a41 as to striking distance4 ,in this particular experiment1 he caused a single interruption in the primary of the induction coil1 and observed the motion of the striae from the anode to the cathode by means of a rotating mirror4 #dc4 ,the luminosity began at the anode and travelled toward the negative with a high velocity1 but upon its arrival at the negative pole its velocity was checked4 ,he said that the striae did not disappear at the cathode like a rabbit would in entering a hole1 but they lingered around the electrode for some time4 ,as a consequence of this delay1 he found as expected1 an accumulation of positive electricity1 #d1 in the neighborhood of the cathode4 ,it is a general principle1 therefore1 that when a discharge passes between a gas and metal1 there is an accumulation1 illustrating that the discharge experiences a difficulty or resistance4 #cb and #cc4 ,the experimenter1 ,prof4 ,j4 ,j4 ,thomson1 acknowledged that ,profs4 ,liveing and ,davy had noticed similar effects4 #dg4 ,,thomson',s ,,experiment4 ,,disruptive ,,discharge ,,and ,,electrolysis4 ,nature1 ,lon4 ,jan4 #ca1 '#ie4 ,lect4 ,s4 ,inst4 ,the ,electr41 ,lon4 vol4 #ca1 p4 #bia1 #caf1 and vol4 #ce1 p4 #egh4 ,trans4 ,r4 ,so41 '#ie4--,the discharge of electricity through conducting liquids is1 with scarcely an exception1 7example1 mercury7 accompanied by a chemical action4 ,faraday and ,davy both performed early experiments in this direction4 ,prof4 ,j4 ,j4 ,thomson has set forth some instructive facts and which act as evidence that there is a close relation between the disruptive discharge and chemical action between the dielectric and electrodes4 #f and #g4 ,he made this experiment in connection with his investigations relating to the difficulty the positive electricity experiences in passing from a gas to the negative electrode4 #df4 ,he carried this experiment further1 by testing gases of different chemical natures4 ,the apparatus he employed consisted first of an alternating current generator1 a high tension converter1 a bulb for containing first one gas and then another1 whose metal electrodes were connected with the secondary of the transformer1 and an electrometer connected to a third electrode which could be moved about within the bulb4 ,the operation was as follows3 when the bulb contained oxygen which is an electro-negative gas1 the third movable electrode received a positive charge in whatever part of the bulb it was moved to1 but with hydrogen instead of oxygen at atmospheric pressure1 the third electrode received a positive charge far away from the arc between the other electrodes1 but very near the arc it received a negative charge4 ,he then rarefied the atmosphere of hydrogen and he noticed that the space where the third electrode became negative1 contracted1 and at about #a_/c of an atmosphere became practically nothing1 so that the said third electrode connected to the electrometer became slightly positive at all points within the hydrogen4 #d4 ,the next step consisted in using a bulb1 having oxydized copper electrodes and a hydrogen atmosphere at the pressure where there was only positive electricity1 that is about #a_/c of an atmosphere4 ,this remarkable phenomenon occurred2 there was no positive electricity1 but only negative4 ,when the copper oxide was reduced1 the positive electricity only1 existed in all parts of the bulb4 ,in brief1 bright copper electrodes left a positive charge in the gas1 while oxydized electrodes left a negative charge4 ,he argued upon the results of this experiment to account for the delay in the passage of the electricity from the gas to the metal1 #df4 ,in later experiments1 he used the spectroscope to detect decomposition4 #f1 at end4 #dh4 ,,de ,,la ,,rue ,,and ,m,,ller',s ,,experiment4 ,,heat ,,striae4 ,phil4 ,trans41 vol4 #aei1 #ahgh--,they arranged for the best conditions1 that is1 when a small number of striae occurred in conjunction with a wide1 dark interval4 #dd4 ,they found that the heat was greatest at the position of maximum luminosity1 but they also found that heat was generated at the dark spaces4 ,a novel feature was the discovery of the development of heat in the middle of the tube even when there was no luminosity1 #i;a1 near end1 so that they thought it probable there may be what might be termed heat striae1 independently of luminous striae4 #di4 ,,spottiswoode ,,and ,,moulton',s ,,experiment4 ,,sensitive ,,state4 ,,air-,,gap ,,in ,,circuit ,,forms ,,best ,,method ,,of ,,obtaining4 ,,branch ,,current ,,to ,,earth ,,verified ,,by ,a ,,telephone4 ,,sensitive ,,state ,,by ,a ,,single ,,quick ,,discharge4 ,phil4 ,trans41 #ahgi1 p4 #afe1 and ,april #h1 #ahhj4--;,by sensitive state of luminous effects in a ,geissler tube is meant the susceptibility of the light 7 #bh7 to an outside conductor connected to earth4 ,fig4 #e1 p4 #ag4 ,when one's hand is brought near a ,geissler tube the change near the hand sometimes occurs and sometimes it does not4 #h4 ,in the first place1 the effect is more easily noticeable if the vacuum tube is comparatively wide or thick in diameter4 ,with the electric egg1 for example1 the luminous effect1 instead of extending more or less across the space between the electrodes1 reaches from one of the poles to a conductor on the outside of the egg1 provided said conductor has an earth connection or large capacity4 ,some of the light continues to exist nevertheless between the two poles4 ,the general principle is that the division exists because of the re-distribution or branching of the disruptive discharge4 ,it was not known why the luminosity should be affected by such an outside conductor sometimes1 and remain the same at other times but the above named experimenters discovered causes which could be depended upon to produce the sensitive state4 ,the apparatus will be described4 ,they had the usual ,geissler tube with the platinum wire electrodes1 and a ,holtz machine as the generator4 ,they were led to believe that intermissions of the current had a great deal to do with the production of the sensitive state1 and accordingly they arranged for an air-gap in circuit with the machine and with the vacuum tube4 #ea4 ,they not only observed that such a gap caused the sensitive state1 but that an increase in the length of the gap made the luminous column more sensitive4 ,they increased the gap so much that the ramifications of the light could be seen4 ,if an induction coil is employed as the secondary generator1 a condenser should be coupled up in connection with it4 ,the two in combination thereby produce the sensitive state1 but upon cutting out the coil and charging the tubes from the condenser the sensitiveness can not be detected4 ,instead of the permanent air-gap1 may be employed a rapid circuit interrupter1 coupled up between a ,holtz machine and a vacuum tube4 ,the manner of coupling up is to place the interrupter in a shunt to the vacuum tube4 ,difficulty had been found in early experiments to obtain the sensitive state with those vacua which give striae4 ,with a rapid circuit interrupter and an induction coil1 the breaks occurring #bdj per second1 the luminous column was not only broken up into striae1 but were acted upon by the approach of an outside conductor connected to earth4 ,the sensitive state is not always made apparent by the appearance of attraction of the luminous light to the outside conductor4 ,sometimes the light seems to be repelled4 ,these two phenomena may be caused in the same tube4 ,this feature of the sensitive state constitutes the beginning of radiations of energy through the walls of a vacuum bulb1 like ,x-rays4 ,some action or other in these cases takes place through the glass4 ,they tried an experiment in which one of the electrodes of the vacuum tube was entirely on the outside4 ,the electrical discharge was found to be sensitive1 for the discharge was changed in its appearances by the presence of an outside conductor connected to earth4 ,another cause of the sensitive state was observed1 namely1 the brevity of the charge4 ,this may be illustrated with a ,leyden jar1 which is known to give an almost practically instantaneous discharge4 ,a single discharge from such a jar produced a flash of light which was in the sensitive state4 ,the nomenclature by which the experimenters defined the cause of the phenomena is made up of the words3 ,re-distribution of electricity1 and a relief of the external strain4 #di;a4 ,no re-distribution took place unless the outside conductor was connected to earth or to a conductor of large capacity1 nor would an outside conductor1 which was already charged1 serve to exhibit the sensitive state4 ,the re-distribution effect was proved by means of a telephone connected in circuit between the outside conductor and the earth ,fig4 #e1 p4 #ag4 ,when the state was sensitive1 that is1 during the use of the air-gap1 the telephone produced a sound in unison with the intermissions occurring at the air-gap4 #i and #i;a4 #ej4 ,,reitlinger ,,and ,,urbanitzky',s ,,experiment4 ,,sensitive ,,state ,,illustrated ,,by ,a ,,flexible ,,conductor ,,within ,,the ,,discharge ,,tube4 ,proc4 ,vienna ,acad41 #ahgi4 ,nature1 ,nov4 #bj1 #ahgi4--,the discharge tube was #bj cm4 long4 ,it had the usual platinum electrodes1 and it stood upright4 ,from the upper electrode1 was suspended a strip of tinfoil in the middle of the tube1 which was connected to a pump so that the density of the gas could be varied4 ,at atmospheric pressure1 the secondary current of a ,ruhmkorff coil connected to the electrodes caused the strip to be attracted to the glass tube4 ,the attraction was less and less as the process of exhaustion was carried on1 and when a pressure indicated by #g mm4 was reached1 the strip was neither attracted nor repelled1 but hung downward the same as without any electricity whatever1 but it was attracted by a neighboring shell-lac rod which had been rubbed with cloth1 and it was repelled by a glass rod which had been rubbed with amalgam1 it being assumed that the strip was connected to the anode4 #cf4 ,the opposite action took place when it was connected to the cathode4 ,as the exhaustion continued and became greater and greater1 these actions died away also up to a rarefaction of about #d mm4 ,independently of the degree of rarefaction1 the flexible strip of tinfoil was always deflected by an outside conductor connected to earth4 #di4 #ea4 ,,tesla',s ,,experiment4 ,,incandescent ,,electrode ,,by ,,high ,,potential ,,and ,,enormous ,,frequency4 ,,system ,,referred ,,to ,,by ,,roentgen ,,for ,,generating ,,powerful ,x-,,rays4 ,u4 ,s4 ,letters ,pat41 ,no4 #ded1 #fbb1 ,june #bc1 '#ia4 ,martin's ,researches of ,tesla2 ,trans4 ,amer4 ,inst4 ,elec4 ,engineers1 ,may #bj1 '#ia2 ,elec4 ,review1 ,n4,y41 ,june #bd1 '#ic1 p4 #bbf2 ,lect4 ,franklin ,inst41 ,feb4 #bd1 '#ic1 and ,nat4 ,elec4 ,light ,asso41 ,mar4 #a1 '#ic2 also ,lect4 in ,europe4 ,later he again experimented in this direction1 see ,elec4 ,review1 ,n4,y41 ,may #bj1 '#if1 p4 #bfc4--;,by the ,u4 ,s4 ,patent ,office he was granted1 among other claims1 the following3 8,the improvement in the art of electric lighting herein described1 which consists in generating and producing for the operation of lighting devices1 currents of enormous frequency and excessively high potential1 substantially as herein described40 ,a simple combination of circuits together with great skill in the construction of apparatus involving high powers of insulation1 resulted in the production1 within a vacuum1 of an electrode radiating intensely white light4 ,the circuit may be easily traced in the diagram ,fig4 #ag p4 #ag4 ,briefly described1 there may be noticed an alternating current generator of comparatively low ,e4 ,m4 ,f4 ,the current from this generates a secondary current by means of an induction coil4 ,this secondary current generates a tertiary current by a second induction coil4 ,an air-gap for automatic and intermittent disruptive discharges1 #di near end1 is in the circuit of the secondary coil of the first named induction coil1 which is directly charged by the alternating current generator4 ,the gap may be noticed between the two balls4 ,in shunt to the air-gap is a condenser 7see ,fizeau1 chapter ,i47 represented by several parallel lines4 ,the lamp consists merely of an evacuated bulb having an electrode of carbon or other refractory material1 which is connected to one pole of the last secondary coil while the other pole may be outside1 and may consist1 for example1 of the walls of a room1 which in such a case should be of some electric conducting material4 ,the higher the vacuum the more intense the light2 he found no limit to this rule4 ,fig4 #af;a p4 #ag illustrates his ideal method of lighting a room4 ,he found that with two plates at a distance apart as indicated and connected to the poles of the coil1 and with electrodeless vacuum bulbs1 the latter became bright in space--no mechanical or electrical connection other than air and the assumed ether4 #eb4 ,,moore',s ,,experiment4 ,,luminosity ,,in ,,discharge ,,tube ,,by ,,self-,,induced ,,currents4 ,trans4 ,amer4 ,inst4 ,elect4 ,eng41 ,sept4 #bj1 '#ic and ,april #bb1 '#if4 ,several ,u4 ,s4 ,letters ,patent4 ,invented #ahib4--;,during or about #ahca1 ,prof4 ,henry discovered that when the circuit of a primary battery was interrupted1 a self-induced current1 which he called an extra current1 was produced4 ,when the circuit was closed1 there was also a self-induced current1 but very much feebler than that obtained on interruption4 ,the self-induced current occurred only at or about the instant of interruption or completion4 ,he found also that the self-induced current produced by interruption was enormously increased in ,e4 ,m4 ,f4 if the circuit included a helix of very long and fine wire4 ,it was further increased by the presence of an iron core4 ,with one or two cells1 the spark upon interruption was scarcely visible1 but with a fine wire #cj or #dj feet long1 an appreciable spark was obtained during interruption4 ,with but a comparatively few cells1 and with a magnet for example like a telegraph relay1 the ,e4 ,m4 ,f4 arose to several thousand volts at the instant of interruption4 ,d4 ,mc,farland ,moore introduced into such a circuit a ,geissler tube and provided a rapid automatic interrupter4 ,page1 ,ruhmkorff and others had1 at an early date1 noticed the desirability1 in operating ,geissler tubes by secondary currents1 to obtain quick interruption in the primary circuit in order to produce the best effects in the ,geissler tube4 ,moore caused the interruptions to take place in a vacuum1 so high that a disruptive electrical discharge could not pass4 ,the break was therefore1 absolutely instantaneous and complete4 ,by this system1 illustrated in diagram in ,fig4 #ah1 p4 #ag1 he obtained all the luminous effects1 actions by magnets1 the sensitive state1 striae and all the other phenomena heretofore noticed in ,geissler tubes and some of those obtained by ,tesla with his apparatus as just described4 ,in greater detail1 it will be noticed that he had a dynamo of rather low ,e4 ,m4 ,f41 generally #ajj volts1 and a high vacuum containing a circuit interrupter operated automatically by a magnet outside like a vibrator in an electric bell4 ,the magnet served also as the self inductive device4 ,the magnet and interrupter were in series with each other1 therefore1 while the ,geissler tube was in series with the magnet1 and the electrodes extended either inside of the ,geissler tube or remained on the outside4 ,he performed numerous experiments on similar lines and developed the system on a large scale1 whereby rooms 7e4g4 the hall of the ,amer4 ,so4 ,mech4 ,eng41 ,n4,y47 have been illuminated as if by other artificial illuminants1 by employing long and numerous vacuum tubes4 ,among several discoveries was that of the production of a bright pencil of light along the axis of a long open helix1 which formed one of the internal electrodes4 ,the ,patent ,office made strenuous efforts to determine the degree of novelty1 assuming that some one else must have conceived the idea of employing a self-induced current to operate ,geissler tubes2 but nothing nearer than ,poggendorff's experiment #db could be found1 and therefore the following claim 7in patent #edhegf1 ,oct4 #bb1 '#ie17 was granted among a hundred or so relating to developments and details and particularly covering the vacuum interrupter4 8,the method of producing luminous effects1 consisting in converting a current of low potential into one of high potential1 by rapidly and repeatedly interrupting the low potential current in its passage through a self-inductive resistance1 and passing the former current through a ,geissler tube1 thereby producing light within the tube40 ,illustration3 ,,edison',s ,,beneficent ,x-,,ray ,,exhibit1 #hb1 p4 #ga1 and #acb1 p4 #abf4 ,calcic tungstate screen at center1 sciascope near right4 ---------------------------------------- -------------------------------- ,,chapter ,v ------- #ec4 ,,crookes' ,,experiment4 ,,dark ,,space ,,around ,,the ,,cathode4 ,lect4 ,brit4 ,asso41 ,shef41 ,eng41 ,aug4 #bb1 '#gi4--;,according to ,lenard 7,the ,electr41 ,lond41 ,mar4 #bc1 '#id7 ,hittorf discovered the cathode rays1 and ,varley1 #fa;a41 and ,crookes studied them4 ,the pressure of the residual gas was #a ,m4 of an atmosphere4 ,prof4 ,crookes1 ,f4,r4,s41 maintained the evacuated space in communication with the air pump and with an absorbent material4 ,before his time most experimenters worked with a vacuum not much less than #cj1jjj ,m4 ,the first experiment is illustrated in diagram1 at ,fig4 #f p4 #ag1 but the vacuum was not the highest in this type4 ,the tube was cylindrical and was provided with electrodes at the ends4 ,another electrode was located at the centre and was made the cathode1 while the two terminal electrodes were made the same pole2 namely1 the anode4 ,upon connecting the tube in circuit with the secondary of a large induction coil1 the luminosity did not extend either continuously or in striae throughout the length of the tube4 ,former investigators had likewise noticed the dark space4 ,the space and glass on each side of the central cathode were dark4 ,the dark space extended for about one inch on each side of the negative pole4 ,it is not intended here1 any more than in former cases1 to present theories in explanation further than to briefly allude to any conclusion at which the experimenter himself arrived4 ,crookes' explanation of the phenomena has not been universally accepted1 nor has it been proved otherwise4 ,the knowledge of the existence of rays1 now known as ,roentgen rays1 will assist in formulating theories upon the ,crookes' phenomena and may either confirm some of his views or overthrow them4 ,crookes considered that the residual atmosphere was in such a state as to be as different in its properties from gas1 as gas is from liquid and liquid from solid1 and therefore he named the attenuated atmosphere radiant matter1 or fourth state of matter4 ,he concluded that the remaining particles of the gas forming the radiant matter moved in straight lines over a great distance as compared with that moved through by molecules at the ordinary pressure4 ,he called this distance the 8mean free path40 ,if his theory is correct1 this dark space is due to the fact that the molecules in motion at and near the cathode do not bombard each other and therefore do not produce the effect of light4 ,when the motion is arrested by particles of gas themselves1 within the bulb1 then is light generated4 ,the force propelling the particles from the positive pole was supposed to be less4 ,in order to let the experiments speak for themselves1 as much as possible1 without being too much influenced by the opinion of the experimenter2 the theory is only briefly alluded to as above1 and will not be further applied in the presentation of his other experiments4 ,in view of the radical discoveries of ,lenard and ,roentgen1 after the installation of the ,crookes phenomena1 it has been the policy of the author to present all the experiments as facts for evidence in behalf of the general theories1 which may be hereafter formulated independently of old theories4 ,therefore1 the reader should bear in mind the teachings of the various experiments with the view of arriving at general principles and hypotheses4 #ed4 ,,relation ,,of ,,vacuum ,,to ,,phosphorescence4--,he started with such a high vacuum that he could not obtain any electrical discharge4 #be4 ,there was1 therefore1 no phosphorescence in the glass tube1 whatever4 ,the caustic potash1 which had been employed to absorb the last trace of moisture and carbonic acid gas1 was slightly heated1 and very gradually4 ,then it was noticed that a current began to pass and that the glass became green1 and apparently on the inner surface4 ,as the heat continued1 the green passed gradually away and was replaced by striae1 which first appeared to extend across the whole diameter of the glass tube 7 #dj7 which was a long cylindrical tube1 and then became concentrated toward the axial line of the tube4 ,finally1 the light consisted of a pencil of purple4 #aj4 ,when the source of heat was removed so that the moisture and carbonic acid gas could be absorbed again by the potash1 the striae appeared1 and then the other effects just named1 only in the reversed order1 until the tube acted like an infinite resistance4 ,phosphorescence is the correct word1 because the light existed for a few seconds after cutting off the current4 #ee4 ,,phosphorescence ,,of ,,objects ,,within ,,the ,,vacuum ,,tube4--,the construction in ,fig4 #g1 p4 #ag1 shows how a diamond was caused to phosphoresce within a ,crookes' tube1 being supported in a convenient manner in the centre of one of the tubes1 while electrodes were located near the ends and were formed of disks facing the diamond4 ,upon connecting the disks to the respective poles of the secondary conductor1 and by performing the experiment in a rather dark room1 the diamond became brilliantly phosphorescent1 radiating light in all directions4 ,he experimented with many substances in this way1 but found that the diamond was the best--almost equal to one candle power4 ,in order to exhibit the phosphorescence of glass in a striking manner1 he charged three small tubes simultaneously4 ,one was made of uranium glass which radiated a green light4 ,another was an ,english glass which appeared blue1 and the remaining one was ,german glass which phosphoresced a bright green4 ,notice difference with respect to light which does not perceptibly cause phosphorescence of glass4 ,the uranium glass was the most luminous4 ,luminous paint1 as prepared by ,becquerel1 and later by ,balmain1 which has the property of storing up light and afterwards radiating it in a dark room for several hours1 became more phosphorescent in the ,crookes tube than when subject to day-light4 ,phosphorescence of the mineral phenakite1 the chemical name of which is glucinic aluminate1 was blue1 the emerald1 crimson1 and spodumene1 which is a double silicate1 were yellow4 ,the ruby phosphoresced red1 whatever its tint by day-light4 ,in one tube he had rubies of all the usual tints by day-light1 but they were all of one shade of red by the action of the disruptive discharge in the tube4 #ef4 ,,darkness ,,and ,,luminosity ,,in ,,arms ,,of ,v ,,tube4 ,see ,fig4 #h1 p4 #ag4 ,it will be noticed that in ,fig4 #f1 p4 #ag1 the tube was straight4 ,crookes desired to see what effect would take place in a bent tube4 ,he therefore employed a ,v shaped tube1 having electrodes in the ends--one in each arm4 ,upon causing the electrical discharge to take place through the tube1 one arm was luminous and the other was dark4 ,whatever the ,e4 ,m4 ,f4 was1 the appearances remained the same4 ,no luminosity would bend from one arm of the ,v shaped tube to the other4 ,the cathode arm was always luminous and the anode dark4 ,with a less degree of vacuum1 both arms were luminous1 according to early experimenters who thus brilliantly lighted tubes of the most fantastic shapes4 #eg4 ,,cathode ,,rays ,,rectilinear4 ,,radiate ,,normally ,,from ,,the ,,surface ,,of ,,the ,,cathode4 ,in his lecture he had1 side by side1 two bulbs1 one1 in which the vacuum was of such a degree1 that a blue stream of light existed between the negative pole and positive pole1 #ed1 at centre4 ,it is evident that the vacuum in this bulb was not very high4 ,fig4 #i1 p4 #ag1 shows a stream extending from the negative to the positive pole1 ,fig4 #aj1 p4 #ag1 is the same kind of a tube only the vacuum is about #a to #b m4 ,in other words1 the vacuum in the latter was just so high that a discharge took place1 and instead of the luminous effect being like that with a low vacuum1 there was a patch of green light directly opposite the concave negative pole4 ,the radiations from this pole were rectilinear1 crossing each other at a focus within the bulb and producing upon the glass a phosphorescent spot4 ,it should be remembered that the word radiations is used as a mere matter of convenience4 ,directly opposite the concave cathode1 there was a green patch of light on the inner surface of the glass4 ,it was shown that it made no difference where the anode was4 ,this fact becomes useful in carrying on experiments in connection with ,roentgen rays1 and it may have a great deal to do with the solution of the theoretical problems in connection with electrical discharges in vacuum tubes4 ,in regard to the three streams shown in ,fig4 #i1 p4 #ag1 it may be stated that only one occurred at a time in the experiment1 for1 first one anode was connected in circuit1 and then the next by itself1 and then the third one by itself1 while the concave pole was always negative4 ,each time the anode was changed1 the stream changed1 and connected that pole which was in circuit1 #dc1 but similar changes made upon the tube with a high vacuum1 did not alter the position of the phosphorescent spot4 ,this and other experiments show that the radiations took place perpendicularly from the surface of the cathode4 #eh4 ,,shadow ,,cast ,,within ,,the ,,discharge ,,tube4 ,this is illustrated in ,fig4 #aa1 p4 #ag1 where there is a negative polar disk at the small end of the egg shaped tube1 and a cross near the large end1 the same forming the positive pole4 ,the cross is made of aluminum4 ,there was a novel action1 however1 discovered in addition to the mere casting of a shadow4 ,the glass which had become phosphorescent except within the shadow1 became after a while1 less phosphorescent4 ,its property to phosphoresce became less as proved by removing the cross1 which was arranged to fall down upon tipping the bulb4 ,immediately1 the part which was within the shadow became brighter than the rest of the glass1 thereby reversing the appearances1 by making a luminous picture of the cross upon only partially phosphorescent glass4 ,a remarkable feature is that the glass never recovered its first exhibited power of phosphorescence1 neither did this power entirely become nothing1 however many times the tube was employed4 ,was the deposit of metal from the cathode the cause8 #eh;a4 ,,mechanical ,,motion ,,produced ,,by ,,radiations ,,from ,,the ,,negative ,,pole4 ,it occured to ,crookes that the radiations from the cathode might perhaps cause a wheel to turn around4 ,he therefore had a minute wheel made by ,mr4 ,gimingham1 like an undershot water wheel1 and its axle rested on two rails of glass1 so that it might roll along from one end of the tube to the other4 ,the vanes were exactly opposite to the plane surface of the cathode4 ,the molecular stream or radiations1 or whatever they may be1 possibly vibrations1 from the cathode1 were so powerful mechanically that the wheel was caused to run up hill1 the tube being inclined very slightly4 ,on the principle that action and reaction are equal1 he built another device in which the negative electrode was movable1 and he observed that when the current was on1 the negative electrode moved slightly4 ,upon these principles he built the well-known ,crookes radiometer in which the vanes rotated by reaction of the radiations4 ,the vanes in this form of radiometer were made of aluminum1 and a cup of hard steel served as the bearing1 ,fig4 #ab1 p4 #ag4 ,one side of each disk was coated with a thin scale of mica4 ,the aluminum disks formed the cathode1 while the anode was located at the top4 ,the operation consisted in connecting the terminals as stated1 so that the vanes were the negative poles and it was observed that the little wheel rotated4 ,the vacuum was not as high as that for obtaining phosphorescence4 ,with a low vacuum1 an envelope of violet light existed near the surface of the aluminum vanes4 ,effects were carefully studied by maintaining connection with the pump4 ,at the pressure of 4#e mm4 there was a dark cylinder opposite the aluminum extending to the glass1 and this was the pressure at which the vanes began to rotate4 ,the dark spaces opposite each vane became larger and larger in width1 until they appeared to be opposed or resisted by the inner surface of the glass1 and then the rotation became very rapid4 ,he modified this experiment by having vanes entirely of mica1 and by having the cathode disconnected electrically from the vanes1 ,fig4 #ac1 p4 #ag4 ,a coil of metal near the vanes served as the cathode4 ,the anode was at a distance in the top of the tube as in ,fig4 #ab1 p4 #ag4 ,during the electrical discharge1 the wheels rotated by radiations from the coil which formed the cathode4 ,he made the discovery that when this coil was heated red hot conveniently by a current from a primary battery1 the vanes also rotated1 showing that there is probably some relation between the radiations from the cathode and heat rays4 ,the fact remains however1 that both kinds of rays produced rotation1 directly or indirectly4 #ei4 ,,action ,,of ,,magnet ,,upon ,,cathode ,,rays4--,he had two tubes1 one of which is shown in ,fig4 #ad and the other in ,fig4 #ae1 on page #ag4 ,in the former1 the vacuum was so low that a violet stream of light existed between the electrodes4 ,in the other1 the rays were invisible1 but were converted into luminosity by projection at an exceedingly slight angle1 upon a phosphorescent screen arranged along the length of the tube and inside thereof4 ,inasmuch as the whole surface of the cathode in the latter case radiated parallel and invisible rays1 he cut off some of them by a mica screen having a hole in the centre and located near the negative pole1 so that only a pencil of invisible rays could go through the mica screen and act upon the phosphorescent screen4 ,in both cases1 there was visible a straight pencil of light4 ,now notice the effect which took place upon locating a magnet as indicated in the figures4 ,with the low vacuum1 the pencil was bent out of its course but returned again to the line of its original path4 #bh4 ,with the high vacuum1 the rays were bent but did not return to their original direction nor parallel thereto4 ,in the former case1 the magnet acted as upon a very delicate flexible conductor1 while in the latter1 it acted1 as ,crookes said1 like the earth upon projectiles4 ,he modified the latter experiment in order to determine if the similarity between this phenomenon and gravitation existed in other respects4 ,he anticipated that if the molecular resistance to the rays were increased they would be bent more out of their course like a horizontally projected bullet4 ,he therefore heated the caustic potash sticks slightly1 and in view of the liberation of molecules of water within the vacuum tube1 the rays1 he thought1 would be resisted2 and such was the case to all appearances1 for then the pencil of light was bent out of its course to a greater extent1 although the magnetic power remained the same as well as the ,e4 ,m4 ,f4 producing the electric discharge4 ,he therefore established1 apparently1 the principle that the magnetic actions upon cathode rays vary somewhat in their nature according to the degree of vacuum4 ,in either case1 it may be stated incidentally1 that when the magnet was moved to and fro1 the pencils of light waved back and forth4 ,in the modified form of construction over that shown in ,fig4 #ae1 p4 #ag1 he caused a wheel to rotate that was located in the high vacuum4 ,the vanes of the wheel were so located that the faces of the same were perpendicular to the direction of the pencil of the rays radiating from the cathode4 ,when the magnet deflected the rays1 the wheel ceased rotation4 #fj4 ,,mutual ,,repulsion ,,of ,,cathode ,,rays4--,if the little mica screen1 as shown in ,fig4 #af1 p4 #ag has two holes1 and if there are two cathodes instead of one1 there will also be two pencils of light4 ,he performed an experiment involving the latter modification1 and the result was something that could not have been predicted4 ,the two pencils1 as displayed by the long fluorescent screen1 repelled each other like molecules similarly electrified4 ,the white pencils1 it will be noticed1 were repelled from each other and showed their condition when both of the negative poles were in circuit4 ,the black pencils show the location of both of the pencils when only one pole is in circuit at a time1 the direction being perpendicular to the plane of the cathode disc 7 #eg7 at end4 #fa4 ,,heating ,,and ,,lighting ,,power ,,of ,,cathode ,,rays4 ,,heat ,,of ,,phosphorescent ,,spot4--,by making the cathode concave as in ,fig4 #aj1 p4 #ag1 and so locating it that the focus of the cathode rays falls upon some substance1 the latter becomes very hot4 ,in this way ,crookes melted wax on the outside of the bulb at the phosphorescent spot4 ,further than this1 the heat was so great that it cracked the glass without at first injuring the vacuum2 next the glass at this point softened1 and the air1 by its pressure1 rushed into the bulb1 forcing a hole through the soft part4 ,he performed an experiment also which illustrated the intensity of the heat when the rays were brought to a focus4 ,he used an unusually large electrode like a concave mirror1 and in the focus1 which was near the centre of the bulb1 he supported a small piece of iridio-platinum4 ,at first1 with a moderately low ,e4 ,m4 ,f41 the metal was made white hot4 ,when a magnet was caused to approach1 the rays were drawn to one side1 #ei1 and the little piece of metal cooled4 ,he then put in all the coils of an inductorium1 and allowed the metal not only to become white hot1 but to become so heated that it melted4 ,how little did ,prof4 ,crookes know about the most important phenomena associated with his experiment4 ,although he was so exceedingly enthusiastic and ingenious in planning his experiments1 and in reasoning1 yet it seems almost mysterious that he should have been subjected to what have become known as ,x-rays1 which passed into his body1 and would have photographed portions of his skeleton1 and which would have performed outside of the tube many of the acts that were noticed within4 ,seventeen years elapsed between the time of ,crookes on the one hand1 and ,lenard and ,roentgen's discoveries on the other4 ,dr4 ,lodge1 ,f4,r4,s41 7,the ,elect41 ,lon41 ,jan4 #ca1 '#if1 p4 #dch17 and ,lenard1 in his first paper1 attributed to ,hittorf the discovery of the mere existence of cathode rays1 but credited to ,crookes the full establishment of their properties1 deduction of their principles and formulation of an ingenious theory4 #fa;a ,as an appropriate conclusion to ,crookes' work1 ,i cannot do better than to let ,lord ,kelvin repeat what he said in his ,pres4 ,addr41 ,ro4 ,so41 ,nov4 '#ic1 see also ,the ,elect41 ,lon4 ,feb4 #ad1 '#if1 p4 #ebb1 showing that a small portion of the credit is due not only to ,hittorf1 #ec1 but to ,varley4 8,his short paper of #ahga1 which1 strange to say has lain almost or quite unperceived in the ,proceedings during the #bb years since its publication1 contains an important first instalment of discovery in a new field1 the molecular torrent #ec1 at centre1 from the #8negative pole1' the control of its course by a magnet1 #ei1 its pressure against either end of a pivoted vane of mica1 #ei1 at end1 and the shadow produced by its interception by a mica screen1 #eh4 ,quite independently of ,varley1 and not knowing what he had done1 ,crookes 7,roy4 ,inst4 ,proc41 ,april #d1 '#gi1 vol4 ,,lx1 p4 #ach4 ,ro4 ,so4 ,trans41 '#gd1 8,on attractions and repulsions resulting from radiation0 ,part ,,ii1 '#gf1 parts ,,iii and ,,iv1 '#gf1 part ,v1 '#gh1 part ,,vi1 '#gi7 was led to the same primary discovery1 not by accident and not merely by experimental skill and acuteness of observation40 99 99 99 99 8,he brought all his work more and more into touch with the kinetic theory of gases2 so much so1 that when he discovered the molecular torrent he immediately gave it its true explanation--molecules of residual air1 or gas or vapor projected at great velocities 7probably1 ,i believe not greater in any case than #b or #c kilometers per second1 #fa;b71 by electric repulsion from the negative electrode4 ,this explanation has been repeatedly and strenuously attacked by many other able investigators1 but ,crookes has defended 7,presidential address to the ,inst4 ,elect4 ,eng41 #ahia47 it1 and thoroughly established it by what ,i believe is irrefragable evidence of experiment4 ,skillful investigations perseveringly continued brought out more and more wonderful and valuable results2 the non-importance of the position of the positive electrode1 #eg1 near end1 the projection of the torrent perpendicularly from the surface of the negative electrode1 #eg1 at end2 its convergence into a focus and divergence thenceforward when the surface is slightly concave1 #dg1 near beginning2 the slight but perceptible repulsion1 #fj1 between two parallel torrents due1 according to ,crookes1 to negative electrifications of their constituent molecules2 the change of the direction of the molecular torrent by a neighboring magnet1 #ei4 the tremendous heating effect of the torrent from a concave electrode when glass1 metal or any ponderable substance is placed in the focus1 #fa4 the phosphorescence procured on a plate coated with sensitive paint by a molecular torrent skirting along it1 ,fig4 #ae1 p4 #ag2 the brilliant colors--turquoise blue1 emerald1 orange1 ruby-red--with which grey1 colorless objects1 and clear1 colorless crystals glow on their struck faces when lying separately or piled up in a heap in the course of a molecular torrent1 #ee4 8electrical evaporation0 of negatively electrified liquids and solids1 #ei4 7,ro4 ,so4 ,proc41 ,june #aa1 '#ia47 the seemingly red-hot glow1 but with no heat conducted inwards from the surface1 of cool solid silver kept negatively electrified in a vacuum #a_/a1jjj1jjj of an atmosphere1 and thereby caused to rapidly evaporate1 #dj and #aci;a4 ,this last named result is almost more surprising than the phosphorescent glow excited by molecular impacts on bodies not rendered perceptibly phosphorescent by light1 #ee1 at centre4 ,both phenomena will usually be found very telling in respect to the molecular constitution of matter and origination of thermal radiation1 whether visible as light or not4 ,in the whole train of ,crookes investigations on the radiometer1 the viscosity of gases at high exhaustion1 and the electro-phenomena of high vacuums1 ether seems to have nothing to do except the humble function of showing to our eye something of what the molecules and atoms are doing4 ,the same confession of ignorance must be made with reference to the subject dealt with in the important researches of ,schuster and ,j4 ,j4 ,thomson on the passage of electricity through gases4 ,even in ,thomson's beautiful experiments1 showing currents produced by circuital electro-magnetic induction in complete poleless circuits1 the presence of molecules of residual gas or vapor seems to be the essential4 ,it seems certainly true that without the molecules1 electricity has no meaning4 ,but in obedience to logic1 ,i must withdraw one expression ,i have used4 ,we must not imagine the 8presence of molecules is the essential40 ,it is certainly an essential4 ,ether is certainly also an essential1 and certainly has more to do than merely to telegraph to our eyes to tell us what the molecules and atoms are about4 ,if the first step towards understanding the relations between ether and ponderable matter is to be made it seems to me that the most hopeful foundation for it is knowledge derived from experiment on electricity in high vacuum2 and if1 as ,i believe is true there is good reason for hoping to see this step made1 we owe a debt of gratitude to the able and persevering workers of the last #dj years who have given us the knowledge we have2 and we may hope for more and more from some of themselves and from others encouraged by the fruitfulness of their labors to persevere in the work40 #fa;b4 ,,thomson',s ,,experiment4 ,,velocity ,,of ,,cathode ,,rays4 ,the ,elect41 ,lon41 ,oct4 #e1 '#id1 p4 #gfb2 ,phil4 ,mag41 '#id4--,the object of the experiment of ,j4 ,j4 ,thomson was to determine whether the velocity approached that of light or that of molecules4 ,the apparatus he employed involved