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,,experiments ,,with ,,alternate        
,,currents ,,of ,,high ,,potential ,,and
 ,,high ,,frequency  ,a ,lecture        
,delivered before the ,institution of   
,electrical ,engineers1 ,london  by     
,,nikola ,,tesla  ,with a ,portrait and 
,biographical ,sketch of the ,author    
,,new ,,york  #ahib        ,biographical
 ,sketch of ,nikola ,tesla4   ,while a  
large portion of the ,european family   
has been surging westward during the    
last three or four hundred years1       
settling the vast continents of         
,america1 another1 but smaller1 portion 
has been doing frontier work in the ,old
 ,world1 protecting the rear by beating 
back the unspeakable ,turk and          

reclaiming gradually the fair lands that
 endure the curse of ,mohammedan rule4  
,for a long time the ,slav people--who1 
after the battle of ,kosovopjolje1 in   
which the ,turks defeated the ,servians1
 retired to the confines of the present 
,montenegro1 ,dalmatia1 ,herzegovina and
 ,bosnia1 and ,borderland of            
,austria--knew what it was to deal1 as  
our ,western pioneers did1 with foes    
ceaselessly fretting against their      
frontier2 and the races of these        
countries1 through their strenuous      
struggle against the armies of the      
,crescent1 have developed notable       
qualities of bravery and sagacity1 while
 maintaining a patriotism and           
independence unsurpassed in any other   
nation4  ,it was in this interesting    
border region1 and from among these     
valiant ,eastern folk1 that ,nikola     
,tesla was born in the year #aheg1 and  
the fact that he1 to-day1 finds himself 
in ,america and one of our foremost     
electricians1 is striking evidence of   

the extraordinary attractiveness alike  
of electrical pursuits and of the       
country where electricity enjoys its    
widest application4 ,mr4 ,tesla's native
 place was ,smiljan1 ,lika1 where his   
father was an eloquent clergyman of the 
,greek ,church1 in which1 by the way1   
his family is still prominently         
represented4 ,his mother enjoyed great  
fame throughout the countryside for her 
skill and originality in needlework1 and
 doubtless transmitted her ingenuity to 
,nikola2 though it naturally took       
another and more masculine direction4   
,the boy was early put to his books1 and
 upon his father's removal to ,gospic he
 spent four years in the public school1 
and later1 three years in the ,real     
,school1 as it is called4 ,his escapades
 were such as most quick witted boys go 
through1 although he varied the         
programme on one occasion by getting    
imprisoned in a remote mountain chapel  
rarely visited for service2 and on      
another occasion by falling headlong    

into a huge kettle of boiling milk1 just
 drawn from the paternal herds4 ,a third
 curious episode was that connected with
 his efforts to fly when1 attempting to 
navigate the air with the aid of an old 
umbrella1 he had1 as might be expected1 
a very bad fall1 and was laid up for six
 weeks4  ,about this period he began to 
take delight in arithmetic and physics4 
,one queer notion he had was to work out
 everything by three or the power of    
three4 ,he was now sent to an aunt at   
,cartstatt1 ,croatia1 to finish his     
studies in what is known as the ,higher 
,real ,school4 ,it was there that1      
coming from the rural fastnesses1 he saw
 a steam engine for the first time with 
a pleasure that he remembers to this    
day4 ,at ,cartstatt he was so diligent  
as to compress the four years' course   
into three1 and graduated in #ahgc4     
,returning home during an epidemic of   
cholera1 he was stricken down by the    
disease and suffered so seriously from  
the consequences that his studies were  

interrupted for fully two years4 ,but   
the time was not wasted1 for he had     
become passionately fond of             
experimenting1 and as much as his means 
and leisure permitted devoted his       
energies to electrical study and        
investigation4 ,up to this period it had
 been his father's intention to make a  
priest of him1 and the idea hung over   
the young physicist like a very sword of
 ,damocles4 ,finally he prevailed upon  
his worthy but reluctant sire to send   
him to ,gratz in ,austria to finish his 
studies at the ,polytechnic ,school1 and
 to prepare for work as professor of    
mathematics and physics4 ,at ,gratz he  
saw and operated a ,gramme machine for  
the first time1 and was so struck with  
the objections to the use of commutators
 and brushes that he made up his mind   
there and then to remedy that defect in 
dynamo-electric machines4 ,in the second
 year of his course he abandoned the    
intention of becoming a teacher and took
 up the engineering curriculum4 ,after  

three years of absence he returned home1
 sadly1 to see his father die2 but1     
having resolved to settle down in       
,austria1 and recognizing the value of  
linguistic acquirements1 he went to     
,prague and then to ,buda-,pesth with   
the view of mastering the languages he  
deemed necessary4 ,up to this time he   
had never realized the enormous         
sacrifices that his parents had made in 
promoting his education1 but he now     
began to feel the pinch and to grow     
unfamiliar with the image of ,francis   
,joseph ,i4 ,there was considerable lag 
between his dispatches and the          
corresponding remittance from home2 and 
when the mathematical expression for the
 value of the lag assumed the shape of  
an eight laid flat on its back1 ,mr4    
,tesla became a very fair example of    
high thinking and plain living1 but he  
made up his mind to the struggle and    
determined to go through depending      
solely on his own resources4 ,not       
desiring the fame of a faster1 he cast  