the rotating mirror1 which was fully described in ,proc4 ,royal ,so41 '#ij1 slightly modified4 ,the rays were caused to produce phosphorescence1 while the mirror was so adjusted that when at rest1 the two images on the phosphorescent strips appeared in the same rectilinear line4 ,many other elements comprised the apparatus4 ,all the steps were performed carefully and according to the best methods1 but the results are those which in this experiment are of particular interest1 for by knowing the velocity of the rays1 their nature is better appreciated and that of the ,x-rays can be better deduced4 ,the velocity bore a close relation to that of the mean square of the molecules of gases at temperatures zero ,c4 or in the case of hydrogen1 #a4h #aje cm4 per second4 ,as compared with such a velocity1 that of the cathode rays was found to be in the neighborhood of #ajj times as great1 and this agrees very nearly with the velocity of a negatively electrified atom of hydrogen acquired under the influence of the potential fall1 which occurred at the cathode4 ,in further evidence of the verity of this statement1 he made a rough calculation upon the curve or displacement produced by a magnet upon the rays4 #ei4 ,he stated3 8,the action of a magnetic force in deflecting the rays shows1 assuming that the deflection is due to the action of a magnet on a moving electrified body1 that the velocity of the atom must be at least of the order we have found40 ,illustration3 ,,fig4 #a4 #fa;b4 ,,perrin',s ,,experiment4 ,,cathode ,,rays ,,charged ,,with ,,negative ,,electricity4 ,,corresponding ,,positive ,,charges ,,propagated ,,in ,,the ,,reverse ,,direction ,,and ,,precipitated ,,upon ,,the ,,cathode4 ,comptes ,rendus1 ,,cxxi41 ,no4 #bj1 p4 #aacj2 ,the ,elect41 ,lon41 ,feb4 #ad1 '#if1 p4 #ebc4--;,jean ,perrin's object was to discover whether or not internal 8,cathode rays were charged with negative electricity40 ,that they were had often been assumed by others1 namely1 ,prof4 ,j4 ,j4 ,thomson1 who considered cathode rays as due to negatively charged matter moving at high speed4 #fa;b4 ,again1 ,prof4 ,crookes1 principally1 and others1 showed that they were possessed of mechanical properties and that they were deflected by a magnet4 #ei4 ,perrin called attention to the above investigations and also alluded to the theoretical considerations of ,goldstein1 ,hertz and ,lenard1 who favored the analogy of cathode rays to light--whose phenomena are well answered by the accepted theory concerning assumed etherial vibrations1 which1 in both cases1 have rectilinear propagation1 #eg1 excite phosphorescence1 #ed and #ee1 and produce chemical action upon photographic plates4 ,great ingenuity was displayed1 as might be expected1 in the manner in which ,jean ,perrin proved the proposition named in the title of this section1 at the ,laboratory of the cole ,normale and also in ,m4 ,pallet's ,laboratory4 ,first1 therefore1 let the elements of the discharge tube be thoroughly understood4 ,as usual1 the disk ,n is the cathode1 referring to accompanying ,fig4 #a4 ,a1 ,b1 ,c1 ,d1 is a metal cylinder having a small opening at the right hand end toward the cathode4 ,concentrically1 is a similar cylinder1 acting as an electrical screen and having a like opening similarly located as indicated4 ,it corresponds to and plays the part of the ,faraday cylinder1 being connected to earth4 ,the principle involved in this apparatus was based upon the laws of influence1 which permitted him to ascertain the introduction of electric charges within a conducting envelope1 and to measure such charges4 ,during the discharge1 the cathode rays were propagated from the cathode to and within the cylinder ,a1 ,b1 ,c1 ,d1 which immediately and invariably became charged with negative electricity4 ,to prove that the charge was due to the cathode rays1 he deflected them away from the opening in the protecting cylinder ,e1 ,f1 ,g1 ,h4 ,the cylinder was not under these circumstances charged1 the rays being outside4 ,he went further and made some quantitative analysis in a rough way to begin with4 ,he related3 8,i may give an idea of the amount of the charges obtained when ,i state that with one of my tubes1 at a pressure of 4#jja m4 of mercury1 and for a single interruption of the primary coil1 the cylinder ,a1 ,b1 ,c1 ,d1 received sufficient electricity to bring a capacity of #fjj ,c4 ,g4 ,s4 units to a potential of #cjj volts40 ,upon the principle of the conservation of energy1 he was induced1 he said1 to search for corresponding positive charges4 8,i believe ,i have found them in the very region where the cathode rays are generated1 and that they travel in the reverse direction and precipitate themselves on to the cathode40 ,he verified this corollary by means of a modified feature of the apparatus shown in ,fig4 #b4 ,the construction was the same except that there was a diaphragm having a perforation within the protecting cylinder and opposite the smaller cylinder exactly as indicated1 so that the positive electricity which had entered through could only act on the cylinder ,a1 ,b1 ,c1 ,d1 by traversing also the hole 4 8,when ,n was the cathode1 the rays emitted traversed the two apertures at and without any difficulty1 and caused the gold leaves of the electroscope to diverge widely4 ,but when the protecting cylinder was the cathode1 the positive flux1 which1 as was shown by a previous experiment1 enters by the aperture 1 did not succeed in separating the gold leaves1 except at very low pressures4 ,if we substitute an electrometer for the electroscope we shall see that the action of the positive flux is real1 but that it is very small and increases as the pressure decreases40 ,illustration3 ,,fig4 #b4 ,he inferred that3 8,these results1 taken as a whole1 do not appear to be easily reconcilable with the theory that the cathode rays are ultra-violet light4 ,on the contrary1 they support the theory that attributes these rays to radiant matter1 #ed1 near centre1 a theory1 which may at present1 it seems to me1 be enunciated as follows3 ,in the vicinity of the cathode the electric field is sufficiently strong to tear asunder into ions some of the molecules of the residual gas4 ,the negative ions start off toward the region where the potential increases1 acquire a considerable velocity1 and form cathode rays2 their electric charge1 and consequently their mass 7at the rate of one gramme equivalent per #ajj1jjj coulombs7 is easily measured4 ,the positive ions move in the reverse direction2 they form a diffused tuft1 susceptible to magnetism1 but are not a regular radiation40 #fa;c4 ,,zeugen4 ,comptes ,rendus1 ,jan4 #bg1 #ahif4--;,in a note regarding the experiments of ,roentgen1 called attention to his own communications to the ,academie des ,sciences in ,february and ,august #ahhf1 describing his photographs of ,mt4 ,blanc taken in the night by the invisible ultra-violet rays4 ,this note is entered as many newspapers reported the photograph to be due to cathode rays1 imagine the intense phosphorescence upon a screen at the top of the mountain1 if such were the case4 #fb4 ,,goldstein',s ,,experiment4 ,,phosphorescence ,,of ,,particular ,,chemicals ,,by ,,cathode ,,rays4 ,nature1 ,lon4 ,feb4 #ba1 '#ie1 p4 #djf4 ,weid4 ,ann41 ,no4 ,,ii1 '#ie4--,lithium chloride when acted upon by cathode rays1 phosphoresced to a dark violet color or heliotrope1 which it retained for some time in a sealed tube4 ,chlorides generally and other haloid salts of potassium and sodium showed similar effects4 ,the colors were superficial and could be driven away rapidly either by heating or the action of moisture4 #fc4 ,,kirn',s ,,experiment4 ,,spectrum ,,of ,,post ,,phosphorescence ,,of ,,discharge ,,tubes4 ,wied4 ,ann41 ,may1 '#id4 ,nature1 ,lon4 ,june #g1 '#id1 p4 #aca4--;,carl ,kirn compared the spectra of the phosphorescence of a vacuum bulb1 during and immediately after the discharge4 ,the details are as follows3 ,the spectrum of the after-glow1 #ed1 at end and #bb1 was found to be continuous4 ,in this connection1 see a plate showing different kinds of spectra1 for example1 ,ganot's ,physics1 frontispiece4 ,the spectrum shortened from both directions to a band between the wave lengths of #eee and #die4 ,the spectrum then continued to grow shorter and shorter until it disappeared at the line ,e1 which is the position of the greatest luminosity of the solar spectrum4 ,for experiments on spectrum1 see ,fraunhofer in ,gilbert's ,ann41 ,,lvi4 ,during the discharge1 the spectroscope showed a line spectrum corresponding very closely to those of carbonic acid gas and nitrogen4 ,some authorities had suggested that perhaps the after phosphorescence and the beginning of the incandescence of a solid body1 were the same kind of light1 but this experiment shows that such is not the case1 unless some relation exists on the ground that the two phenomena are exactly opposite to each other1 and it confirms similar results obtained by ,morrin and ,riess4 ,the result indicates that the nature of the phenomenon is not identical in all respects with light produced at a high temperature4 #fc;a4 ,,de ,,metz',s ,,experiment4 ,,chemical ,,action ,,in ,,the ,,interior ,,of ,,the ,,discharge ,,tube4 ,,internal ,,cathode ,,rays4 ,l',ind4 ,eler41 ,may #aj1 '#if1 and ,comptes ,rendus1 about ,april1 '#if4 ,translated by ,louis ,m4 ,pignolet4 ,he used a cylindrical discharge tube divided into two halves which fitted together by an air-tight ground joint4 ,in one-half were the anode and the cathode2 in the other half was the holder containing the sensitive paper or films4 ,the holder was exposed to the direct action of the cathode rays and was closed by a cover of cardboard or sheet aluminum4 ,the objects to be photographed were placed between the cover and the sensitive film or paper4 ,the tube was connected to a ,sprengel pump which maintained its vacuum during the experiments4 ,in this way1 twelve photographs were taken from which it appeared that cathode rays1 like ,x-rays1 penetrate cardboard and aluminum1 but are stopped by copper 7#a4bf mm47 and platinum 7#j4cb mm474 ,poincar1 in a note in the same publications as the foregoing1 criticised the results of the experiments of ,de ,metz1 claiming they did not prove irrefutably that cathode rays possessed the essential properties of ,x-rays1 for the cathode rays in impinging on the cover of the holder would generate ,x-rays1 #ia1 which would give the results obtained4 ,poincar did not deny the fact4 #fc;b4 ,,hertz',s ,,experiment4 ,,the ,,passage ,,of ,,cathode ,,rays ,,through ,,thin ,,metal ,,plates ,,within ,,the ,,discharge ,,tube4 ,,diffusion4 ,wied4 ,ann41 ,n4 ,f4 #de2 #bh1 #ahib4 ,contributed by request1 by ,mr4 ,n4 ,d4 ,c4 ,hodges of the ,hodges ,scientific ,news ,agency1 ,n4,y4 ,found in records at ,astor ,library4--,a piece of uranium glass was covered partly on one side 7which he calls the front side7 with gold-leaf1 and on the gold leaf were attached several pieces of mica4 ,this front side was then exposed to cathode rays4 ,so long as the exhaustion had not proceeded far1 and the cathode rays filled the whole tube with a blue cone of light1 only the portion of the uranium glass outside the gold-leaf screen showed any phosphorescence4 ,but as soon as the exhaustion had progressed far enough1 and the light began to disappear1 the genuine cathode rays struck the covered glass1 and the phosphorescence manifested itself behind the gold-leaf4 ,when the cathode rays were fully developed1 the gold-leaf hardly had any effect1 while the mica cast deep black shadows4 ,the same experiment was tried with silver-leaf1 aluminum and alloys of tin1 zinc and copper4 ,aluminum showed the best results2 sheets which allowed no light to pass1 allowing the cathode rays free passage4 ,the rays after their passage through the metal screens did not continue their straight course1 but seemed to be diffused much as light is diffused by passing through a cloudy medium4 ,in this connection reference is made to the work of ,goldstein1 who had noticed also the reflection of 8electric0 rays4 ,wied4 ,ann41 ,n4 ,f4 #ae2 #bdf1 #ahhb4 ,in #ahic1 ,goldstein published further accounts concerning actions in discharge tube4 ,wied4 ,ann41 vol4 #dh1 p4 #ghe4 ,illustration3 ,,diagram ,,of ,,lenard',s ,,apparatus4 pp4 #ec to #fi4 ---------------------------------------- -------------------------------- ,,chapter ,,vi ------- #fe4 ,,lenard',s ,,experiments4 ,,cathode ,,rays ,,outside ,,of ,,the ,,discharge ,,tube4 ,wied4 ,ann41 ,jan41 '#id1 ,vol4 ,,lvi41 p4 #bbe2 ,the ,elect41 ,lon41 ,mar4 #bc and #cj1 '#id1 ,apr4 #f1 '#id2 and ,elect4 ,rev41 ,lon41 ,jan4 #bd1 '#if1 p4 #ii4--,of more importance in connection with ,x-rays is the consideration of ,lenard's experiments than any others4 ,the reader must bear in mind that his exhaustive investigations resulted from his discovery 7founded upon a hint from ,hertz7 that the cathode rays might be transmitted to the outside of the generating discharge tube4 ,his interest1 therefore1 in the discovery was so great that his researches extended to the minutest details4 ,passing from these introductory remarks1 the characteristics of the tube that he employed will be explained first4 ,reference may now be made to the accompanying ,fig4 ,a4 ,he employed several different kinds of tubes1 but finally settled upon one of which the essential elements are shown in the said figures4 ,it was permanently connected to the pump1 #ec1 so that the pressure within could be varied4 ,opposite the cathode1 which consisted of a thin disk of aluminum1 the end of the tube was provided with a thick metal cap1 having a perforation1 which in turn was closed by a thin aluminum sheet secured by marine glue in an air-tight manner1 and called a window4 ,the anode was a heavy brass cylinder1 shown in section1 within the discharge tube and surrounding the leading-in wire of the cathode4 ,the anode and the aluminum window were connected to each other1 electrically1 and to earth1 as well as two a secondary terminal of an induction coil1 whose electrodes were in shunt to those of the discharge tube1 in order that the operator might adjust the sparking distance which rapidly increased with the exhaustion4 ,the induction coil had a mercury interrupter4 #fe4 ,,properties ,,of ,,cathode ,,rays ,,in ,,open ,,air4--,in all directions around the window upon the outside and in the open air1 a faint bluish glow 7 #aa and #adj7 extended and vanished at a distance of #e cm41 as indicated by dotted lines in ,fig4 ,b at beginning of this chapter4 ,the degree of luminosity may be judged by saying that it was not sufficient to admit of investigation by the ordinary pocket spectroscope4 ,a new window was void of luminosity2 but with use1 bluish gray and green and yellow spots occurred thereon4 #ff4 ,,phosphorescence ,,by ,,cathode ,,rays4--,substances which generally phosphoresced by light and cathode rays in the generating bulb1 #ee1 also phosphoresced under the influence of the rays in open air1 excepting eosin1 gelatin1 both phosphorescent in light1 were not so in cathode rays2 so also with solutions of fluorescein1 magdala red1 sulphate of quinine and chlorophyll4 ,phosphorescence was less if the rays first passed through a tube of glass or tinfoil lengthwise4 ,the phosphorescent light of the phosphides of the alkaline group1 uranium glass1 calcspar and some other substances1 was so great that the luminosity of the air was invisible by contrast4 ,the maximum distance at which phosphorescense was discernable in open air was about #h cm4 ,the best phosphorescent screen consisted of paper saturated with pentadecylparatatolylketone4 ,in order to prepare it1 he laid a sheet of paper upon glass and applied the fused chemical with a brush4 ,as to the color of the phosphorescence and fluorescence of different substances1 and as to the degree of luminosity outside of the vacuum tube1 they were about the same as reported by ,crookes when located within the discharge tube4 #ee4 ,baric and potassic and other double cyanides of platinum1 common flint1 glass1 chalk and asaron all exhibited the same property as when exposed to ultra-violet light1 that is1 fluoresced or phosphoresced4 ,sulphide of quinine in the solid state fluoresced1 but not in solution4 ,petroleum spread on a piece of wood fluoresced1 and also fluorescent-hydrocarbons generally4 #ff;a4 ,the cathode rays were not easily transmitted by tinfoil or glass1 because the degree of phosphorescence on the screen was greatly reduced by interposing such sheets4 ,the phosphorescense ceased also by deflecting internal cathode rays from the window by a magnet4 ,for full treatment of the phenomena of phosphorescence1 see ,stokes' experiments1 described in ,phil4 ,trans41 #aheb1 ,art4 8,change of ,refrangibility of ,light40 ,in brief1 ,stokes' theory assumes that such substances have the power of reducing the refrangibility4 ,example3 ,ultra-violet light1 highly refractive1 is changed to yellowish green1 less refrangible1 by reflection from uranium glass4 #fg4 ,,the ,,aluminum ,,window1 ,a ,,diffuser ,,of ,,cathode ,,rays4 #fc;b4 ,the conclusion arrived at by mounting the phosphorescent screen in different positions and at different angles as well as by observance of the gaseous luminosity1 was that the aluminum window scattered the rectilinear parallel cathode rays in all directions1 #eg4 #fh4 ,,transmission ,,of ,,external ,,cathode ,,rays ,,through ,,metals4--,the phosphorescence was not diminished apparently by an intervening gold-leaf or silver or aluminum foil1 while it was extinguished by quartz 4#e mm4 thick which also cut off the atmospheric glow beyond itself4 ,the leaves and foil did not so act4 ,the difference of thickness should be borne in mind1 as metal1 as thick as the quartz did not transmit4 ,as to other substances1 tissue paper cast a slight shadow1 which was darker with an additional sheet2 but the shadow was independent of color and blackness1 #aed4 ,ordinary writing paper was roughly1 proportionally opaque1 while the shadow was black with cardboard 4#c mm4 thick4 ,glass films as made by blowing glass1 cast faint shadows when 4#ja mm4 thick4 ,he proved that there was little difference as to the transmitting power of conductors and dielectrics when thin4 ,mica and collodion sheets 4#ja mm4 thick cast scarcely any shadow4 ,the reader may bear in mind the striking differences between these properties of cathode rays1 and ,x-rays1 #ace1 it being assumed always that the generating devices are the same2 for example1 water permitted the cathode rays 7were these simply feeble ,x-rays87 to be transmitted only when in very thin layers4 ,even soap water films which were only 4#jjab mm4 thick cast shadows1 although very faintly4 ,the shadows of drops of water were black1 while water several feet thick has been traversed by ,x-rays from a small set of apparatus4 ,by careful measurements he found that the law of transmission must be different from that of light1 for in the latter1 many substances are opaque although exceedingly thin1 while with cathode rays1 the same will traverse all films4 ,goldstein and ,crookes reported that thin mica1 glass and collodion films made very dark shadows1 #eh1 within the discharge tube1 whereas ,lenard found that outside of the vacuum tube1 in open air1 the transparency was greater than according to the earlier experimenters1 but he acknowledged that ,crookes and ,goldstein were inconvenienced and limited in the number of observations because it is so difficult to carry on such experiments within an hermetically sealed tube4 ,again1 he acknowledged that perhaps the cathode rays of those experimenters were of a different kind4 ,the construction shown in the above figures was modified by using a very thin glass window instead of aluminum1 and the results were the same allowing for the different opacity1 to ordinary light1 of aluminum and glass4 ,the cathode rays acted upon the sense of smell and taste as the nose and mouth could detect ozone1 #hd1 at end4 #fi4 ,,propagation4 ,,turbidity ,,of ,,air4 ,upon studying the shadows on the phosphorescent screen1 it was noticed that the rays were bent around the edges of the object4 ,again1 when the object had a slit1 diffusion could be noticed by the shape 7as in ,crookes ,ex41 ,fig4 #ae1 p4 #ag17 of the luminous portion of the phosphorescent screen4 ,in ,fig4 ,b1 at beginning of this chapter1 the spatter work represents the shape of the luminous portion1 the darker part representing the most luminous surface of the screen1 the latter being held at right angles to the thick plate1 having the slit and opposite the aluminum window4 ,by varying these experiments1 especially by changing the angle of the screen he found that not the all rays were diffused1 but as in the passage of light through milk1 some were transmitted in rectilinear lines4 #gj4 ,,photographic ,,action4--,he performed with sensitive silver compound papers1 an experiment somewhat similar to those with phosphorescent bodies and also others4 ,behind a rather thick opaque plate the chemical film was not acted upon1 but the rate of blackening near the aluminum window without obstruction of intermediate bodies was about the same as that with befogged sunlight4 ,the former1 moreover1 was acted upon at a much greater distance than that at which phosphorescence was exhibited and beyond the atmospheric luminosity4 ,by means of shadow pictures or sciagraphs1 he compared the shadows produced by the external cathode rays with those which would have been obtained by light4 ,referring to ,fig4 ,c1 beginning of this chapter1 the sensitive plate was half covered with a plate of quartz1 ,q1 and half with a plate of aluminum1 ,a overlapping the quartz4 ,with light1 the shadows would have appeared as in said figure1 that is1 one-half black as produced by aluminum1 a quarter rather light as produced by quartz1 and the other quarter bright1 or a similar arrangement1 according to whether the negative or the positive photograph is considered2 but with the cathode rays1 the appearance of the developed plate was as in ,fig4 ,d41 beginning of this chapter4 ,the quartz cast the black shadow1 while the aluminum1 the lighter one4 ,furthermore1 the luminosity of the air produced a variable light on the other quarters4 ,a similar appearance was produced by casting shadows of such plates upon the phosphorescent screen2 but1 of course1 the picture was not a permanent one4 ,the photographic plate served to accumulate the power1 for the cardboard which cast a faint shadow upon the phosphorescent screen1 showed a black shadow upon the photographic paper by sufficiently long exposure4 ,at the same time1 strips of thin metal were placed side by side between the chemical paper and the cardboard1 and they showed different degrees of shading4 ,the cardboard was quite thick1 being 4#c mm4 ,prof4 ,slaby 7see ,elect4 ,rev41 ,lon41 ,feb4 #g1 '#if71 after ,rntgen's discovery1 produced sciagraphs of the bones of the hand at the window of the ,lenard tube4 ,lenard doubted whether the cathode rays produced direct chemical action4 ,iodine paper became bluish1 but he could not obtain other chemical effects usually produced by light1 and other agencies1 for example1 oxygen and hydrogen mixed together in the proportion to form water1 and which were in their nascent state1 and which were located in a soap-bubble1 did not explode or ignite4 ,no effect was produced upon carbon bi-sulphide nor hydrogen-sulphide1 although the exposure was very long4 ,ammonia was not formed when the rays acted upon a mixture of three parts hydrogen and one part nitrogen1 as to volume4 ,he thought that he noticed a small expansion of air1 hydrogen and carbonic acid separately located in a vessel having a capillary tube and water to indicate the expansion4 ,he attributed the slight expansion to an indirect action1 although very slight1 caused by heat produced by the cathode rays1 #bg1 and yet neither the thermopile nor the thermometer showed any calorific effects although the thermopile responded to the flame of a candle #ej cm4 distant4 #ga4 ,,cathode ,,rays ,,and ,,electric ,,forces ,,distinguished4 ,the earth connection heretofore mentioned with the aluminum window was for the purpose of dispensing with sparking1 but even then the approach of another conductor connected to earth would cause some sparking4 ,sparks could be drawn when the cathode rays were deflected from the aluminum window by a magnet4 ,fig4 ,e1 at beginning of chapter4 ,he argued that the rays and the electric forces of the spark are non-identical4 ,he was not satisfied with this as an absolute proof1 and he instituted others4 ,he enclosed the whole generator in a large metal box4 ,in the observation space1 that is1 around and near the window1 he located another box1 having an aluminum front facing the window4 ,see ,fig4 ,e1 at beginning of chapter4 ,it was within this second box that he took the sciagraph shown in ,fig4 ,d1 at beginning of chapter4 ,it is important to notice that sparks could not be drawn at points within the said second box1 shown at the left1 even by a metallic point shown projecting thereinto4 ,no spark occurred whatever1 not even from the aluminum front4 ,sparking occurred when the pointed wire was extended to a considerable distance outside of the back of the small box1 but it was remarked that the electric force did not enter through the front wall but was introduced 8from behind into the box1 by the insulation of the wire40 ,no one can1 therefore1 enter the objection that the cathode rays experimented with1 were generated from the aluminum window as a cathode4 ,they came from the cathode referred to entirely within the vacuum tube4 ,prof4 ,j4 ,j4 ,thomson1 ,f4 ,r4 ,s41 had at an early date conjectured that cathode rays did not pass through thin films of metal1 but that these films acted as intermediate cathodes themselves4 ,see his book on 8,recent ,researches10 p4 #bf1 also ,the ,elect41 ,lon4 ,march #bc1 '#id1 p4 #egc1 in an article by ,prof4 ,fitzgerald1 who names that citation4 #gb4 ,,cathode ,,rays ,,propagated1 ,,but ,,not ,,generated ,,in ,a ,,high ,,vacuum4--,the proposition was proved by having two tubes1 one called the generating tube and one the observation tube1 the former being like that shown in ,fig4 ,a1 at beginning of chapter1 which is partly repeated in ,fig4 ,f1 at beginning of chapter1 combined with the observation tube1 which contains the two electrodes for casual use2 but the one on the right is a disk extending nearly throughout the cross sectional area1 and having a small central opening4 ,although both tubes were connected to the air pump1 yet1 by means of stop-cocks1 the vacuum in one tube could be maintained at a maximum degree for hours1 while the other was at a minimum4 ,the first experiment was performed with a vacuum1 about as high as that employed in ,crookes' phosphorescent experiments1 #ec4 ,there was a patch of green light1 #eg1 at the extreme left end of the observation tube and the glass was green at the right1 #ed1 and a little to the left of the perforated disk electrode a4 ,the other electrode of this tube was located at the upper left and lettered k4 #gb;a4 ,the magnet deflected the rays in the observing tube as indicated by the partial extinction of the phosphorescent patch4 ,he noticed that with the rarefied atmosphere the amount of turbidity was enormously reduced1 or in other words1 that the rays were propagated more nearly in rectilinear lines4 ,all the experiments on the cathode rays1 in this observing tube1 were of about the same nature as those which could be produced in the discharge tube4 ,illustration3 ,,from ,,sciagraph ,,of ,,cat',s ,,leg1 ,,by ,,prof4 ,,william ,f4 ,,magie4 ,copyright1 #ahif1 by ,william ,beverly ,harison1 pub4 of ,x-ray pictures1 #ei ,fifth ,ave41 ,new ,york ,city4 #gb;b4 ,the principal experiment consisted in exhausting the observing tube to such a degree that cathode rays could not be generated therein4 ,the vacuum was so perfect that when used as a discharge tube all phosphorescence gradually died away until it disappeared1 and no current passed 7 #be7 except on the outside surface of the glass4 ,the coil was so large1 electrically1 that the length of the spark between spheres was #ae cm4 ,upon charging the right hand tube and generating cathode rays1 it was determined by means of magnetic deflection1 phosphorescence and other effects1 that the cathode rays traversed the highest possible vacuum 7 #ai1 near end1 where energy must have passed through the high vacuum to produce luminosity in the inner bulb74 ,the external and internal rays were certainly different forms of energy4 ,inasmuch as he noticed that rarefied air was less turbid and less absorptive than air at ordinary pressures1 it occurred to him to make a very long tube1 namely1 #a m1 or a little over #c feet4 ,he employed very severe steps for obtaining an exceedingly high vacuum1 the operation occupying several days4 ,the pump used was a ,toepler-,hagen1 while a ,geissler pump was employed separately for the discharge tube4 ,the pencil of cathode rays traversed the whole length of the long tube4 ,see a portion of the apparatus in ,fig4 ,g1 at beginning of this chapter4 ,one disk was of metal and perforated with a pin hole and the other was a phosphorescent screen1 so that when the cathode pencil passed through the hole in the plate a patch was seen upon the phosphorescent screen4 ,the phosphorescent spot was always1 no matter what the relative distances of the disks were from each other1 and from the end of the tube1 substantially the same as it would have been by calculation assuming that there was no turbidity effect4 ,the patches1 in each instance1 were a little smaller in diameter than the calculated ones4 ,for example with one measurement1 at certain distances1 the actual diameter of the patch was #b4e mm41 while the calculated diameter was #b4i mm4 ,in his experiments with light under the same conditions1 the luminous spots were also a little smaller than the calculated or geometrical4 ,the disks had iron shoes and were moved to different positions by a magnet4 ,he concluded1 therefore1 that in what may be called a perfect vacuum1 light and cathode rays have a common medium of propagation1 namely1 the assumed ether4 ,prof4 ,fitzgerald1 in ,the ,elect41 ,lon4 ,mar4 #bc1 '#id1 does not agree broadly with him in this2 neither does he contradict him4 ,he argues rather on the point that the cathode rays and light rays are not identical1 but ,lenard does not affirm this1 because the magnet will attract the former and not the other4 ,prof4 ,fitzgerald admits this and calls to mind that even in a vacuum1 as obtained by ,lenard1 there were still ten thousand million molecules per cu4 mm4 and therefore he thinks it is better to look to matter rather than ether as the medium of propagation of cathode rays4 #fa;b4 ,on the other hand1 ,lenard agrees with certain other predecessors1 ,wiedemann1 ,hertz and ,goldstein1 in favor of cathode rays being etheric phenomena4 ,see ,wied4 ,ann41 ,,ix41 p4 #aei1 '#hj2 ,x41 p4 #bea1 '#hj1 ,,xii41 p4 #bfd1 '#ha2 ,,xix41 p4 #haf1 '#hc2 ,,xx41 p4 #gha1 '#hc4 ,the vacuum with which ,lenard operated1 was 4#jjjjb mm4 pressure1 obtained by cooling down the mercury to minus #ba ,c4 ,this vacuum was so high that all attempts to prove the presence of matter failed4 ,neither did the exceedingly high vacuum deaden the cathode rays4 ,on the other hand1 as noted1 they were assisted rather than hindered4 #ace4 #gc4 ,,cathode ,,rays4 ,,phenomena ,,in ,,different ,,gases4--,the apparatus consisted of an observing tube having a tubular gas inlet and outlet both in one end and arranged in line with the cathode of the discharge tube4 ,see construction in ,fig4 ,h1 at beginning of this chapter1 the tube being about #dj cm4 long and #c cm4 in diameter4 ,he was very careful in every case to chemically purify and dry the particular gas4 ,he omitted the perforated disk and provided an opaque strip of the phosphorescent screen on the side toward the window and made his observations from the other side1 the object of the experiment being particularly to test the transmission of cathode rays in different gases4 ,with any particular gas1 he moved the phosphorescent screen along by means of a magnet until the shadow on the screen became invisible4 ,it is evident that the distances of the screen from the window for different gases would indicate the relative transmitting powers4 ,he also modified the experiment by varying the density of the gases1 hydrogen being taken as #a as usual1 nitrogen #ad1 and so on4 ,the transmitting power of hydrogen was nearly five times as great as that of nitrogen1 air1 oxygen and carbonic acid gas1 which did not much differ4 #aj and #ah4 ,sulphurous acid was a very weak transmitter4 ,all the gases became luminous near the window as in air4 #fe4 ,the colors were all about the same as far as distinguishable1 #aa1 which was difficult in view of the brightness of the phosphorescence on the glass4 ,it was a universal rule1 that when the density decreased1 the transmitting power increased4 ,in high vacua1 in all gases1 the rays went through the space in rectilinear lines in all directions from the window1 and generally it made no difference what gas was employed provided the vacuum was as high as hundredths of a millimetre4 ,at this pressure all gases acted the same4 ,to be sure1 the phosphorescence did not occur at this high vacuum at a great distance as might be expected1 but it should be remembered that the intensity of the rays varied as the square of the distance1 and1 therefore1 at very great distances1 the action was very weak4 #gd4 ,,cause ,,of ,,luminosity ,,of ,,gas ,,outside ,,the ,,discharge ,,tube4--,at ordinary pressures1 in the cases of hydrogen and air1 as has been noted1 the gas became luminous in the observing tube1 the effect being1 of course1 the same as entering open air1 represented in ,fig4 ,a1 beginning of this chapter4 ,in order to determine the luminosity at less pressures1 the gas1 of whichever kind1 was enclosed in a rather long observing tube and only at rather high vacua did the bluish and sometimes reddish gaseous luminosity disappear4 ,upon grasping the tube with the hand or approaching any conductor connected to earth1 of large capacity1 the column stopped at that point so that the remainder of the tube1 beyond the hand1 measured from the discharge1 was dark4 ,the phosphorescence on the glass wall of the tube produced by the cathode rays was not influenced in any way by outside conductors1 such as the hand4 ,cathode rays themselves were not stopped apparently by the hand1 because the phosphorescent screen and glass1 located beyond the hand1 became luminous4 ,he concluded1 therefore1 that the glowing of the gas had no close connection with the cathode rays4 ,he proved this also by deflecting the cathode rays in the discharge tube from a certain space1 and yet the gaseous luminosity remained4 ,as an exception1 the cathode rays sometimes appeared to be closely associated with the light column4 ,he attributed the luminosity of the gas in general1 at low pressures1 not to the cathode rays1 but directly to the electric current or some kind of electric force1 #aa and #ad1 which1 as already remarked1 permitted sparks to be drawn from the aluminum window and surrounding points4 ,the negative glow light in ,geissler tubes1 #cj1 is also to be regarded as gas illuminated by cathode rays4 7,compare ,hertz1 ,wied4 ,ann41 ,,xix41 p4 #hjg1 '#hc47 ,between that phenomenon and the glow observed here and attributed to irradiation1 there exists a correspondence1 inasmuch as in both cases the light disappears at high exhaustions1 #ec1 appears fainter and larger when the pressure increases1 #ed1 and then becomes brighter and smaller1 #ed4 ,but1 whereas1 the glow in the ,geissler tube has become very bright and small at #j4e mm4 pressure1 the gas in our experiment remains much darker up to #gfj mm4 pressure1 and yet the illuminated spot is much larger4 ,this difference cannot1 therefore1 be attributed to an inferior intensity of the rays here used4 ,but it will be explained1 #gf1 as soon as we can show that at higher pressures cathode rays of a different kind are produced1 which are much more strongly absorbed by gases than the rays investigated hitherto and produced at very low pressures4 ,illustration3 ,,use ,,of ,,stops ,,in ,,sciagraphy4 7,,perch47 #ajg41 p4 #aja4 ,by ,leeds and ,stokes4 ,fig4 ,i1 p4 #eb1 illustrates the apparatus by which he studied the rectilinear propagation and whereby he found that it was rectilinear only in a very high vacuum4 ,in the figure1 the gas is at ordinary pressure1 and it will be noticed that the turbidity of the same is indicated by the curved lines while the dotted lines show the volume that would be occupied by light or other rectilinear rays1 unaccompanied by any kind of diffusion4 ,in the observing tube1 there was a disc having a central hole at a4 ,beyond this disc1 measured from the aluminum window1 was a fluorescent screen which1 as well as the perforated disc1 could be moved to different distances by means of a magnet acting on a little iron base4 ,it is evident that upon moving the fluorescent screen to different distances1 the diameter of the luminous patch would be a measure of the amount of turbidity4 ,the curved lines intersecting the peripheries of the luminous spots indicate1 therefore1 the field of the cathode rays1 so that said field would appear like a kind of curved cone if the same were visible4 ,although hydrogen is the least turbid gas1 yet the phosphorescent patches were all larger except with a high vacuum than they could have been with rectilinear propagation4 ,an additional characteristic of the phosphorescent spot1 was its being made up of a central bright spot and a halo less luminous1 appearing like some of the pictures of a nebula1 see ,fig4 ,i1 p4 #eb1 the darker or centre indicating the brighter portion4 ,in a perfect vacuum the halo did not exist4 ,he performed a similar experiment with ordinary light4 ,no halo occurred on a paper screen which was used instead of the phosphorescent screen1 but upon introducing a glass trough of dilute milk between the window and the perforated disc1 or between the disc and the paper screen1 nuclei and halos were obtained1 illustrating a case of the effect of a turbid fluid upon light1 and assisting in proving that gases act as a turbid medium to cathode rays as milk and similar substances do to light2 also in other gases than hydrogen1 and by the use of cathode rays1 nuclei and halos were not obtained at high exhaustion1 all the gases becoming limpid4 ,taking into account pressure and density1 all gases behaved the same as to the power of transmission when they were of the same density1 without any regard whatever to their chemical nature4 ,density alone determined the matter1 according to ,lenard4 #ge4 ,,cathode ,,rays ,,of ,,different ,,kinds ,,are ,,variably ,,diffused4--,he discovered the remarkable property1 contrary to his expectation1 that if the rays are generated at high pressures1 they are capable of more diffusion than when generated at lower pressures4 ,this can be easily proved by any one1 for it will be noticed that upon increasing the pressure in the discharge tubes the spots on the phosphorescent screen will not only grow darker but larger and more indefinite as to the nucleus and halo4 ,he called attention to the agreement with ,hertz1 who also found that there were two different kinds of rays1 see ,wied4 ,ann41 ,,xix1 p4 #haf1 '#hc1 also see ,hertz's experiment4 ,lenard also pointed out the analogue in respect to light1 which1 when of short wave length1 is more diffused in certain turbid media than that of greater wave length4 ,although ,lenard held that his experiment proved that cathode rays were phenomena in some way connected with the ether1 yet he pointed out an important difference in connection with the property of deflection of the rays by the molecules even of elementary gases like hydrogen1 producing diffusion of the rays1 which accordingly may be considered as behaving like light in passing through1 not gases1 but vapors1 liquids and dust4 ,in the case of the cathode rays the molecules of a gas acted as a turbid medium1 but in the case of light1 turbidity is only exhibited by vapors or certain liquids1 as so eloquently explained by ,tyndall1 in 8,fragments of ,science10 #ahga1 where it is shown that aggregation of molecules1 like vapors or dust in the presence of light1 make themselves known by color and diffusion1 whereas the substances in a molecular or atomic state do not serve to show the presence of rays of light4 #gf4 ,,law ,,of ,,propagation4--,lenard recognized continually that there were two kinds of cathode rays4 ,one of them may have been ,x-rays without his knowing it4 ,in the latter part of '#ie1 he made some experiments especially of a quantitative nature as to the principle of absorption of the rays by gases4 ,by mathematical analysis1 based upon experiments1 he arrived at the principle that the absorptivity of a gas is proportional to its pressure1 or what is the same thing1 to its density1 or as to another way of stating the law1 8the same mass of gas absorbs at all pressures the same quantity of cathode rays40 ,see ,elect4 ,rev41 ,lon41 as cited1 p4 #ajj4 #gg4 ,,charged ,,bodies ,,discharged ,,by ,,cathode ,,rays4--,an insulated metallic plate was charged first with positive electricity and in another experiment with negative electricity4 ,in each instance1 the plate was discharged rapidly by the cathode rays as indicated by the electroscope1 and the same held true when a wire cage in contact with the aluminum window1 surrounded the electroscope and the metallic plate4 ,the effect was stopped by cutting off the cathode rays by quartz 4#e mm4 thick4 ,the discharge took place1 however1 through aluminum foil4 ,a magnet was made to deflect the internal cathode rays1 whereupon the discharge did not take place1 all showing that the discharge of the insulated plate was directly due to those rays4 ,a remarkable occurrence was the accomplishment of the discharge at a much greater distance than that at which phosphorescence was exhibited4 ,see also ,roentgen's experiment--who suggested that ,lenard had to do with ,x-rays in this experiment1 but thought they were cathode rays4 ,the maximum distance for the discharge was about #cj cm4 measured normally to the aluminum window4 ,he caused a discharge of a plate also in rarefied air4 ,he admitted that the experiments were not carried far enough to know whether the effect was due to the action of the cathode rays upon the surface of the window1 or upon the surrounding air1 or upon the plate4 ,the author could not find in ,lenard's paper any positive or negative proof that he had actually deflected the external cathode rays by a magnet while passing through air or gas at ordinary pressure4 ,he had deflected them while passing through a very high vacuum in the observing tube4 ,dr4 ,lodge1 who briefly reviewed ,lenard's experiments1 expressed the same opinion4 ,see ,the ,elect41 ,lon41 ,jan4 #ca1 '#if1 p4 #dci4 ,for theoretical considerations of the electric nature of light1 the discharge law in the photo-electric phenomena1 the simple validity of the discharge law1 the occurrence of interference surfaces in the blue cathode light1 the cathode rays in the axis of symmetry1 the necessary degrees of longitudinal electric waves1 the frequency of the cathode rays1 and proof of longitudinal character of cathode rays1 see ,jaumann in ,the ,elect41 ,lon41 ,mar4 #f1 '#if2 translated from ,wied4 ,ann41 #ega1 pp4 #adg to #ahd1 '#if1 and succeeding numbers of ,the ,elect41 ,lon41 which were freely discussed in foreign literature contemporaneously4 #gh4 ,,de ,,kowalskie',s ,,experiment4 ,,source1 ,,propagation ,,and ,,direction ,,of ,,cathode ,,rays4 ,acad4 ,sci41 ,paris1 ,jan4 #ad1 '#ie2 ,so4 ,fran4 ,phys4 ,jan4 '#ie2 ,nature1 ,lon4 ,jan4 #bd1 '#ie2 ,feb4 #ba1 '#ie4--,the conclusions he arrived at are1 #a4 ,the production of the cathode rays does not depend on the discharge from metallic electrodes across a rarefied gas1 nor is their production connected with the disintegration of metallic electrodes4 #b4 ,they are produced chiefly where the primary illumination attains suitable intensity1 that is1 where the density of the current lines is very considerable4 #c4 ,their direction of propagation is that of the current lines at the place where the rays are produced1 from the negative to the positive poles4 ,they are propagated in the opposite direction to that in which the positive luminosity is supposed to flow4 #dc4 ,he employed a ,goldstein tube reduced at the centre4 #da4 ,it was found that the cathode rays are formed not only at the negative electrode1 but also at the constriction1 directly opposite the cathode4 ,de ,kowalskie carried on further experiments in this line in order to be satisfied with the principles named above1 which he formulated4 ,in one tube1 he was able to produce cathode rays at either end of the capillary tube forming the constricted part of a long vacuum tube4 ,no electrodes were employed4 ,the tube was merely placed near a discharger through which 8,tesla currents0 were passed8 ,he seems to have been working with ,x-rays without knowing it2 for his results agree with those of ,roentgen and later experimenters that the source of ,x-rays is the surface of a substance where it is struck by cathode rays4 ,the statements were about as definite as could be expected at that date4 ,illustration3 ,,hand1 ,,by ,,oliver ,b4 ,,shallenberger1 ,,taken ,,with ,,focus ,,tube4 #acg1 p4 #acf4 ---------------------------------------- -------------------------------- ,,chapter ,,vii ------- #gi4 ,,roentgen',s ,,experiments4 ,x-,,rays1 ,,and ,a ,,new ,,art4 ,wurz4 ,physik4 ,med4 ,gesell4 ,jan4 '#ie2 ,nature1 ,lon41 ,jan4 '#if2 ,the ,elect41 ,lon4 ,april #bd1 #if2 ,sitz4 ,wurz4 ,physik4 ,inst4 ,d4 ,uni4 ,mar4 #i1 #if4--,,uninfluenced ,,by ,a ,,magnet ,,in ,,open ,,air4--,although ,lenard recognized several kinds of cathode rays1 which differed as to penetrating and phosphorescing power1 yet he always held1 or inferred at least that they were deflected by a magnet1 outside1 as well as inside1 7proved #gb;a47 of the discharge tube4 #ei4 ,prof4 ,wilhelm ,konrad ,roentgen subjected his newly discovered rays to the action of very strong magnetic fields in the open air1 but no deviation was detected4 ,this is the characteristic which more than anything else has served to distinguish ,x-rays from cathode rays4 ,this property has been confirmed by others4 ,he employed the principle of magnetic attraction of internal cathode #ei1 rays to shift the phosphorescent spot1 for then he noticed that the source of ,x-rays fluctuated also4 #hj4 ,,source ,,of ,x-,,rays ,,may ,,be ,,at ,,points ,,within ,,the ,,vacuum ,,space4--,in one case1 he employed a ,lenard tube1 and found that the ,x-rays were generated from the window which was in the path of the cathode rays4 #fg4 ,different bodies within the discharge tube were found to have different quantitative powers of radiating ,x-rays when struck by the cathode rays4 ,he stated 8,if for example1 we let the cathode rays fall on a plate1 one half consisting of a #j4c mm4 sheet of platinum and the other half a #a mm4 sheet of aluminum1 the pin-hole photograph of this double plate will show that the sheet of platinum emits a far greater number of ,x-rays than does the aluminum1 this remark applying in every case to the side upon which the cathode rays impinge40 ,on the reverse side1 however1 of the platinum1 no rays were emitted1 but a large amount was radiated from the reverse side of the aluminum4 #fg4 ,he admitted that the explanation was simple2 but1 at the same time1 he pointed out that this1 together with other experiments1 showed that platinum is the best for generating the most powerful ,x-rays4 ,one form with which he experimented is illustrated in ,fig4 ,j1 in principle1 being described as a bulb in which a concave cathode was opposite a sheet of platinum1 placed at an angle of #de to the axis of the curved cathode1 and at the focus thereof4 ,illustration3 ,j #ha4 ,,reflection ,,of ,x-,,rays4--,he emphasized the knowledge that there is a certain kind and a certain amount of reflection1 such as that produced upon light and1 as pointed out by ,lenard1 upon cathode rays1 by certain turbid media4 ,the following quotation sets forth the exact experiment to show slight reflection at metal surfaces4 8,i exposed a plate1 protected by a black paper sheet #a to the ,x-rays 7e4g4 from bulb ,j7 so that the glass side #b lay next to the discharge tube4 ,the sensitive film was partly covered with star-shaped pieces 7#d slightly displaced in the ,fig47 of platinum1 lead1 zinc and aluminum4 ,on the developed negative the star-shaped impressions showed dark 7comparatively7 under platinum1 lead and more markedly1 under zinc2 the aluminum gave no image4 ,it seems1 therefore1 that the former three metals can reflect the ,x-rays2 as1 however1 another explanation is possible1 ,i repeated the experiment with only this difference1 that a film of thin aluminum foil was interposed between the sensitive film and the metal stars4 ,such an aluminum plate is opaque to the ultra-violet rays1 but transparent to ,x-rays4 ,in the result the images appeared as before1 this pointing still to the existence of reflection at metal surfaces40 #hb4 ,,penetrating ,,power4 ,the transmitted energy was tested both by a fluorescent screen and by a sensitive photographic plate4 ,either one was acted upon by the rays after transmission through what have ordinarily been called opaque objects4 #fh4 for example1 #ajjj pages of a book4 ,as in ,lenard's results1 so in ,roentgen's1 the color of the object had no effect1 even when the material was black4 #fh1 near beginning4 ,a single thickness of tinfoil scarcely cast a shadow on the screen4 #ff;a4 ,the same was true with reference to a pine board #b or #c cm4 thick4 ,they passed also through aluminum #ae mm4 thick4 #fc;b4 ,glass was comparatively opaque1 #ff;a1 as compared with its power of transmitting light1 but nevertheless it must be remembered that the rays passed through considerable thickness of glass4 ,the tissues of the body1 water #fh1 near centre1 and certain other liquids and gases were found exceedingly permeable #fg4 ,fluorescence could be detected through platinum #b mm4 thick and lead #a4e mm4 thick4 ,through air the screen was illuminated at a maximum distance of #a m4 ,a rod of wood painted with white lead cast a great deal more shadow than without the paint1 and in general1 bones1 salts of the metals1 whether solid or in solution1 metals themselves and minerals generally were among the most resisting materials4 #aee4 ,the experiments were performed in a dark room by excluding the luminosity of the tube by a thick cloth or card board entirely surrounding the tube4 ,he performed the wonderful experiment1 so often since repeated1 of holding the hand between the screen of barium platino cyanide and the discharge tube1 and beholding the shadow picture of the bones4 ,this was the accidental step which initiated the new department of photography1 and which gave to the whole science of electric discharge1 a new interest among scientists and electricians and which thoroughly awakened popular interest4 ,the whole world concedes to him the honor of being the originator of the new art4 ,in view of sciagraphs of the bones of the hand upon the screen1 it occurred to him in view also of ,lenard's experiments1 on the photographic plate1 to produce a permanent picture of the skeleton of the hand with the flesh faintly outlined4 #hd4 ,the accompanying half tone illustration1 page #cg1 was made by the ,elect4 ,eng4 ,n4,y4 7,june #c1 '#if7 by permission1 and it represents the ,edison ,x-ray exhibit at the ,new ,york ,electrical ,exposition of the ,electric ,light ,association1 #ahif4 ,thousands of people1 through the beneficence of ,dr4 ,edison1 were permitted to see the shadows of their bones surrounded by living flesh4 ,the screen was made of calcic tungstate4 ,the hand and arm were placed behind and viewed from the front4 #acb1 near beginning4 #hc4 ,,penetrating ,,power ,,and ,,density ,,of ,,substances4--,although he found that there was some general relation between the thickness of materials and the penetrating power1 yet he was satisfied that the variation of the power did not bear a direct relation to the density1 7referring to solids7 especially as he noticed a peculiar result when shadows were cast by ,iceland spar1 glass1 aluminum and quartz of equal thickness4 ,the ,iceland spar cast the least shadow upon suitable fluorescent or photographic plate4 ,the increased thickness of any one substance increased the darkness of the shadow1 as exhibited by tinfoil in layers forming steps4 ,other metals1 namely platinum1 lead1 zinc and aluminum foil were similarly arranged and a table of the results recorded4 #fc;b4 ,,relative ,,thickness4 ,,thickness4 ,,density4 ,platinum 4#jah mm4 #a #ba4e ,lead 4#jej mm4 #c #aa4c ,zinc 4#ajj mm4 #f #g4a ,aluminum #c4ejj #bjj #b4f mm4 ,he concluded from these data that the permeability increased much more rapidly than the thickness decreased4 #hd4 ,,fluorescence ,,and ,,chemical ,,action4 #gj and #fc;a4--,among the substances that fluoresced were barium platino cyanide1 calcium sulphide1 uranium glass1 ,iceland spar and rock salt4 ,in producing sciagraphs on the photographic plates1 he found it entirely unnecessary to remove the usual ebonite cover1 which1 although black1 and so opaque to light1 produced scarcely any resistance to the rays4 ,the sensitive plate1 even when protected in a box1 could not be kept near a discharge tube1 for he noticed that it became clouded4 ,he was not sure whether the effect upon the sensitive plate was directly due to the ,x-rays or to a secondary action1 namely1 the fluorescent light which must have been produced upon the glass plate having the film1 it being well known that light of fluorescence possesses chemical power4 ,he called attention to the fact that inasmuch as fluorescent light which can be reflected1 refracted1 polarized1 etc41 was produced by the rays2 therefore1 all the ,x-rays which fell upon a body did not leave it as such4 #fg4 ,no effect was produced upon the retina of the eye although he temporarily concluded that the rays must have struck the retina in view of the great permeability of animal tissue and liquids4 #fh1 at end4 ,conclusions of this kind not based on experiment1 are never reliable1 even when offered by very high authorities4 ,again the rays were weak4 ,roentgen himself admitted that the salts of metals in solution 7 #hb1 near centre7 rendered the latter rather opaque4 ,the eye ball is continually moistened with the solution of common salt4 ,further than this1 ,mr4 ,pignolet noticed in ,comptes ,rendus1 ,feb4 #bd1 '#if1 an account of an experiment of ,darien and de ,rochas4 ,in anatomy it is common to experiment on fresh pig's eyes in order to make comparisons with human eyes4 ,the above named ,frenchmen submitted the former to ,x-rays4 ,the eyes were but slightly permeable thereto4 ,illustration3 ,,the ,,physical ,,institute1 ,,university ,,of ,w,,rzburg1 ,,where ,,prof4 ,,roentgen ,,has ,,his ,,residence1 ,,delivers ,,his ,,lectures1 ,,and ,,performs ,,his ,,experiments4 ,from photograph by ,g4 ,glock1 ,wrzburg4 7,not referred to in book47 #he4 ,,non-,,refraction ,,and ,,but ,,little ,,reflection ,,of ,x-,,rays4--,he employed a very powerful refracting prism made of mica and containing carbon bi-sulphide and water4 ,the same prism refracted light but did not refract ,x-rays4 ,no one would think of making prisms for examining light1 of ebonite or aluminum1 but he made such a prism for testing ,x-rays4 ,but if there were any refraction he concluded that the refractive index could not have been more than #a4je1 which may be considered as a proof that the rays cannot be refracted4 ,he tried heavier metals1 but the difficulty of arriving at any satisfactory results was due to the resistance of such metals to the transmission of the rays4 ,among other tests was one consisting in passing the rays through layers of powdered materials through which the rays were transmitted in the same quantity as through the same substances not powdered4 ,it is well known that light passed into powdered transparent materials1 is enormously cut off1 deviated1 diffused1 refracted etc41 in view of the innumerable small surfaces of the particles4 ,hence he concluded that there was little if anything in the nature of refraction or reflection of ,x-rays4 #adf4 ,the powdered materials employed were rock salt1 and fine electrolytic and zinc dust4 ,the shadows1 both on the screen and as recorded on the photographic plate were of substantially the same shade as given by the same materials of the same thickness in the coherent state4 ,one of the most usual ways of testing refraction of light is by means of a lens4 ,x-rays could not be brought to a focus with the lens of what ever material it was made4 ,among the substances tried were ebonite and glass4 ,as expected1 therefore1 the sciagraph of a round rod was darker in the middle than at the edges2 and a hollow cylinder filled with a more transparent liquid showed the centre portion brighter than its edges4 ,if one considers this observation in connection with others1 namely the transparency of powders1 and the state of the surface not being effective in altering the passage of the ,x-rays through a body1 it leads to the probable conclusion that regular reflection does not exist1 but that bodies behave to the ,x-rays as turbid media to light1 #fi4 #hf4 ,,velocity ,,of ,x-,,rays ,,in ,,different ,,bodies4 p4 #df4--;,although he performed no direct experiment in this direction yet he inferred in view of the absence of refraction at the surfaces of different media1 that the rays travel with equal velocities in all bodies4 #hg4 ,,double ,,refraction ,,and ,,polarization4--,neither could he detect any action upon the rays by way of refraction by ,iceland spar at whatever angle the crystal was placed4 ,as to this property of light see ,huygen's ,works of #afij and ,malus' ,works of #ahaj4 quartz also gave negative results4 ,prof4 ,mayer of ,stevens ,institute submitted to ,sci41 ,mar4 #bg1 '#if1 the report of a crucial test for showing the non-polarization of ,x-rays4 ,on six discs of glass1 #j4ae mm4 thick and #be mm4 in diameter1 were placed very thin plates of ,herapath's iodo-sulphate of quinine4 ,the axes of these crystals crossed one another at various angles4 ,when the axes of two plates were crossed at right angles no light was transmitted2 the overlapping surfaces of the plates appearing black4 ,if the ,roentgen rays be polarizable1 the ,herapath crystals1 crossed at right angles1 should act as lead and not allow any of the ,roentgen rays to be transmitted4 ,prof4 ,mayer is well known as exceedingly expert in connection with minute measurements and in the manipulation of scientific experiments4 ,dr4 ,morton1 ,pres4 ,stevens ,inst41 attested the results as an absolute demonstration that ,x-rays are incapable of polarization4 ,stevens ,indicator1 ,jan41 '#if4 #hh4 ,,the ,,propagation ,,of ,x-,,rays ,,rectilinear4--,there would be no difficulty in producing photographs of the bones of the hand with the rays of light1 if it were not for the tremendous amount of reflection and refraction causing so much diffusion that no sharply defined shadow of the bones would be produced4 ,by means of a powerful lens and a funnel pointed into a dark room1 the author noticed that the condensed light thereby obtained when passed through the hand1 and when the incident rays were parallel1 came out so diffused that one would think that the light went through bones as easily as any part of the hand4 ,an experiment of this kind serves to emphasize that the success of sciagraphy by ,x-rays is due not only to the great penetrating power1 but to practically no refraction nor reflection4 ,in view of the sharp shadows cast of objects even when located in vegetable or animal media1 ,roentgen was justified in giving the name of ray to the energy4 ,he tested the sharpness of the shadow by making sciagraphs and fluorescent pictures not only of the bones of the hand1 but of a wire wound upon a bobbin1 of a set of weights in a box1 of a compass1 card and needle1 conveniently closed in a metal case1 and of the elements of a non-homogeneous metal4 ,to prove the rectilinear propagation further1 he received the image of the discharge tube upon a photographic plate by means of a pinhole camera4 ,the picture was faint but unmistakable4 #hi4 ,,interference4 ,the rays of light may be caused to interfere with each other4 ,see ,newton's ,principia1 ,vol4 ,,iii42 ,young's ,works1 ,vol4 ,i4--,theory points out that waves of ether of two pencils of light1 when caused to be propagated at certain relative phases partially or wholly neutralize or strengthen each other4 ,roentgen could obtain no interference effects of the ,x-rays1 but did not conclude that the interference property was absent4 ,he was not satisfied with the intensity of the rays and therefore could not test the matter severely4 ,illustration3 ,,fig4 ,l4 #ij4 ,,electrified ,,bodies ,,discharged ,,by ,x-,,rays4 p4 #dg4--;,after ,roentgen's first announcement1 others1 and probably ,j4 ,j4 ,thomson as the first1 found that the ,x-rays would discharge both negatively and positively electrified bodies4 ,roentgen1 in his second announcement1 stated that he had already made such a discovery1 but had not carried the investigation far enough to report satisfactorily on the details4 ,at last he put forth an account of the whole phenomena and stated that the discharge varied somewhat with the intensity of the rays1 which was tested in each instance by the relative luminosity of the fluorescent screen1 and by the relative darkness produced upon the photographic plate in several instances4 ,electrified bodies1 whether conductors or insulators1 were discharged when placed in the path of the rays4 ,all bodies whatsoever behaved in the same manner when charged4 ,they were all discharged equally by the ,x-rays4 ,he noticed that 8,if an electrical conductor is surrounded by a solid insulator such as paraffin instead of by air1 the radiation acts as if the insulating envelope were swept by a flame connected to earth40 ,upon surrounding said paraffin by a conductor connected to earth1 the radiation no longer acted on the inner electrified conductor4 ,the above observations led him to believe that the action was indirect and had something to do with the air through which the ,x-rays passed4 ,in order to prove this1 it was necessary for him to show that air ought to be able to discharge the bodies if first subjected to the rays1 and then passed over the bodies4 ,the apparatus for performing an experiment to test this prediction is shown in ,fig4 ,l1 which serves to illustrate also the manner in which he prevented electro-static influences of the discharge tube1 leading in wires and induction coil4 #ga1 near centre4 ,for this purpose he built a large room in which the walls were of zinc covered with lead4 ,the door for his entrance and exit was arranged to be closed in an air-tight manner4 ,in the side wall opposite the door there was a slit #d cm4 wide1 covered hermetically with a thin sheet of aluminum for the entrance of ,x-rays from the vacuum tube outside of the room4 ,all the electrical apparatus connected with the generation of the ,x-rays was outside of the room4 ,no force whatever came into the room1 therefore1 except the ,x-rays through the aluminum4 #ga4 ,in order to show that air which had been subjected to the ,x-rays would discharge a body immediately afterwards upon coming in contact therewith1 he arranged matters so that the air was propelled by an aspirator4 ,he passed air along a tube made of thick metal so that the rays could enter only through a small aluminum window near the open end4 ,at over a distance of #bj cm4 from the window was an insulated ball charged with electricity1 and connected to any electroscope or electrometer4 ,the professor used a ,hankel electroscope4 ,no published sketch was made by ,roentgen2 therefore1 that shown in the figure was produced by inference from the description4 ,the operation was as follows3 ,the ,x-rays passed into the room through the aluminum window1 and then into the metal tube through its aluminum window4 ,when the air was at rest1 the ball was not discharged4 ,when the aspirator was at work1 however1 so that the air moved past the aluminum window and past the ball1 the latter was discharged whether electrified positively or negatively4 ,he modified the operation by maintaining the ball at a constant potential by means of accumulators1 while the air which had been treated by ,x-rays was passed by the ball4 8,an electric current was started as if the ball had been connected with the wall of the tube by a bad conductor40 ,he was not sure whether the air would retain its power to discharge bodies as long as it remained out of contact with any bodies4 ,he determined1 however1 that any slight 8disturbance0 of the air by a body having a large surface and not electrified1 rendered the air inoperative4 ,he illustrated this by saying that 8,if one pushes1 for example1 a sufficiently thick plug of cotton-wool so far into the tube that the air which has been traversed by the rays must stream through the cotton-wool before it reaches the ball1 the charge of the ball remains unchanged when suction is commenced40 ,with the cotton-wool immediately in front of the window1 it had no effect1 showing1 therefore1 that dust particles in the air are not the cause of the communication of the force of the discharge from the ,x-rays to the electrified body4 ,very fine wire gauze in several thicknesses also prevented the air from discharging the body when placed between the aluminum window and the ball within the thick metal tube1 as in the case of the cotton plug4 ,similar experiments were instituted with dry hydrogen instead of air1 and1 as far as he could discern1 the bodies were equally well discharged1 except possibly a little slower in hydrogen4 ,he experienced difficulty in obtaining equally powerful ,x-rays at different times4 ,all experimenters are acquainted with this difficulty4 ,further1 he called attention also to the thin layer of air which clings to the surface of the bodies1 and which1 therefore1 plays an appreciable part in connection with the discharge4 #af1 near end4 ,in order to test the matter further as to discharge of electrified bodies1 he placed the same in a highly exhausted bulb and found that the discharge was in one case1 for example1 only #a_/gj as rapid as in air and hydrogen at ordinary pressure1 thereby serving as another proof that gas was the intermediate agency4 ,allowance should be made in all experiments in connection with the discharging quality of ,x-rays4 ,the surrounding gas should be taken into account4 #ij;a4 ,,application ,,of ,,principle ,,of ,,discharge ,,by ,x-,,rays4--,professor ,robb1 of ,trinity ,college1 7,science1 ,apr4 #aj1 '#if71 proposed and explained and practically tested the principle of the discharge of ,x-rays to determine the relative transparencies of substances to ,x-rays4 ,he plotted a curve in which the co-ordinate represented the charge of the condenser in micro-coulombs1 and the absciss the time between charging and discharging the condenser4 ,the same plan could be adopted1 he suggested1 for making quantitative measurements of the intensity of ,x-rays from different tubes or the same discharge tube at different times4 ,j4 ,j4 ,borgmann1 of ,st4 ,petersburg1 probably was the first to show that ,x-rays charged as well as discharged bodies4 ,see ,the ,elect41 ,lon41 ,feb4 #ad1 '#if1 p4 #eja4 ,soon1 a similar announcement was made by ,prof4 ,righi1 of ,bologna4 #ij4 #ij;,a4 ,,borgmann ,,and ,,gerchun',s ,,experiments4 ,,action ,,of ,,the ,x-,,rays ,,on ,,electro-,,static ,,charges ,,and 7,,la ,,distance ,,explosive47 ,comptes ,rendus1 ,feb4 #ag1 '#if2 from ,trans41 by ,louis ,m4 ,pignolet4--,a positively charged zinc disk connected to an electroscope lost its charge almost instantly and acquired a negative charge4 ,when the charge on the zinc disk was negative1 the loss was much slower and was not complete1 a certain charge remaining4 ,when the rays fell upon two small platinum balls connected to the terminals of an induction coil but separated beyond its sparking distance1 sparking took place between them1 showing that ,x-rays1 like ultra-violet rays1 increase the sparking distance of static charges4 #ij;b4 ,,righi',s ,,experiments4 ,,bodies ,,in ,,the ,,neutral ,,or ,,negative ,,state1 ,,positively ,,electrified ,,by ,x-,,rays4 ,comptes ,rendus1 ,feb4 #ag1 #ahif4 ,from ,trans4 by ,louis ,m4 ,pignolet4--,the measurements were made by this eminent ,italian physicist1 with a ,mascart electrometer connected with the bodies upon which the ,x-rays impinged and enclosed in a grounded metallic case 7,faraday cylinder7 provided with an aluminum window for the entrance of the rays4 ,a metallic disk connected with the electrometer lost its charge rapidly whether positive or negative4 #ii,s4 ,initial positive charges were not completely dissipated2 negative charges were not only completely dissipated but the bodies acquired positive charges4 ,disks in the neutral state were charged positively by the ,x-rays the same as takes place with ultra-violet rays4 ,the final positive potential was greater for copper than for zinc and still greater for retort carbon 78le carbon de cornue07 #ij;c4 at end4 ,the various results are not conflicting if the particular materials are taken into accounts4 #ij;c at end4 #ij;c4 ,the experiments of ,prof4 ,minchin1 an expert in such measurements1 are properly described here1 in that they seem to clear up the superficial ambiguity4 ,he formulated the conclusion 7,the ,elect41 ,lon41 ,mar4 #bg1 '#if1 p4 #gcf7 thus3--8,the ,x-rays charge some bodies positively and some negatively1 and whatever charge a body may receive by other means1 the ,x-rays change it1 both in magnitude and sign1 to the charge which they independently give to the body40 ,thus1 in the case of magnesium1 if the same is first positively charged by any suitable means1 then will the ,x-rays not only discharge it1 but electrify it negatively1 while if this metal is first negatively charged1 the ,x-rays either diminish or increase the discharge4 ,it must be remembered1 however1 that this is not true with all metals1 for he found that gold1 silver1 copper1 platinum1 iron1 aluminum1 bismuth1 steel and antimony1 are all positively electrified4 #ij;d4 ,,benoist ,,hermuzescu',s ,,experiment4 ,,negative ,,charges ,,dissipated ,,faster ,,than ,,positive ,,by ,x-,,rays4 ,,rate ,,depends ,,upon ,,absorption4 ,,law ,,formulated4 ,comptes ,rendus1 ,feb4 #c1 ,mar4 #ag and ,april #bg1 '#if4 ,they observed that the rays dissipated entirely the charge of electrified bodies in their path1 and that negative charges were dissipated more rapidly than positive4 #ii,q4 ,they also noticed the discharge augments with the opaqueness of the body and that the effect is more considerable with two thin superposed sheets than with one4 ,in experimenting upon the influence of the discharge of the gaseous dielectric in which the bodies were located1 they formulated the following law4 ,the rapidity of the dissipation of the electric charge of an electrified body under the same condition varies as the square root of the density of the gas surrounding the body4 ,the dissipation of the electric charge depends upon the nature of the electrified body1 due to a sort of absorbing power 7 #ii,m7 connected with the opaqueness of the body and upon the nature of the surrounding gas1 due to the density of the gas or when passing from one gas to another4 7,from trans4 by ,louis ,m4 ,pignolet47 #ia4 ,before ,roentgen published in his second paper of ,mar4 #i1 '#if1 an account of his focus tube1 the ,kings ,college published a description of an exactly similar one1 represented in the cut4 ,see ,elec4 ,rev41 ,lon41 ,mar4 #ac4 '#if1 p4 #cdj4 ,the cathode is concave and the anode is formed of platinum and is plane and at such an angle that the ,x-rays generated1 #fc;b41 on diffusion of internal cathode rays1 will be thrown out through the thin walls of the bulb4 #ee and #eg4 ,as the rays emanate from a point1 the shadows are much clearer1 especially in conjunction with powerful rays permitting several feet between the object and the tube4 ,mr4 ,shallenberger was among the first1 and was the first as far as the author knows 7,elect4 ,world1 ,mar4 #g1 '#if1 see cut reproduced7 to originate the use of an ,x-ray focus tube4 ,illustration3 ,,typical ,,focus ,,tube4 #ia;a4 ,,apparatus ,,employed4--,prof4 ,roentgen paid tribute to ,tesla1 by alluding to the advantages resulting from the use of the ,tesla condenser and transformer4 ,in the first place1 he noticed that the discharge apparatus became less hot1 and that there was less probability of its being pierced4 ,again the vacuum lasted longer1 at least in the case of his particular apparatus4 ,above all1 stronger ,x-rays were produced4 ,again careful adjustment of the vacuum was not as necessary as with the ,ruhmkorff coil4 #ib4 ,x-,,rays ,,and ,,longitudinal ,,vibrations4--,prof4 ,roentgen did not consider ,x-rays and ultra-violet rays to be of the same nature1 although they produced many common effects4 ,the ,x-rays1 as he found1 by the above related experiments1 behaved quite differently from the ultra-violet rays1 which are highly refrangible1 practically all subject to reflection1 capable of being polarized1 and absorbed according to the density of the absorbents4 ,for valid reasons1 the ,x-rays cannot be infra-red rays4 ,while he does not affirm any theory1 yet he suggests the theory of longitudinal waves for explaining the properties of ,x-rays4 7,this was not suggested again in his second announcement47 ,he stated that the hypothesis needs a more solid foundation before acceptance4 ,the reason why ,roentgen termed the energy ,x-rays is simply because ,x in algebra represents an unknown quantity4 ,illustration3 ,,shallenberger ,,apparatus ,,and ,,focus ,,tube4 #ia4 #ic4 ,at the ,johns ,hopkins ,university1 ,u4 ,s41 in #ahhd1 ,sir ,william ,thomson1 7,kelvin7 delivered a lecture in which he argued that the production of longitudinal vibrations1 by electrical means1 is reasonable and possible of occurrence4 ,j4 ,t4 ,bottomly1 in ,nature1 ,lon4 ,feb41 7see also ,elect4 ,eng41 ,n4,y41 ,feb4 #ai1 '#if1 p4 #ahg7 called attention to this lecture as being of interest in view of ,roentgen's suggestion about longitudinal vibrations4 ,lord ,kelvin called attention to what had been developed in connection with the electro-magnetic theory of light and referred to his own work in #ahed1 in connection with the propagation of electric impulses along an insulated wire surrounded by gutta percha1 but he said that at that time no one knew the relation between electro-static and electro-magnetic units4 ,the part of the lecture referring particularly to the possibility of longitudinal waves in luminiferous ether by electrical means reads as follows4 8,suppose that we have at any place in air1 or in luminiferous ether 7,i cannot now distinguish between the two ideas7 a body that1 through some action we need not describe1 but which is conceivable1 is alternately1 positively and negatively electrified2 may it not be that this will give rise to condensational waves8 ,suppose1 for example1 that we have two spherical conductors united by a fine wire1 and that an alternating ,e4 ,m4 ,f4 is produced in that fine wire1 for instance1 by an alternate current dynamo-electric machine1 and suppose that sort of thing goes on away from all other disturbance--at a great distance up in the air1 for example4 ,the result of the action of the dynamo-electric machine will be that one conductor will be alternately1 positively and negatively electrified1 and the other conductor negatively and positively electrified4 ,it is perfectly certain1 if we turn the machine slowly1 that in the air in the neighborhood of the conductors1 we shall have alternately1 positively and negatively directed electric force with reversals of1 for example1 two or three hundred per second of time1 with a gradual transition from negative1 through zero to positive1 and so on2 and the same thing all through space2 and we can tell exactly what the potential and what the electric force are at each instant at any point4 ,now1 does any one believe that1 if that revolution were made fast enough1 the electro-static law of force1 pure and simple1 would apply to the air at different distances from each globe8 ,every one believes that if the process can be conducted fast enough1 several million times1 or millions of millions times per second1 we should have large deviations from the electro-static law in the distribution of electric force through the air in the neighborhood4 ,it seems absolutely certain that such an action as that going on would give rise to electrical waves4 ,now1 it does seem to me probable that these electrical waves are condensational waves in luminiferous ether2 and probably it would be that the propagation of these waves would be enormously faster than the propagation of ordinary light waves40 ,notice that the above was written twelve years prior to ,roentgen's discovery4 #id4 ,prof4 ,schuster1 in ,nature1 ,lon41 ,jan4 '#if1 stated that the great argument against the supposition of waves of very small length lies in the absence of refraction1 but questioned whether this objection is conclusive4 ,he further stated3 8,the properties of the ether may remain unaltered within the greater part of the sphere of action of a molecule4 ,the number of molecules lying within a wave length of ordinary light is not greater than the number of motes which lie within a sound wave1 but1 as far as ,i know1 the velocity of sound is not materially affected by the presence of dust in the air4 ,hence there seems nothing impossible in the supposition that light waves1 smaller than those we know of1 may traverse solids with the same velocity as a vacuum4 ,we know that absorption bands greatly affect the refractive index in neighboring regions2 and as probably the whole question of refraction resolves itself into one of resonance effects1 the rate of propagation of waves of very small lengths does not seem to me to be prejudged by our present knowledge4 ,if ,roentgen rays contain waves of very small length1 the vibrations in the molecule which respond to them1 would seem to be of a different order of magnitude from those so far known4 ,possibly1 we have here the vibration of the electron with the molecule1 instead of the molecule carrying with it that of the electron40 #ie4 ,prof4 ,j4 ,j4 ,thomson showed how it was possible that 8longitudinal waves can exist in a medium containing moving charged ions1 and in any medium1 provided the wave length is so small as to be compared with molecular dimensions1 and provided the ether in the medium is in motion4 ,it follows from the equation of the electro-magnetic field that the ether is set in motion in a varying electric field4 ,these short waves would not be refracted1 but in this respect they do not differ from transverse waves1 which on the electro-magnetic theory would not be refracted if the wave length were comparable with molecular distances40 ,from ,elect4 ,eng41 ,n4,y41 ,mar4 #ah1 '#if1 p4 #bhf1 in reference to a paper before the ,cam4 ,phil4 ,so4 #if4 ,one of the very first questions asked in reference to a discovery is as to its practical utility4 ,already1 we have important applications in one of the most humane directions1 and that is in connection with diagnosis4 ,sciagraphs can also be employed in schools for the purpose of education1 in some departments of anatomy1 etc4 ,the interest that it excites and the amusement that it affords are not to be overlooked1 for anything in the nature of recreation possesses utility4 ,however1 we may greatly thank all experimenters who have investigated the subject1 and who have not left its development alone to ,roentgen2 for predictions as to the utility of a discovery1 however1 apparently exaggerated1 are very often proved1 by subsequent developments1 to have been underrated4 ,upon this point ,prof4 ,boltzmann1 in ,zeit4 ,elect41 ,jan4 #ae1 '#if1 see also1 ,the ,elec41 ,lon41 ,jan4 #ca1 '#if1 p4 #ddg1 stated1 8,if we remember to what discoveries the most insignificant new natural phenomenon1 such as the attraction of small objects by rubbed amber1 of iron by the lode-stone1 the convulsive twitches of a frog's leg due to electric discharges1 the influence of the electric current upon the magnetic needle1 electro-magnetic induction etc41 has led us1 one can imagine to what applications an agent will be turned1 which a few weeks after its discovery has given rise to such surprising results40 #ig4 ,soon after hearing1 7about the first of ,feb4 '#if17 of the ,roentgen discovery1 it occurred to the author to carry on experiments with fluorescence1 but finding that it was inconvenient to work in a perfectly dark room1 and1 recognizing that black cardboard had practically no effect upon absorbing the ,x-rays1 he devised a sciascope 7daily papers1 ,feb4 #ac1 and ,elect4 ,eng41 ,feb4 #ai7 which he afterwards learned was independently invented and used at about the same time by ,prof4 ,william ,f4 ,magie1 of ,princeton ,university1 7see ,amer4 ,jour4 ,med4 ,sci41 ,feb4 #g1 '#if and ,feb4 #ae1 '#if7 and by ,prof4 ,e4 ,salvioni1 of ,italy under the name of cryptoscope1 7see ,med4 ,sur4 ,acad4 of ,perugia1 ,italy1 ,feb4 #h1 '#if47 ,in about a month afterwards 7,elect4 ,eng41 ,n4,y41 ,apr4 #a1 '#if1 p4 #cdj7 the instrument 7with phosphorescent calcic tungstate #ac4 in place of fluorescent barium platino cyanide7 was again published under the name of the ,edison fluoroscope4 ,there are probably many other claimants--some professor in ,london--name forgotten4 ,they all consist of a tapering tube with a sight hole at one end and a fluorescent screen in the other1 which is closed by opaque card