about for a livelihood1 and through the 
help of friends he secured a berth as   
assistant in the engineering department 
of the government telegraphs4 ,the      
salary was five dollars a week4 ,this   
brought him into direct contact with    
practical electrical work and ideas1 but
 it is needless to say that his means   
did not admit of much experimenting4 ,by
 the time he had extracted several      
hundred thousand square and cube roots  
for the public benefit1 the limitations1
 financial and otherwise1 of the        
position had become painfully apparent1 
and he concluded that the best thing to 
do was to make a valuable invention4 ,he
 proceeded at once to make inventions1  
but their value was visible only to the 
eye of faith1 and they brought no grist 
to the mill4 ,just at this time the     
telephone made its appearance in        
,hungary1 and the success of that great 
invention determined his career1        
hopeless as the profession had thus far 
seemed to him4 ,he associated himself at

 once with telephonic work1 and made    
various telephonic inventions1 including
 an operative repeater2 but it did not  
take him long to discover that1 being so
 remote from the scenes of electrical   
activity1 he was apt to spend time on   
aims and results already reached by     
others1 and to lose touch4 ,longing for 
new opportunities and anxious for the   
development of which he felt himself    
possible1 if once he could place himself
 within the genial and direct influences
 of the gulf streams of electrical      
thought1 he broke away from the ties and
 traditions of the past1 and in #ahha   
made his way to ,paris4 ,arriving in    
that city1 the ardent young ,likan      
obtained employment as an electrical    
engineer with one of the largest        
electric lighting companies4 ,the next  
year he went to ,strasburg to install a 
plant1 and on returning to ,paris sought
 to carry out a number of ideas that had
 now ripened into inventions4 ,about    
this time1 however1 the remarkable      

progress of ,america in electrical      
industry attracted his attention1 and   
once again staking everything on a      
single throw1 he crossed the ,atlantic4 
,mr4 ,tesla buckled down to work as soon
 as he landed on these shores1 put his  
best thought and skill into it1 and soon
 saw openings for his talent4 ,in a     
short while a proposition was made to   
him to start his own company1 and1      
accepting the terms1 he at once worked  
up a practical system of arc lighting1  
as well as a potential method of dynamo 
regulation1 which in one form is now    
known as the third brush regulation4 ,he
 also devised a thermo-magnetic motor   
and other kindred devices1 about which  
little was published1 owing to legal    
complications4 ,early in #ahhg the      
,tesla ,electric ,company of ,new ,york 
was formed1 and not long after that ,mr4
 ,tesla produced his admirable and      
epoch-marking motors for multiphase     
alternating currents1 in which1 going   
back to his ideas of long ago1 he       

evolved machines having neither         
commutator nor brushes4 ,it will be     
remembered that about the time that ,mr4
 ,tesla brought out his motors1 and read
 his thoughtful paper before the        
,american ,institute of ,electrical     
,engineers1 ,professor ,ferraris1 in    
,europe1 published his discovery of     
principles analogous to those enunciated
 by ,mr4 ,tesla4 ,there is no doubt1    
however1 that ,mr4 ,tesla was an        
independent inventor of this rotary     
field motor1 for although anticipated in
 dates by ,ferraris1 he could not have  
known about ,ferraris' work as it had   
not been published4 ,professor ,ferraris
 stated himself1 with becoming modesty1 
that he did not think ,tesla could have 
known of his 7,ferraris'7 experiments at
 that time1 and adds that he thinks     
,tesla was an independent and original  
inventor of this principle4 ,with such  
an acknowledgment from ,ferraris there  
can be little doubt about ,tesla's      
originality in this matter4  ,mr4       

,tesla's work in this field was         
wonderfully timely1 and its worth was   
promptly appreciated in various         
quarters4 ,the ,tesla patents were      
acquired by the ,westinghouse ,electric 
,company1 who undertook to develop his  
motor and to apply it to work of        
different kinds4 ,its use in mining1 and
 its employment in printing1            
ventilation1 etc41 was described and    
illustrated in ,the ,electrical ,world  
some years ago4 ,the immense stimulus   
that the announcement of ,mr4 ,tesla's  
work gave to the study of alternating   
current motors would1 in itself1 be     
enough to stamp him as a leader4  ,mr4  
,tesla is only #ce years of age4 ,he is 
tall and spare with a clean-cut1 thin1  
refined face1 and eyes that recall all  
the stories one has read of keenness of 
vision and phenomenal ability to see    
through things4 ,he is an omnivorous    
reader1 who never forgets2 and he       
possesses the peculiar facility in      
languages that enables the least        

educated native of eastern ,europe to   
talk and write in at least half a dozen 
tongues4 ,a more congenial companion    
cannot be desired for the hours when one
 pours out heart affluence in discursive
 talk1 and when the conversation1       
dealing at first with things near at    
hand and next to us1 reaches out and    
rises to the greater questions of life1 
duty and destiny4  ,in the year #ahij he
 severed his connection with the        
,westinghouse ,company1 since which time
 he has devoted himself entirely to the 
study of alternating currents of high   
frequencies and very high potentials1   
with which study he is at present       
engaged4 ,no comment is necessary on his
 interesting achievements in this field2
 the famous ,london lecture published in
 this volume is a proof in itself4 ,his 
first lecture on his researches in this 
new branch of electricity1 which he may 
be said to have created1 was delivered  
before the ,american ,institute of      
,electrical ,engineers on ,may #bj1     

#ahia1 and remains one of the most      
interesting papers read before that     
society4 ,it will be found reprinted in 
full in ,the ,electrical ,world1 ,july  
#aa1 #ahia4 ,its publication excited    
such interest abroad that he received   
numerous requests from ,english and     
,french electrical engineers and        
scientists to repeat it in those        
countries1 the result of which has been 
the interesting lecture published in    
this volume4  ,the present lecture      
presupposes a knowledge of the former1  
but it may be read and understood by any
 one even though he has not read the    
earlier one4 ,it forms a sort of        
continuation of the latter1 and includes
 chiefly the results of his researches  
since that time4      ,,experiments     
,,with ,,alternate ,,currents ,,of      
,,high ,,potential ,,and ,,high         
,,frequency   ,i cannot find words to   
express how deeply ,i feel the honor of 
addressing some of the foremost thinkers
 of the present time1 and so many able  

scientific men1 engineers and           
electricians1 of the country greatest in
 scientific achievements4  ,the results 
which ,i have the honor to present      
before such a gathering ,i cannot call  
my own4 ,there are among you not a few  
who can lay better claim than myself on 
any feature of merit which this work may
 contain4 ,i need not mention many names
 which are world-known--names of those  
among you who are recognized as the     
leaders in this enchanting science2 but 
one1 at least1 ,i must mention--a name  
which could not be omitted in a         
demonstration of this kind4 ,it is a    
name associated with the most beautiful 
invention ever made3 it is ,crookes6    
,when ,i was at college1 a good time    
ago1 ,i read1 in a translation 7for then
 ,i was not familiar with your          
magnificent language71 the description  
of his experiments on radiant matter4 ,i
 read it only once in my life--that     
time--yet every detail about that       
charming work ,i can remember this day4 

,few are the books1 let me say1 which   
can make such an impression upon the    
mind of a student4  ,but if1 on the     
present occasion1 ,i mention this name  
as one of many your institution can     
boast of1 it is because ,i have more    
than one reason to do so4 ,for what ,i  
have to tell you and to show you this   
evening concerns1 in a large measure1   
that same vague world which ,professor  
,crookes has so ably explored2 and1 more
 than this1 when ,i trace back the      
mental process which led me to these    
advances--which even by myself cannot be
 considered trifling1 since they are so 
appreciated by you--,i believe that     
their real origin1 that which started me
 to work in this direction1 and brought 
me to them1 after a long period of      
constant thought1 was that fascinating  
little book which ,i read many years    
ago4  ,and now that ,i have made a      
feeble effort to express my homage and  
acknowledge my indebtedness to him and  
others among you1 ,i will make a second 

effort1 which ,i hope you will not find 
so feeble as the first1 to entertain    
you4  ,give me leave to introduce the   
subject in a few words4  ,a short time  
ago ,i had the honor to bring before our
 ,american ,institute of ,electrical    
,engineers,a some results then arrived  
at by me in a novel line of work4 ,i    
need not assure you that the many       
evidences which ,i have received that   
,english scientific men and engineers   
were interested in this work have been  
for me a great reward and encouragement4
 ,i will not dwell upon the experiments 
already described1 except with the view 
of completing1 or more clearly          
expressing1 some ideas advanced by me   
before1 and also with the view of       
rendering the study here presented      
self-contained1 and my remarks on the   
subject of this evening's lecture       
consistent4  ,footnote ,a3 ,for ,mr4    
,tesla's ,american lecture on this      
subject see ,,the ,,electrical ,,world  
of ,july #aa1 #ahia1 and for a report of

 his ,french lecture see ,,the          
,,electrical ,,world of ,march #bf1     
#ahib4  ,this investigation1 then1 it   
goes without saying1 deals with         
alternating currents1 and1 to be more   
precise1 with alternating currents of   
high potential and high frequency4 ,just
 in how much a very high frequency is   
essential for the production of the     
results presented is a question which   
even with my present experience1 would  
embarrass me to answer4 ,some of the    
experiments may be performed with low   
frequencies2 but very high frequencies  
are desirable1 not only on account of   
the many effects secured by their use1  
but also as a convenient means of       
obtaining1 in the induction apparatus   
employed1 the high potentials1 which in 
their turn are necessary to the         
demonstration of most of the experiments
 here contemplated4  ,of the various    
branches of electrical investigation1   
perhaps the most interesting and        
immediately the most promising is that  