board4 7,frontispiece at ,chap4 ,x74 ,for the sake of conformity1 the words sciagraph and sciagraphy and similar derivatives1 and in view of the meaning of the radical definitions1 have been employed throughout the book4 ,the objection to the word fluoroscope is that the instrument is practically universally employed in seeing the shadows of objects1 otherwise invisible to the naked eye1 rather than to test fluorescence4 ,the name sciascope was early suggested by ,prof4 ,magie4 ,for those who wish to make a screen1 the author may state that he obtained a good one by mixing pulverized barium platino cyanide with varnish and spreading the mixture over a sheet of tracing cloth4 ---------------------------------------- -------------------------------- ,,chapter ,,viii ------- ,illustration #ig;a4 ,,hertz' ,,experiments4 ,,electrified ,,bodies ,,discharged ,,by ,,ultra-,,violet ,,light ,,of ,a ,,spark ,,and ,,by ,,other ,,sources ,,of ,,light4 ,berlin ,akad4 ,,ii41 p4 #dhg1 '#hg4 ,wied ,ann4 ,,xxxi1 p4 #ihc4 ,english translation of the above4 ,lon4 and ,n4,y4 ,macmillan1 p4 #fc1 '#ic4 ,from notes by ,mr4 ,n4 ,d4 ,c4 ,hodges4--,this is the all-important initial work of ,h4 ,hertz4 ,the source of light was a spark1 and the great discovery resulted from a combination of circumstances and was unsought2 but by studying and testing the matter1 he found the cause4 ,two induction coils1 a and b1 having interrupter d1 were included in the same circuit1 as shown in the figure4 ,the sparking of the active one 7,a7 increased the length of the spark of the passive 7,b7 #aj4 ,he sought the cause4 ,the discharge was more marked as the distance between the sparks was reduced4 ,sparks between the knobs had the same effect as those between points2 but the effect was best displayed when the spark ,b was between knobs4 ,the relation between the two sparks was reciprocal4 ,the discharging effect of the active spark 7,a7 spread out on all sides1 according to the laws of light1 first suggesting that light was the cause4 ,most solid bodies acted as screens1 s4 ,liquid and gases served more or less as screens4 ,the intensity of the action increased by the rarefaction of the air around the passive spark1 i4e41 in a discharge tube4 ,the radiations from the spark1 ,a1 reflected from most surfaces1 according to the laws of light1 and refracted according to the same laws1 caused the discharge4 ,the ultra-violet light of the spark ,a was inferred to be the active agent in producing the discharge4 ,the same effect was produced by other sources of light than the electric spark4 ,the conclusions were afterwards confirmed by many1 and subordinate discoveries originated4 #ih--ii,t4 #ig;b4 ,,wiedemann ,,and ,,ebert',s ,,experiment4 ,,light ,,discharges ,,cathode1 ,,but ,,has ,,no ,,influence ,,upon ,,anode1 ,,nor ,,air-,,gap4 ,,different ,,gases ,,and ,,different ,,pressures4 ,wied4 ,ann4 ,,xxxiii1 p4 #bda4 #ahhh4 ,from notes by ,n4 ,d4 ,c4 ,hodges4--,the arc light was used in place of the active spark of ,hertz4 ,principal result was that the effect depended on the illumination of the cathode 7 #ii47 ,the illumination of the anode or of the spark-gap did not influence the discharge4 ,the very character of the charge was altered by the action of light upon the cathode4 ,the influence of the illumination of the cathode did not consist solely at the starting of the spark1 but lasted as long as the sparks continued to pass4 ,with decreasing pressure of surrounding gas1 the effect first increased 7 #ig;a7 to a maximum1 and then decreased 7 #ed74 ,the illumination had an effect on the path of the sparks1 the path being perpendicular to the rays of light4 ,the best results were obtained with carbonic acid gas4 ,hydrogen was next1 and then air4 ,they were contained in the tubes surrounding the poles4 ,the character of the gas also had an influence on the rays which would produce the effect1 with carbonic acid gas the effect showing itself even with the visible rays4 #ih4 ,,elster ,,and ,,geitel',s ,,experiment4 ,,negatively ,,charged ,,bodies ,,discharged ,,by ,,light4 ,wien4 ,berichte4 ,vol4 ,,ci1 p4 #gjc1 '#ib4 ,wied4 ,ann4 ,vols4 ,,xxxviii1 ,,xxxix1 ,,xli1 ,,xlii1 ,,xliii1 ,,xliv1 ,,xlvi1 ,,xlvii1 ,,lii4 ,nature1 ,lon41 ,sept4 #f1 '#id1 p4 #dea4--,the elements employed for carrying on the experiment consisted of a delicate electroscope and certain metals1 including aluminum1 amalgamated zinc1 magnesium1 rubidium1 potassium and sodium4 ,some of the experiments were made on the top of ,mount ,sonnblick1 the same being #c1ajj m4 high1 where the discharging power of light was found to be about twice as great as at ,wolfenbuttel1 which was at the level of #hj m4 ,the whole time for the discharge was only a matter of a few seconds4 ,the greater rapidity of discharge at the higher level was attributed to the greater proportion of ultra-violet rays 7,hertz71 which are the most easily absorbed by the atmosphere1 according to ,langley4 ,all metals are not discharged alike by the action of light4 ,the law follows the electro-positive series in such a way that the more electro-positive the metal1 the longer the wave length of light necessary to produce the discharge4 ,in experiments with potassium1 sodium and rubidium1 they made them successively1 the cathode in a bulb of rarefied hydrogen4 ,in this case it was found that the light of a candle1 even at so great a distance as #g m41 would cause the discharge4 ,rubidium was sensitive in this respect to the red light from a heated rod of glass4 ,elster and ,geitel were able also to discharge1 by light1 some non-metallic bodies1 like calcic sulphide1 when so prepared that it had the property of phosphorescing1 and also darkly colored fluorites4 ,independently1 the phenomenon is of importance1 because ,elster and ,geitel determined that there was some common cause as to the discharge of bodies of light and the discharge from the earth's surface4 ,a series of experiments lasting three years1 consisted in investigating the relation of the ultra-violet rays from the sun simultaneously to the quantity of charge in the atmosphere4 ,the results acted as evidence of the explanation of the daily and annual variation of atmospheric potentials4 ,these experiments are of importance in connection with ,x-rays1 because ,rntgen and ,prof4 ,j4 ,j4 ,thomson subsequently1 and possibly others independently1 discovered that ,x-rays produce1 not only a like1 but a more extended action in that there is not so great a difference between their power to discharge negatively and positively electrified bodies4 #ij;a4 ,in the further developments of their ideas1 they tried the action of diffused day-light upon a ,geissler tube traversed by vibrations which were produced by a ,hertz vibrator 7see recent book on ,hertzian waves71 the tube having an electrode of metal of the alkaline group4 ,they were able to adjust the combination so that the presence of a little day-light would initiate a luminous discharge1 while in the dark such a charge ceased4 #ad;a4 #ii4 ,,elster ,,and ,,geitel',s ,,experiment4 ,,effect ,,of ,,polarized ,,light ,,upon ,,the ,,cathode4 ,berlin ,akad4 '#ie4 ,nature1 ,lon41 ,march #bh1 '#ie1 p4 #ead4 ,proc4 ,brit4 ,asso41 ,aug4 #af1 '#id2 ,aug4 #bc1 '#id1 p4 #djf4--,the ,x-rays have properties similar to those of light1 and have their source in electricity4 ,quincke discovered that light which has been polarized perpendicularly to the plane of incidence is greatly increased as to its power of penetrating metals4 ,elster and ,geitel used the following apparatus to determine the relation between polarized light and electricity4 ,the current varied according to the angle of incidence and the plane of polarization4 ,the apparatus comprised the following elements3 ,an exhausted bulb1 provided with a platinum anode1 and a cathode consisting of potassium and sodium1 combined in the form of a liquid alloy having a bright surface of reflection4 ,the source of light was an oxyhydrogen flame1 which played upon zircon instead of lime2 a lens changed the diverging rays to parallel rays1 which were polarized by a ,nichol prism and allowed to fall upon the cathode4 ,the electrodes of the vacuum bulb were connected to the poles of a generator of a current of about #djj volts4 8,the strength1 of the current was greatest when the plane of polarization was perpendicular to the plane of incidence--i4e41 when the electric displacements constituting light1 took place in the plane of incidence1 and when the angle of incidence was about #fj1 i4e41 the polarizing angle of the alloy itself40 ,prof4 ,sylvanus ,p4 ,thompson confirmed these results by experiment4 ,the rate of discharge was greatest1 he said1 when the plane of polarization was such that the ,fresnellian vibration 8chopped into0 the surface4 ,polarized light1 he reminded them1 produced similar results upon selenium4 ,although the domain of this book is necessarily limited to the consideration of phenomena connected with the internal and external energy of a discharge tube1 yet if any other one subject is of special interest and utility in connection with the consideration of ,x-rays1 it is that concerning the relation between the electric discharge and light1 which has been thoroughly studied only during the past few years1 and the accounts of the researches recorded in various periodicals and academy papers4 ,those readers1 however1 who desire to study this exceedingly interesting and novel branch of science1 which in connection with the action of the internal cathode rays and ,x-rays upon electrified bodies1 tends to uphold ,maxwell's theory as developed by mathematics and based upon early known facts and predicted discoveries1 may find volumes upon this subject by referring to the citations below1 named by ,mr4 ,n4 ,d4 ,c4 ,hodges and obtained by him by a search in the archives of the ,astor ,library4 ,of especial interest are those of ,branly1 #ii;,i1 #ii;,j1 #ii,q1 #ii,s1 #ii,t4 ,some notion as to the contents of the citations are given here and there4 #ii;,a4 ,,koch',s ,,experiment4 ,,the ,,loss ,,of ,,electricity ,,from ,a ,,glowing ,,electrified ,,body4 ,wied4 ,ann41 ,,xxxiii41 p4 #ded1 '#hh4 #ii;,b4 ,,schuster ,,and ,,anpenius' ,,experiment4 ,,the ,,influence ,,of ,,light ,,on ,,electrostatically ,,charged ,,bodies4 ,proc4 ,r4 ,so41 ,lon41 ,,lxii41 p4 #cga1 '#hg2 ,proc4 ,swedish ,acad41 ,,lxiv41 p4 #dje1 '#hg4--,many recent periodicals have set forth that ultra-violet light will discharge only negatively charged bodies4 ,while this is practically or sometimes the case1 yet these experimenters found that a positive charge was dissipated very slowly4 ,they confirmed the results that the ultra-violet rays played the principle part in the removal of a negative charge4 ,polishing the surface accelerated the action4 #ii1 near beginning4 #ii;,c4 ,,righi',s ,,experiment4 ,,some ,,new ,,electric ,,phenomena ,,produced ,,by ,,light4 ,note #b-d1 ,rend4 ,r4 ,acad4 die ,lincei1 ,may #f1 #bj1 and ,june #c1 '#hh4 #ii;,d4 ,,righi',s ,,experiment4 ,,some ,,new ,,electric ,,phenomena ,,produced ,,by ,,illumination4 ,rend4 ,r4 ,acad4 die ,lincei4 ,,vi41 p4 #ace1 #ahg1 '#hh4--;,confirmation of the results of other physicists1 and a quantitative measurement determining that the ,e4 ,m4 ,f4 between copper and selenium was increased #be per cent4 by illumination by an arc light4 ,the selenium was in the form of crystals mounted upon a metal plate4 #ii;,e4 ,,stolstow',s ,,experiment4 ,,actino-,,current ,,through ,,air4 ,c4 ,r41 ,,cvi41 pp4 #aeic to #ie1 '#hh4--,liquids tested4 ,greatest absorbents of active rays most quickly discharged4 #ii;,f4 ,,righi ,,and ,,stolstow',s ,,experiments4 ,,kind ,,of ,,electric ,,current ,,produced ,,by ,,ultra-,,violet ,,rays4 ,c4 ,r41 ,,cvi1 pp4 #aadi to #eb1 '#hh4--,the discharge was accelerated by using a chemically clean surface4 ,the burning of metals1 for example1 aluminum1 zinc or lead in the arc light increased the discharging power4 #ii;,g4 ,,bichat ,,blondot',s ,,experiment4 ,,action ,,of ,,ultra-,,violet ,,rays ,,on ,,the ,,passage ,,of ,,electricity ,,of ,,low ,,tension ,,through ,,air4 ,comptes ,rendus4 ,,cvi1 pp4 #a1cdi to #ea4 '#hh4--,they employed arc lamps whose carbons had aluminum cores4 #ii;,h4 ,,nacarri',s ,,experiment4 ,,the ,,dissipation ,,of ,,electricity ,,through ,,the ,,action ,,of ,,phosphorous ,,and ,,the ,,electric ,,spark4 ,atti di ,torino4 ,,xxv1 pp4 #beb to #beg4 '#ij4--,the loss of charge was eighteen times less rapid in the dark through the air in a bottle1 than when a piece of luminous phosphorous was placed in the bottle4 ,the introduction of turpentine1 which checked the glowing of the phosphorous1 retarded the loss of charge4 ,illustration3 ,,from ,,sciagraph ,,of ,,frog1 ,,through ,,small ,,hole ,,in ,,diaphragm1 ,,as ,,in ,,fig4 #a1 p4 #ajj4 #ii;,i4 ,,branly',s ,,experiment4 ,,photo-,,electric ,,current ,,between ,,the ,,two ,,plates ,,of ,a ,,condenser4 ,c4 ,r4 ,,cx1 pp4 #hih to #ija4 '#ia4--;,a positive charge was dissipated1 and by a peculiar arrangement of the plates1 screens1 etc41 and with particular materials1 he was able to show that the rates of loss of a positive and negative charge were about equal4 ,numerous tests were instituted4 ,if he is not mistaken1 how closely related are ,x-rays and light4 #ij4 ,those who wish to more thoroughly investigate this matter and verify the same1 should study these experiments more in detail in connection with ,schuster's and ,anpenius' experiments 7 #ii;,b71 whose arrangement of the plates was the same as those of ,branly4 #ii;,j4 ,,branly',s ,,experiment4 ,,loss ,,of ,,both ,,electricities ,,by ,,illumination ,,with ,,rays ,,of ,,great ,,refrangibility4 ,c4 ,r4 ,,cx1 pp4 #gea to #ged4 '#ij4 #ii,k4 ,,righi',s ,,experiment4 ,,electric ,,phenomena ,,produced ,,by ,,illumination4 ,luer's ,rep4 ,,xxv1 pp4 #chj to #chb4 '#hi4 #ii,l4 ,,borgmann4 ,,actino-,,electric ,,phenomena4 ,c4 ,r4 ,,cviii1 p4 #gcc4 '#hi4 ,jour4 d4 ,russ4 ,phys4 ,chan4 ,ges4 7#b7 ,,xxi1 pp4 #bc to #bf4 '#hi4--,the photo-electric effect not instantaneous4 ,a telephone served in the place of the galvanometer to detect the discharge4 #ii,m4 ,,stolstow',s ,,experiment4 ,,actino-,,electric ,,investigations4 ,jour4 d4 ,russ4 ,phys4 ,chan4 ,ges4 7#g-h7 ,,xxi1 pp4 #aei to #bjg4--;,it is necessary that the rays of light should be absorbed by the charged surface before having the discharging influence4 #ii;,e4 ,all metals are subject to the action1 and also the aniline dyes4 ,two plates between which there is a contact difference of potential generate a current so long as the negative plate is illuminated4 ,the effect is increased with the increase of temperature and is only found in gases1 and is therefore of the nature of convection4 ,he determined these principles by continuous work for two years4 ,it should be remembered that in all these researches1 the arc light is preferable1 because the ultra-violet spectrum is six times as long as that given by the sun4 #ii,n4 ,,mebius' ,,experiment4 ,,an ,,electric ,,spark ,,and ,a ,,small ,,flame ,,employed4 ,bihang till ,k4 ,svenska ,vet4-,akad4 ,hand4 #ae1 ,afd4 #a1 ,no4 #d1 p4 #cj1 '#hi4 #ii,o4 ,,worthington',s ,,experiment4 ,,discharge ,,of ,,electrification ,,by ,,flames4 ,brit4 ,asso4 ,rep41 '#ij1 p4 #bbe4 #ii,p4 ,,fleming',s ,,experiment4 ,,discharge ,,between ,,electrodes ,,at ,,different ,,temperatures ,,in ,,air ,,and ,,in ,,high ,,vacua4 #ii,m1 near end4 ,proc4 ,ro4 ,so41 ,,lxvii41 p4 #aah4 #ii,q4 ,,branly',s ,,experiment4 ,,hallwach ,,and ,,stolstow',s ,,experiment4 ,,loss ,,of ,,electric ,,charge4 ,lum4 ,elect41 ,,lxi41 pp4 #adc to #add1 '#ia4--;,branly obtained quantitative results4 ,hallwach found with the use of the arc light1 a very small loss of positive electricity at high potentials2 ,stolstow1 no such loss at potentials under #bjj volts4 ,branly1 with a #ej element battery and an arc light as the source of illumination1 caused a discharge and thereby a constant deflection of #abd degrees of the galvanometer needle4 ,the action of the light upon a positive disk caused a deflection of only three degrees by the same battery4 ,with aluminum in the electrodes1 the deflections were about #adjj and #bd respectively4 ,is it not sufficiently fully established that ultra-violet light will discharge not only negative but positive electricity8 ,he experimented with substances heated to glowing or incandescence4 ,glass lamp chimneys at a dull1 red heat1 when covered with aluminum1 oxide of bismuth1 or lead oxides1 withdraw positive charges4 ,in the same way1 for example1 behaves a nickel tube in place of the lamp chimney4 #ii,r4 ,,wanka',s ,,experiment4 ,a ,,new ,,discharge ,,experiment4 ,abk4 d4 ,deuts4 ,math4 ,ges4 in ,rrag41 '#ib1 pp4 #eg to #fc4--;,he confirms the principle that the ultra-violet rays are the most powerful4 ,a glass plate1 which1 as well known1 cuts off most of the ultra-violet rays1 was properly interposed and then removed and the difference noted4 #ii,s4 ,,branly',s ,,experiment4 ,,discharge ,,of ,,both ,,positive ,,and ,,negative ,,electricity ,,by ,,ultra-,,violet ,,rays4 ,c4 ,r41 ,,cxiv41 pp4 #fh to #gj1 '#ib4--;,he further proves that ultra-violet rays of light will dissipate a positive charge4 ,the experiments in this connection seem to prove more and more that the discharging power is only a matter of sufficiently high refrangibility of the rays of light4 #ii,t4 ,,branly',s ,,experiment4 ,,loss ,,of ,,electric ,,charge ,,in ,,diffuse ,,light ,,and ,,in ,,the ,,dark4 ,c4 ,r41 ,,cxvi41 pp4 #gda to #gdd4 '#ic4--;,a polished aluminum sheet was attached to the terminal of an electroscope properly surrounded by a metal screen4 ,after a few days1 the plate acted like any other metal plate polished or unpolished2 it lost its charge very slowly1 positive or negative alike1 independently of the illumination4 ,if it is then again polished1 as for example1 with emery paper and turpentine1 it loses its charge rapidly in diffused light1 which has passed through a pane of window glass1 for example4 ,therefore1 the ultra-violet rays are not alone effective1 although most effective4 ,the longer the time elapsing1 after polishing1 the slower the discharge takes place4 ,zinc behaved likewise1 only more slowly4 ,other metals were tried4 ,bismuth acted differently from most metals4 ,whether charged positively or negatively1 they exhibited rapid loss in the dark1 in dry air under a metal bell1 independently of the state of the polish4 ---------------------------------------- -------------------------------- ,,chapter ,,ix ------- #ajj4 ,,thomson',s ,,experiments4 ,elect4 ,eng41 ,n4,y41 ,mar4 #aa1 ,apr4 #h and ,apr4 #bb1 '#if4 ,elect4 ,rev41 ,n4,y41 ,apr4 #h1 '#if1 p4 #ahc4 ,,stereoscopic ,,sciagraphs4 ,elect4 ,world1 ,n4,y41 ,mar4 #ad1 '#if4--,prof4 ,elihu ,thomson1 of the ,thomson-,houston ,electric ,company1 described experiments to determine the practicability of making stereoscopic pictures by ,x-rays4 ,a solid object may be considered as composed of points which are at different distances from the eye4 ,by monocular vision1 the solidity of an object is not assured4 ,however1 by the use of both eyes1 the objects appear less flat4 ,the experimenter used1 as the different objects1 a mouse1 also metal wires twisted together1 and1 again1 a block of wood having projecting nails4 ,in order to produce a stereoscopic picture with ,x-rays1 he took a sciagraph in the ordinary way4 ,he then caused the relative displacement of the discharge-tube and the object1 and took another sciagraph4 ,by mounting the two sciagraphs in a stereoscope1 he found that the effect was as expected1 and in the case especially of the skeleton of the mouse1 it was very curious1--less like a shadow picture and more like the real object4 ,the picture was more realistic1 as in the well-known stereoscope for viewing photographs4 ,illustration3 ,,multiple ,,sciagraphs4 ,,fig4 #a1 #aja1 p4 #ie4 ,illustration3 ,,multiple ,,sciagraphs4 ,,fig4 #b1 #aja1 p4 #ie4 #aja4 ,,thomson',s ,,experiment4 ,,manifolding ,,by ,x-,,rays4--,if one desires to take a print of a negative1 for example by means of sun-light1 it is evident that1 on account of the opacity of the photographic paper1 only one sheet would be placed under the negative for receiving a print4 ,however1 the ,x-rays are so penetrating in their power that it is possible for them to produce sciagraphs through several sheets1 and thereby to result in the production of several pictures of the same object with one exposure4 ,without an experiment to prove this1 one might argue that the chemical action of one sheet would absorb all the energy4 ,the experiment of ,prof4 ,thomson shows that this is not so4 ,the elements were arranged as follows3 ,first a discharge tube2 then an object1 namely1 a key escutcheon of iron2 then yellow paper2 then paste board2 then black paper2 then two layers of albumen or sensitized paper2 then two clrit printing papers2 then two platinum printing papers2 then one clrit2 then six layers of sensitive bromide paper2 then four layers of heavy sensitive bromide paper 7heavier72 then three layers of black paper1 and finally1 at the maximum distance from the discharge-tube1 a sensitive glass plate of dry gelatine1 with its face up1 thereby making twenty-five layers in the aggregate4 ,it is interesting to notice that an induction coil was not employed1 but a small ,wimshurst machine1 having connected to each pole a small ,leyden jar4 #ajf4 #a1bjj discharges occurred during exposure4 ,the results were as follows3 ,no sciagraphs developed upon the albumen1 clrit nor platinum1 which1 it should be noticed1 were merely printing papers4 #abh4 ,the impressions on the ten bromide papers were weak4 ,see ,multiple ,sciagraphs1 ,fig4 #b1 p4 #id4 ,he attributed the reason of this to the thinness of the film4 ,although the glass plate was furthest away from the discharge tube1 yet the impression was greater than on any of the papers1 the result being shown in ,multiple ,sciagraphs1 ,fig4 #a1 p4 #id4 ,he suggested that the plates for use with ,x-rays should have unusually thick films4 ,incidentally he found that the intensifying process could be employed with profit to bring out the small details distinctly4 ,dr4 ,lodge also recommended thick films4 ,see ,the ,elect41 ,lon41 ,apr4 #bd1 '#if41 p4 #hfe4 #aja;a4 ,,lumi,,re',s ,,experiment4 ,,enormous ,,transparency ,,of ,,sensitive ,,photographic ,,paper4 ,comptes ,rendus1 ,feb4 #ag1 '#if4 ,translated by ,mr4 ,louis ,m4 ,pignolet4--,with a ten-minutes exposure1 objects were sciagraphed through #bej super-imposed sheets of gelatino-bromide of silver paper1 to observe the absorption of the ,x-rays by the sensitive films4 ,the one hundred and fiftieth sheet was found to have an impression4 #ajb4 ,,proposed ,,double ,,cathode ,,tube4 ,see also ,elect4 ,rev41 ,n4,y41 ,apr4 #ae1 p4 #aia4--,the nature of this will be apparent immediately from the cut which is herewith presented and entitled 8,standard ,x-,ray ,tube40 ,with unidirectional currents the concave electrodes in the opposite ends may each be a permanent cathode1 while the upper terminal connected to the angular sheet of platinum may be the anode4 ,cathode rays1 therefore1 will be sent out from each concave disk1 and striking upon the platinum will be converted into ,x-rays1 assuming that the platinum is the surface upon which the transformation from one kind of ray to another takes place4 #fc1 at end4 ,this is called a standard tube1 because it may be employed with efficiency with any kind of generator4 #h;a1 #bf;a1 #aae1 #aaf and #ade4 ,it is interesting to notice a confirmation of the efficiency of such a tube1 for ,mr4 ,swinton1 in a communication to the ,wurz ,phys4 ,med4 ,so4 7see ,the ,elect41 ,lon41 and ,elect4 ,eng41 ,n4,y41 ,june #c17 showed and described a picture of an exactly similar tube4 ,by an experiment1 the tube operated as expected4 ,first proposed by ,prof4 ,elihu ,thomson1 who is an author also of the following experiment3 ,illustration3 ,,standard ,x-,,ray ,,tube4 #ajc4 ,x-,,rays4 ,,opalescence ,,and ,,diffusion4 ,elect4 ,world1 ,apr4 #be1 '#if4--;,he alluded to opal glass and milk to illustrate that light is reflected not only at the surface of a body1 but from points1 or molecules1 or particles1 located underneath the surface4 ,by some experiments with ,x-rays1 he found that they had a similar property only not to such a large per cent41 but on the other hand by the way of contrast1 there are many more substances opalescent to ,x-rays than there are to light1 for the reason that the former will penetrate more substances and to greater distances4 ,he made many observations with a modified sciascope1 #aje1 by pointing it away from the discharge tube and towards different substances struck by ,x-rays4 ,to all appearances1 such substances became the sources of the ,x-rays4 ,he alluded to ,mr4 ,tesla's experiments on reflection1 #adf1 but noticed that there was a slight difference between reflection and diffusion and he was satisfied that reflection took place from the interior of the substances as well as from the surface4 ,metal plates1 he said1 gave apparently little diffusive effect1 appearing to reflect feebly at angles equal to the incident angles4 ,he alluded to ,edison's experiment also1 #acc1 with a large thick plate cutting off the ,x-rays and attributed the luminosity of his modified sciascope to rays both reflected and diffused from surrounding objects1 which generally as a matter of course1 are more of non-metallic objects than metallic1 such as floor1 ceiling1 walls1 tables1 chairs and so on4 ,evidently1 the interior of one's hand causes diffusion2 very little1 however1 for a sciagraph by means of a focus tube gives wonderfully clear outlines1 and yet the rays do not come from a mathematical point4 #hh4 ,prof4 ,thomson acknowledged that independently of himself1 ,dr4 ,m4 ,i4 ,pupin1 of ,columbia ,college1 had reported in ,science1 ,apr4 #aj1 '#if1 see also ,electricity1 ,apr4 #ae1 '#if1 p4 #bjh1 upon investigations on the same general subject1 namely diffusion1 and also referred to experiments of ,lenard1 #fi1 and ,roentgen on diffusion4 ,agrees also with experiments of ,a4 ,imbert and ,h4 ,bertin-,sans in ,comptes ,rendus1 ,mar4 #b1 '#if4 ,he suggested that this property of diffusion acted as an explanation why sciagraphs can never have absolutely clearly cut shadows of the bones or other objects imbedded in a considerable depth of flesh4 #ajc;a4 ,a4 ,,imbert ,,and ,h4 ,,bertin-,,sans' ,,diffusion ,,and ,,reflection ,,in ,,relation ,,to ,,polish4 ,x-,,rays4 ,comptes ,rendus1 ,mar4 #b1 '#if4 ,translated by ,louis ,m4 ,pignolet4--,they concluded1 under the conditions of their experiments1 that if ,x-rays were capable of reflection it was only in a very small proportion2 on the other hand1 the rays can be diffused en assez grande quantit1 the intensity of the diffusion appearing to depend much more upon the nature of the diffusing body than upon its degree of polish4 ,from this they attributed to the rays a very small wave length1 such that it would be impossible to get in the degree of polish necessary to obtain their regular deflection4 ,perrin attempted unsuccessfully to reflect the rays from a polished steel mirror and a plate of 8flint10 but with exposures of one hour and seven hours respectively1 nothing was obtained4 ,from trans4 by ,l4 ,m4 ,pignolet1 ,comptes ,rendus1 ,jan41 #if4 ,by exposing a metal plate to the rays and suitably inclining it in front of the opening1 ,lafay also proved reflection1 for it was possible to discharge the electrified screen2 hence1 as he called it1 diffused reflection4 ,comptes ,rendus1 ,apr4 #bg1 '#if2 from trans4 by ,l4 ,m4 ,pignolet4 #ajd4 ,,fluorometer4--,he constructed an instrument for comparing the merits of different discharge tubes1 and for indicating the comparative luminosity of different screens subjected to the action of the same discharge tube4 ,the instrument served also to act as an indicator of the diffusing power of different materials4 8,by placing two exactly similar fluorescent screens at opposite ends of a dark tube1 and employing a ,bunsen photometer screen1 movable as usual between the screens1 a comparison of the diffusing power of different materials might be made by subjecting the pieces placed near the ends of the photometer tube outside1 to equal radiation from the ,crookes' tube40 ,from ,prof4 ,thomson's description4 ,the author performed some experiments 7,elect4 ,eng41 ,n4,y41 ,apr4 #ae1 '#if1 p4 #cgi7 in relation to candle-power of ,x-rays by looking into a sciascope and moving it away until the luminosity just disappeared4 ,he then detached the black paper cover from the phosphorescent screen and pointed the sciascope toward a candle flame and receded away until the fluorescence also disappeared4 ,the distances1 with different candles1 would1 of course1 somewhat vary1 but it would in the rough be a constant quantity1 while different discharge tubes would cause the vanishing fluorescence at different distances4 ,now1 assuming that the ,x-rays vary inversely as the square of the distance1 as believed by ,rntgen1 their power to fluoresce could1 therefore1 always be named as so much of a candle-power4 #aje4 ,,simple ,,device ,,for ,,comparing ,,and ,,locating ,,the ,,source ,,and ,,direction ,,of ,x-,,rays4 ,,phosphorescence ,,not ,,essential4--,in the ordinary sciascope1 the fluorescent screen is located at one end1 and the eyehole at the other4 ,he modified this construction by employing a long straight tube1 made of thick metal1 so that ,x-rays could not enter through the wall4 ,about at the centre of the tube was a diaphragm of a fluorescent material4 ,now1 it is evident that if this is directed toward the phosphorescent spot and placed very close to the same1 and the other end be looked into1 the screen will become fluorescent1 if ,x-rays are emitted from the area expected4 ,such a result occurred4 ,with this instrument1 he was able to show1 in a similar way1 that ,x-rays did not come from the anode1 nor from the cathode directly4 ,in one case1 he provided a piece of platinum within the discharge tube1 in such a position as to be struck by the cathode rays4 #ia and #aaf4 ,the instrument showed that ,x-rays radiated from the platinum1 although the latter was not luminous nor phosphorescent1--illustrating again that phosphorescence is not a necessary accompaniment of ,x-rays1 and assisting in upholding the principle that as the phosphorescence diminishes by increase of vacuum and increase of ,e4 ,m4 ,f41 the ,x-rays increase4 ,it should be noticed that ,prof4 ,thomson emphasizes that the tube should be made of thick metal4 #ajf4 ,,rice',s ,,experiment4 ,,apparatus ,,for ,,obtaining ,x-,,rays4 #aji1 #aad1 #aca1 #acg4 ,,tube ,,energized ,,by ,a ,,wimshurst ,,machine4 ,elect4 ,eng41 ,n4,y41 ,apr4 #bb1 p4 #daj4--,roentgen had always employed the induction coil4 ,as to those who first excited the discharge tube by the ,holtz or ,wimshurst machine or generators of like nature1 it is not certain2 but1 according to public records1 they were independently ,prof4 ,m4 ,i4 ,pupin1 of ,columbia ,college1 and ,dr4 ,william ,j4 ,morton1 of ,new ,york4 ,see ,electricity1 ,n4,y41 ,feb4 #ai1 '#if4 ,the accompanying cut marked 8,rice's ,experiment1 ,fig4 #a10 is a diagram representing the several elements of the apparatus1 while 8,rice's ,experiment1 ,fig4 #b10 shows what kind of a sciagraph can be obtained by means of a ,wimshurst machine4 #aja1 at centre4 ,the details of the apparatus as employed by ,mr4 ,e4 ,wilbur ,rice1 ,jr41 ,technical ,director of the ,general ,electric ,co41 were as follows3 ,a ,wimshurst machine1 having a glass plate #af inches diameter1 coupled up with the usual small ,leyden jars1 spark under best conditions of atmosphere1 etc41 #d inches4 8,the usual method of taking pictures with such a machine is to connect the interior coatings of the two jars1 respectively1 to the positive and negative conductors of the machine1 the terminals of the discharge tube being connected between the external coatings of the ,leyden jars4 ,in this condition1 the disruptive discharge of the ,leyden jars passes through the tube and across the balls upon the terminals of the conductors of the machine1 the length of spark being regulated by separating the balls in the usual way40 ,later1 he found that by omitting the ,leyden jars1 the generation of the ,x-rays was practically non-intermittent4 ,he therefore connected the terminals of the discharge tube directly to those of the ,wimshurst machine as indicated in 8,rice's ,experiment1 ,fig4 #a10 which also illustrates the details in the carrying out of the experiment for obtaining the picture1 ,fig4 #b1 of the purse containing the coins and a key4 ,the principal feature was the introduction of a lead diaphragm containing a small central opening #g-h inch diameter opposite the fluorescent spot4 ,sciagraphs taken thus required a little more time1 about #fj minutes1 while without the diaphragm1 the time could be shortened to about #cj minutes1 but the shadows were not so clear in the latter case4 ,the figures are on p4 #ajj4 ,illustration3 ,,rice',s ,,experiment4 ,,fig4 #a1 #ajf1 p4 #ii4 ,diagram4 ,illustration3 ,,rice',s ,,experiment4 ,,fig4 #b1 #ajf1 p4 #ii4 ,taken with the above apparatus4 #ajg4 ,,source ,,of ,x-,,rays ,,tested ,,by ,,propagation ,,through ,a ,,small ,,hole4--,this would illustrate not only that the fluorescent spot is the source of ,x-rays1 but also that a very small portion comes from other parts that are probably bombarded by stray cathode rays 7due to irregular surface of cathode #eg1 or by reflected ,x-rays or cathode rays4 ,he tested the source of the ,x-rays by means of the following arrangement of the apparatus3 ,it will be noticed that the lead diaphragm is quite close to the fluorescent spot4 ,upon holding the sciascope on the opposite side1 and pointing it toward the spot1 the luminous area of the fluorescent screen was about the same as that of the opening in the diaphragm1 but the size grew rapidly upon receding from the diaphragm4 ,if the rays had come from the cathode1 however1 the fluorescent spot on the screen would not have increased in size so rapidly during recession1 and1 therefore1 the rays must have come from the spot on the glass struck by the cathode rays4 #aac1 #aaf1 #aag4 #ajg;a4 ,,leeds' ,,and ,,stokes' ,,experiment4 ,,use ,,of ,,stops ,,in ,,sciagraphy4 ,western ,electrician1 ,mar4 #ad1 '#if4--;,in order to obtain clear definitions of the shadows1 ,messrs4 ,m4 ,e4 ,leeds and ,j4 ,b4 ,stokes provided lead plates with holes1 varying in size from #a_/d inch to an inch between the discharge tube on one side and the object and photographic plate on the other4 ,in this manner they obtained excellent sciagraphs of animals having very fine skeletons4 ,see the picture of the rattlesnake at #ace and of a fish on page #fc4 ,see also the frog taken abroad page #ij4 #ajg;b4 ,,macfarlane1 ,,morton1 ,,klink1 ,,webb ,,and ,,clark',s ,,experiment4 ,x-,,rays ,,from ,,two ,,phosphorescent ,,spots4 ,elect4 ,world1 ,mar4 #ad1 '#if4--;,by means of nails projecting vertically from a board 7similar to the process carried out by ,dr4 ,william ,j4 ,morton1 ,elect4 ,eng41 ,n4,y41 ,mar4 #e1 '#if71 they proved1 undoubtedly1 that the source of the ,x-rays was at the surface of the glass directly opposite the cathode4 ,by modification1 which acted as further proof1 a tube was provided with a cathode at the centre4 ,there was a phosphorescent spot at each end4 ,one board was placed laterally to the tube1 and two shadows of each of certain nails were cast1 which were caused as proved by measurement1 by a double source of ,x-rays4 ,this experiment illustrates the importance of preventing double shadows4 ,the plate should be perpendicular to the line joining the two sources of the ,x-rays when there are two such sources4 ,even with the focus tube ,dr4 ,philip ,m4 ,jones1 of ,san ,francisco1 determined that there were two phosphorescent spots4 ,these should be taken into account in all cases and attempts made to produce but one strong focus upon the platinum4 ,elect4 ,world1 ,n4,y41 ,may #bc1 '#if4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 #a1 #ajh1 p4 #ajd4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 #b1 #ajh1 p4 #ajd4 #ajh4 ,,stine',s ,,experiments4 ,,source ,,of ,x-,,rays ,,determined ,,by ,,sciagraphs ,,of ,,short ,,tubes4 ,elect4 ,world1 ,n4,y41 ,apr4 #aa1 '#if1 pp4 #cib1 #cic4--,prof4 ,stine1 of the ,armour4 ,inst4 of ,tech41 by means of the diagram shown in ,fig4 #a1 p4 #ajb1 clearly proved that the ,x-rays have their source at the area struck by the cathode rays located directly opposite the disk marked 8cathode40 ,if the reader will investigate the diagram and the sciagraphs1 he will obtain a clearer knowledge of the evidence than by any verbal description1 further than to explain how the elements are related to one another4 ,in ,fig4 #a1 therefore1 will be noticed covered photographic plates1 located as indicated with reference to the extreme left-hand end of the discharge tube1 where the cathode rays strike4 ,the surface of ,plate #e is parallel to that of the cathode1 and the phosphorescent spot is in line between the two above named elements4 ,the result is shown in ,fig4 #b1 p4 #ajb1 the objects sciagraphed being several short sections of tubes with diameters varying from #a_/b to #c inches4 ,a1 in ,figs4 #c1 #d1 p4 #ajd and in ,figs4 #e1 #f1 p4 #aab1 identifies the ends lettered ,a in ,fig4 #a4 ,the sciagraph in ,fig4 #c was obtained on the plate shown at the top in ,fig4 #a2 that in ,fig4 #d1 on ,plate #b2 that in ,fig4 #e1 on ,plate #c2 and that in ,fig4 #f1 on ,plate #d4 ,not only were direct shadows visible1 but also secondary shadows1 indicating1 therefore1 that1 although the source of practically all the rays was at the phosphorescent spot1 yet a portion of the rays came slightly from other directions1 either by reflection or by actual production of rays1 upon other portions of the tube4 ,look now especially at ,fig4 #c1 p4 #ajd4 ,if the rays came from the anode1 then would this appearance necessarily be the same as that in ,fig4 #b4 ,similarly1 the other sciagraphs may be considered to show that the rays do not come from the anode4 ,in the case of the sciagraphs in ,figs4 #d1 #e and #f1 only a single tube acted as the body for casting a shadow4 ,prof4 ,stine stated that the experiments were repeated over and over again1 thereby establishing the phenomena as uniform4 #aji4 ,,stine',s ,,electrical ,,apparatus ,,employed4 #ajf1 #aab1 #aad1 #aca1 #acg4--,prof4 ,stine gave the following suggestive points3 8,among the first points investigated was the influence of the interrupter4 ,the coil was provided1 first with the familiar mercury make and break1 and then an ordinary vibrator4 ,the mercurial device gave very good results4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 #c1 #ajh1 p4 #ajd4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 #d1 #ajh1 p4 #ajd4 ,the small interrupter was found the more reliable1 and seemed to shorten the needed time of exposure4 ,a rotary contact-maker1 giving two interruptions of the current per revolution1 was also tested4 ,this was driven by a motor with a condenser capacity of fourteen microfarads connected across the brushes4 ,owing to the large capacity of the condenser1 a heavy current could be broken without marked sparking4 ,the circuit breaker was tested at speeds ranging from #ejj to #d1jjj per minute1 to note the influence on the time of exposure4 ,the best results were obtained at the lower speed4444 ,as no especial advantage could be noted when using the mercury breaker1 it was abandoned for the vibrating interrupter40 ,this point is noted in detail1 since so many experimenters seem to prefer such cumbersome devices1 but they are1 in reality1 unnecessary4 ,illustration3 ,,stine',s ,,experiment1 ,,fig4 ,a4 #aaj4 #aaj4 ,,apparent ,,diffraction ,,of ,x-,,rays ,,really ,,due ,,to ,,penumbral ,,shadows4 ,elec4 ,eng41 ,apr4 #bb1 '#if1 p4 #djh4--;,by referring to the diagram marked 8,stine's ,experiment1 ,fig4 ,a10 the arrangement of the elements may be seen1 while the photographic print is shown in 8,stine's ,experiment1 ,fig4 ,b40 p4 #ajf4 ,prof4 ,stine described the investigation as follows3 ,diffraction is naturally one of the first kinematical points to be investigated in the ,roentgen experiments4 ,it was noticed that when the opaque object was some distance from the plate1 pronounced penumbral shadows resulted4 ,these were of such width as to indicate diffraction4 ,however1 when such shadows are plotted back to the tube they are found to be purely penumbral1 and not caused by diffraction4 ,to completely demonstrate this point the experiment illustrated in ,fig4 ,a was undertaken4 ,here ,a#a to ,a#d are brass plates one inch wide and #a_/h inch thick1 and of the length of the dry plate employed4 ,they were first fastened together1 so as to leave two parallel slots #a_/h of an inch wide4 ,these plates are placed within #c_/h of an inch of the bulb1 were one inch apart1 and rested #a-a_/h inches above the dry plate4 ,the resulting sciagraph is shown in ,fig4 ,b4 ,in the diagram ,s#a ,s#b1 the edges