dealing with alternating currents4 ,the 
progress in this branch of applied      
science has been so great in recent     
years that it justifies the most        
sanguine hopes4 ,hardly have we become  
familiar with one fact1 when novel      
experiences are met with and new avenues
 of research are opened4 ,even at this  
hour possibilities not dreamed of before
 are1 by the use of these currents1     
partly realized4 ,as in nature all is   
ebb and tide1 all is wave motion1 so it 
seems that2 in all branches of industry 
alternating currents--electric wave     
motion--will have the sway4  ,one       
reason1 perhaps1 why this branch of     
science is being so rapidly developed is
 to be found in the interest which is   
attached to its experimental study4 ,we 
wind a simple ring of iron with coils2  
we establish the connections to the     
generator1 and with wonder and delight  
we note the effects of strange forces   
which we bring into play1 which allow us
 to transform1 to transmit and direct   

energy at will4 ,we arrange the circuits
 properly1 and we see the mass of iron  
and wires behave as though it were      
endowed with life1 spinning a heavy     
armature1 through invisible connections1
 with great speed and power--with the   
energy possibly conveyed from a great   
distance4 ,we observe how the energy of 
an alternating current traversing the   
wire manifests itself--not so much in   
the wire as in the surrounding space--in
 the most surprising manner1 taking the 
forms of heat1 light1 mechanical energy1
 and1 most surprising of all1 even      
chemical affinity4 ,all these           
observations fascinate us1 and fill us  
with an intense desire to know more     
about the nature of these phenomena4    
,each day we go to our work in the hope 
of discovering1--in the hope that some  
one1 no matter who1 may find a solution 
of one of the pending great             
problems1--and each succeeding day we   
return to our task with renewed ardor2  
and even if we are unsuccessful1 our    

work has not been in vain1 for in these 
strivings1 in these efforts1 we have    
found hours of untold pleasure1 and we  
have directed our energies to the       
benefit of mankind4  ,we may take--at   
random1 if you choose--any of the many  
experiments which may be performed with 
alternating currents2 a few of which    
only1 and by no means the most striking1
 form the subject of this evening's     
demonstration3 they are all equally     
interesting1 equally inciting to        
thought4  ,here is a simple glass tube  
from which the air has been partially   
exhausted4 ,i take hold of it2 ,i bring 
my body in contact with a wire conveying
 alternating currents of high potential1
 and the tube in my hand is brilliantly 
lighted4 ,in whatever position ,i may   
put it1 wherever ,i may move it in      
space1 as far as ,i can reach1 its soft1
 pleasing light persists with           
undiminished brightness4  ,here is an   
exhausted bulb suspended from a single  
wire4 ,standing on an insulated support4

 ,i grasp it1 and a platinum button     
mounted in it is brought to vivid       
incandescence4  ,here1 attached to a    
leading wire1 is another bulb1 which1 as
 ,i touch its metallic socket1 is filled
 with magnificent colors of             
phosphorescent light4  ,here still      
another1 which by my fingers' touch     
casts a shadow--the ,crookes shadow1 of 
the stem inside of it4  ,here1 again1   
insulated as ,i stand on this platform1 
,i bring my body in contact with one of 
the terminals of the secondary of this  
induction coil--with the end of a wire  
many miles long--and you see streams of 
light break forth from its distant end1 
which is set in violent vibration4      
,here1 once more1 ,i attach these two   
plates of wire gauze to the terminals of
 the coil4 ,i set them a distance apart1
 and ,i set the coil to work4 ,you may  
see a small spark pass between the      
plates4 ,i insert a thick plate of one  
of the best dielectrics between them1   
and instead of rendering altogether     

impossible1 as we are used to expect1 ,i
 aid the passage of the discharge1      
which1 as ,i insert the plate1 merely   
changes in appearance and assumes the   
form of luminous streams4  ,is there1 ,i
 ask1 can there be1 a more interesting  
study than that of alternating currents8
  ,in all these investigations1 in all  
these experiments1 which are so very1   
very interesting1 for many years        
past--ever since the greatest           
experimenter who lectured in this hall  
discovered its principle--we have had a 
steady companion1 an appliance familiar 
to every one1 a plaything once1 a thing 
of momentous importance now--the        
induction coil4 ,there is no dearer     
appliance to the electrician4 ,from the 
ablest among you1 ,i dare say1 down to  
the inexperienced student1 to your      
lecturer1 we all have passed many       
delightful hours in experimenting with  
the induction coil4 ,we have watched its
 play1 and thought and pondered over the
 beautiful phenomena which it disclosed 

to our ravished eyes4 ,so well known is 
this apparatus1 so familiar are these   
phenomena to every one1 that my courage 
nearly fails me when ,i think that ,i   
have ventured to address so able an     
audience1 that ,i have ventured to      
entertain you with that same old        
subject4 ,here in reality is the same   
apparatus1 and here are the same        
phenomena1 only the apparatus is        
operated somewhat differently1 the      
phenomena are presented in a different  
aspect4 ,some of the results we find as 
expected1 others surprise us1 but all   
captivate our attention1 for in         
scientific investigation each novel     
result achieved may be the centre of a  
new departure1 each novel fact learned  
may lead to important developments4     
,usually in operating an induction coil 
we have set up a vibration of moderate  
frequency in the primary1 either by     
means of an interrupter or break1 or by 
the use of an alternator4 ,earlier      
,english investigators1 to mention only 

,spottiswoode and ,j4,e4,h4 ,gordon1    
have used a rapid break in connection   
with the coil4 ,our knowledge and       
experience of to-day enables us to see  
clearly why these coils under the       
conditions of the tests did not disclose
 any remarkable phenomena1 and why able 
experimenters failed to perceive many of
 the curious effects which have since   
been observed4  ,in the experiments such
 as performed this evening1 we operate  
the coil either from a specially        
constructed alternator capable of giving
 many thousands of reversals of current 
per second1 or1 by disruptively         
discharging a condenser through the     
primary1 we set up a vibration in the   
secondary circuit of a frequency of many
 hundred thousand or millions per       
second1 if we so desire2 and in using   
either of these means we enter a field  
as yet unexplored4  ,it is impossible to
 pursue an investigation in any novel   
line without finally making some        
interesting observation or learning some

 useful fact4 ,that this statement is   
applicable to the subject of this       
lecture the many curious and unexpected 
phenomena which we observe afford a     
convincing proof4 ,by way of            
illustration1 take for instance the most
 obvious phenomena1 those of the        
discharge of the induction coil4  ,here 
is a coil which is operated by currents 
vibrating with extreme rapidity1        
obtained by disruptively discharging a  
,leyden jar4 ,it would not surprise a   
student were the lecturer to say that   
the secondary of this coil consists of a
 small length of comparatively stout    
wire2 it would not surprise him were the
 lecturer to state that1 in spite of    
this1 the coil is capable of giving any 
potential which the best insulation of  
the turns is able to withstand3 but     
although he may be prepared1 and even be
 indifferent as to the anticipated      
result1 yet the aspect of the discharge 
of the coil will surprise and interest  
him4 ,every one is familiar with the    

discharge of an ordinary coil2 it need  
not be reproduced here4 ,but1 by way of 
contrast1 here is a form of discharge of
 a coil1 the primary current of which is
 vibrating several hundred thousand     
times per second4 ,the discharge of an  
ordinary coil appears as a simple line  
or band of light4 ,the discharge of this
 coil appears in the form of powerful   
brushes and luminous streams issuing    
from all points of the two straight     
wires attached to the terminals of the  
secondary4 7,fig4 #a47  ,illustration3  
,,fig4 #a4--;,,discharge ,,between ,,two
 ,,wires ,,with ,,frequencies ,,of ,a   
,,few ,,hundred ,,thousand ,,per        
,,second4  ,now compare this phenomenon 
which you have just witnessed with the  
discharge of a ,holtz or ,wimshurst     
machine--that other interesting         
appliance so dear to the experimenter4  
,what a difference there is between     
these phenomena6 ,and yet1 had ,i made  
the necessary arrangements--which could 
have been made easily1 were it not that 

they would interfere with other         
experiments--,i could have produced with
 this coil sparks which1 had ,i the coil
 hidden from your view and only two     
knobs exposed1 even the keenest observer
 among you would find it difficult1 if  
not impossible1 to distinguish from     
those of an influence or friction       
machine4 ,this may be done in many      
ways--for instance1 by operating the    
induction coil which charges the        
condenser from an alternating-current   
machine of very low frequency1 and      
preferably adjusting the discharge      
circuit so that there are no            
oscillations set up in it4 ,we then     
obtain in the secondary circuit1 if the 
knobs are of the required size and      
properly set1 a more or less rapid      
succession of sparks of great intensity 
and small quantity1 which possess the   
same brilliancy1 and are accompanied by 
the same sharp crackling sound1 as those
 obtained from a friction or influence  
machine4  ,another way is to pass       

through two primary circuits1 having a  
common secondary1 two currents of a     
slightly different period1 which produce
 in the secondary circuit sparks        
occurring at comparatively long         
intervals4 ,but1 even with the means at 
hand this evening1 ,i may succeed in    
imitating the spark of a ,holtz machine4
 ,for this purpose ,i establish between 
the terminals of the coil which charges 
the condenser a long1 unsteady arc1     
which is periodically interrupted by the
 upward current of air produced by it4  
,to increase the current of air ,i place
 on each side of the arc1 and close to  
it1 a large plate of mica4 ,the         
condenser charged from this coil        
discharges into the primary circuit of a
 second coil through a small air gap1   
which is necessary to produce a sudden  
rush of current through the primary4    
,the scheme of connections in the       
present experiment is indicated in ,fig4
 #b4  ,illustration3 ,,fig4             
#b4--;,,imitating ,,the ,,spark ,,of ,a 