of the penumbral shadow are very sharp and distinct4 ,the direction of the rays is indicated1 showing that there was absolutely no diffraction4 ,this experiment has been modified in a variety of tests1 with always the same result40 #aaj;a4 ,,jean ,,perrin',s ,,non-,,diffraction4 ,comptes ,rendus1 ,jan4 #bg1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4--,the active part of a tube was placed before a very narrow slit2 #e cm4 further1 there was a slit #a mm4 wide2 #aj cm4 further1 there was the photographic plate4 ,an exposure of nine hours gave an image with sharply defined borders1 upon which there was no diffraction fringe4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 ,b4 #aaj4 #aei;a4 ,,non-,,refraction4--,refraction was attempted with prisms of paraffine and of wax1 but no refraction was noticed4 #aaa4 ,,scribner ,,and ,m',,berty',s ,,experiment4 ,,source ,,of ,x-,,rays ,,determined ,,by ,,interception ,,of ,,assumed ,,rectilinear ,,rays ,,from ,,the ,,cathode4 ,elect4 ,eng41 ,n4,y41 ,apr4 #h1 '#if1 p4 #ceh2 ,amer4 ,inst4 ,elec4 ,eng41 ,mar4 #be1 '#if4 ,west4 ,branch4--,refer now solely to ,fig4 #a1 ,s4 and ,m4's experiment4 ,notice the relative arrangement of the elements4 ,first1 the discharge tube with the cathode at the upper part and the phosphorescent spot opposite thereto2 then below a thick lead plate with a single opening2 then a second lead plate with two small openings placed laterally at such a distance that if there were rectilinear rays from the cathode they could not strike 7by passing through the small hole71 the covered photographic plate which was the next element in order4 ,the description did not state that the photographic plate was covered1 but the experimenters must have had the usual opaque cover upon it or else the luminous rays could have produced images4 ,the developed plate showed two spots strongly acted upon and surrounded by portions which were less acted upon1 the same as would be produced by light radiating from a surface as distinguished from a point4 ,from the fact that they stated that the exposures were very long1 it may be concluded also that the plates were covered by a material opaque to ordinary light4 ,measurement showed that the rays which produced the images came from the phosphorescent spot 7 #ajf1 #aji1 #aad1 #aca1 #aci7 and not from the cathode directly by rectilinear propagation4 ,illustration3 ,s4 ,m4',s ,,experiment1 ,,fig4 #a4 #b4 #aab4 ,,source ,,on ,,inner ,,surface ,,of ,,the ,,discharge ,,tube ,,determined ,,by ,,pin-,,hole ,,images4 ,reference may now be made to ,s4 and ,m4's ,experiment1 ,fig4 #b4--,the discharge tube has1 as before1 a cathode on one side1 and the phosphorescent spot during operation on the opposite side4 ,lead plates were provided in positions indicated by the heavy black straight lines1 there being a pin hole in each one4 ,behind these lead plates1 measured from the discharge tube1 were the covered photographic plates1 as indicated4 ,by measurement1 it was afterwards determined that practically all the ,x-rays started from the phosphorescent spot4 ,the electrode was put in an oblique position1 as indicated1 so that the same would not obstruct any ,x-rays trying to pass through the pin hole in the uppermost plate4 ,the experiment served specifically to show that the ,x-rays started from the inner surface of the glass1 because images produced on the upper and lower plates were equally strong4 ,perrin also found that the ,x-rays are developed at the interior sides of the tubes4 7,comptes ,rendus1 ,mar4 #bc1 '#if4 ,from trans4 by ,l4 ,m4 ,p47 ,the rays1 in producing each image1 had to pass through an equal thickness of glass4 ,if the rays had come from the outer surface1 for example1 two thicknesses would have been traversed by the rays striking the upper plate1 and no thickness by those impinging upon the lower plate4 ,that no rays came from any other portion or element of the discharge tube was evident1 because a picture of the phosphorescent spot was the only one produced1 and this picture was inverted1 as usual1 with pin hole cameras4 7,a pin-hole camera is the same as any other1 with the lens replaced by a very small hole1 which acts as a lens47 ,in the way of further evidence1 if not enough already1 ,meslans early determined that the phosphorescent spot on the glass is the source of ,x-rays 7,comptes ,rendus1 ,feb4 #bd1 '#if4 ,from ,trans4 by ,mr4 ,louis ,m4 ,pignolet74 ,,jean ,,perrin',s ,,experiments4 ,,the ,,origin ,,of ,x-,,rays4 ,comptes ,rendus1 ,mar #bc1 '#if4 ,from ,trans4 by ,louis ,m4 ,pignolet4--,he also confirmed that ,x-rays radiate from the phosphorescent spot4 #aab;a4 ,,de ,,heen',s ,,experiment4 ,,the ,,anode ,,believed ,,to ,,be ,,the ,,source ,,of ,x-,,rays4 ,comptes ,rendus1 ,feb4 #ag1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4--,a lead screen1 pierced by several holes1 was placed between the discharge tube and the photographic plate4 ,the shadows of the holes on the plate indicated that the rays emanate from the positive pole of the tube4 ,as both ,thomson 7,e47 and ,rowland1 as well as ,de ,heen1 at first concluded likewise1 is it not probable that the anode was struck by the cathode rays 7see #aac1 #aaf78 ,for it was fully admitted that the anode1 otherwise1 does not emit ,x-rays4 ,illustration #aac4 ,,lodge',s ,,experiment4 ,x-,,rays ,,most ,,powerful ,,when ,,the ,,anode ,,is ,,the ,,part ,,struck ,,by ,,the ,,cathode ,,rays4 ,,pin-,,hole ,,pictures ,,by ,x-,,rays ,,to ,,determine ,,source ,,of ,x-,,rays1 ,,and ,,pin-,,hole ,,images ,,upon ,,glass ,,compared4 ,the ,elect41 ,lon4 ,apr4 #aj1 '#if1 p4 #ghd4--,the object of the experiment was to confirm1 if possible1 by a modified construction1 the source of the ,x-rays1 as being the surface struck by cathode rays1 whether the surface is that of glass or any other substance4 ,he had constructed1 for this purpose1 a discharge tube1 as illustrated in the diagram1 which may be seen1 at a glance1 to contain a concave electrode at one end1 and a flat electrode at the other4 ,between them1 and connected to the concave electrode1 is an inclined sheet of aluminum1 shading both electrodes4 ,the wires leading to the aluminum sheet are well protected by glass4 ,he arranged matters so that either the concave or the flat electrode could be made positive or negative4 ,the operation consisted first in taking through a pin hole1 #a_/d of an inch in diameter1 ,x-ray pictures on photographic plates1 from different points1 at measured distances4 ,after these were taken1 glass plates received the luminous images at the positions of the sensitive plate4 ,pencil drawings were then made1 and compared with the ,x-ray pictures4 ,the experiment involved also the repetition of this operation1 except that the polarity of the terminals was changed4 8,when the small flat disk was cathode1 every part of the complicated anode appeared strongly and quickly on the plate1 especially the tilted and first bombarded portion on a photographic plate placed above the tube4 ,the cathode disk itself did not show at all4 ,on a plate placed below the bulb1 the anode cup appeared strong1 but the tilted disk did not appear4 ,on the other hand1 ''' its focus spot acted as a feeble point source1 by reason of a few rays reflected back on to it from the cup4 8,when the current was reversed1 the small disk anode showed faintly1 being excited by rays which had penetrated the interposed tilted disk1 but again the cathode hardly showed at all1 not even the tilted portion on a plate placed below the bulb4 ,this is confirmed by ,j4 ,perrin4 ,in no case could an image of the cathode be obtained4 7,comptes ,rendus7 ,mar4 #bc1 '#if4 ,from trans4 by ,l4 ,m4 ,p47 ,by giving a very long exposure 7two hours71 some impression was obtained by ,dr4 ,lodge about equal to that from the shaded anode disk2 but1 of course1 if the tilted plate had been under these circumstances an anode1 it is well known that a few minutes would have sufficed to show it strong upon the plate beneath4 8,hence1 undoubtedly1 the ,x-rays do not start from the cathode or from anything attached to the cathode but do start from a surface upon which the cathode rays strike1 whether it be an actual anode or only an #8anti-cathodic' surface4 ,best1 however1 if it be an actual anode4 7,independently discovered by ,rowland1 #aaf4 and ,roentgen1 #ia407 8,when the glass walls1 instead of receiving cathode rays1 are pierced only by the true ,roentgen rays from the disk in the middle1 no evidence is afforded by my photograph that the glass under these circumstances acts as a source4 ,it is well that it does not1 for its only effect would be a blurring one4 #ia4 ,with focus tubes1 the glass phosphoresces under the action of the ,x-rays as anything else would phosphoresce1 but its phosphorescence is not of the least use4 ,it is a sign that a tube is working well1 and that the rays are powerful2 but if by reason of fatigue 7 #eh7 the glass ceases to phosphoresce strongly1 the fact constitutes not the slightest detriment40 ,illustration ,x-,,ray ,,uninfluenced ,,by ,a ,,magnet4 ,,severe ,,test4--,his first experiment on magnetic deflection1 the sciagraph of a magnet with a background of wire gauze1 only showed that if there were any shift by reason of passage of rays between the poles it was very small2 but he definitely asserted1 as in accompanying diagram1 that a further experiment has been made which effectually removes the idea of deflectibility from his mind1 and confirms the statement of ,professor ,roentgen4 #gi4 ,a strong though small electro-magnet1 with concentrated field1 had a photograph of its pole-pieces taken with a couple of wires1 ,a and ,c1 stretched across them on the further side from the plate--nearer the source--and a third wire1 ,b1 also stretched across them1 but on the side close to the plate4 ,these three wires left shadows on the plate1 of which ,b was sharp and definite1 while ,a and ,c were blurred4 ,two sciagraphs were taken by ,mr4 ,robinson1 one with the magnet on1 and one with the magnet reversed4 ,on subsequently superposing the two plates1 with the sharp shadows of ,b coincident1 the very slightest displacement of shadows ,a and ,c could have been observed1 although those shadows were not sharp4 ,but there was absolutely no perceptible displacement1 the fit was perfect4 ,consequently the hypothesis of a stream of electrified particles is definitely disproved as no doubt had already been effectively done in reality by ,professor ,roentgen himself4 ,but it must be noted1 he stated1 that the hypothesis of a simple molecular stream--not an electrified one--remains a possibility4 ,the only question is whether such an unelectrified bombardment would be able to produce the observed effects4 ,it must be remembered1 ,dr4 ,lodge stated1 that ,dr4 ,lenard found among his rays two classes as regards deflectibility--some much deflected1 others less deflected2 and it must be clearly understood that his deflections were observed1 not in the originating discharge tube1 where the fact of deflection is a commonplace1 but outside1 after the rays had been1 as it were1 8filtered0 through an aluminum window4 ,he did not1 indeed1 observe the deflection in air of ordinary density2 it was in moderately rarefied air that he observed it1 #gb;a1 but he showed that the variation of air density did not affect the amount1 but only the clearness of the minimum magnetic deflection4 ,the circumstance that affected the amount of the deflection was a variation in the contents of the originating or high-vacuum tube4 #aad4 ,,lodge',s ,,experiment4 ,,apparatus ,,employed4 ,the ,elect41 ,lon41 ,april #aj1 '#if1 p4 #ghc4--,with his apparatus1 he was able to obtain rays sufficiently powerful to illuminate the usual fluorescent screen after passing through one's skull4 ,it is of interest to note about the details of the electrical apparatus 7 #ajf1 #aji1 #aca1 #acg7 used by those who experimented4 ,the best results were obtained by a make and break of a direct primary current at a point under alcohol1 the primary battery consisting of three storage cells1 and the current of the primary acting on a large secondary coil4 ,leyden jars he considered entirely unnecessary1 and he preferred direct currents to alternating currents for the primary4 ,he did not give the exact dimensions of the primary and secondary coils1 but1 judging from reports of others and the author's own experience1 it is highly preferable to have what is called a very large inductorium1 #ae in4 spark in open air1 or else the ,tesla system 7 #ea1 #acg74 ,there is little satisfaction in trying to perform the experiments with induction coils adapted to give only a #b or #c in4 spark in open air4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 #e1 #ajh1 p4 #ajc4 ,illustration3 ,,stine',s ,,experiment4 ,,fig4 #f1 #ajh1 p4 #ajc4 #aae4 ,,lodge',s ,,experiment4 ,x-,,rays ,,equally ,,strong ,,during ,,fatigue ,,of ,,glass ,,by ,,phosphorescence4 ,the ,elect41 ,lon41 ,apr4 #aj1 '#if4--;,in order to explain in what way the rays were propagated1 he says that it is not as if the glass surface were a wave front from every point of which rays proceed normally1 but that the glass radiates ,x-rays just as a red-hot surface radiates light1 namely1 a cone of rays starts from each point1 and all the rays of each cone start in a different direction4 ,every point of the glass radiates the rays independently of all other points4 ,crookes' ,experiment 7 #eh7 may now be called to mind in reference to the fatiguing of the glass after phosphorescing for a while4 ,lodge tested the fatiguing as to the power to emit ,x-rays1 but found that there was no such property whatever4 ,the glass which became fatigued as to luminous phosphorescence 7 #aje7 was not fatigued as to the power of ,x-rays4 ,he noticed that the phosphorescent spot became less and less bright1 and yet the ,x-rays remained of the same power4 #aaf4 ,,rowland1 ,,carmichael ,,and ,,briggs' ,,experiment4 ,,area ,,struck ,,by ,,cathode ,,rays ,,only ,,an ,,efficient ,,source ,,when ,,positively ,,electrified4 ,electricity1 ,n4,y41 ,apr4 #bb1 '#if1 p4 #bai4--;,experiments carried on at the ,johns ,hopkins ,university led the above named investigators to think at first that the source of the ,x-rays was at the anode4 ,amer4 ,jour4 ,sci41 ,march1 '#if4 ,prof4 ,elihu ,thomson was led to give the same opinion during his first experiments4 ,elect4 ,rev41 ,n4,y41 ,mar4 #be1 '#if4 ,see also #aab;a4 ,many other experiments certify to the allegation that ,x-rays are certainly generated at the phosphorescent spot on the glass4 #gi1 #aje1 #ajg1 #ajh1 #aaa1 #aab1 #aac4 ,from the experiments of ,prof4 ,rowland1 et al41 the confusion is accounted for by the fact that they overlooked the electrical condition of the spot struck by the cathode rays4 ,prof4 ,rowland1 et al41 constructed a tube having a platinum sheet located at the focus of the concave electrode1 and not connected to the anode4 ,although the platinum became red hot1 it emitted no ,x-rays1 but when the platinum was made the anode1 there was profuse radiation of ,x-rays in all directions from that side of the platinum struck by the cathode rays1 and no radiation from the other side4 #ia4 7,see also ,roentgen and ,tesla1 concerning #a_/b platinum and #a_/b aluminum and radiation therefrom47 ,they inferred as a final conclusion in connection with this point1 8,that the necessary condition for the production of ,x-rays is an anode bombardment by the cathode discharge40 #aac4 ,they recognized apparently that it had been conclusively proved that ,x-rays radiated from the phosphorescent spot on the glass4 ,they held that such a spot is 8,the induced anode formed on the glass40 #di1 at end4 ,they did not prove this by an experiment according to the article referred to1 but based it upon 8,the fact that the bombarding cathode rays coming in periodical electrified showers alternately raise and lower the potential of the glass1 thus making it alternately an anode and a cathode4 ,in the case of the platinum1 this could not occur to the same extent40 #aag4 ,,salvioni',s ,,experiment4 ,,transposition ,,of ,,phosphorescent ,,spot4 ,elect4 ,rev41 ,lon41 ,apr4 #bd1 '#if1 p4 #eej2 ,med4 ,sur4 ,acad41 of ,perugia1 ,italy1 ,feb4 #bb1 '#if4 ,personal interview with ,prof4 ,salvioni in ,elect4 ,rev41 ,n4,y41 ,apr4 #h1 '#if1 p4 #aha4--;,in order to change the location of the phosphorescent spot when desired1 without a magnet1 and at the same time to concentrate or intensify the source of ,x-rays1 he placed near the same1 on the outside of the tube1 the hand or a metal mass connected to earth4 ,the spot immediately jumped to the other side of the tube1 #di1 near centre1 and to all appearances was smaller and brighter4 ,elster and ,geitel had performed similar experiments at an earlier date4 7,see ,wied4 ,ann41 ,,lvi41 #ab1 p4 #gcc1 also ,elect4 ,eng41 about ,april1 '#if47 ,they carried on the most minute investigations as to the deflection of the cathode rays by an outside conductor4 ,tesla had also noticed a similar deviation4 ,see ,martin's ,tesla's ,researches4 ,he used alternating currents as described in his system in #ea4 ,elster and ,geitel used the ,tuma ,alternating system4 7,see ,wied4 ,ann41 ,ber4 #ajb1 part #b;,a1 p4 #aceb1 '#id47 ,the source from which ,salvioni's description was taken had no sketch1 therefore the diagram made by ,elster and ,geitel is reproduced4 ,see ,fig4 #a4 ,the cathode was aluminum and was connected to one terminal of the transformer4 ,the anode was connected to earth1 and also was the other terminal4 ,upon bringing the hand or other conductor connected to earth to the phosphorescent spot1 the cathode rays deviated and the spot jumped over to the other side4 #ej4 ,the anode was a ring surrounding the leading-in wires of the cathode1 and the two leading-in wires were surrounded by glass4 ,it may be asked why the cathode rays bent downward in the first place8 ,elster and ,geitel found that they were thrown thus in view of the nearness of some neighboring object connected to earth4 ,to overcome the action of surrounding objects1 the tube was surrounded by a ring as shown in ,fig4 #b4 ,however1 the rays were still sensitive to objects well connected to earth1 and when brought quite close to the tube4 ,illustration3 ,figs4 #a and #b4 #aag;a4 ,,hammer ,,and ,,fleming',s ,,molecular ,,sciagraph1 ,,within ,a ,,vacuum ,,tube4 7,citations below47--,in view of the overwhelming evidence concerning the generation of ,x-rays by the impact of cathode rays1 within a high vacuum upon the glass or material which preferably forms the anode1 it becomes appropriate1 it is thought1 to review the state of this department of science1 in order to arrive a little more closely at the relations which exist between phenomena of low and high vacua4 ,with the former1 in that condition in which striae are formed1 permanent black bands or deposits are produced upon the surface of the glass2 the motion of the particles1 therefore1 appearing to be in planes at right angles to the line joining the anode and cathode4 #dj4 ,that the striae should touch the walls of the tube seems to be necessary for the production of the deposit4 #dd4 ,with a high vacuum1 the direction of the cathode rays may be any that one desires1 it being only necessary to shape the cathode properly1 on the principle that the rays radiate normally from the surface4 ,it is known that the radiation is normal as much from the position of the deposit as from that of the phosphorescent spot4 ,it is certain that they are rectilinear4 #eg and #eh4 ,the phosphorescent spot becomes always1 sooner or later1 when occurring upon the same part of the glass1 the location of a deposit from the cathode 7 #abc71 even when the cathode is aluminum4 #abc4 ,the deposit is not the cause of the fatigue of the glass4 #eh4 ,puluj verified this4 ,a wheel was made to rotate by the radiations from the cathode1 and therefore it is highly probable that the motion of the molecules1 which caused the deposit1 is the force that made the wheel rotate4 #eh;a4 ,why does it not follow that with increase of ,e4 ,m4 ,f4 the particles are thrown with such rapidity that upon striking the proper surface 7 #hj71 ,x-rays are generated1 but that they are not generated when the velocity of the molecules is insufficient4 #fa;b1 p4 #df4 ,attention is now invited to a phenomenon which illustrates that a permanent sciagraph of objects may be impressed upon the inner surface of a vacuum tube1 by the deposit of molecules of one of the electrodes4 ,refer1 therefore1 to the figure on page #cj1 8,hammer and ,fleming's ,molecular ,sciagraph40 ,as will be seen from further explanation and from the picture itself1 the sciagraph a b is made because of the projection1 in rectilinear lines1 of molecules of carbon or metal1 from one of the electrodes1 or at least from one more than the other4 ,one leg of the carbon1 being in the way of the other1 causes a less deposit to be produced upon the glass at the intersection of the plane of the horse-shoe filament and the wall of the vacuum tube4 ,electrodes exist because the filament is of such a high resistance as to produce a difference of potential between the two straight lower portions of the filament4 ,mr4 ,william ,j4 ,hammer possesses a remarkable faculty for observing phenomena often overlooked by others4 ,he first observed a molecular shadow in #ahhj and made records of his observations in the ,edison ,laboratory note book4 ,since that time he has examined over #fjj lamps1 which were made at various periods during thirteen or fourteen years1 by twelve different manufacturers4 7,trans4 ,amer4 ,inst4 ,electrical ,eng41 ,mar4 #ba1 p4 #afa47 ,every one1 more or less1 exhibited the molecular shadow4 ,it is a principle1 therefore1 that if the carbon filament has both legs in the same plane1 a sciagraph of one of them will be produced4 ,as the shadow is on one side of the bulb only1 the molecules fly off from only one electrode1 viz41 the cathode4 ,by means of photography1 the effect is increased because of certain well-known principles4 ,the figure heretofore referred to is taken from a photograph1 but1 of course1 does not represent the sciagraph as well as the original photograph1 in view of the loss of effect by re-production by the half-tone process4 ,for further theoretical considerations1 see the ,institute paper referred to1 where the matter was discussed by ,profs4 ,elihu ,thomson1 ,anthony and others4 ,independently of ,mr4 ,hammer's discovery1 ,prof4 ,j4 ,a4 ,fleming1 professor of electrical engineering in the ,university ,college1 ,london1 ,england1 discovered and studied the matter1 and presented it before the ,phys4 ,soc4 of ,london1 appearing about #ahhe 7from memory74 ,the name 8molecular sciagraph0 is given by the author because it is an accepted explanation that the deposit is due to either molecules or atoms of the electrode1 given off by evaporation 7page #df1 lines #e to #aj71 or electrical repulsion 7 #fa;a1 lines #bb to #be71 or1 as some hold1 by mere volatilization by the intense heat of incandescence1 or one or more combined2 but electrical repulsion certainly has something to do with the rectilinear propagation1 for the molecules are charged according to #d4 ,illustration ---------------------------------------- -------------------------------- ,,chapter ,x ------- #aah4 ,,edison',s ,,experiments4 ,,characteristics ,,of ,,discharge ,,tube1 ,,photographic ,,plates1 ,,electrical ,,apparatus1 ,,fluorescence1 ,,etc4 ,elec4 ,eng41 ,n4,y41 ,feb4 #ai1 '#if2 ,mar4 #ah and #be2 ,apr4 #a1 #h1 #ae and #bi1 '#if4 ,x-,,rays ,,begin ,,before ,,striae ,,end4--,the reader may remember a former section1 #aj1 pointing out that striae were usually obtainable without very high vacua1 and that phosphorescence of the glass occurs only with high vacua4 #ed4 ,in carrying the vacuum up higher and higher1 ,edison observed that feeble ,roentgen rays were detected before the striae ceased4 ,prof4 ,elihu ,thomson independently performed a like experiment and found that the ,roentgen rays could be obtained even when the vacuum was so low as to produce striae4 7,elec4 ,eng41 ,n4,y41 ,apr4 #ae1 '#if47 ,victor ,chabaud and ,d4 ,hurmuzescu also obtained ,x-rays from a vacuum 4#jbe mm41 being lower than ,crookes employed1 which was at a maximum 4#jja mm4 7,l',industrie ,elect41 ,paris1 ,may #be1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet47 #aai4 ,,reason ,,why ,,thin ,,walls ,,are ,,better ,,than ,,thick4 ,x-,,rays ,,and ,,post-,,phosphorescence4--,this may be understood by explanation of the discharge tube in ,fig4 #a4 ,in one experiment1 the portion struck by the cathode rays1 namely ,b1 was made #a_/h inch thick4 ,it became soon hot and very luminous and melted1 #fa1 but the ,x-rays were weak4 ,when blown thin1 7 #hc7 however1 the glass remained cool and the ,x-rays were much stronger4 ,what is known on the market as ,german glass 7phosphoresces green1 #ee1 at centre7 was found more permeable than lead glass1 the thickness of the walls being the same in both cases4 ,there were no lingering ,x-rays from after-phosphorescence1 7 #ed1 at end7 or1 if any1 could not be detected by the sciascope4 ,the photographic test would be objectionable because of the brief duration4 ,prof4 ,battelli and ,dr4 ,garbasso1 of ,pisa1 made a very sensitive test in this connection1 proving by the discharge of an electrified body 7 #ij and #ij;a7 that feeble ,x-rays were emitted after the current was cut off from the discharge tube4 7,from trans4 by ,mr4 ,pignolet47 ,illustration3 ,,discharge ,,tube1 ,,fig4 #a4 #aai4 ,,discharge ,,tube1 ,,fig4 #c4 #abj4 #abj4 ,,to ,,prevent ,,puncture ,,of ,,the ,,discharge ,,tube ,,by ,,sparks4--,in the illustration1 ,discharge ,tube ,fig4 #b4 shows a suitable type4 ,it is drawn to scale1 showing the correct proportion of the length to the diameter4 ,the shaded ends represent tinfoil on the outside and connecting with the leading-in wires1 the same preventing puncture of the glass by the spark4 ,they may be caused to adhere by shellac or similar glue4 ,in place of the metallic coating detached supplementary electrodes may be employed1 as seen in the illustration marked 8,discharge ,tube ,fig4 #c40 ,the power of the ,x-rays was increased1 being due1 it was thought1 to the fact that the construction embodied the combination of internal and external electrodes4 #aba4 #aba4 ,,variation ,,of ,,vacuum ,,by ,,discharge ,,and ,,by ,,rest4--,prof4 ,pupin was among the first to test the efficiency of external electrodes for generating ,x-rays4 ,independently of the quality of the glass and of the kind of pump and of the presence or absence of phosphoric anhydride1 the following peculiarities were noticed1 which ,edison attributed to a kind of atomic electrolysis4 #dg4 #hj per cent4 of the lamps exhibited the phenomena as follows3 ,first1 such a high vacuum was obtained by the pump that the line spectrum disappeared and pure fluorescence and generation of ,x-rays at a maximum occurred4 ,the lamp was then sealed off4 ,after three or four hours of rest1 the vacuum deteriorated1 so that striae and other characteristics of low vacuum were obtained when connected up in circuit1 but upon continuing the current1 the high vacuum gradually came back1 the line spectrum vanished1 and suddenly ,x-rays were generated4 ,again the bulb was left at rest for #bd hours1 after which ,x-rays could not be generated until the discharge had been continued for #d-a_/b hours4 ,illustration3 ,,discharge ,,tube1 ,,fig4 #b4 #abj4 #abb4 ,,external ,,electrodes ,,discharge ,,through ,,higher ,,vacuum ,,than ,,internal4--,a vacuum that was so high that no discharge took place with internal electrodes was made luminous by the use of electrodes on the outside of the glass bulb4 ,then he made the vacuum so high that even with a #ab-;inch spark from ,leyden jars1 no discharge took place with external electrodes1 and the tube was dark1 this part of the experiment indicating another limit at which an extremely high vacuum is not a conductor and appearing to overthrow1 as ,edison intimated1 ,edlund's theory that a vacuum is a perfect conductor4 #be4 #abc4 ,,deposit ,,on ,,glass ,,from ,,aluminum ,,electrode4--,it has always been common to employ aluminum for electrodes in vacuum tubes1 on the ground that no deposit took place1 and therefore no blackening1 nor whitening of the glass wall4 #dj4 ,edison observed also that no blackening was visible1 but stated that his glass blower1 ,mr4 ,dally1 upon breaking the bulb and submitting the interior surface of the glass to an oxydizing process1 the oxide of aluminum was so thick as to be opaque to light4 ,with magnesium1 also1 a mirror was produced1 of a lavender color1 by transmitted light4 ,in the case of aluminum1 he was able to obtain a visible spot at the phosphorescent portion1 but only after a great many hours of use4 ,see cut from a photograph of a discharge tube used for several months by ,prof4 ,dayton ,c4 ,miller1 and having a heavy aluminum deposit opposite the aluminum cathode4 ,with the increase of the deposit1 the power of the ,x-rays diminished1 but1 he thought1 not on account of the absorption1 but because1 8through lack of elasticity at the surface40 ,illustration3 ,,discharge ,,tube1 #abc4 #abd4 ,,fluorescent ,,lamp4 ,in an ,english patent of '#hb1 granted to ,rankin ,kennedy1 there is described a vacuum bulb in which the electrodes are covered with fluorescent or phosphorescent substances1 intended for the purpose of obtaining greater candle power by impact of cathode rays upon anode of platinum1 covered with alumina or magnesia4 ,edison coated the inner wall of the discharge tube1 for generating ,x-rays1 with calcic tungstate in the crystalline form4 ,the luminosity1 when measured1 amounted to about #b-a_/b ,c4 ,p4 ,as to the efficiency1 he stated that this was accomplished 8with an extremely small amount of energy40 ,such a coating was found to weaken the ,x-rays radiated therefrom1 which1 of course1 was natural1 because they had been converted into phosphorescent light4 ,the spectrum showed strongly at the red line1 thereby suggesting the reason why the light was of a pleasant character4 #abd;a4 ,,piltchikoff',s ,,experiment4 ,greater emission of ,x-rays by a tube containing an easily fluorescent substance4 ,comptes ,rendus1 ,feb41 #bd1 '#if4 ,from trans4 by ,mr4 ,louis ,m4 ,pignolet4 ,as the ,x-rays emanate from the fluorescent spots on the glass of the discharge tube1 he reasoned that more powerful effects would be obtained by replacing the glass by a more fluorescent material4 ,he therefore tried a ,puluj tube and found that it shortened the time necessary for taking a photograph in a 8singular0 degree4 ,experiments of others have certainly shown that as phosphorescence decreases with increase of vacuum1 the ,x-rays increase to a certain maximum1 #aje4 ,let it be noticed however1 that this does not prove that with the same vacuum1 an increase of phosphorescence by a superior phosphorescent material of equal thickness would not increase the power of the ,x-rays4 ,the best way to determine such points1 is to go to extremes4 ,edison applied so much easily phosphorescent material 7calcic tungstate7 to the inside of the discharge tube1 that much light was radiated1 but only feeble ,x-rays4 ,on the other hand1 without any of the tungstate1 the rays were strong1 #abd4 ,experiments generally tend to prove that it depends upon the chemical nature of the material rather than its phosphorescing power1 in other words upon the permeability4 #aai1 near end4 #abe4 ,,electrodes ,,of ,,silicon ,,carbide4 7,carborundum47 ,edison called attention to ,tesla's discovery that this substance is a good conductor for high tension currents4 ,its advantages for electrodes in the discharge tube are its high conductivity1 no absorbed nor released gas bubbles1 and its infusibility and non-blackening power of glass even when the voltage was increased to a point where the glass melted4 ,illustration3 ,,edison 7,,at ,,right7 ,,and ,t4 ,,commerford ,,martin ,,using ,,the ,,sciascope4 #ig1 p4 #hd4 ,cut also shows ,sprengel vacuum-pump4 ,discharge-tube is in the box4 #abf4 ,,chemical ,,decomposition ,,of ,,the ,,glass ,,bulb4 ,during the generation of the ,x-rays the sodium line of the spectrum appeared in the spectroscope1 thereby indicating decomposition of the glass4 ,with combustion tubes the glass gave the weakest soda line1 while lime soda glass gave the strongest1 and was most permeable to the ,x-rays4 8,the continuous decomposition of the glass makes it almost impossible to maintain a vacuum except when connected to the pump and even then the effect of the current is greater in producing gas than the capacity of the pump to exhaust1 but the ray is very powerful40 ,it is supposed that for this reason1 as well as for others easily apparent that ,edison as well as other experimenters have always carried on their investigations with the discharge tube permanently connected to the pump4 ,the next best thing is to let the tube contain a stick of caustic potash for maintaining an exceedingly high vacuum4 ,by gradually heating this1 the desired degree of vacuum can be obtained4 #ed4 #abg4 ,,sciagraphs4 ,,duration ,,of ,,exposure ,,dependent ,,upon ,,distances4 ,with the given discharge tube1 he obtained sciagraphs at a distance of #c_/h inch from the phosphorescent spot in one second1 a vulcanized cover being between2 at two ft4 distant the time was #aej sec42 at three ft41 #dej sec42 the opaque plate being interposed each time4 ,consequently 8,roughly1 the duration of exposure may be reckoned as proportional to the square of the distance40 #abh4 ,,difference ,,between ,x-,,rays ,,and ,,light ,,illustrated ,,by ,,different ,,photographic ,,plates4 ,,time ,,of ,,exposure4 ,the rapid plate for light gave not the deepest images by ,x-rays4 ,several different kinds of small sensitive plates were laid side by side4 ,a sciagraph of a metal bar was taken upon them all simultaneously4 ,in this way1 he obtained the result1 whereby it would appear preferable to employ the mean rapid plate for the purpose of obtaining sciagraphs4 ,on account of the opacity of platinum1 it occured to ,e4 ,b4 ,frost1 7,sci41 ,n4,y41 ,mar4 #bg1 '#if17 to try platinum photographic paper of the kind used for portraits1 but such paper 7intended for long exposures in printing in sunlight7 was far too lacking in sensitiveness to produce any effect4 #abh;a4 ,,georges ,,meslins ,,insured ,a ,,reduction ,,of ,,time ,,for ,,taking ,,sciagraphs ,,by ,,the ,,deflection ,,of ,,the ,,cathode ,,rays ,,by ,,means ,,of ,a ,,magnetic ,,field4 ,comptes ,rendus1 ,march #bc and #cj1 #ahif4 ,from trans4 by ,louis ,m4 ,pignolet4 ,the method consists in using a permanent or electro-magnet to create a magnetic field perpendicular to the cathode rays in the tube4 ,by this means1 the active fluorescent spot on the tube is condensed1 and the intensity of the ,x-rays generated there is increased4 ,another advantage is that1 when the active part of the tube becomes inactive owing to the formation of a light brown deposit upon it1 another part can be used by very slightly altering the position of the magnets4 ,thus1 each time a new part of the tube can be used4 ,the magnetic field must not be uniform but must have a suitable variation to produce the desired concentration of the cathode rays4 ,a4 ,,imbert ,,and ,h4 ,,bertin-,,sans' ,,experiment4 7,comptes ,rendus1 ,march #bc1 '#if4 7,from trans4 by ,l4 ,m4 ,p47 ,they shortened the time by use of a magnet4 ,,james ,,chappin',s ,,experiment4 7,comptes ,rendus1 ,mar4 #cj1'if4 7,from trans4 by ,l4 ,m4 ,p47--,claimed priority in having shown publicly1 on ,feb4 #ai1 a sciagraph of a hand1 marked 8,photograph obtained by concentration of the cathode rays1 by means of a magnetic field40 ,the increase of the intensity of the ,x-rays obtained by this means was in the proportion of #h to #e1 as measured by the time of fall of the leaves of a ,hurmuzescu electroscope4 ,prof4 ,trowbridge1 of ,harvard ,university1 in a lecture1 gave an interesting review 7,western ,elect41 ,feb4 #bi1 '#if7 of the length of time required in the early days of photography4 ,improvements are being made whereby the duration required in sciagraphy becomes less and less4 ,in #ahbg1 by heliography1 #f hours' exposure was necessary2 in #ahci1 by daguerreotype1 #cj minutes2 in #ahda1 by calotype1 #c minutes2 in #ahea1 by collodion1 #aj seconds2 in #ahfd1 by collodion1 #e seconds2 in #ahgh1 by gelatine1 #a second4 ,the author remembers the photographs for use in the ,edison kinetoscope were taken at the rate of #bj per second4 ,the focus tube brings the time of exposure in behalf of ,x-rays down to a matter of seconds instead of minutes4 ,for an admirable review of authorities1 facts and theories relating to the causes of the darkening of photographic plates by light1 see ,cottier1 in ,elect4 ,world1 ,n4,y41 ,may #bc1 '#if4 #abi4 ,,size ,,of ,,discharge ,,tube ,,to ,,employ ,,for ,,given ,,apparatus4--,a small tube required but a small ,e4 ,m4 ,f41 and therefore should be employed with a small induction coil4 ,the greater the distance of the sensitive plate and the object1 considered together1 from the discharge tube1 the sharper the shadow4 ,in short exposures1 the tube should be small and at a short distance4 #acj4 ,,preventing ,,puncture ,,at ,,the ,,phosphorescent ,,spot4--,in experiments where he employed a flat cathode1 a very thin pencil of rays of increased power came from the exact centre1 and in two or three seconds made the glass red hot at the centre of the phosphorescent spot4 ,immediately1 the atmospheric pressure perforated the bulb4 ,this occurred several times4 ,he stated that 8the best remedy is to permit the central ray to strike the glass at a low angle2 this greatly increases the area and prevents the trouble40 ,,edison4 ,mr4 ,ludwig ,gutmann furnished a translation of a note by ,prof4 ,walter ,knig1 found in ,eleck4 ,zeit4 of ,may #ad1 '#if1 relating to this same subject matter4 ,recognizing that the sharpness of the outlines is the most important requirement in connection with sciagraphy1 and that if the rays start from a large surface the impressed shadows will be uncertain in configuration1 and noticing1 as ,edison and ,tesla did1 #acj1 the frequent destruction of the tube at the place where the rays were concentrated to a focus1 he placed over the inner surface of the glass1 aluminum foil for distributing the heat over a larger area1 at the same time causing radiation of ,x-rays from a single point4 ,the focus tube outweighs this in importance4 #ia4 #aca4 ,,electrical ,,dimensions ,,of ,,apparatus4 ,the best kind of instruction for the student in reference to equipping a plant is to follow the construction employed by those who have been successful4 #ajf1 #aji1 #aad1 #acg4 ,edison used the usual incandescent-lamp current1 voltage at #aaj to #abj volts1 current being continuous1 but not connected directly to the induction coil1 there being a bank of eight to twenty #af candle power incandescent lamps arranged in parallel4 ,the interrupter for the primary consisted of a rotating wheel in appearance like a commutator of a dynamo1 and was rotated rapidly by a small electric motor1 making about #djj interruptions per second1 and so constructed that the circuit was closed twice as long as it was open4 ,a sudden interruption was caused by an air blast playing at the point of make and break1 the use of which made that of a condenser needless4 #c4 ,the discharge tube terminals were connected respectively and directly to those of the secondary4 ,prof4 ,pupin1 ,columbia ,univ4 ,n4,y4 7,lect4 ,n4,y41 ,acad4 ,sci41 ,april #f1 '#if1 and ,science1 ,n4,y41 ,april #aj1 '#if7 gave valuable and practical instruction concerning the apparatus1 which the author witnessed4 8,a powerful coil was found indispensable for strong effects and satisfactory work4 ,the vibrating interrupter is too slow and otherwise unsatisfactory1 and it was replaced by a rotary interrupter1 consisting of a brass pulley1 #f inches in diameter and #a-a_/d inches in thickness4 ,a slab of slate #c_/d inch thick was inserted and the circumference was kept carefully polished4 ,this pulley was mounted on the shaft of a ,crocker-,wheeler #a_/h ,h4 ,p4 motor giving #cj revolutions1 and1 therefore1 #fj breaks per second4 ,two adjustable ,marshall condensers of three microfarads each were connected in shunt with the break1 and the capacity adjusted carefully until the break-spark was a minimum and gave a sharp cracking sound4 ,too much capacity will not necessarily increase the sparking1 but it will diminish the inductive effect which is noticed immediately in the diminished intensity of the discharge4 ,a powerful coil with a smoothly working rotary interrupter will be found a most satisfactory apparatus in experiments with ,rntgen radiance40 #ajf1 #aji1 #aad1 #aca1 #acg4 #acb4 ,,salts ,,fluorescence ,,by ,x-,,rays4 ,see also1 ,elect4 ,rev41 ,n4,y41 ,april #ai1 '#if1 p4 #afe4 ,edison examined over #ahjj chemicals to detect and compare their fluorescent powers if any1 under the action of ,x-rays first transmitted through