,,holtz ,,machine4  ,g is an ordinarily 
constructed alternator1 supplying the   
primary ,p of an induction coil1 the    
secondary ,s of which charges the       
condensers or jars ,,cc4 ,the terminals 
of the secondary are connected to the   
inside coatings of the jars1 the outer  
coatings being connected to the ends of 
the primary pp of a second induction    
coil4 ,this primary pp has a small air  
gap ab4  ,the secondary s of this coil  
is provided with knobs or spheres ,,kk  
of the proper size and set at a distance
 suitable for the experiment4  ,a long  
arc is established between the terminals
 ,,ab of the first induction coil4 ,,mm 
are the mica plates4  ,each time the arc
 is broken between ,a and ,b the jars   
are quickly charged and discharged      
through the primary pp1 producing a     
snapping spark between the knobs ,,kk4  
,upon the arc forming between ,a and ,b 
the potential falls1 and the jars cannot
 be charged to such high potential as to
 break through the air gap ab until the 

arc is again broken by the draught4  ,in
 this manner sudden impulses1 at long   
intervals1 are produced in the primary  
pp1 which in the secondary s give a     
corresponding number of impulses of     
great intensity4 ,if the secondary knobs
 or spheres1 ,,kk1 are of the proper    
size1 the sparks show much resemblance  
to those of a ,holtz machine4  ,but     
these two effects1 which to the eye     
appear so very different1 are only two  
of the many discharge phenomena4 ,we    
only need to change the conditions of   
the test1 and again we make other       
observations of interest4  ,when1       
instead of operating the induction coil 
as in the last two experiments1 we      
operate it from a high frequency        
alternator1 as in the next experiment1 a
 systematic study of the phenomena is   
rendered much more easy4 ,in such case1 
in varying the strength and frequency of
 the currents through the primary1 we   
may observe five distinct forms of      
discharge1 which ,i have described in my

 former paper on the subject,a before   
the ,american ,institute of ,electrical 
,engineers1 ,may #bj1 #ahia4  ,footnote 
,a3 ,see ,,the ,,electrical ,,world1    
,july #aa1 #ahia4  ,it would take too   
much time1 and it would lead us too far 
from the subject presented this evening1
 to reproduce all these forms1 but it   
seems to me desirable to show you one of
 them4 ,it is a brush discharge1 which  
is interesting in more than one respect4
 ,viewed from a near position it        
resembles much a jet of gas escaping    
under great pressure4 ,we know that the 
phenomenon is due to the agitation of   
the molecules near the terminal1 and we 
anticipate that some heat must be       
developed by the impact of the molecules
 against the terminal or against each   
other4 ,indeed1 we find that the brush  
is hot1 and only a little thought leads 
us to the conclusion that1 could we but 
reach sufficiently high frequencies1 we 
could produce a brush which would give  
intense light and heat1 and which would 

resemble in every particular an ordinary
 flame1 save1 perhaps1 that both        
phenomena might not be due to the same  
agent--save1 perhaps1 that chemical     
affinity might not be electrical in its 
nature4  ,as the production of heat and 
light is here due to the impact of the  
molecules1 or atoms of air1 or something
 else besides1 and1 as we can augment   
the energy simply by raising the        
potential1 we might1 even with          
frequencies obtained from a dynamo      
machine1 intensify the action to such a 
degree as to bring the terminal to      
melting heat4 ,but with such low        
frequencies we would have to deal always
 with something of the nature of an     
electric current4 ,if ,i approach a     
conducting object to the brush1 a thin  
little spark passes1 yet1 even with the 
frequencies used this evening1 the      
tendency to spark is not very great4    
,so1 for instance1 if ,i hold a metallic
 sphere at some distance above the      
terminal you may see the whole space    

between the terminal and sphere         
illuminated by the streams without the  
spark passing2 and with the much higher 
frequencies obtainable by the disruptive
 discharge of a condenser1 were it not  
for the sudden impulses1 which are      
comparatively few in number1 sparking   
would not occur even at very small      
distances4 ,however1 with incomparably  
higher frequencies1 which we may yet    
find means to produce efficiently1 and  
provided that electric impulses of such 
high frequencies could be transmitted   
through a conductor1 the electrical     
characteristics of the brush discharge  
would completely vanish--no spark would 
pass1 no shock would be felt--yet we    
would still have to deal with an        
electric phenomenon1 but in the broad1  
modern interpretation of the word4 ,in  
my first paper before referred to ,i    
have pointed out the curious properties 
of the brush1 and described the best    
manner of producing it1 but ,i have     
thought it worth while to endeavor to   

express myself more clearly in regard to
 this phenomenon1 because of its        
absorbing interest4  ,when a coil is    
operated with currents of very high     
frequency1 beautiful brush effects may  
be produced1 even if the coil be of     
comparatively small dimensions4 ,the    
experimenter may vary them in many ways1
 and1 if it were nothing else1 they     
afford a pleasing sight4 ,what adds to  
their interest is that they may be      
produced with one single terminal as    
well as with two--in fact1 often better 
with one than with two4  ,but of all the
 discharge phenomena observed1 the most 
pleasing to the eye1 and the most       
instructive1 are those observed with a  
coil which is operated by means of the  
disruptive discharge of a condenser4    
,the power of the brushes1 the abundance
 of the sparks1 when the conditions are 
patiently adjusted1 is often amazing4   
,with even a very small coil1 if it be  
so well insulated as to stand a         
difference of potential of several      

thousand volts per turn1 the sparks may 
be so abundant that the whole coil may  
appear a complete mass of fire4         
,curiously enough the sparks1 when the  
terminals of the coil are set at a      
considerable distance1 seem to dart in  
every possible direction as though the  
terminals were perfectly independent of 
each other4 ,as the sparks would soon   
destroy the insulation it is necessary  
to prevent them4 ,this is best done by  
immersing the coil in a good liquid     
insulator1 such as boiled-out oil4      
,immersion in a liquid may be considered
 almost an absolute necessity for the   
continued and successful working of such
 a coil4  ,it is of course out of the   
question1 in an experimental lecture1   
with only a few minutes at disposal for 
the performance of each experiment1 to  
show these discharge phenomena to       
advantage1 as to produce each phenomenon
 at its best a very careful adjustment  
is required4 ,but even if imperfectly   
produced1 as they are likely to be this 

evening1 they are sufficiently striking 
to interest an intelligent audience4    
,before showing some of these curious   
effects ,i must1 for the sake of        
completeness1 give a short description  
of the coil and other apparatus used in 
the experiments with the disruptive     
discharge this evening4  ,illustration3 
,,fig4 #c4--;,,disruptive ,,discharge   
,,coil4  ,it is contained in a box ,b   
7,fig4 #c7 of thick boards of hard wood1
 covered on the outside with zinc sheet 
,z1 which is carefully soldered all     
around4 ,it might be advisable1 in a    
strictly scientific investigation1 when 
accuracy is of great importance1 to do  
away with the metal cover1 as it might  
introduce many errors1 principally on   
account of its complex action upon the  
coil1 as a condenser of very small      
capacity and as an electrostatic and    
electromagnetic screen4 ,when the coil  
is used for such experiments as are here
 contemplated1 the employment of the    
metal cover offers some practical       

advantages1 but these are not of        
sufficient importance to be dwelt upon4 
,the coil should be placed symmetrically
 to the metal cover1 and the space      
between should1 of course1 not be too   
small1 certainly not less than1 say1    
five centimetres1 but much more if      
possible2 especially the two sides of   
the zinc box1 which are at right angles 
to the axis of the coil1 should be      
sufficiently remote from the latter1 as 
otherwise they might impair its action  
and be a source of loss4  ,the coil     
consists of two spools of hard rubber   
,,rr1 held apart at a distance of #aj   
centimetres by bolts c and nuts n1      
likewise of hard rubber4 ,each spool    
comprises a tube ,t of approximately #h 
centimetres inside diameter1 and #c     
millimetres thick1 upon which are       
screwed two flanges ,,ff1 #bd           
centimetres square1 the space between   
the flanges being about #c centimetres4 
,the secondary1 ,,ss1 of the best gutta 
percha-covered wire1 has #bf layers1 #aj

 turns in each1 giving for each half a  
total of #bfj turns4 ,the two halves are
 wound oppositely and connected in      
series1 the connection between both     
being made over the primary4 ,this      
disposition1 besides being convenient1  
has the advantage that when the coil is 
well balanced--that is1 when both of its
 terminals ,t#a ,t#a are connected to   
bodies or devices of equal              
capacity--there is not much danger of   
breaking through to the primary1 and the
 insulation between the primary and the 
secondary need not be thick4 ,in using  
the coil it is advisable to attach to   
both terminals devices of nearly equal  
capacity1 as1 when the capacity of the  
terminals is not equal1 sparks will be  
apt to pass to the primary4 ,to avoid   
this1 the middle point of the secondary 
may be connected to the primary1 but    
this is not always practicable4  ,the   
primary ,,pp is wound in two parts1 and 
oppositely1 upon a wooden spool ,w1 and 
the four ends are led out of the oil    