some opaque material such as thick cardboard4 ,of all these1 calcic tungstate by measurement1 fluoresced with six times the luminosity of barium platino cyanide1 which was referred to in connection with ,roentgen's experiment4 ,other authorities agree as to its great sensitiveness4 ,in making this comparison1 it was assumed that the power of the ,x-rays varied inversely as the square of the distance from the discharge tube4 ,between the two above chemicals came strontic tungstate4 ,baric and plumbic tungstate scarcely fluoresced4 ,salicylate of ammonium crystals equalled the double cyanide of platinum and barium1 and differed therefrom in that the fluorescence increased with the thickness of the layer of crystals up to #a_/d of an inch1 showing great fluorescing power and low absorptivity4 ,this experiment showed that the best fluorescent materials were not necessarily the salts of the heaviest metals1 like platinum4 ,it is assumed that the reader knows the difference between phosphorescence and fluorescence1 but the dividing line is so difficult in some cases and the one not being distinguished from the other by experimenters1 that the author has used the same words as the experimenters1 although he admits that fluorescence is often meant where phosphorescence is stated1 and vice versa4 ,an anomaly presented itself as to rock salt1 which although transparent to light yet powerfully absorbed ,x-rays and was strongly fluoresced thereby4 ,again1 fluorite which is transparent to light1 fluoresced strongly with the ,x-rays1 and under their action became brighter and brighter and continued after cutting off the ,x-rays1 the material therefore1 being highly phosphorescent1 the light enduring for several minutes4 ,upon watching the phosphorescence of fluorite1 the same penetrated the plate very slowly to the depth of one-sixteenth of an inch1 but beyond that depth there was complete darkness4 ,the only other truly phosphorescent substance noticed was calcic tungstate1 especially in thick layers1 so that the shadow of the bones of the hand remained thereon for a minute or two upon cutting out the discharge tube from the circuit4 ,some chemicals1 within a dark box and very close to the discharge tube1 phosphoresced by giving spots here and there1 but they did not phosphoresce at a greater distance1 and the light was probably not due to the ,x-rays4 ,edison attributed the result directly to the 8electrical discharge40 ,the list is as follows3 ammonium sulphur cyanide1 calcic formate1 and nitrate1 ferric citrate1 argentic nitrate1 calcic and iron citrate1 soda1 lime1 8zinc1 cyanide0 7perhaps this means cyanide of zinc71 zinc hypermanganate1 and zinc valeriate4 ,the salts of the following metals did not fluoresce under the influence of the ,x-rays4 ,aluminum1 antimony1 arsenic1 boron1 beryllium1 bismuth1 barium1 chromium1 cobalt1 copper1 gold1 iridium1 magnesium1 manganese1 nickel1 tin1 and titanium4 ,illustration3 ,,roentgen ,,rays ,,at ,,the ,,university ,,of ,,minnesota4 #a4 ,watch and chain4 #b4 ,college badges in mahogany box4 #c4 ,copper coin4 #d4 ,weights in heavy velvet-lined mahogany box2 blank space contains aluminum4 #e4 ,coins in inner pocket of heavy seal purse4 #f and #g4 ,colored glass4 #h4 ,key #i4 ,lead-pencil4 ,west4 ,elect41 ,mar4 '#if4 ,edison stated that the following substances were among those which fluoresced more or less under the action of the ,x-rays4 ,mercurous chloride1 mercury diphenyl1 cadmic iodide1 calcic sulphide1 potassic bromide1 plumbic tetrametaphosphate1 potassic iodide1 plumbic bromide1 plumbic sulphate1 fluorite1 powdered lead glass1 pectolite1 sodic cressotinate1 ammonic salicylate1 and salicylic acid4 ,compared with the above1 the following fluoresced less4 ,powdered ,german glass1 baric1 calcic and sodic fluorides1 sodic1 mercuric1 cadmic1 argentic and plumbic chlorides1 plumbic iodide1 sodic bromide1 cadmic and 8cadmium1 lithia bromide1 mercury1 cadmium sulphate10 uranic sulphate1 phosphate1 nitrate1 and acetate1 molybdic acid1 dry potassic silicate1 sodic bromide1 wulfenite1 orthoclase1 andalucite1 herdinite1 pyromorphite1 apatite1 calcite1 danburnite1 calcic carbonate1 strontic acetate1 sodic tartrate1 baric sulphobenzoic1 calcic iodide1 and natural and artificial ammonium benzoic4 ,not one of all the #ahjj crystals and precipitates fluoresced through a thick cardboard under the influence of the arc light1 #af inch spark in air1 a vacuum tube so highly exhausted that a #aj inch spark left it dark1 nor the direct rays of the sun at noon time4 ,as calcic tungstate was phosphorescent by friction1 he theorized that the ,x-ray is a wave due to concussion4 ,flame sensitive to ,x-rays4 ,edison stated that his assistants submitted the sensitive flame and the phonographic listening tube to the action of the ,x-rays1 and found that they were responsive thereto4 #acc4 ,x-,,rays ,,apparently ,,passed ,,around ,a ,,corner4 ,referring to the figure 8,x-ray ,diffusion ,fig4 #a01 p4 #abi1 it will be noticed that there were three principal elements4 ,first a discharge tube1 then a thick steel plate and then a sciascope1 all arranged in the proportion indicated in the figure1 where the sciascope was within six inches of the edge of the plate1 8well within the shadow0 thereof4 #fi4 ,fluorescence was seen under these conditions4 ,when the sciascope was directly behind the middle of the plate and opposite the discharge tube1 there was no fluorescence1 showing that the plate was thick enough to cut off all the rays and therefore the energy must have traveled in two directions for some reason or other4 ,prof4 ,elihu ,thomson remarked concerning this experiment that he considered1 in view of some experiments of his own1 on diffusion and opalescence 7 #ajc71 that the sciascope was luminous in view of reflection 7 #adf7 of the ,x-rays from various objects in the room1 as from the walls and floor of the room1 tables1 metal objects1 electrical apparatus and so on4 ,theory admits the property of diffraction1 which would cause the rays to turn around the edge of the plate1 according to the principles of diffraction of light1 provided the ,x-rays were due to transverse or longitudinal or any vibrations4 ,see ,elect4 ,eng41 ,n4,y41 ,april #ae1 p4 #cgh4 ,while ,edison generally devotes his energy to actual experiments and dealings with facts and principles1 rather than with theories1 yet1 in this instance1 he merely suggested that the fluorescence under the conditions named might indicate that the propagation of ,x-rays was similar to that of sound in air1 the wave being of exceedingly short length4 ,he referred to ,le ,conte's experiment of '#hb 7see ,phil4 ,mag41 ,feb4 '#hb71 where an experiment of a somewhat similar nature was performed in connection with the propagation of sound4 ,illustration3 ,x-,,ray ,,diffusion1 ,,fig4 #a1 #acc4 ,prof4 ,william ,a4 ,anthony 7see ,elect4 ,eng41 ,apr4 #c1 '#if1 p4 #cgh7 held that the ,le ,conte experiment did not warrant ,edison's conclusion1 for the experiment of ,le ,conte showed comparatively sharp sound shadows2 for even at a distance of twelve feet there was no apparent penetration within the geometrical boundary4 ,he referred to ,stine's1 #aaj4 ,scribner and ,m',berty's1 #aaa1 as upholding rectilinear propagation4 ,while he did not explain what the ,edison result was due to1 yet he argued that the cause was other than that ascribed by ,edison4 ,in this connection1 the author performed an experiment 7,elect4 ,eng41 ,apr4 #bb1 '#if1 p4 #dji7 to substantiate that ,x-rays were propagated through such a high vacuum that it was necessary to have electrodes within #a_/h of an inch of each other1 in order to obtain a discharge with a coil that gave #ae in4 spark in open air4 ,the experiment consisted in casting the shadow of an uncharged tube upon the screen of a sciascope4 ,the shadows of the wire forming the electrodes within the vacuum were produced very sharply1 while the glass tube was faintly outlined4 ,inasmuch as the shadows of objects within the vacuum tube were obtained1 therefore the ,x-rays must have passed through the evacuated space4 ,sound and ,x-rays are therefore dissimilar4 ,the shadows were as sharp and as dark as those made by similar wires in open air4 ,in this connection1 see also ,lenard's experiment1 #gb1 showing that external cathode rays were also transmitted by a vacuum in a 8dead0 tube4 ,roentgen's experiment showed that ,x-rays from a mass located entirely within the vacuum in the discharge tube radiated ,x-rays into the outside atmosphere4 #ia4 ,this experiment would hardly prove1 however1 that ,x-rays1 after having been liberated in open air1 would pass through a second vacuum space1 because there may have been some ,x-rays1 generated at the surface of the glass in ,roentgen's experiment1 struck by those rays which radiated from the mass at the centre of the vacuum space4 ,did not ,lenard and ,roentgen experiment with the same radiant energy8 ,the author answers1 yes4 #gg4 #acd4 ,,permeability ,,of ,,different ,,substances4 ,lenard #fh4 determined the permeability of several substances to cathode rays4 ,roentgen also the same in regard to ,x-rays4 #hb and #hc4 ,others have made comparisons4 ,from the sciagraph made by ,edison1 the following classification is made1 each sheet of material being about #a_/cb inch thick4 ,the most opaque were coin silver1 antimony1 lead1 platinum1 bismuth1 copper1 brass1 and iron1 which were about the same as one another4 ,slate1 ivory1 glacial phosphoric acid shellacked1 and gutta percha1 were about the same as one another and less than the above4 ,aluminum1 tin1 celluloid1 hard rubber1 soft rubber1 vulcanized fibre1 paper1 shellac1 gelatine1 phonographic cylinder composition1 asphalt1 stearic acid1 rosin1 and albumen1 were about the same as one another and less than the above group1 as to permeability4 ,the accompanying picture1 p4 #f1 marked ,terry's ,sciagraph1 ,fig4 #a1 is a sciagraph of pieces of different materials named as in the following list1 taken by ,prof4 ,n4 ,m4 ,terry of the ,u4,s4,n4,a41 see also p4 #abg4 8#a1 rock salt1 #j4f inch thick2 #b1 cork1 #j4d inch thick2 #c1 quartz1 #j4de inch thick1 cut parallel to optic axis2 #d1 verre trempe1 #j4d inch thick2 #e1 glass1 #j4g inch thick2 #f1 chalk2 #g1 ,iceland spar2 #h1 mica1 very thin2 #i1 quartz1 over a square piece of glass2 #aj1 aluminum foil1 a four thicknesses1 b two thicknesses1 c one thickness2 #aa1 platinum foil2 #ab1 tourmaline2 #ac1 aragonite2 #ad1 paraffine1 #j4d inch thick4 #ae1 tin foil1 a one thickness1 b two thicknesses1 c three thicknesses2 #af1 rubber insulated wire2 #ag1 electric light carbon2 #ah1 glass1 #j4cb inch thick2 #ai1 alum41 #a4d inch thick2 #bj1 tourmaline2 #ba1 gas coal2 #bb1 bee's wax2 #bc1 pocket-book1 #aj thicknesses of leather2 #bd coin in pocket-book2 #be1 key in pocket-book2 #bf1 machine oil in ebonite cup2 #bg1 ebonite1 #j4be inch thick2 other samples have given very faint shadows like wood and leather2 this was polished2 #bh1 wood1 #j4b inch thick2 #bi1 steel key40 ,elect4 ,eng41 ,n4,y4 #acd;a4 ,,hodges' ,,experiment4 ,,illustration ,,of ,,penetrating ,,power ,,of ,,light4 ,elec4 ,eng41 ,n4,y41 ,march #d1 '#if4 ,attention has been invited in the scientific press to the penetrating power of heat rays and of light rays of low refrangibility4 ,in conjunction with this1 let it be remembered that the photographic plate has the property of being impressed practically1 only by rays having a higher refrangibility than red4 ,it would be natural1 therefore1 to conclude that if the spectrum could be turned around1 the photographic impression might be produced through opaque bodies4 ,this perhaps1 was the kind of reasoning which prompted ,mr4 ,n4 ,d4 ,c4 ,hodges1 formerly editor of ,science1 to perform an experiment1 the gist of which consisted in attesting the permeability of rays of light which had been passed through fuchsine4 ,christiansen1 ,soret and ,kundt performed experiments with an alcoholic solution of this material and found that the order of the colors in the spectrum was somewhat reversed1 namely1 violet was the least refracted1 then red1 and then yellow1 which was the most refracted4 ,mr4 ,hodges used a pocket kodak1 carrying a strip for twelve exposures4 ,this camera was placed in a closely fitting pasteboard box4 ,thus protected1 some portions of the film were exposed to sunlight1 so far as it could penetrate the end of the pasteboard box1 while other exposures were made with a prism1 on the end of the box1 containing an alcoholic solution of fuchsine4 ,the portions of film exposed to the anomalous rays produced by the fuchsine solution were fogged1 while the control experiments with ordinary light showed none4 ,the anomalous rays must have penetrated the pasteboard1 and probably the wood and leather of which the camera was made4 #ace4 ,,penetrating ,,power ,,of ,x-,,rays ,,increased ,,by ,,reduction ,,of ,,temperature4 #bc and #gb;b at end4 ,among the hundreds of ideas that occured to ,edison in connection with ,roentgen ray tests was that concerning what might happen by cooling the discharge tube to a very low temperature4 ,as before1 he maintained the tube in connection with the air pump so as to be able to vary the vacuum4 ,the reduction of temperature was obtained by means of ice water4 ,of course the bulb could not be placed in the water itself on account of trouble which would occur from electrolysis1 therefore1 the discharge tube was immersed in a vessel of oil1 #ac1 which in turn was surrounded by a freezing mixture4 ,the vessel was a stout battery jar #ad inches high1 eight inches in diameter with glass walls #e_/aj of an inch thick4 ,the oil employed was paraffine4 ,the refrigerating jar was #ab inches high and #ab inches in diameter and the glass wall thereof1 #c_/h inch thick4 ,he tested the difference in the power of the rays by first noticing the thickness of steel that was not penetrated by the rays generated from the tube while in air4 ,crucible steel #a_/af of an inch thick did not transmit rays sufficiently to illuminate the sciascope1 and yet with the use of oil and reduction of temperature1 and after the rays had passed through two thicknesses of glass as well as through the oil and ice water1 the sciascope was made luminous by rays after passing through a plate of steel of double the thickness1 i4e4 #a_/h in4 thick4 ,see in this connection1 ,tesla's experiment1 #ace1 where powerful rays were obtained by immersing the discharge tube in oil4 ,accounts of these two experiments were published simultaneously4 ,tesla attributed the idea of this use of oil to ,prof4 ,trowbridge of ,harvard ,university1 who showed that a discharge tube immersed in oil is adapted to the generation of ,x-rays of increased penetrating power4 ,see cut at p4 #ace4 ,illustration3 ,,sciagraph ,,of ,,rattlesnake ,,by ,,use ,,of ,,stops4 #ajg41 p4 #aja4 ,by ,leeds and ,stokes4 ,,non-,,reflection ,,of ,x-,,rays4 7,elect4 ,eng41 ,feb4 #ai1 '#if1 p4 #aij4 ,apparently extracted from the daily press47--,that the ,x-rays were only slightly reflected 7,roentgen1 #ha41 and even when very powerful 7,tesla1 #adf41 was determined in a severe manner by ,edison4 ,the first experiment consisted in employing a funnel #h inches long and #c_/d inch at the smaller end4 ,the discharge tube was in the larger end1 and the photographic plate across the smaller end4 ,after experiment and development1 the plate showed overlapping circular images1 which would indicate reflection from the inner surface of the funnel4 ,this may have been due to a jarring vibration of the funnel4 ,therefore1 he carried the experiment further by using a funnel #i feet long4 ,the plate did not indicate any signs of reflection1 as it merely became generally fogged4 ,the material of the tube is not named1 but if of brass or other impermeable metal1 it is thought that his experiment would have shown a result agreeing with that of others herein4 ,again1 the reporter may have been in error4 ,also1 the rays may have been very weak1 as the experiment was performed when ,edison first started to investigate the subject4 #acf4 ,x-,,rays ,,not ,,yet ,,obtainable ,,from ,,other ,,sources ,,than ,,discharge ,,tubes4--,edison exposed covered plates to the direct sun-light at noon for three or four hours2 no photographic impression2 also to electric sparks in open air1 of twelve or more inches in length2 no clouding even of the photographic plate4 ,profs4 ,rowland et4 al41 of the ,johns ,hopkins ,university1 in a contribution to ,electricity1 ,apr4 #bb1 '#if1 p4 #bai1 confirmed this point by stating3 8,as to other sources of ,roentgen rays1 we have tried a torrent of electric sparks in air from a large battery1 and have obtained none4 ,of course1 coins laid on or near the plate1 under these circumstances1 produce impressions1 but these are1 of course1 induction phenomena40 7,see ,sandford and ,mc,kay's ,fig4 p4 #bj74 8,as to sun-light1 ,tyndall1 ,abney1 ,graham1 ,bell and others have shown that some of the rays penetrate vulcanite and other opaque objects40 ,poincar1 at an early date1 advanced the hypothesis that ,x-rays are due to phosphorescence1 whether produced by electrical or other means4 ,elect4 ,world1 ,digest41 ,mar4 #bh1 '#if1 p4 #cdc1 where it is also stated that ,chas4 ,henry thought a certain experiment of his own was in favor of the hypothesis4 ,the experiment was performed with a phosphorescent material which had been exposed to the light and then brought into darkness4 ,niewengloswski inferred1 from an experiment1 that phosphorescent bodies increase the penetrating power of sun-light4 ,tesla admitted the possibility of the radiation of ,x-rays from the sun4 ,in an article describing important experiments in the ,elect4 ,rev41 ,n4,y41 ,apr4 #bb1 '#if1 p4 #bjg1 he stated3 8,i infer1 therefore1 that the sun-light and other sources of radiant energy must1 in a less degree1 emit radiations or streamers of matter similar to those thrown off by an electrode in a highly exhausted enclosure4 ,this seems to be at this moment still a matter of controversy40 ,roentgen1 in his first announcement1 showed that the phosphorescent spot was the source of the ,x-rays4 #gi and #hj4 ,all the different opinions and theories1 therefore1 indicated that phosphorescence by sun-light might possibly emit ,x-rays4 ,probably few had sufficient belief in the matter1 one way or the other1 to try the experiment in an extreme manner4 ,the author was curious to prove the question1 but he only obtained negative results4 ,it cannot be conceived how the matter could have been more severely tested1 for he concentrated the light of the sun nearly to a focus by a large lens1 namely #e in4 in diameter1 together with a reflecting funnel4 ,the maximum phosphorescence was therefore obtained by placing suitable chemicals at the opening in the funnel4 ,the sciascope showed absolutely no ,x-rays present4 ,photographic plates were not in the least acted upon1 even after hours of exposure1 the same having opaque covers of aluminum4 ,see ,elect4 ,eng41 ,n4,y41 ,apr4 #h1 '#if1 p4 #cef4 ,if ,x-rays are emitted from the sun1 they are all absorbed by the atmosphere of the earth1 or are overcome by some other force4 ,illustration3 ,,cooling ,,discharge ,,tube4 ,,edison4 #ace4 ---------------------------------------- -------------------------------- ,,chapter ,,xi #acg4 ,,tesla',s ,,experiments4 ,elec4 ,rev41 ,n4,y41 ,march #aa1 '#if1 page #aca1 ,march #ah1 page #adg1 ,april #a1 page #aga1 and ,april #h1 page #ahc4 ,,kind ,,of ,,electrical ,,apparatus ,,for ,,operating ,,discharge ,,tubes ,,for ,,powerful ,x-,,rays4 #ajf1 #aji1 #aad1 #aca4 ,the experiments performed by ,nikola ,tesla were particularly noteworthy for the magnitude and intensity of the rays generated by his apparatus1 under his skilful manipulation of the adjustments and circuits particularly as to resonance4 ,the remarkable results that he obtained are not surprising when we learn that he employed his well-known system for producing exceedingly enormous potential and unusually high frequency4 #ea4 ,the primary electrical generator as he indicated and as apparent from his system referred to in the above section1 could be either a direct or alternating current generator1 or other form4 ,if the first is employed1 of course an interrupter is necessary in order that there may be a current induced in the secondary4 ,illustration3 ,,sciagraph ,,of ,,rat1 ,,taken ,,by ,,oliver ,b4 ,,shallenberger ,,with ,,focus ,,tube 7,,cut ,,at p4 #ha7 ,,and ,,tesla ,,system4 #acg1 pp4 #acf and #ach4 ,mr4 ,oliver ,b4 ,shallenberger1 7,mem4 ,amer4 ,inst4 ,elec4 ,eng47 whose laboratory is in ,rochester1 ,pa41 gave some important general instructions concerning the ,tesla system #ea1 that he employed in the production of remarkably clear sciagraphs1 in conjunction with the focus tube1 #ia1 representing the hand at page #fh1 and showing a rat shown at this #acg4 7,elec4 ,world1 ,n4,y41 ,march #ag1 '#if47 ,even the ligaments were clearly shown in the sciagraph of the rat1 and some of them are dimly reproduced by the half tone process4 ,as to the apparatus and operation1 which are especially important1 it may be stated that the current was taken from an alternator1 of a frequency of #acc periods per second1 and passed through a primary coil of a transformer for increasing the ,e4 ,m4 ,f4 from #ajj volts to from #af to #be thousand4 ,the secondary current was then passed through ,leyden jars and a double cascade of slightly separated brass cylinders1 whereby it was changed into an oscillatory current of an extremely high frequency1 which was then conducted through the primary of a second induction coil having very few turns of wire1 and no iron core and having a ratio of #g to #a4 ,by this means the ,e4 ,m4 ,f4 was raised to somewhere between #afj1jjj volts to #bej1jjj1 and was used to energize the discharge tube for the generation of ,x-rays4 ,caution should be taken1 because the current coming from the first transformer1 being of large quantity and very high ,e4 ,m4 ,f4 is exceedingly dangerous1 but the current of the second secondary has been passed through one's body without danger1 as reported by ,mr4 ,tesla several years ago1 and confirmed by ,mr4 ,shallenberger4 #ach4 ,,phosphorescent ,,spot ,,maintained ,,cool4--,in testing the power of the ,x-rays in connection with the appearance of the phosphorescent spot1 ,tesla noticed that they were most powerful when the cathode rays caused the glass to appear as if it were in a fluid state4 #fa4 ,to prevent actual puncture1 he maintained the spot cool by means of jets of cold air4 ,it became possible thereby to use bulbs of thin glass at the location of the generation of the ,x-rays4 #aai4 ,he concluded from certain results that not only was glass a better material for discharge tubes than aluminum1 but because1 by other tests1 he found that thin aluminum cast more shadow with ,x-rays than thicker glass4 ,there are1 of course1 many other reasons1 based on mechanical construction1 why glass is preferable1 and also why a tube with an aluminum window is not to be desired4 ,principally1 the latter will soon leak4 #aci4 ,,expulsion ,,of ,,material ,,particles ,,through ,,the ,,walls ,,of ,a ,,discharge ,,tube4--,at quite a low vacuum1 and after sealing off the lamp1 he attached its terminal to that of the disruptive coil4 ,after a while1 the vacuum became enormously higher1 as indicated by the following steps3 ,first1 a turbid and whitish light existed throughout the bulb4 ,this was the first principal characteristic4 ,next1 the color changed to red1 and the electrode became very hot1 in that case where powerful apparatus was employed4 ,the precaution should be taken to regulate the ,e4 ,m4 ,f41 to prevent destruction of the electrode4 ,gradually1 the reddish light subsided1 and white cathode rays1 which had begun1 grew dimmer and dimmer until invisible4 ,at the same time1 the phosphorescent spot became brighter and brighter and hotter and hotter1 while the electrode cooled1 until the glass adjacent thereto was uncomfortably cold to the touch4 ,at this stage1 the required degree of exhaustion was reached1 and yet without any kind of a pump4 ,he was enabled to hasten the process by alternate heating and cooling1 and by the use of a small electrode4 ,this whole phenomenon was exhibited with external electrodes as well4 ,he acknowledged that instead of the disruptive coil1 a static machine could be used1 or1 in fact1 any generator or combination of devices adapted to produce a very high ,e4 ,m4 ,f4 ,the reduction of temperature of the electrode he attributed to its volatilization4 ,without actually testing the rays with a fluorescent screen or photographic plate1 he could always know their presence by the relative temperatures of the phosphorescent spot and the electrode1 for when the latter was at a low temperature and the former at a high temperature1 ,x-rays were sure to be strong4 ,from the fact that the vacuum became higher and higher by the means stated1 he was very much inclined to believe that there was an expulsion of material particles through the walls of the bulb4 ,when these particles which were passing with very great velocities struck the sensitive photographic plate they should produce chemical action4 ,he referred to the great velocity of projected particles within a discharge tube1 pages #df and #dg1 and to ,lord ,kelvin's estimate upon the same1 and reasoned that with very high potentials1 the speed might be #ajj km per second4 ,the phenomenon indicated1 he said1 that the particles were projected through the wall of the tube and he entered into an elaborate discussion on this point4 ,he referred to his own experiment of causing the rays from an electrode in the open air to pass directly through a thick glass plate4 #ac4 ,he performed an experiment also of producing a blackening upon a photographic plate apparently by the projected particles1 an electrical screen being employed to prevent the formation of sparks4 #ce4 which as well known will cause chemical action upon the plate4 ,no stronger proof as to the expulsion of material particles could be desired than an operation in which the eyes can see for themselves that such an action must have taken place4 ,usually he was troubled by the streamers 7cathode rays7 from the electrode suddenly breaking the glass of the discharge tube4 ,this occurred when the spot struck was at or near the point where the same was sealed from the pump4 ,he arranged a tube in which the streamers did not strike the sealing point1 but rather the side of the tube4 ,it was extraordinary that a visible but fine hole was made through the wall of the tube1 and especially that no air rushed into the vacuum4 ,on the other hand1 the pressure of the air was overcome by something rushing out of the tube through the hole4 ,the glass around the hole was not very hot1 although if care were not taken1 it would become much hotter1 and soften and bulge out1 also indicating a pressure within1 #bg4 greater than the atmospheric pressure4 ,he maintained the punctured tube in this condition for some time and the rarefaction continued to increase4 ,as to the appearances1 the streamers were not only visible within the tube1 but could be seen passing through the hole1 but as the vacuum became higher and higher1 the streamers became less and less bright4 ,at a little higher degree of vacuum1 the streamers were still visible at the heated spot1 but finally disappeared4 ,this electrical process of evacuating varies in its rapidity according to the thinness of the glass4 ,here again he noted the application of his theory in that an easier passage was afforded for the ions4 #dg4 ,a few minutes of operation produced through thin glass1 a vacuum from very low to very high1 whereas1 to obtain the same vacuum through much thicker glass over #a_/b hour was necessary4 ,again with a thick electrode the time required was much greater4 ,the small hole was not always visible and it was thought that the material went through the pores4 ,the result obtained by the following experiment tends to uphold ,mr4 ,tesla's emission theory4 #aci;a4 ,,lafay',s ,,experiment4 ,,giving ,,to ,x-,,rays ,,the ,,property ,,of ,,being ,,deflected ,,by ,a ,,magnet ,,by ,,passing ,,them ,,through ,a ,,charged ,,silver ,,leaf4 ,comptes ,rendus1 ,march #bc1 '#if and ,april #g1 #ac1 #bg1 and ,l',ind4 ,elec41 ,april and ,may '#if4 ,from trans4 by ,louis ,m4 ,pignolet4 ,he placed at about 4#e cm4 below a discharge tube1 a lead screen pierced by a slit #b mm4 wide2 and #j4jd m4 lower1 a second lead screen having a slit #e mm4 wide completely covered by an extremely thin leaf of silver4 ,opposite the silver leaf and exactly in the axis of the slit1 was fixed a platinum wire #a4e mm4 diameter4 ,thus1 the rays which passed successively through the two slits projected a shadow of the wire on a photographic plate below4 ,when the silver leaf was connected to the negative pole of the induction coil that excited the tube1 the rays1 which had become electrified 7 #fa;b1 p4 #dg7 bypassing through the leaf1 were deflected by a magnetic field of about #djj ,l4 ,g4 ,s4 units1 whose lines of force were parallel to the slit4 ,the direction of the deflection was determined by the same law as that of the deflection by a magnetic field of the cathode rays in the interior of a discharge tube4 #ei4 ,when the silver leaf was not connected to the coil1 no deflection was produced4 #gi4 ,to double the apparent deflection1 one part of the slit was covered by a lead plate during the first half of the experiment4 ,the lead plate was removed and placed over the other part of the slit1 and the direction of the magnetic field reversed during the last half of the experiment4 ,thus the distance on the sciagraph between the two parts of the wire1 was double the deflection produced by the magnetic field4 ,the deflection was in the same direction when the silver leaf was connected to the negative pole of a static electric machine1 but was in the opposite direction when the leaf was connected to the positive pole of the machine4 ,the test was criticised in the scientific press1 and1 therefore1 in order to be certain that the deflections observed were not due to the combined effects of the electro-magnet which produced the magnetic field and the electric field of the charged silver leaf1 the experiments were modified4 ,to remove this uncertainty1 the electrified rays were caused to enter a grounded ,faraday cylinder 7see figure at ,e4 ,f4 ,g4 ,h41 p4 #dg71 through a small opening1 before passing between the poles of the electro-magnet4 ,the deviations which were recorded on a photographic plate in the box were the same as before4 ,additional experiments showed that the deflections by the magnetic field took place as well when the rays were electrified1 after their passage through another magnetic field1 as before4 ,lafay continued the experiments in great detail and by many control tests1 and he took accurate measurements and followed the suggestions of others4 ,it would be well for those who have facilities to repeat these most interesting and important researches1 to determine for themselves some satisfaction4 ,it is of interest to note that an ,american1 ,paul ,a4 ,n4 ,winand1 7,mem4 ,amer4 ,inst4 ,elect4 ,engs471 in the absence of facilities for experimenting1 proposed 7,elect4 ,world1 ,n4,y41 ,june #f1 '#if7 to interpose a hollow sphere1 which had high potential1 in the path of ,x-rays1 and to learn in what manner1 if any1 the rays are influenced4 ,he argued that it would seem natural that1 inasmuch as the rays produce a discharge1 there should be a reaction of the charged surface upon the rays4 ,it is evident that if any one repeats these experiments1 expert manipulation is required4 #aci;b4 ,,gouy',s ,,experiments4 ,,the ,,penetration ,,of ,,gases ,,into ,,the ,,glass ,,walls ,,of ,,discharge ,,tubes4 ,comptes ,rendus1 ,march #cj1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4 ,from observations with slightly different glass from four tubes1 it seemed that the cathode rays cause the gases in the tubes to penetrate the glass where they remain occluded until the glass is nearly softened 7after cutting off the current71 by heat1 whereby they are set at liberty as minute bubbles visible by the microscope1 which finally partly combine and become visible to the naked eye4 ,illustration3 ,,halos #a ,,ft4 ,,diam41 ,,in ,,clear ,,air1 ,,around ,,incandescent ,,electric ,,lamps ,,of ,,usual ,,size4 ,,cross ,,at ,,center ,,of ,,each ,,halo4 #adj1 p4 #adc4 ,observed by means of a photograph1 in #ahhb1 by ,william ,j4 ,hammer4 ,illustration3 ,,mortification ,,of ,,the ,,ulna4 #bjd4 ,from sciagraph by ,prof ,miller4 ,under the same conditions1 tubes which have been used for a long time exhibit numerous wrinkles1 indicating a superficial modification of the glass4 ,these may exist with or without the bubbles4 #adj4 ,,discharge ,,tube ,,surrounded ,,by ,a ,,violet ,,halo4 ,by means of enormous potential and high frequency1 the tube was surrounded1 ,tesla stated1 by violet luminosity or halo4 #f4 and #gd4 ,from the fact that ,lenard obtained a similar appearance in front of the aluminum window1 it might be reasonable to conclude that there is some close relationship between the two phenomena4 ,as an illustration of halo by light1 may be mentioned the well known appearance so often occurring in the atmosphere concentrically with the moon1 and sometimes surrounding the sun4 ,under favorable circumstances1 7in a mist or dust in the air71 a halo1 at some distance from a flame or other light is faintly visible4 ,it has generally been assumed that the reason of a halo by light is based upon the laws of reflection1 or refraction or both1 the bending of the rays taking place1 through1 or upon the surface of the particles of moisture4 ,others have held that particles of ice in the upper atmosphere1 are the reflectors or refractors1 or both4 ,more puzzling has been the attempt to explain the novel appearance reproduced fairly well in the cut1 page #adj4 ,it is here represented in print for the first time1 but the photograph from which it was taken1 was at various times1 shown to different physicists1 some of whom attributed the beautiful effect to the property of interference of light1 and naming ,newton's rings as an analogous production4 ,prof4 ,anthony in an interview expressed himself as well satisfied that interference could not occur under the circumstances named4 ,he recognized that there was a curved surface of glass which might be considered as made up of an infinite number of layers4 ,the author introduces the matter for the purpose of consideration by others1 and especially because it is so intimately connected with the subject of the vacuum tube and electricity4 ,the details must be understood for the purpose of proper appreciation4 ,mr4 ,william ,j4 ,hammer1 of ,new ,york1 had a photograph taken of the large ,concert ,hall at the ,crystal ,palace1 ,sydenham1 ,eng41 by the light of the ,edison incandescent lamps with which the ,hall was illuminated4 ,this photograph was made in #ahhb during the ,international ,electrical ,exhibition held at the ,crystal ,palace4 ,the picture shows a small section of the whole photograph and represents 7although probably no one would judge so by looking at the picture7 a festoon of pear-shaped incandescent electric lamps1 each one hanging downward1 and separated from its neighbor by between three and four feet4 ,they were so far away from the camera that a picture of the lamps unlighted1 would have represented them as mere specks4 ,the bright circles with the bright central crosses in the centre of the dark spaces were1 therefore1 fully one foot in diameter1 while the lamp bulbs themselves were only about two or three inches thick1 as usual4 ,why then should there be the halos8 ,why should the crosses appear8 ,and why should the black area be so large8 ,if the electricity and vacuum have nothing to do with it1 why should not the halos appear when photographs are taken of flames and other sources of light in the absence of mist and dust8 ,in order to answer questions which will perhaps be proposed1 let it be stated that there was no visible dust nor moisture in the room1 the photograph being taken early in the evening and at a time when the ,hall was not in use4 ,the halos were not apparent except when reproduced by a photograph4 ,the lamps had the usual carbon filaments hanging so that the several filaments were in different planes1 and they were of #af candle power and were connected in parallel circuit1 the average ,e4 ,m4 ,f4 being about #aaj volts4 ,the lamps were fed by the ,edison direct current dynamos4 ,the festoon shown1 is one of a dozen or more which were suspended between the columns rising from the gallery and supporting the roof and were hung about forty feet from the floor4 ,the hall was further illuminated by a huge electrolier pendant from the centre of the ceiling4 ,these details were obtained from ,mr4 ,hammer1 who planned the installation4 #ada4 ,,an,,sthetic ,,properties ,,of ,x-,,rays4--,tesla reported that he and his assistants tested the action of the rays upon the human system1 and found that upon continued impact and penetration of the head by very powerful radiations1 strange effects were noticed4 ,he was sure that from this cause a tendency to sleep occurred 7 #hd1 at end71 and the faculties were benumbed4 ,he said that time seemed to pass quickly4 ,the general effect was of a soothing nature1 and the top of the head seemed to feel warm under the influence of the rays4 ,incidentally1 he noticed1 as he stated1 8,when working with highly strained bulbs1 ,i frequently experienced a sudden and sometimes even painful shock in the eye4 ,such shocks may occur so often that the eye gets inflamed1 and one cannot be considered cautious if he abstains from watching the bulb too closely40 ,the author calls to mind the reports in the daily press that ,edison also noticed that the eyes were in some way sensitive to the rays4 ,the eye1 it was reported1 became fatigued at the time1 and yet later1 objects could be more easily distinguished4 ,in this connection1 it should be remembered that there are not only cathode rays1 ,x-rays1 etc41 but the electric force that ,lenard spoke of in the neighborhood of the discharge tube1 and in testing the effects upon the eyes1 of course1 the precaution should be taken to determine whether cathode rays1 ,x-rays or the electric sparks are answerable for the peculiar effects4 ,roentgen reasoned1 #hd1 that the eyes were not sensitive1 but the rays1 in his case1 were not strong enough to travel #dj to #fj feet1 as in ,tesla's experiments1 but only #b m4 7about #g ft474 #adb4 ,,sciagraphs ,,of ,,hair1 ,,fur1 ,,heart1 ,,etc41 ,,by ,x-,,rays4--,tesla was probably the first to be at all successful in the representation in sciagraphs of such objects as hair and cloth and similar easily permeable objects4 ,in the case of a rabbit1 not only was the skeleton visible1 but also the fur4 ,sciagraphs of birds exhibited the feathers fairly distinctly4 ,the picture of a foot in a shoe not only represented the bones of the foot1 and nails of the shoe1 but every fold of the leather1 trowsers1 stockings1 etc4 ,his opinion as to the useful application of the rays was that any metal object1 or bony or chalky deposit could be 8infallibly detected in any part of the body40 ,in obtaining a sciagraph of a skull1 vertebral column1 and arm1 even the shadows of the hair were clearly apparent4 ,it was during such an experiment that the ansthetic qualities were noticed4 ,the author saw several of the above named sciagraphs4 ,furthermore1 on the screen he believed he detected the pulsations of the heart4 ,elect4 ,rev41 ,n4,y41 ,may1 #bj1 '#if4 ,although we do not doubt this report concerning what ,mr4 ,tesla saw1 yet some scientific men are exceedingly dubious concerning the results obtained by other scientists1 unless the same are confirmed by additional witnesses4 ,it will certainly be of interest to such skeptics to have corroboratory evidence4 ,in company with ,prof4 ,anthony1 ,mr4 ,wm4 ,j4 ,hammer and ,mr4 ,price1 editor of the ,elect4 ,rev41 ,n4,y41 the author visited a laboratory at #ca ,west #eeth street1 ,new ,york ,city1 for the purpose of beholding the pulsations of the human heart by means of an experiment performed by ,mr4 ,h4 ,d4 ,hawkes1 of ,tarrytown1 ,n4,y4 ,there was nothing new about his apparatus1 the admirable results being due merely to accurately proportioned electrical and mechanical details and skillful manipulation4 ,the ,tesla system was not used1 but merely a large induction coil and rotary interrupter1 and a direct current from the incandescent lamp circuit of #aaj volts1 all substantially as ,roentgen himself employed4 ,the sciascope was provided with the ,edison calcic tungstate screen4 ,in order to overcome the sparking between the terminals on the outside of the tube after a few minutes of use1 he heated the cathode end by means of a ,bunsen burner flame4 #aci1 near beginning4 ,the utility consisted in the evaporation of condensed moisture upon the cool end of the discharge tube4 ,the temporary heating always prevented1 for several minutes1 any sparking on the outside4 ,after some preliminary experiments1 each person1 in turn1 pressed the sciascope upon the breast of another1 at the location of the heart1 while the discharge tube was directly at the back of a young man4 ,the ribs and spinal column were visible1 and1 projecting from the spine1 appeared a semi-circular area1 which expanded and contracted4 ,any one viewing such an operation1 and knowing that he is looking at the movements of the heart1 cannot but be impressed with weird wonder1 and cannot but credit great honor1 not only to ,roentgen and ,lenard1 but to all those early workers who have gradually but surely1 successfully made discovery after discovery in the department of the science of discharges1 finally culminating in the most wonderful discovery of all4 ,the author remembers seeing in some medical paper that ,william ,j4 ,morton1 ,m4,d41 of ,new ,york1 had also witnessed the beating of the heart with the sciascope at an early date4 ,similar reports are occurring weekly4 #adb;a4 ,mr4 ,norton1 of ,boston 7,elect4 ,world41 ,n4,y41 ,may #bc1 '#if7 also stated that the heart could be seen in faint outline1 and also its pulsations4 ,the lungs were very transparent4 ,the liver being quite opaque1 its rise and fall with the diaphragm was plainly followed4 ,others have suggested drinking an opaque 7to ,x-rays7 liquid1 like salt water1 and tracing its path4 #adc4 ,,propagation ,,of ,x-,,rays ,,through ,,air ,,to ,,distances ,,of #fj ,,ft4--,in ,roentgen's first experiments1 the maximum distances at which the fluorescent screen was excited was about #g ft4 ,tesla obtained similar action at a distance of over #dj ft4 ,photographic plates were found clouded if left at a distance of #fj ft4 for any length of time4 ,this trouble occurred when some plates were in the floor above and #fj ft4 distant from the discharge tube4 ,he attributed the wonderful increase largely to the employment of a single electrode discharge tube1 because the same permitted the highest obtainable ,e4 ,m4 ,f4 that could be desired4 ,illustration3 ,,sciagraph ,,of ,,foot ,,in ,,lace ,,shoe4 #bjd4 ,by ,prof4 ,miller4 #add4 ,x-,,rays ,,with ,,poor ,,vacuum ,,and ,,high ,,potential4--,in the course of ,tesla's experiments1 he observed that the ,crookes' phenomena and ,x-rays could be produced without the high degree of vacuum usually considered necessary1 #aah4 but by way of compensation1 the ,e4 ,m4 ,f4 must be exceedingly high1 and1 of course1 the tube and electrical apparatus substantially of those dimensions involved in ,tesla's work4 ,one must be careful not to over-heat the discharge tube1 which is likely to occur by increase of potential4 ,he gave definite instructions for preventing the destruction of the tube by heating1 by stating that it is only necessary to reduce the number of impulses1 or to lengthen their duration1 while at the same time raising their potential4 ,for this purpose1 it is best to have a rotary circuit interrupter in the primary instead of a vibrating make and break1 for then it becomes convenient to vary the speed of the interrupter1 which may be1 evidently1 so constructed that the duration of the impulses may also be varied1 for example1 by different sets of contact points arranged on the rotary interrupter1 and made of different widths4 #ade4 ,,detail ,,construction ,,and ,,use ,,of ,,single ,,electrode ,,discharge ,,tubes ,,for ,x-,,rays4 ,he pointed out that with two electrodes in a bulb as previously employed by nearly all experimenters1 or an internal one in combination with an adjacent external one the ,e4 ,m4 ,f4 applicable was necessarily greatly limited for the reason that the presence of both1 or the nearness of any conducting object 8had the effect of producing the practicable potential on the cathode40 ,consequently he was driven1 as he said1 to a discharge tube having a single internal electrode1 the other one being as far away as required4 #i4 ,in view of his ingenious arrangements of the disruptive coil1 and circuits1 condensers and static screens for the bulb1 he found it immaterial to pay attention to some other details followed by experimenters4 ,for example1 it made comparatively little difference in his results whether the electrode was a flat disk or had a concave surface4 ,illustration3 ,,tesla',s ,,figs4 #a ,,and #b1 ,,reflection ,,and ,,transmission ,,of ,x-,,rays ,,by ,,different ,,substances4 #ade and #adf;a4 ,the form of tube described by ,tesla in full1 will hereinafter be alluded to as exhibited in the several figures accompanying this description1 and it consisted1 therefore1 of the long tube 8b0 made of very thick glass except at the end opposite the electrode 8e01 where it was blown thin1 p4 #adi4 ,the electrode was an aluminum disk having a diameter only slightly less than that of the tube and located about one inch beyond the rather long narrow neck n1 into which the leading-in wire c entered4 ,it is important that a wrapping w be provided around this wire1 both inside and outside of the tube4 ,the sealing point was on the side of the neck4 ,an electric screen has been referred to heretofore4 ,it is lettered s1 and was formed of a coating of bronze paint applied on the glass between the electrode and neck n4 ,the screen could be made in other ways1 for example1 as shown at s1 ,fig4 #b1 where it consists of an annular disk behind and parallel to the electrode disk4 ,this ring s in ,fig4 #b4 must be placed at the right distance back of the electrode e1 but just how far can only be determined by experience4 ,the unique service of the screen was that of an automatic system for preventing the vacuum from becoming too high by use4 ,the peculiar action was as follows1 namely from time to time1 a spark jumped through the wrapping w within the tube to the screen and liberated just about enough gas to maintain the vacuum at an approximately constant degree4 ,another way in which he was able to guard against too high a vacuum1 consisted in extending the wrapping w to such a distance inside of the tube1 that the same became heated sufficiently to liberate occluded gases4 ,as to the long length of the leading-in wire within a long neck behind the cathode1 ,lenard found the same to be valuable in conjunction with a wrapping around the wire4 ,with high potential1 a spark1 at a certain high degree of vacuum1 formed behind the electrode1 and prevented the use of very high potential1 but by having the wire extend far into the tube and providing wrappers1 the sparking was much less likely to occur4 ,by proper adjustment as before intimated1 ,tesla could produce just about enough to compensate for the electrical increase of the vacuum4 ,another difficulty that presented itself in connection with high ,e4 ,m4 ,f4 was the undue formation of streamers heretofore referred to1 apparently issuing from the glass1 and so often disabling it4 ,he therefore immersed the discharge tube in oil as pointed out in detail hereinafter4 ,the walls of the tube served to throw forward to the thin glass many of those rays that otherwise would have been scattered laterally4 ,upon comparing a long thick tube of this kind with a spherical one1 the sensitive plate was acted upon by the rays in #a_/d the time with the tube4 ,a modification consisted in surrounding a lower portion of the tube1 with an outside terminal e1 indicated in dotted lines in ,fig4 #a4 ,in this way the discharge tube had two terminals4 ,the greatest advantage probably in using a long tube1 was that the longer it was1 within the proper limits1 the greater the potential which could be applied with advantages4 ,as to the aluminum electrode1 he noticed that it was superior1 in comparison with one made of platinum which gave inferior results1 and caused the bulb to become disabled in an inconveniently short period of time4 #adf4 ,,percentage ,,of ,,reflected ,x-,,rays4 ,he performed some preliminary experiments1 testing roughly as to whether any appreciable amount of radiation could be reflected or not from any given surface4 ,within #de minutes he was enabled to obtain clear and sharp sciagraphs of metal objects1 and the same could have been obtained only by the reflected rays1 because he screened the direct rays by means of very thick copper4 ,by a rough calculation he found that the percentage of the total amount of rays reflected was somewhere in the neighborhood of #b per cent4 ,prof4 ,rood1 of ,columbia ,university1 ,n4,y41 7,sci41 ,mar4 #bg1 '#if47 by means of an experiment with platinum foil1 #hj1 concluded that the per centage was about 4#jje1 the incident angle being #de degrees4 ,he regarded this figure as the mere first approximation4 ,judging from ,roentgen1 #he1 ,tesla1 ,rood and others1 therefore1 it seems to be established that the percentage of ,x-rays reflected is very small4 ,prof4 ,mayer1 of ,stevens ,institute1 7,science1 ,may #h1 '#if17 is of the opinion that there is a regular or specular reflection1 having witnessed some experiments obtained by ,prof4 ,rood1 of ,columbia ,univ41 ,n4,y4 ,prof4 ,mayer reported that the original negatives were taken in such a way as to substantiate regular reflection1 and were carefully examined by six eminent physicists at the ,national ,acad4 of ,sci4 at ,washington1 ,april #bc1 '#if1 and none had the slightest doubt concerning the completeness of the demonstration4 ,the material employed for reflecting was platinum foil4 #ajc;a4 ,,difference ,,between ,,diffusion ,,and ,,reflection4 ,judging from the experiments above related1 as well as those considered in #ajc;a1 there might at first appear to be contradictory results1 reported by different authorities4 ,experts1 it is thought will1 without argument1 discover the harmonious agreement1 and will commend the work of scientists1 who1 in different parts of the world1 and at about the same time1 made similar experiments1 which now being considered jointly1 are found to agree so wonderfully closely4 ,upon reading the above sections and those referred to1 there can be no doubt whatever but that ,x-rays1 upon striking a body are1 to a certain per cent4 scattered1 or thrown back1 or bent from their straight course1 and sent in a backward and different direction1 at one angle or another4 ,the only apparent absolute contradiction to this is that of ,perrin1 #ajc;a1 near the end4 ,but his is a case of one witness against scores1 and1 therefore1 evidence based upon his experiments1 must be counted out4 ,the error was either due to some oversight of his own1 or more probably the mistake is merely a typographical one1 for often a mistake creeps in between a man's dictation and the printed work4 ,it is difficult to accuse ,perrin of a mistake1 for he is a great ,french authority in such matters4 ,assuming that no error has occured1 let it be noticed that he does not pronounce non-reflection from all substances1 but only from steel p4 #aed1 l4 #i1 and flint1 which have been so polished as to form a mirror-like surface1 whereas all other experimenters1 with scarcely an exception1 have not employed such surfaces4 ,the difficult point to believe is that1 after six hours1 no energy from the mirror could be collected4 ,if we accept ,perrin's results it must be only in regard to those two particular materials1 polished steel and flint4 ,another feature which is on the edge of conjecture1 is that of true or specular reflection1 referred to by ,prof4 ,mayer1 #adf4 ,many attempts have been undertaken to prove whether the rays were thrown backward on the principle of reflection as light from a mirror1 or of diffusion as light from chalk4 ,let the student notice that the evidence is overwhelming in favor of the turning back of the rays to a very small per cent4 upon striking any object4 ,as to specular reflection1 which means similar to the reflection of light from a polished mirror1 it is practically the same as diffusion1 the difference being substantially of a technical nature4 ,this allegation is based upon the detail distinction between reflection and diffusion given by ,p4 ,g4 ,tait1 professor of natural philosophy1 ,univ4 of ,edinburgh1 who states1 in ,encyclo4 ,brit41 vol4 #ada1 p4 #ehf3-- 8,it is by scattered light that non-luminous objects are1 in general1 made visible4 ,contrast1 for instance1 the effect when a ray of sunlight in a dark room falls upon a piece of polished silver1 and when it falls on a piece of chalk4 ,unless there be dust or scratches on the silver1 you cannot see it1 because no light is given from it from surrounding bodies except in one definite direction1 into which 7practically7 the whole ray of sunlight is diverted4 ,but the chalk sends light to all surrounding bodies1 from which any part of its illuminated sides can be seen2 and there is no special direction in which it sends a more powerful ray than in others4 ,it is probable that if we could1 with sufficient closeness1 examine the surface of the chalk1 we should find its behavior to be in the nature of reflection1 but reflection due to little mirrors inclined to all conceivable aspects1 and to all conceivable angles to the incident light4 ,thus scattering may be looked upon as ultimately due to reflection4 ,when the sea is perfectly calm1 we see it in one intolerably bright image of the sun only4 ,but when it is continuously covered with slight ripples1 the definite image is broken up1 and we have a large surface of the water shining by what is virtually scattered light1 though it is really made up of parts each of which is as truly reflected as it was when the surface was flat40 #adf;a4 ,,reflected ,,and ,,transmitted ,x-,,rays ,,compared4--,in order to carry on a series of investigations1 ,mr4 ,tesla constructed a complete special apparatus represented in ,fig4 #b1 p4 #adi1 and embodied in it also an idea which he attributed to ,prof4 ,william ,a4 ,anthony1 which consisted in arranging for sciagraphs to be produced by the rays transmitted through the reflecting substance as well as by the reflected rays themselves4 ,the figure serves to show at a glance the construction and1 therefore1 the explanation need be but brief4 ,it consisted of a ,t tube1 having three openings1 those at the base and side being closed by photographic plates in their opaque holders1 which carried on the outside the objects o and o to be sciagraphed4 ,at an angle to both plates1 and centrally located1 was a reflecting plate1 r1 which could be replaced by plates of different materials4 ,at the upper opening of the plate ,b was a discharge tube1 b1 placed in a heavy ,bohemian glass tube1 t1 to direct the scattered rays downward as much as possible from the electrode1 e1 to and through the thin end of the discharge tube4 ,the objects to be sciagraphed1 namely o and o1 were exact duplicates of each other4 ,no statement could be found as to the thickness of the tested plates1 r1 except that they were all of equal size4 ,the distance from the bottom of the discharge tube to the reflecting plate1 r1 was #ac inches1 and from the latter to each photographic plate about #g inches1 so that both pencils of rays had to travel #bj inches in each instance4 ,one hour was taken as the time of exposure4 ,after a series of experiments with a great many different kinds of metals1 they arranged themselves as to their reflecting power1 in an order corresponding to ,volta's electric contact series in air4 #aec4 ,the most electro-positive metal was the best reflector1 and so on4 ,for exhaustive investigations upon the discovery of ,volta1 see 8,experimental ,researches0 of ,kohlrausch1 ,pogg4 ,ann41 '#ec1 and ,gerland1 ,pogg4 ,ann41 '#fh4 ,the metals ,tesla tested were zinc1 lead1 tin1 copper and silver1 which were1 in their order1 less and less reflecting1 and the order is the same in the electro-positive series1 zinc being the most positive1 and the others less and less so1 in the order named4 ,for a complete list of the metals arranged by the ,volta series1 see any standard electrical text-book4 ,he could not notice much difference between the reflecting powers of tin and lead1 but he attributed this to an error in the observation4 ,he tried other metals1 but they were either alloys or impure4 ,those named in the list above were the pure metals4 ,however1 he carried on experiments with sheets of many different substances1 and arrived at the following table1 which shows particularly the relative transmitting and reflecting powers of the various substances in the rough4 ,impression by ,impression by ,reflecting ,transmitted ,rays4 ,reflected ,rays4 ,body ,brass ,strong ,fairly good ,toolsteel ,barely perceptible ,very feeble ,zinc ,none ,very strong ,aluminum ,very strong ,none ,copper ,none ,fairly strong but much less than zinc ,lead ,none ,very strong but a little weaker than zinc ,silver ,strong1 a thin plate ,weaker than copper being used ,tin ,none ,very strong about like lead ,nickel ,none ,about like copper ,lead-glass ,very strong ,feeble ,mica ,very strong ,very strong about like lead ,ebonite ,strong ,about like copper4 ,by comparing1 as in previous experiments1 the intensity of the photographic impression by reflected rays with an equivalent impression due to a direct exposure of the same bulb and at the same distance1 that is1 by calculations from the times of exposure under assumption that the action upon the plate was proportionate to the time1 the following approximate results were obtained3 ,impression ,reflecting by ,impression ,body ,direct by ,action ,reflected ,rays4 ,brass #ajj #b ,tool steel #ajj #j4e ,zinc #ajj #c ,aluminum #ajj #j ,copper #ajj #b ,lead #ajj #b4e ,silver #ajj #a4ge ,tin #ajj #b4e ,nickel #ajj #b ,lead-glass #ajj #a ,mica #ajj #b4e ,ebonite #ajj #b ,he stated that while these figures can be but rough approximations1 there is1 nevertheless a fair probability that they are correct1 in so far as the relative values of the sciagraphic impressions of the various objects by reflected rays are concerned4 ,in order to devise means for testing the comparative reflecting power in a more decided manner1 he laid pieces of different metals side by side upon a lead plate4 ,consequently the reflecting surface was formed of two parts corresponding to the two metals4 #hj4 ,the vertically perpendicular partition of lead served to prevent the mingling of the rays from the two metals4 ,ingenious precautions were taken2 as for example1 so arranging matters that upon equal areas of the two plates1 equal amounts of ,x-rays impinged4 #hj4 ,he undertook to determine the position of iron in the series by thus comparing it with copper4 ,it was impossible to be sure which metal reflected better4 ,the same regarding tin and lead and also in reference to magnesium and zinc4 ,here1 a difference was noticed1 namely that the magnesium was a better reflector4 ,he has made practical application of the power of the substances to reflect a certain per cent4 of the rays by employing reflectors for the purpose of reducing the time required for exposure of the photographic plates4 ,it admits1 he stated1 of the use of reflectors in combination with a whole set of discharge tubes1 whereby rays which would be otherwise scattered in all directions are brought more nearly to a single direction of propagation4 ,illustration3 ,,from ,,sciagraph ,,of ,,knee-,,joint4 ,,straight1 ,,front ,,view4 ,by ,prof4 ,goodspeed4 ,photo4 ,times1 ,july1 '#if4 ,it might be argued1 that in as much as zinc would reflect only about three per cent4 of the incident rays1 no practical gain would ensue in sciagraphy by the use of a reflector4 ,he pointed out the falsity of such an argument4 ,in the first place1 the angle employed in these tests was #de4 ,with greater angles1 the proportion of reflected rays would be greater assuming that the law of reflection is the same as that of light4 ,by mathematical calculation and tests1 he showed that there was no doubt whatever about the advantage of using reflectors4 ,he obtained a sciagraph1 on a single plate1 of the ribs1 arms and shoulder1 clearly represented4 ,he stated the details as follows4 8,a funnel shaped zinc reflector two feet high1 with an opening of five inches at the bottom and #bc inches at the top1 was used in the experiment4 ,a tube similar in every respect to those previously described1 was suspended in the funnel1 so that only the static screen of the tube was above the former4 ,the exact distance from the electrode to the sensitive plate was four and one-half feet40 #adg4 ,,discharge ,,tube ,,placed ,,in ,,oil4--,when the ,e4 ,m4 ,f4 was increased1 by having the discharge tube1 as usual1 in open air1 sparks formed behind the electrode1 and within the vacuum1 and endangered the life of the discharge tube4 ,he obviated this difficulty partly by having the electrode located well within the evacuated space1 so that the wire leading to it was unusually long4 ,by excessive ,e4 ,m4 ,f41 also1 streamers broke out at the end of the tube4 ,to overcome all difficulties in connection with sparking and breaking of the tube1 he followed the proposition of ,prof4 ,trowbridge1 and submerged the discharge tube in oil1 #aa1 at end1 and #ac1 which was continually renewed by flowing into and out of the vessel in which the discharge tube was contained1 all as shown in the accompanying figure1 p4 #aeg1 8,discharge ,tube ,immersed in ,oil40 ,the discharge tube1 t1 may be recognized by its shape1 and it is located horizontally in a cylindrical tube lying sidewise upon a table4 ,to regulate the flow of the oil1 the reservoir may be raised and lowered by a bracket1 s4 ,the ,x-rays enter the outside atmosphere by passing first through glass1 then oil1 and then through a diaphragm of 8pergament0 forming the right hand end of the oil vessel4 ,when the results were compared with those obtained by ,roentgen in his first experiments1 the rays were found so powerful that it is not surprising that ,tesla was able to obtain more definitely a closer knowledge of the properties of the rays4 ,roentgen obtained1 with his tube and a screen of barium platino cyanide1 a shadow picture of the bones of the hand at a distance of less than #g ft41 while ,tesla obtained a similar picture with a screen of calcic tungstate1 and with his tube immersed in oil at a distance of #de ft4 ,tesla also made sciagraphs with but a few minutes' exposure at a distance of #dj ft41 by the help of ,prof4 ,henry's method1 i4e41 with the assistance of a fluorescent powder4 #aea4 ,he referred also to ,salvioni's suggestion of a fluorescent emulsion4 ,he attributed to ,mr4 ,e4 ,r4 ,hewitt the conjecture that the sharpness of the sciagraphs might be increased by a thin aluminum sheet having parallel groves4 ,several experiments were made1 therefore1 with wire gauze1 as well as with a screen formed of a mixture of fluorescent and iron-fluorescent powders4 ,with the strong power of the rays as obtained by ,tesla in combination with such adjuncts1 the shadows were sharper1 although the radiation1 of course1 was weakened by the obstruction4 #ajg;b4 ,illustration3 ,,discharge ,,tube ,,immersed ,,in ,,oil1 #adg1 ,,page #aef4 ,with the apparatus involving the discharge tube in oil1 and with tremendously high potential1 he obtained what may be called wonderful results2 for with the sciascope he obtained shadow pictures of the vertebral column1 outline of the hip bones1 the location of the heart 7and later detected its pulsations71 ribs and shorter bones1 and1 without the least difficulty1 the bones of all the limbs4 ,more than this1 a sciagraph of the skeleton of the hand was perceived through copper1 iron or brass very nearly #a_/d inch thick1 while glass #a_/b inch thick scarcely dimmed the fluorescence4 ,the skull of the head of an assistant acted likewise1 while at a distance of three feet from the discharge tube4 ,the motion of the hand was detected upon the screen although the rays first passed through one's body4 ,in making observations with the screen1 he advised that experimenters should surround the oil box closely1 except at the end1 with thick metal plates1 to prevent ,x-rays from coming in undesired directions by reflection from different objects in the room4 ,obviously the shadows will be sharper4 #adh4 ,,bodies ,,not ,,made ,,conductors ,,by ,x-,,rays4 ,tesla referred to ,prof4 ,j4 ,j4 ,thomson as having announced some time ago 8that all bodies traversed by ,roentgen radiations become conductors of electricity40 ,the author has witnessed other similar expressions giving credit to ,thomson in this respect1 but he understands that ,prof4 ,thomson1 having discovered that ,x-rays discharge both negatively and positively charged bodies1 conjectured or drew a corallary as to the probability of the bodies therefore becoming conductors4 ,tesla1 nevertheless1 seems to have proved that the corallary does not hold4 ,in the first place he employed the very powerful rays1 and next1 he let the oil be the substance traversed by the rays4 ,besides this1 he applied a sensitive resonance test4 ,see detail treatment of his experiments on this subject in ,elect4 ,rev41 ,n4,y41 ,june #bd1 '#ic1 p4 #bbh4 ,in brief 8a secondary not in very close inductive relation to the primary circuit1 was connected to the latter and to the ground1 and the vibration through the primary was so adjusted that true resonance took place4 ,as the secondary had a considerable number of turns1 very small bodies attached to the free terminal produced considerable variations of potential of the latter4 ,placing a tube in a box of wood filled with oil and attaching it to the terminal1 ,i adjusted the vibration through the primary so that resonance took place without the bulb radiating ,roentgen rays to any appreciable extent4 ,i then changed the conditions so that the bulb became very active in the production of the rays40 ,according to the corallary above referred to1 the oil should be1 with such an environment and under such subjection1 a conductor of electricity1 but it was not4 ,he emphasized his satisfaction in the results by saying 8the method ,i followed is so delicate that a mistake is almost an impossibility40 ,prof4 ,w4 ,c4 ,peckham1 ,elect4 ,world1 ,n4,y41 ,may #cj1 '#if1 reasoned that the oscillating electro-static action upon the outside of the tube1 is concerned in the production of fluorescence1 and other properties of ,x-rays4 8,these oscillations are certainly synchronous with the vibrations of the cathode rays in the tube1 which in turn synchronize with the oscillation in the induction coil4 ,if the vibrations of the tube cannot keep time with those of its coil1 few or no ,x-rays will be given out4 ,the cause seems to be similar to that of sympathetic vibrations in sound4 ,in a word1 the discharge tube is a resonator for its coil1 and when the coil and tube are properly attuned1 the maximum effect is obtained4 #adi4 ,,appleyard',s ,,experiment4 ,,non-,,conductors ,,made ,,conductors ,,by ,,current4 ,proc4 ,phil4 ,so41 ,may #aa1 ,nature1 ,lon41 ,may #bd1 '#fd1 p4 #ic4 ,a piece of celluloid was pressed between two metal plates serving as terminals4 ,a galvanometer was employed to indicate the diminution of resistance by time1 and it also showed that the electrification was negative4 ,when mercury was one of the metals1 the abnormal results did not occur1 except to a very small extent4 ,when the celluloid was replaced by gutta percha tissue1 the electrification was normal4 ,many non-metals were employed1 and several were lowered in resistance4 #adi;a4 ,,resistance ,,somewhat ,,independent ,,of ,,metal ,,particles4--,through a mixture of conducting and non-conducting materials1 like a sheet of gutta percha1 having brass filings imbedded therein1--with #gej volts1 no current passed1 and this held true until the proportion in weight of the metal to the gutta percha was #b to #a4 ,let it be remembered1 also1 that selenium is reduced as to resistance under the influence of light4 #aej4 ,,minchin',s ,,experiment4 ,,resistance ,,lowered ,,by ,,electro-,,magnetic ,,waves4 ,nature1 ,lon41 ,may #bd1 '#id1 p4 #ic4--,referring to ,appleyard's experiment1 it will be noticed that he found that mixtures of certain limited per cents4 of metallic particles and insulators were exceedingly high in resistance4 ,prof4 ,g4 ,m4 ,minchin found that such materials became conductors under the influence of powerful electro-magnetic disturbances1 and that after the current was conducted1 its resistance remained greatly lowered in behalf of very weak impulses1 although1 before the experiment1 the resistance was so high4 #ad;a4 ,but after the current was interrupted by moving the terminal away from the mixture1 the high resisting power returned slowly1 at a rate somewhat in proportion to the hardness of the mixture4 ,the film employed consisted of shellac or gelatine or sealing wax1 while among the metals was pulverized tin4 ,in the latter case1 the resistance was reduced by the electro-magnetic waves from apparent infinity to #acj ohms1 the electrodes being displaced by #a cm4 ---------------------------------------- -------------------------------- ,,chapter ,,xii ,,miscellaneous ,,researches ,,on ,,roentgen ,,rays4 ------- #aea4 ,,pupin ,,and ,,swinton',s ,,experiment4 ,,sciagraphic ,,plates ,,combined ,,with ,,fluorescent ,,salts4 ,the ,elect41 ,lon41 ,apr4 #bd1 '#if4--,prof4 ,pupin1 of ,columbia ,college 7,electricity1 ,n4,y41 ,feb4 #ab1 '#if--the author saw him use it ,feb4 #g1 '#if--71 was among the first1 and probably actually the first1 to lessen the time of exposure by a fluorescent screen4 ,prof4 ,salvioni also worked in this direction at an early date4 ,prof4 ,swinton reported some details in the matter1 and he was able to obtain a sciagraph of the bones of the hand in less than #aj seconds1 with a moderately excited discharge tube1 whereas1 without the screen the time was two minutes4 ,he experimented first with barium platino cyanide1 but the results referred to were obtained with calcic tungstate1 finely ground1 and made up into paste by means of gum1 and dried4 ,he spread the same upon a celluloid sheet which was placed with the celluloid side against the photographic film4 ,the difficulty experienced first was in the formation of spots on the negative1 because some of the crystals fluoresced more than others4 ,such a defect1 however1 showed that the fluorescent salt increased the rapidity of the action upon the photographic film4 ,the result of this experiment1 as well as that of others1 has sufficiently established the fact that the fluorescent screen is of great importance in connection with the art of rapid sciagraphy4 ,phosphor sulphide of zinc is among those which hasten photographic action4 7,chas4 ,henry1 in ,comptes ,rendus1 ,feb4 #aj1 '#if47 ,dr4 ,w4 ,j4 ,morton employed the screen in taking the sciagraph of the thorax1 p4 #fa4 ,the advantageous use is also confirmed by ,,basilewski 7,comptes ,rendus1 ,march #bc1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet74--,the photographic plate was covered with a sheet of paper coated with barium and platino cyanide1 so that the two prepared surfaces were in contact1 and the fluorescent paper was between the object and the plate4 ,illustration3 ,,thorax4 #bjf4 ,by ,w4 ,j4 ,morton1 ,m4,d4 ,fluorescent screen used 7 #aea74 ,illustration3 ,,normal ,,elbow4 #bjd4 ,by ,prof4 ,miller4 ,j4 ,w4 ,gifford1 7,nature1 ,may #ba1 '#if7 tried a great variety of fluorescent bodies in combination with the photographic plate1 and found that potassium platino cyanide was decidedly the best4 #aeb4 ,,thompson',s 7,s4 ,p47 ,,experiment4 ,,penetrating ,,power ,,of ,x-,,rays ,,varies ,,with ,,the ,,vacuum4 ,comptes ,rendus4 ,,cxiii41 p4 #hji4 ,the ,elect41 ,lon41 ,april #bd1 '#if1 p4 #hff4 ,in a communication to the ,acadmie des ,sciences ,prof4 ,sylvanus ,p4 ,thompson of the ,university ,college of ,liverpool1 argued that by one kind of ,x-rays the bones of the hand were more easily penetrated than by another kind4 ,the two varieties were produced by different vacua4 #ge and #gf4 ,let the vacuum be supposed to become higher and higher4 ,at the first generation of the ,x-rays1 the fluorescent screen showed that the bones of the hand cast very dark shadows4 ,with increase of the vacuum1 the shadows of the bones were very faint4 ,this result is also obtained by reduction of temperature4 #aeb;a4 #aeb;a4 ,,bleekrode',s ,,experiment4 ,,permeability ,,at ,,low ,,temperatures ,,increased4 ,elect4 ,rev41 ,lon41 ,june #ab1 '#if4--;,experiments performed by him confirmed those of ,edison4 #ace4 ,an experiment by ,prof4 ,dewar strongly confirmed the results4 ,they noticed the same peculiarity that ,edison did1 namely1 that the shadow of the finger exhibited the flesh and bones as if they were equally transparent4 ,varied tests showed that the reduction of the temperature of glass increased its permeability4 #aec4 ,,murray',s ,,experiment4 ,,reduction ,,of ,,the ,,contact ,,potential ,,of ,,metals ,,by ,x-,,rays4 ,trans4 ,r4 ,so41 ,mar4 #ai1 '#if4 ,the ,elect41 ,lon41 ,apr4 #bd1 '#if1 p4 #heg4 ,j4 ,r4 ,e4 ,murray of the ,cavendish ,laboratory1 at the suggestion of ,prof4 ,j4 ,j4 ,thomson1 carried on a long series of careful experiments1 to find whether the contact potential of a pair of plates of different metals was1 in any way1 affected by the passage of ,x-rays between the plates4 ,all the ordinary precautions were taken4 ,the contact potential was measured by ,thomson's 7,kelvin7 method1 see ,trans4 ,brit4 ,asso41 #ahhj4 ,the important result obtained1 was that 8the air through which the rays pass1 #ij1 is temporarily converted into an electrolyte1 #dg1 and when in this condition forms a connection between the plates1 which has the same properties as a drop of acidulated water1 namely1 it rapidly reduces the potential between the opposing surfaces of the plates to zero1 and may even reverse it to a small extent40 #aed4 ,,nodon',s ,,experiment4 ,,transparency ,,of ,,differently ,,colored ,,media ,,to ,,the ,x-,,rays4 ,comptes ,rendus1 ,feb4 #c1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4 ,the rays were passed through two openings in a thick metal diaphragm1 one of which was covered by an uncolored piece of gelatine and the other by a piece tinted with the color to be tested4 ,the two images were received on the same plate4 ,the various colors tested were traversed with equal facility by the rays1 #fh and #hb4 ,the investigation described above was made by ,albert ,nodon at the ,laboratoire des ,recherches ,physiques la ,sorbonne4 ,this agrees with ,bleunard who found that colors seemed to have no influence on the passage of the rays as water colored with various aniline colors offered no more resistance than when pure4 ,from trans4 by ,l4 ,m4 ,p4 ,comptes ,rendus1 ,march1 '#if4 ,a4 and ,l4 ,lumire 7,comptes ,rendus1 ,feb4 #ag1 '#if17 observed that the ,x-rays act in the same manner upon colored photographic plates rendered sensitive to various regions of the spectrum4 ,thus1 plates sensitive to red1 yellow and green gave exactly the same impression1 provided they had the same general sensibility to white light4 ,while this may not be accurately so1 it illustrates that materials are penetrated by ,x-rays independently of the laws of color4 #aee4 ,,meslans4 ,,chlorine1 ,,iodine1 ,,sulphur1 ,,phosphorus1 ,,combined ,,with ,,certain ,,compounds1 ,,increase ,,opacity ,,to ,,the ,x-,,rays 7,comptes ,rendus1 ,feb4 #aj1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet47--,carbon in its various forms was found to be very transparent1 also organic substances containing1 besides carbon1 only the gaseous elements hydrogen1 oxygen and nitrogen2 but this transparency was far from uniform4 ,organic substances1--ethers1 acids1 nitrogenized compounds 7corps azotes71--were easily traversed by the rays2 but the introduction of an inorganic element1 as particularly1 chlorine1 sulphur1 phosphorus1 and1 above all1 iodine1 renders them opaque4 #hb4 ,this occurs also with sulphates of the alkaloids4 ,iodoform1 the alkaloids1 picric acid1 fuchsine and urea are very transparent4 ,metallic salts are very opaque1 but this varies with the metal and the acid4 ,bleunard went further into details4 ,the opacity of solutions of salts increased with the atomic weight of the metal and of the metalloid4 ,water was easily traversed by the rays4 ,solutions of bromide of potassium1 chloride of antimony1 bichromate of potash offered considerable opposition to the passage of the rays4 ,solutions of borate of soda1 permanganate of potassium were easily traversed4 ,the liquids were held in paper boxes4 ,the experiments above related were conducted by ,maurice ,meslans at l'cole de ,pharmacie de ,nancy4 ,illustration3 ,,from ,,sciagraph ,,of ,,pencil1 ,,key1 ,,fountain-,,pen1 ,,and ,,coin4 #afa4 ,by ,prof4 ,mc,kay1 ,packer ,institute4 ,illustration3 ,,from ,,sciagraph ,,by ,,prof4 ,,miller4 #aef4 #a4 ,real diamond4 #b4 ,paste4 #c4 ,glass4 #d4 ,real diamond mounted in gold ring4 #aef4 ,,buquet ,,gascard',s ,,experiments4 ,,action ,,of ,,the ,x-,,rays ,,upon ,,the ,,diamond ,,and ,,its ,,imitations2 ,,also ,,upon ,,jet4 ,comptes ,rendus1 ,feb4 #bd1 #if4 ,from trans4 by ,louis ,m4 ,pignolet4--,sciagraphs taken by the ,x-rays showed that diamonds became transparent1 and their shadows disappeared with long exposures2 but imitation diamonds remained opaque under the same conditions4 ,jet was distinguished from its imitations by the same method4 ,the diamond and jet cast clearer shadows on a fluorescent screen than their imitations4 ,the above tests were made by ,albert ,buquet and ,albert ,gascard1 at the ,cabinet de ,physique de l'cole des ,sciences de ,rouen4 ,the half-tone on lower half of adjacent page1 #afd1 was taken from a sciagraph by ,prof4 ,dayton ,c4 ,miller1 of ,case ,school of ,applied ,science4 ,the differences of opacity are proved1 because all were of same thickness and exposed simultaneously4 ,prof4 ,sylvanus ,p4 ,thompson 7,the ,elect41 ,lon41 ,may #ah1 '#if7 confirmed the above1 and also found that1 although the diamond is more transparent than glass1 it is more opaque than block carbon or graphite4 ,mineralogists are thus enabled to submit minerals to the ,x-ray test in making analyses4 #aeg4 ,,dufour',s ,,experiment4 ,,inactive ,,discharge ,,tubes ,,made ,,luminous ,,by ,x-,,rays4 ,comptes ,rendus1 ,feb4 #bd1 '#if4 ,from trans4 by ,mr4 ,pignolet4--,he observed that very small and sensitive ,geissler tubes phosphoresced when exposed to ,x-rays4 #bb1 #bc4 #aeh4 ,,beaulard',s ,,experiments4 ,,non-,,refraction ,,of ,x-,,rays ,,in ,a ,,vacuum4 ,comptes ,rendus1 ,mar4 #cj1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4 ,with prisms of ebonite1 ,f4 ,beaulard held that no decided deviation could be observed within the vacuum4 #aei4 ,,carpentier',s ,,experiment4 ,,sciagraph ,,showing ,,the ,,parts ,,in ,,relief ,,on ,a ,,coin4 ,comptes ,rendus1 ,mar4 #b1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4 ,an imprint of a coin stamped upon a thin piece of well annealed aluminum by pressing the coin against the aluminum1 was reproduced in a sciagraph4 ,the raised parts of the coin were scarcely #h_/ajj of a millimeter high4 ,the aluminum was #e_/aj millimeter thick4 ,this result is admirably represented by the sciagraph of an aluminum medal on page #aff1 taken by ,prof4 ,dayton ,c4 ,miller1 of ,case ,school of ,applied ,science1 ,elect4 ,world1 ,n4,y41 ,mar4 #ba1 '#if1 who also made a sciagraph of a copper plate #a_/d inch thick having blow holes which appeared in the picture1 but they could not be detected by light1 serving to illustrate an application of the new discovery in testing the homogeneity of metals4 #afj4 ,,wuillomenet',s ,,experiments4 ,,transparency ,,of ,,the ,,eye ,,to ,,the ,x-,,rays ,,determined ,,by ,,sciagraph ,,of ,,bullet ,,therein4 ,comptes ,rendus1 ,mar4 #bc1 '#if4 ,a sciagraph taken with an exposure of three hours showed perfectly a lead shot introduced into the vitreous media of the eye of a full grown rabbit4 ,therefore the opacity of the media of the eye was not absolute4 ,in a second series of experiments by ,dr4 ,wuillomenet a human head was used1 but the results were negative in spite of a great intensity of the rays and a long exposure1 #hb4 #afa4 ,,fernand ,,ranwez',s ,,experiments4 ,,application ,,of ,,the ,x-,,rays ,,to ,,analysis ,,of ,,vegetable ,,matter4 ,comptes ,rendus1 ,apr4 #ac1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4 ,sciagraphy can render valuable services in analytical researches and specially in the analysis of vegetable foods where they will show the most usual adulterations consisting of mineral substances4 ,illustration3 ,,bas-,,relief ,,sciagraph1 #aei1 ,,by ,,prof4 ,,dayton ,c4 ,,miller4 ,this method offers several advantages for small samples of the substances can be examined4 ,the samples are not chemically changed4 ,a great number of tests can be made in a short time4 ,lastly1 the sciagraph obtained affords a permanent record4 ,the tests were made on samples of adulterated saffron composed of mixtures of pure saffron and saffron coated with sulphate of barium4 ,a sciagraph taken with an exposure of three minutes showed scarcely visible imprints of the pure but strong impressions of the adulterated4 ,see sciagraph of pen1 7mineral7 in holder1 7vegetable71 in cut at upper part of p4 #afd1 which also shows the graphite in a wooden pencil4 #afb4 ,,errera',s ,,experiment4 ,,action ,,of ,,the ,x-,,rays ,,on ,,phycomyces4 ,,hertz ,,waves ,,and ,,roentgen ,,rays ,,not ,,identical4 ,comptes ,rendus1 ,march #cj1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4--,phycomyces ,nitens1 when submitted to the asymmetrical action of ,hertz electric waves1 became curved1 according to ,hegler4 ,errera found a ,phycomyces was not affected by the ,x-rays1 thus denoting an absence of ,hertz waves in the rays4 ,credit for the above result is due to ,l4 ,errera1 from experiments made at the ,laboratoire ,physique and the l',institut ,solvay 7,universit de ,bruxelles74 #afc4 ,,gossart1 ,,chevallier1 ,,foutana ,,and ,,uruanni',s ,,experiment1 ,,in ,,conjunction ,,with ,j4 ,r4 ,,rydberg4 ,,no ,,mechanical ,,action ,,of ,x-,,rays4 ,comptes ,rendus1 ,feb4 #aj1 ,mar4 #bc1 ,apr4 #ac1 '#if4 ,from trans4 by ,louis ,m4 ,pignolet4--,the former party alleged that radiations from a discharge tube caused a cessation of the rotation of the vane of the radiometer4 ,j4 ,a4 ,rydberg was not inclined to confirm such action4 ,a4 ,foutana and ,a4 ,uruanni made experiments and concluded that the action was due to an electro-static force1 having noticed that a ,leyden jar would also produce such effect4 ,the author made some experiments to determine the matter in reference to ,x-rays at a distance outside of the electro-static field4 ,the rays would neither stop the vanes nor cause them to rotate4 ,he made some other experiments to detect whether there was any direct mechanical power possessed by the rays2 but if any1 it was exceedingly feeble4 ,t4 ,c4 ,porter made some experiments at ,eton ,college1 7,nature1 ,june #ah1 '#if17 which confirmed the above results1 finding that the radiometer is entirely inert to the ,roentgen rays1 whether they be from a properly electrically screened hot or cold tube4 ,he distinguished between the caloric conditions1 for he found that1 not only will reduction of temperature vary the penetrating power of the rays1 #ace and #aeb;a1 but also will an increase of temperature4 #afd4 ,,battelli',s ,,experiment4 ,x-,,rays ,,within ,,discharge ,,tube4 ,nuovo ,cimento1 ,apr41 '#if1 p4 #aic2 ,elect4 ,rev41 ,lon41 ,june #ab1 '#if4--,shortly after the announcement of the discoveries of ,lenard and ,roentgen1 it would have been considered strange to assert that ,x-rays may exist inside of the discharge tube4 ,battelli certainly correctly infers1 that inasmuch as ,x-rays apparently originate from the point where a material object is struck by the cathode rays1 #aae1 it would follow that when the said object is within the vacuum space1 ,x-rays are propagated before they reach the glass wall of the discharge tube4 ,it has already been noted 7,de,metz1 #fc;a7 that photographic action may be produced within the discharge tube4 ,battelli has confirmed this1 not by a crude experiment1 like that 7failure7 of some authority in ,england1 but by a series of severe tests1 leaving no doubt as to the production of photographic action4 ,he discovered in connection with several subordinate phenomena that among the rays capable of producing a photographic impression within the discharge tube1 some were deflected by a magnet and others were not1 from which he concluded that ,x-rays may exist inside the tube1 in conjunction with cathode rays1 before collision with the anti-cathode4 ,the experiment consisted in deflecting the rays by a magnet1 the film being in the path that the rays would have had without a magnet4 ,there was also a film in the path of the deflected rays4 ,photographic action was produced upon both4 ,he varied the vacuum4 ,photographic action began at #c-aj mm41 had its maximum at #a-gj mm41 after which it remained constant4 ,no photographic action was obtained upon a film placed within the tube opposite the anode1 except in one case where it was exceedingly weak4 ,lenard continually inferred that there must be two kinds of cathode rays4 #ge4 ,battelli has certainly sifted the two rays apart and thus proved ,lenard's conjectures4 #fa;b1 p4 #dg4 ,the ,elect4 ,rev41 ,lon41 pays tribute to ,battelli1 by offering the following opinion3 8,we have no hesitation in saying that ,battelli1 by means of interesting and ingenious experiments1 has made the greatest advances in the theory of the ,x-rays since their discovery by ,roentgen40 ,in many cases the author has omitted stating1 in taking sciagraphs1 that the films were protected from ordinary light by opaque material4 ,this1 as a matter of course1 has always been understood4 ,battelli also had the films wrapped in material opaque to ordinary light4 ,experimenters should1 if possible1 always employ aluminum for this purpose1 because the author has always noticed that black paper or cloth permits a great deal of light to come through1 even when in double thickness4 ,prof4 ,sylvanus ,p4 ,thompson 7,the ,electr41 ,lon41 ,june #bf1 '#if7 located a wire in a focus tube in the path of the rays between the platinum reflector and the wall of the tube4 ,not only was there a sciagraph of this wire produced in the sciascope1 but also the ,crookesian shadow of the wire on the wall of the bulb4 ,for this experiment the exhaustion must be quite high4 8,at no state of exhaustion did the platinum reflector convert all the internal cathode rays into ,x-rays40 ,both shadows were cast by the platinum reflector as the origin4 ,more or less of the rays between the reflector and the glass were sensitive to a magnet4 ,illustration3 ,,bleyer',s ,,experiment4 #afe4 ,combined camera and sciascope at the left3 and showing induction coil and discharge-tube at the right4 #afe4 ,,bleyer',s ,,experiment4 ,,combined ,,camera ,,and ,,sciascope4 ,elect4 ,eng41 ,july #a1 '#if2 ,royal ,acad4 ,med4 ,sur41 of ,naples1 ,italy4--,as early as ,april #g1 ,j4 ,mount ,bleyer1 ,m4,d41 of ,naples1 constructed and used the apparatus shown in the adjacent cut1 p4 #afi4 ,the picture is self-explanatory4 ,attached to an ordinary camera is a flaring sciascope1 for receiving the temporary sciagraph of the hand1 for example4 ,the ,x-rays are converted into luminous rays by the fluorescent screen1 and1 therefore1 the camera will serve to take a picture by means of the luminous rays from the sciagraph of the hand4 ,the cut represents also an induction coil and a discharge tube4 ,soon afterwards1 it was reported by an ,english paper that ,dr4 ,levy1 of ,berlin1 and others of ,england1 had also made similar tests with success4 ,in order to illustrate the applicability of the combination1 ,dr4 ,bleyer took many sciagraphs with the camera4 ,he calls it the photofluoroscope1 which1 however1 will probably not meet with favor for the name does not suggest the nature of the instrument4 ,when two radically different devices are combined into one1 it is difficult to formulate an acceptable single word1 and1 therefore1 the instrument will probably always be called by some of the following terms3 ,a camera with sciascopic adjustment1 or combined sciascope and camera1 or corresponding combinations with the word fluoroscope4 ,from the time that ,roentgen's discovery was announced1 scientists throughout the world have made careful experiments1 up to date1 in all possible directions1 and the time has now come when the number of experiments is rapidly decreasing1 only one or two being noted now and then in the scientific press1 and consisting mostly in repetition1 with occasionally a slight departure1 involving a radically new subordinate discovery2 but in view of the great number of scientists1 and of their high standing as careful experimenters1 and because also of their desire to be correct in their inferences1 there might seem to be little else to be investigated4 ,time only will tell4 ,before passing to the final chapters relating to other matters1 a few more experiments are related in the briefest manner4 #aff4 ,prof4 ,sylvanus ,p4 ,thompson confirmed non-polarization1 7,phil4 ,so41 ,june #ab1 '#if1 and ,the ,electr41 ,lon41 ,june #bf1 '#if47 ,dr4 ,john ,macintyre 7,nature1 ,june #bd1 '#if7 carried on a long series of experiments with tourmaline1 and also arrived at the conclusion that polarization of ,x-rays is practically impossible1 #ig1 at end4 ,illustration3 ,,from ,,sciagraph ,,by ,,prof4 ,,goodspeed1 ,,showing ,,curvature ,,of ,,the ,,radius1 ,,due ,,to ,,arrested ,,development ,,of ,,the ,,ulna ,,at ,,its ,,distal ,,epiphysis4 ,,one ,,bone ,,shown ,,through ,,another4 #afg4 ,in the same paper ,prof4 ,thompson showed conclusively that there is a diffuse reflection of ,x-rays4 #ha and #ajc4 ,a curious experiment consisted in his obtaining dust figures1 #cf4 by the discharge of an electrified body by ,x-rays4 ,in another experiment he caused reflection of the rays from the surface of sodium located in a vacuum4 ,the amount reflected was a minimum for normal incidence and increased at oblique incidence4 #afh4 ,prof4 ,oliver ,j4 ,lodge1 ,f4,r4,s41 reported in ,the ,electr41 ,lon41 ,june #e1 '#if1 further detail experiments in the line set out in #aac4 ,he proved conclusively1 as stated by the editorial in ,the ,electrician1 that a positive charge has increasing effect upon the ray-emitting power of the surface exposed to the cathodic radiation4 #afi4 ,at ,eton ,college1 ,t4 ,c4 ,porter 7,nature1 ,june #ah1 '#if7 confirmed the experiments of others by showing that the blackened face of the thermopile connected with a very sensitive galvanometer was not influenced in any manner by ,x-rays4 #agj4 ,prof4 ,william ,f4 ,magie1 of ,princeton1 ,n4 ,j41 made a careful experiment in relation to diffraction4 ,princeton ,college ,bulletin1 ,may1 '#if4 ,the experiment would certainly prove that if ,x-rays are due to vibrations1 the latter are of a different order from those occurring in light rays1 for the slits exhibited light diffraction very well1 but there was no evidence1 by a widening of the image on the plate1 that ,x-rays had been diffracted in the slightest degree4 #aaj and #aaj;a4 #aga4 ,prof4 ,haga1 of ,groningen ,university1 at the suggestion of ,mr4 ,j4 ,w4 ,giltay1 7,nature1 ,june #d1 '#if17 made some very crucial tests1 with numerous precautions1 in reference to the action of ,x-rays upon selenium1 and the results were so positive that they thought that a practical application could be made by using selenium for detecting ,x-rays1 both qualitatively and quantitatively4 ,in repeating the experiments1 it must be borne in mind that one half hour or so is required for selenium to return to its former degree of ohmic resistance after being struck by light or heat or ,x-rays4 ,total number of to this place1 #aii4 ---------------------------------------- -------------------------------- ,,chapter ,,xiii ,a ,,few ,,typical ,,applications ,,of ,x-,,rays ,,in ,,anatomy1 ,,surgery1 ,,diagnosis1 ,,etc4 ------- #bjj4 ,,hogarth',s ,,experiment4 ,,needle ,,located ,,by ,x-,,rays ,,and ,,removed4 ,the ,lancet1 ,lon41 ,mar4 #bh1 '#if4--;,dr4 ,hogarth is the medical officer of the general hospital1 ,nottingham4 ,a young woman was suffering with a pain in her hand near the metacarpal bone of the ring finger4 ,a slight swelling existed4 ,ten weeks before1 a needle had entered the palm while washing the floor4 ,it had entered at the base of the fifth metacarpal bone4 ,chloroform had been given and an incision made1 but no needle found and its presence doubted4 ,a sciagraph was taken and the needle was accurately located and the next day removed4 #bja4 ,,savary',s ,,experiment4 ,,needle ,,located ,,by ,,sciascope ,,and ,,removed4 ,the ,lancet1 ,mar4 #bh1 '#if4--;,dr4 ,savary located a needle by a sciascope although efforts by all other methods had failed4 ,a line was drawn between two points intersecting the needle at right angles4 ,about half an inch below the surface of the skin of the wrist the blade of the scalpel impinged upon the needle1 which was removed without difficulty4 #bjb4 ,,renton ,,somerville',s ,,experiment4 ,,diagnosis4 ,the ,lancet1 ,lon41 ,apr4 #d1 '#if4--;,a writer for the ,lancet reported that ,drs4 ,renton and ,somerville made a diagnosis with the assistance of the screen4 ,in one1 the suspected case of unreduced dislocation of the phalanx1 they saw that the parts were in the proper position4 ,he showed to medical men an old fracture of the forearm where the fragments of the bones were distinct as to the shadows4 ,illustration3 ,,from ,,sciagraph ,,of 8,,colles' ,,fracture0 ,,in ,,the ,,right ,,wrist1 ,,by ,a ,,fall ,,on ,,the ,,sidewalk4 #bjg4 ,by ,william ,j4 ,morton1 ,m4,d4 #bjc4 ,,miller',s ,,experiments4 ,,location ,,of ,,bullets4 ,elect4 ,world1 ,mar4 #ba1 '#if4--;,bullets were clearly located in the hands of two different men by ,prof4 ,dayton ,c4 ,miller1 of the ,case ,school of ,applied ,science4 ,in one1 the bullet had been lodged for #ad years and had always been thought to lie between the bones of the forearm1 but two sciagraphs from different directions located the ball at the base of the little finger4 ,by means of five sciagraphs from different directions1 the ball in the other hand was located at the base of the thumb4 #bjd4 ,,injuries ,,by ,,accident ,,and ,,miscellaneous ,,cases4 ,the ,integral1 ,cleveland1 ,ohio1 '#if4--,many fingers and hands were examined by ,prof4 ,miller that had been injured by planing machines1 cog-wheels1 base balls1 pistols1 etc41 and in each case the nature of the injuries was determined4 ,several cases of fractured arms were studied--some through splints and bandages4 ,some sciagraphs indicated that the ends of the broken bones had not been placed in apposition4 ,subsequently1 an operation was performed to remedy the setting4 ,in one case1 he sciagraphed the arm from which a piece of the ulna had been removed five years previously4 ,the necrosis had increased4 ,two sciagraphs at right angles to each other clearly exhibited the nature of the disease4 ,the permanent set of the toes by wearing pointed shoes was clearly exhibited 7p4 #cj47 ,the figure on page #adg is the side view of a foot in a laced shoe4 ,the outlines of the bones can be traced1 also the eyelets and the pegs in the heel1 while the uppers scarcely appear4 ,in ,fig4 #a 7introduction7 is shown a head1 only the skull being clearly reproduced4 ,in the negative1 the teeth appear and places whence the teeth have been extracted1 also the jaw bones1 nasal cavities and the ragged junction of the bones and cartilage4 ,the varying thickness is represented in the cut1 at the temples and ears4 ,fig4 #b 7introduction7 shows that a broken bone was badly set1 the ends overlapping each other instead of meeting end to end4 ,a sciagraph of an elbow is shown on p4 #afa4 ,the flesh is scarcely visible4 ,fig4 #c 7introduction7 is a picture which reproduced the mere indication of the spine and ribs4 ,in the original negative the collar bones1 pelvis1 clavicles1 buckle of clothing and location of the heart and stomach were faintly outlined4 ,fig4 #d 7introduction7 is a representation of the knee of a boy #ae years old1 in knickerbockers1 showing the buttons clearly1 and dimly a #cb caliber bullet which is imbedded in the end of the femur4 #bjd;a4 ,,necrosis4 ,mortification of the ulna is represented on p4 #adb4 ,necrosis of the bone corresponds to gangrene of the soft parts2 life is extinct4 #bje4 ,,morton',s ,,experiment4 ,,diagnosis4 ,elect4 ,eng41 ,n4,y41 ,june #ag1 '#if4 ,lect4 before ,odontological ,so41 ,n4,y41 ,apr4 #bd1 '#if2 repeated in ,dental ,cosmos1 ,june1 '#if4--;,dr4 ,william ,j4 ,morton1 of ,new ,york1 made several important examinations of the human system by the use of ,x-rays4 ,in regard to application in dentistry1 he stated3--8,each errant fang is distinctly placed1 however deeply imbedded within its alveolar socket2 teeth before their eruption stand forth in plain view2 an unsuspected exostosis is revealed2 a pocket of necrosis1 of suppuration1 or of tuberculosis is revealed in its exact outlines2 the extent and area and location of metallic fillings are sharply delineated1 whether above or below the alveolar line4 ,most interesting is the fact that the pulp-chamber is beautifully outlined1 and that erosions and enlargements may be readily detected40 #bjf4 ,the author saw one of ,dr4 ,morton's original photographed sciagraphs of the thorax1 #ae inches by #aa inches1 not at all creditably reproduced at page #afa4 ,in the original1 to the surgeon's eye3 8,the acromion and coracoid processes of the shoulder blade are clearly shown in their relations to the head of the humerus1 or arm bone1 and also the end of the clavicle1 or collar bone1 is shown in its relations to the shoulder joint4 ,we have1 in short1 an inner inspection in a living person of this rather complicated joint1 the shoulder1 and there can be no doubt that in defined pictures of this nature even very slight deformities and diseases would be detected4 ,it is noticeable that the front portions of the ribs are not shown1 only the posterior portions lying nearest to the sensitized plate appear2 also the breastbone was sufficiently dense to almost entirely obstruct the ,x-rays4 ,a collar button at the back of the neck is taken through the backbone4 ,in some of my negatives the dark outline of the heart and liver is shown as well as the outlines of tumors in the brain2 but this is evidently for purposes of demonstrating the location of organs1 an over-exposure1 and does not1 therefore1 indicate the outlines of the heart40 ,the time of exposure was reduced by the use of a fluorescent screen in conjunction with the photographic plate4 #bjg4 ,a woman was troubled with a stiffened wrist4 ,dr4 ,morton took a single sciagraph of both wrists side by side as shown at page #agd1 7the photographic print being presented for this book by ,e4 ,b4 ,meyrowitz1 #ajd ,east #bc;d ,street1 ,n4,y47 ,the injured wrist in the picture exhibited the ,colles' ,fracture--the ulna and radius bones being telescoped into their fractured ends by a fall upon the sidewalk a year before4 ,by knowing the cause1 the manner of cure became evident1 and1 accordingly1 the patient is expected to bend the wrist backward and forward and laterally several times a day4 ,illustration3 ,from sciagraph of club foot of child by ,prof4 ,goodspeed4 ,copyright1 '#if1 by ,william ,beverley ,harison1 ,pub4 of ,x-ray pictures1 ,new ,york4 ,this linograph 7woodcut71 engraved and donated by ,stephen ,j4 ,cox1 ,downing ,building1 #ajh ,fulton ,st41 ,new ,york1 affords an exact likeness of the sciagraph1--well-nigh impossible by an untouched half-tone4 ,dr4 ,morton1 in a lecture before the ,medical ,society of the ,county of ,new ,york1 to be printed in the ,medical ,record1 related that another promising field of research and application is in the detection of calcareous infiltrations involving1 for instance1 the arteries1 or occurring in the lungs and other tissues4 ,calculi in kidneys1 in the bladder1 in the salivary ducts have already been successfully located4 ,the stages of ossification1 and the epiphyseal relations of the osseous structure in children may be pictured as is demonstrated in the picture of the entire skeleton of an infant five months of age4 ,the sciagraph shows plainly that it will be possible to detect spinal diseases1 either in children or in adults4 7,not reproduced47 #bjh4 ,,norton',s ,,experiment4 ,,diagnosis4 ,elect4 ,world1 ,n4,y41 ,may #bc1 '#if4--;,in conjunction with ,dr4 ,francis ,h4 ,williams1 ,dr4 ,norton examined several patients from the city hospital to determine how an ,x-ray diagnosis would agree with that previously made by the hospital staff4 7,see also #adb1 at end47 ,the outline of an enlarged liver1 #g inches in diameter1 was easily distinguished1 the two outlines1 one by percussion and one by ,x-rays1 agreeing better in favor of the latter by #a_/b inch4 ,an enlarged spleen was perfectly outlined4 ,the tuberculosis of one lung caused it to be more opaque than the sound lung4 ,it was found necessary to take into account the seams of clothing1 buttons1 buckles1 etc4 ,a bullet was found exactly under the spot which they marked as being over the bullet4 ,a foreign metallic body can be easily detected in the sophagus1 because the latter is quite transparent4 ,they could see the shadows of the cartilaginous rings in the trachea1 glottis1 and epiglottis4 ,younger persons1 up to #aj years of age1 are more transparent than older4 #bji4 ,,lannelongue1 ,,barthelemy ,,and ,,oudin',s ,,experiments4 ,,osteomyelitis ,,distinguished ,,from ,,periostitis4 ,elec4 ,rev41 ,lon41 ,feb4 #ad1 '#if4--;,in a sciagraph of a person diseased with the former1 the surface of the bone was proved to be intact1 while the internal parts were destroyed4 ,in the latter disease the changes proceed from the surface to the interior4 ,the art of sciagraphy1 more nearly1 as every month passes1 becomes developed by means of improved apparatus1 screens1 photographic plates and other elements which at present are only dimly predicted4 ,nevertheless1 how can a better sciagraph of bones1 showing their thickness and porosity1 be desired than that reproduced on page #agg1 and taken by ,prof4 ,arthur ,w4 ,goodspeed1 and representing a club foot of a child8 ,in the race to excel in this new art1 no one1 to the author's knowledge1 has surpassed ,prof4 ,goodspeed1 of the ,university of ,penn41 considered jointly from the standpoints of priority1 superiority1 quantity and variety4 ,dr4 ,keen1 ,l4,l4,d41 ,professor in the ,jefferson ,medical ,college1 of ,philadelphia1 stated 7,inter4 ,nat4 ,med4 ,mag41 ,june1 '#if7 that ,prof4 ,goodspeed 8has far eclipsed all others in these most beautifully clear sciagraphs40 #baj4 ,a book could be filled with the numerous cases of diagnosis by ,x-rays showing the utility4 ,in closing this chapter1 let it suffice to mention some of the sources of literature relating to this subject directly or indirectly3 location of shot 7by ,dr4 ,ashhurst1 ,phila47 in lady's wrist1 not located by other means4 ,dr4 ,packard's case of acromegaly2 ,dr4 ,muller's 7,germantown7 location of needle in boy's foot2 cause of pain not before known2 needle subsequently removed2 a perfect thorax1 or trunk1 by ,prof4 ,arthur ,w4 ,goodspeed1 ,university of ,pennsylvania2 ,thomas ,g4 ,morton's 7,m4 ,d4 ,pres4 ,acad4 ,surg41 ,phila47 application to painful affection of the foot1 called metatarsaligia4 ,all of the above noticed in ,inter4 ,med4 ,mag41 ,june1 #ahif4 ,case of a burned hand with anchylosis of the fingers1 by ,w4 ,w4 ,keen1 ,m4,d41 ,l4,l4,d4 ,bacteria not killed by ,x-rays4 ,normal and abnormal phalanx distinguished4 ,fracture and dislocation sometimes differentiated by ,x-rays4 ,amer4 ,jour4 ,med4 ,sci41 ,mar41 '#if4 ---------------------------------------- -------------------------------- ,,chapter ,,xiv ,,theoretical ,,considerations4 ------- ,before attempting to discuss the facts now known in regard to the ,roentgen phenomena1 it is well to review briefly the known ways in which radiant energy may be transmitted4 ,by radiant energy is1 of course1 meant energy proceeding outward from a source and producing effects at some distant point4 ,there are two well understood ways in which energy may be transmitted1--first1 by an actual transfer to the distant point of matter to which the energy has been imparted from the source1 as in the flight of a common ball1 a bullet1 or a charge of shot4 ,in this mode of transmission1 it is evident that the flying particles1 assuming that they are subject to no forces on the way1 will move in straight lines from the source to the distant point4 ,they constitute real rays1 diverging from the source2 an obstacle in their path1 would1 if the radiations proceeded from a point1 cast a shadow with sharply defined edges4 ,second1--by a transfer of the energy from part to part of an intervening medium1 each part as it receives the energy1 transmitting it at once to the parts around it1 no part undergoing more than a slight displacement from its normal position4 ,this mode of transmission constitutes wave motion4 ,the source imparts its energy to the particles of the medium near it4 ,each of those particles transfers its energy to the particles all around it4 ,each of these particles in turn transfers its energy to the particles around it1 and so on through the medium4 ,it is plain that there are here no such things as genuine rays4 ,as the energy is transferred from particle to particle1 each in turn becomes a centre of disturbance transmitting its motion in all directions4 ,it is only because the movements transmitted from different points annul one another except along certain lines1 that we have apparent straight lines of transmission1 and1 therefore1 fairly sharp shadows4 ,but shadows produced by wave transmissions are never absolutely sharp4 ,the wave movement is always propagated to some extent within the boundary of the geometrical shadow1 less as the wave lengths are shorter4 ,with sound waves whose lengths are measured in inches or feet1 the penetration into the shadow is considerable4 ,with light waves #a_/cgjjj to #a_/gjjjj of an inch in length1 the penetration into the shadow is very small and requires specially arranged apparatus to show that it exists4 ,this penetration into the geometrical shadow is characteristic of energy propagated by wave motion1 and if the fact of such penetration can be demonstrated1 it is conclusive proof of propagation by waves4 ,another characteristic of wave motion is found in the phenomena of interference4 ,this is the mutual effect of two wave systems1 which1 when meeting at a given point1 may strengthen or annul each other according to the conditions under which they meet4 ,either of those characteristics should enable us to distinguish between propagation by wave motion and by projected particles4 ,but when wave lengths are very short and radiations feeble1 the tests are not easy to apply4 ,again1 a wave is in general propagated with different velocities in different media4 ,this causes a deflection or deformation of the wave as it passes from one medium into another1 and results in refraction1 as in the cases of light and sound4 ,absence of refraction would be strong though not conclusive evidence against a wave theory of propagation4 ,in wave propagation1 each particle of the medium suffers a small displacement from its equilibrium position and performs a periodic motion about that position4 ,this displacement may be in the line of propagation--longitudinal vibration--or it may be in a plane at right angles to that line--transverse vibration4 ,all the phenomena mentioned above1 diffraction1 interference1 refraction1 and also reflection1 belong equally to either mode of wave propagation4 ,other phenomena must be made use of to distinguish between these4 ,when the vibrations are transverse they may all be brought into one plane through the line of propagation4 ,they may be polarized1 when the ray will present different phenomena upon different sides4 ,when the vibrations are longitudinal1 no such phenomena can be produced4 ,polarization1 then1 serves to distinguish between longitudinal and transverse vibrations4 ,now let us consider briefly the ,roentgen ray phenomena that bear upon the question of the nature of the propagation4 ,illustration3 ,,from ,,sciagraph ,,of ,,normal ,,elbow-,,joint2 ,,straight1 ,,in ,,position ,,of ,,supination4 ,by ,a4 ,w4 ,goodspeed4 ,phot4 ,times1 ,july1 '#if4 ,copyright1 #ahif1 by ,william ,beverley ,harrison1 ,publisher of 8,x-ray0 ,pictures1 ,new ,york4 ,it seems to be settled beyond question that the origin of the ,roentgen rays is the fluorescent spot in the discharge tube4 #ajg1 #ajh1 #aaa4 ,the evidence seems overwhelming that within the tube1 the phenomena are the result of streams of electrified particles of the residual matter1 shot off from the cathode in straight lines1 perpendicular to its surface4 #eg4 ,this was ,crookes' original theory1 #ec1 near centre1 and it seems to have stood well the test of scientific criticism4 ,these flying particles falling upon anything in their path1 give rise to ,x-rays4 ,it is preferable1 but not essential1 that the bombarded surface should be connected electrically with the anode4 #aac1 and #aaf4 ,the best results are obtained by using a concave cathode1 and placing at its centre the surface which is to receive the bombardment1 thereby concentrating the effect upon a small area4 ,nearly all experimenters agree in locating the origin of the ,x-rays at this bombarded spot4 ,the energy here undergoes a transformation1 and the ,x-rays represent one of the forms of energy developed4 ,what are the characteristics of this particular form of radiant energy8 ,it causes certain salts to fluoresce1 #ff1 #hd1 and #acb1 and it affects the photographic plate4 #gj and #hd4 ,in these respects1 it is like the short wave length radiations from a luminous source4 ,it is1 however1 totally unlike these in its power of penetrating numerous substances entirely opaque to light1 such as wood1 paper1 hard rubber1 flesh1 etc4 ,in passing through hard rubber and some other opaque insulators1 ,x-rays are like the long wave length radiations from heated bodies1 but ,x-rays penetrate many substances that are opaque to these long wave length radiations1 and they are especially distinguished from all forms of radiant energy previously recognized1 in their relative penetrating power for flesh and bones which makes it possible to obtain the remarkable shadow pictures which have become within three or four months1 so familiar to all the world4 ,but these phenomena1 although they serve to distinguish the ,x-rays from all other forms of radiant energy1 do not furnish any clew to the nature of the ,x-rays themselves4 ,in attempting to formulate a theory of ,x-rays1 the idea that first naturally presents itself is that they are due to some form of wave motion4 ,illustration3 ,,from ,,sciagraph ,,of ,,knee-,,joint1 ,,straight1 ,,side ,,view1 ,,showing ,,patella1 ,,or ,,knee-,,cap4 ,by ,prof4 ,goodspeed4 ,phot4 ,times1 ,july1 '#if4 ,the characteristics of wave motion are diffraction and interference phenomena4 ,so far1 no positive evidence of diffraction1 #aaj1 nor interference1 #hi1 have been recognized1 although experiments1 have been tried that would have shown plainly1 diffraction phenomena1 had light been used in place of the ,roentgen radiations4 #agj4 ,we must1 therefore1 conclude1 either that the ,roentgen radiations in the experiments were too feeble to produce a record of the diffraction effects1 or1 that they are not due to wave motion at all1 unless of a wave length very small even when compared with waves of light4 ,the absence of refraction is also opposed to any wave theory of the ,roentgen radiations1 for it is difficult to believe that waves of any kind could travel with the same velocity through all media1 which they must do if they suffer no deviation4 #hf4 ,the next supposition naturally is1 that the phenomena are due to streams of particles4 ,it has been suggested that the rays may be streams of material particles1 but this theory cannot be maintained in view of the fact that the rays proceed1 without hindrance1 through the highest vacuum4 #gb;b and #acc1 near end4 ,neither is it consistent with the high velocity of propagation4 ,molecules of gas could not be propelled through air with any such velocity or to any such distance as ,x-rays are propagated4 ,tesla has claimed #aci1 that the residual gases are driven out through the glass of the vacuum bulb by the high potential that he employs4 ,this has not been confirmed by other experimenters4 ,it has been observed that the vacuum may be greatly improved by working the bulb1 #aba1 that is1 sending the discharge through it1 but experimenters generally have found that heating the bulb impairs the vacuum and restores the original condition4 ,the gases1 were1 therefore1 occluded during the electrical discharge1 to be again set free by heating the bulb4 #aci;b4 ,the rays may be ether streams1 perhaps in the form of moving vortices1 but of such streams we have no independent knowledge1 and can only determine by mathematical analysis1 what their characteristics should be4 ,they would not suffer refraction1 and would not produce interference nor diffraction phenomena4 ,whether they would do what the ,x-rays do1 go through the flesh and not through bone1 through wood and not through metal1 excite fluorescence1 or affect the photographic plate1 cannot be said4 ,there is evidence that there are at least two kinds of ,x-rays1 #aeb1 differing in penetrating power1 though perhaps not differing in other respects4 ,illustration3 ,,from ,,sciagraph ,,of ,,normal ,,knee-,,joint1 ,,flexed4 ,phot4 ,times1 ,july1 #if4 ,copyright1 #ahif1 by ,william ,beverley ,harison1 ,publisher of 8,x-ray0 ,pictures1 ,new ,york4 ,x-rays have their origin only in electrical discharges in high vacua4 ,they are absent from sun-light and from light of the electric arc1 and other sources of artificial illumination1 #acf4 ,proceeding from the bombarded spot1 they are not deflected by a magnet1 except in an evacuated observing tube1 as proved by ,lenard1 #gb;a1 and show no evidence of carrying an electric charge like cathode rays1 #fa;b1 p4 #dg4 ,on the contrary1 they will discharge either a negatively or positively charged body in their path4 ,the evidence seems conclusive 7,chap4 ,,viii47 that the ultra-violet rays from an illuminating source also discharge charged conductors4 ,in this respect1 therefore1 there is a similarity between the ,x-rays and ultra-violet light4 ,the action of the waves of light upon a cell formed of selenium lowers the resistance of the latter and herein is circumstantial evidence at least1 concerning the similarity of the properties of ,x-rays and light1 because the former are also found to increase the conducting power of selenium4 #aga4 ,the experiments of ,roentgen1 #ij1 seem to show that the discharging effect of ,x-rays is due to the air through which the rays have passed4 ,it is certain that the discharge of electrified bodies by light occurs more generally for negatively than for positively charged bodies1 #ii;,b1 #ii;,i1 and #ii,s1 that it depends upon the nature1 #ig;b1 and density1 #ig;a1 of the gas surrounding the body1 and also upon the material of the charged body itself4 #ih4 ,the discharge would1 therefore1 seem to be connected with a chemical action1 #aec1 near end1 which is promoted by the rays4 ,this seems all the more probable1 since it was found1 #ih1 that the more electro-positive the metal1 the longer the wave length that would influence the discharge4 ,in this connection1 it is well to note that ,tesla found1 #adf;a1 that in their power of reflecting 7or diffusing ,x-rays71 the different metals stand in the same order as in the electric contact series in air1 the most electro-positive being the best reflectors4 ,it would be interesting to know whether connecting the reflecting plate to earth1 would1 in any way1 vary its reflecting power4 ,the ,x-rays seem to discharge some bodies1 when positively charged1 and other bodies when negatively charged4 ,they will also give to some bodies a positive1 and to others a negative charge 7 #ij;c74 ,is the order here also that of the electrical contact series in air8 ,are not all the phenomena of electrical charge and discharge1 of reflection or diffusion1 and of ,x-rays1 connected with chemical action1 as the apparent difference of potential1 due to contact1 undoubtedly is8 #aec4 ,an experiment by ,la ,fay 7 #aci;a7 seems to show that ,x-rays1 in air1 after passing through a charged silver leaf1 acquire the property of being deflected by a magnet1 as are the cathode rays inside the generating or exhausted observing tube1 #gb;a4 ,if this is confirmed1 it would go far to support the theory that these rays are streams of something4 ,illustration3 ,,from ,,sciagraph ,,of ,,head ,,by ,,prof4 ,,goodspeed4 ,,nasal ,,bones ,,appear ,,like ,,eyelashes4 ,inter4 ,med4 ,mag41 ,june1 '#if4 ,the cervical vertebr are distinguishable in the original1 but barely so in the half-tone4 ,fillings are located4 ,the burden of proof1 up to the present1 seems to be against any wave theory of the ,x-rays1 for1 although they are like the ultra-violet rays in producing fluorescence and in affecting the photographic plate1 and have some points of similarity to these rays in their effect upon charged bodies1 the ,x-rays are totally unlike the ultra-violet1 in respect to diffraction and interference phenomena4 ,in fact1 the absence of such phenomena1 if they are really absent1 is conclusive proof that the ,x-rays cannot be wave motions1 unless of a wave length extremely short even as compared to waves of light4 ,since writing the above1 ,i have seen an account of experiments in relation to diffraction of ,x-rays1 presented to the ,french ,academy by ,,mm4 ,l4 ,calmette and ,g4 ,t4 ,huillier1 in which the authors claim to have obtained evidence that diffraction occurs4 ,the following translation of ,,mm4 ,calmette and ,huillier's paper is taken from the ,electrical ,engineer1 ,n4,y41 for ,july #bb1 #ahif4 8,we have the honor of submitting to the ,academy some photographic proofs obtained with the ,rntgen rays by means of the following arrangement40 8,very near the ,crookes tube there is a screen 8,e0 7diagram omitted71 of brass1 perforated by a slit1 the width of which has rarely reached a half mm4 ,a second metal screen1 ,e1 is formed of a plate provided with two slits or pierced with a window in which is fixed a metal rod of #a mm4 in diameter4 ,this screen is placed at the distance1 a1 behind the former4 ,lastly1 a photographic plate1 enfolded in two leaves of black paper1 is placed at the distance1 b1 behind the second screen1 ,e40 8,the following table indicates1 for each proof1 what is the screen ,e used1 and the value of a and b a3 ,e4 ,no4 a b ,cm4 a ,cm4 #a4 ,rod of #a mm4 in #e #ai4e diameter #c4 ,rod of #a mm4 in #e4e #bj diameter #e4 ,rod of #a mm4 in #h4i #cj diameter #g4 ,two narrow slits1 8 8 separated by a cylindrical rod of #a mm4 in diameter 8,on the proofs #a1 #c1 #e the shadow thrown by the metallic rod is bordered on each side by a light band which shows a maximum of intensity4 ,within this shade we observe a zone less dark1 which seems to indicate that the ,rntgen rays penetrate into the geometrical shadow4 ,lastly1 in proofs #c and #e we see1 in like manner1 a maximum of intensity along the margins of the window in which the rod is placed40 8,in the proof ,no4 #g we perceive1 in the middle of the two white bands1 a fine dark ray1 while in the shadow of the rod which separates the two slits there is seen a light ray40 8,if we compare these results with those obtained with light in the same conditions1 the slit being relatively wide and the intensity weak1 it seems difficult not to ascribe them to the diffraction of the ,rntgen rays40 8,the proofs obtained in these experiments--which we propose to continue--are not yet so distinct that we can measure the wave length with any precision4 ,but we are still led to believe that this wave length is greater than that of the luminous rays4--,comptes ,rendus40 ,of course1 if diffraction phenomena can be demonstrated1 the question as to the radiations being wave propagations1 is settled1 though the question whether the vibrations are longitudinal or transverse1 is still open4 ,before accepting any stream or vortex motion theory1 we need to know more about the ,x-ray phenomena1 and more about stream and vortex motion4 ---------------------------------------- -------------------------------- ,transcriber's ,notes3 ,since this is a collection of articles by different scientists1 there may be differences in spelling and usage4 ,there is no experiment #fd4 ,there last experiment on page #ea is number #fc;b1 and the first experiment page #eb is #fe4 7,a note attached to the #fc;b table of contents entry says that there is no experiment #fd47 ,the missing entries in the ,table of ,contents for experiments #abh;a and #adi;a were added4 ,there are two experiments labeled #fa;b1 page #df 7,thomson's ,experiment7 and #dg 7,perrin's ,experiment74 ,the instance on page #dg was relabeled #fa;c4 ,there are two experiments numbered #aei in the ,table of ,contents4 ,the first follows entry #aaj;a and the other is in order1 after experiment #aeh4 ,the first instance was changed to #aei;a4 ,missing or obscured punctuation was silently corrected4 ,typographical errors were silently corrected4 ,inconsistent spelling and hyphenation were made consistent only when a predominant form was found in this book4 ,text that was in italics is enclosed by underscores 7italics72 text that was bold by 8equal0 signs 7bold74 ,the use of a caret 77 before a letter1 or letters1 shows that the following letter or letters was intended to be a superscript1 as in ,st ,bartholomew or #ajth ,century4 ,superscripts are used to indicate numbers raised to a power4 ,in this plain text document1 they are represented by characters like this3 8,p#c0 or 8#ajah01 i4e4 ,p cubed or #aj to the #ahth power4 ,variables in formul sometimes use subscripts1 which look like this3 8,a#j04 ,this would be read 8,a sub #j04