through hard rubber tubes tt4 ,the ends 
of the secondary ,t#a ,t#a are also led 
out of the oil through rubber tubes t#a 
t#a of great thickness4 ,the primary and
 secondary layers are insulated by      
cotton cloth1 the thickness of the      
insulation1 of course1 bearing some     
proportion to the difference of         
potential between the turns of the      
different layers4 ,each half of the     
primary has four layers1 #bd turns in   
each1 this giving a total of #if turns4 
,when both the parts are connected in   
series1 this gives a ratio of conversion
 of about #a3b4g1 and with the primaries
 in multiple1 #a3e4d2 but in operating  
with very rapidly alternating currents  
this ratio does not convey even an      
approximate idea of the ratio of the    
,e4,m4,fs4 in the primary and secondary 
circuits4 ,the coil is held in position 
in the oil on wooden supports1 there    
being about #e centimetres thickness of 
oil all round4 ,where the oil is not    
specially needed1 the space is filled   

with pieces of wood1 and for this       
purpose principally the wooden box ,b   
surrounding the whole is used4  ,the    
construction here shown is1 of course1  
not the best on general principles1 but 
,i believe it is a good and convenient  
one for the production of effects in    
which an excessive potential and a very 
small current are needed4  ,in          
connection with the coil ,i use either  
the ordinary form of discharger or a    
modified form4 ,in the former ,i have   
introduced two changes which secure some
 advantages1 and which are obvious4 ,if 
they are mentioned1 it is only in the   
hope that some experimenter may find    
them of use4  ,illustration3 ,,fig4     
#d4--;,,arrangement ,,of ,,improved     
,,discharger ,,and ,,magnet4  ,one of   
the changes is that the adjustable knobs
 ,a and ,b 7,fig4 #d71 of the discharger
 are held in jaws of brass1 ,,jj1 by    
spring pressure1 this allowing of       
turning them successively into different
 positions1 and so doing away with the  

tedious process of frequent polishing   
up4  ,the other change consists in the  
employment of a strong electromagnet    
,,ns1 which is placed with its axis at  
right angles to the line joining the    
knobs ,a and ,b1 and produces a strong  
magnetic field between them4 ,the pole  
pieces of the magnet are movable and    
properly formed so as to protrude       
between the brass knobs1 in order to    
make the field as intense as possible2  
but to prevent the discharge from       
jumping to the magnet the pole pieces   
are protected by a layer of mica1 ,,mm1 
of sufficient thickness4 s#a s#a and s#b
 s#b are screws for fastening the wires4
 ,on each side one of the screws is for 
large and the other for small wires4    
,,ll are screws for fixing in position  
the rods ,,rr1 which support the knobs4 
,in another arrangement with the magnet 
,i take the discharge between the       
rounded pole pieces themselves1 which in
 such case are insulated and preferably 
provided with polished brass caps4  ,the

 employment of an intense magnetic field
 is of advantage principally when the   
induction coil or transformer which     
charges the condenser is operated by    
currents of very low frequency4 ,in such
 a case the number of the fundamental   
discharges between the knobs may be so  
small as to render the currents produced
 in the secondary unsuitable for many   
experiments4 ,the intense magnetic field
 then serves to blow out the arc between
 the knobs as soon as it is formed1 and 
the fundamental discharges occur in     
quicker succession4  ,instead of the    
magnet1 a draught or blast of air may be
 employed with some advantage4 ,in this 
case the arc is preferably established  
between the knobs ,,ab1 in ,fig4 #b 7the
 knobs ab being generally joined1 or    
entirely done away with71 as in this    
disposition the arc is long and         
unsteady1 and is easily affected by the 
draught4  ,when a magnet is employed to 
break the arc1 it is better to choose   
the connection indicated                

diagrammatically in ,fig4 #e1 as in this
 case the currents forming the arc are  
much more powerful1 and the magnetic    
field exercises a greater influence4    
,the use of the magnet permits1 however1
 of the arc being replaced by a vacuum  
tube1 but ,i have encountered great     
difficulties in working with an         
exhausted tube4  ,illustration3 ,,fig4  
#e4--;,,arrangement ,,with              
,,low-,,frequency ,,alternator ,,and    
,,improved ,,discharger4  ,illustration3
 ,,fig4 #f4--;,,discharger ,,with       
,,multiple ,,gaps4  ,the other form of  
discharger used in these and similar    
experiments is indicated in ,figs4 #f   
and #g4 ,it consists of a number of     
brass pieces cc 7,fig4 #f71 each of     
which comprises a spherical middle      
portion m with an extension e           
below--which is merely used to fasten   
the piece in a lathe when polishing up  
the discharging surface--and a column   
above1 which consists of a knurled      
flange f surmounted by a threaded stem l

 carrying a nut n1 by means of which a  
wire is fastened to the column4 ,the    
flange f conveniently serves for holding
 the brass piece when fastening the     
wire1 and also for turning it in any    
position when it becomes necessary to   
present a fresh discharging surface4    
,two stout strips of hard rubber ,,rr1  
with planed grooves gg 7,fig4 #g7 to fit
 the middle portion of the pieces cc1   
serve to clamp the latter and hold them 
firmly in position by means of two bolts
 ,,cc 7of which only one is shown7      
passing through the ends of the strips4 
,illustration3 ,,fig4 #g4--;,,discharger
 ,,with ,,multiple ,,gaps4  ,in the use 
of this kind of discharger ,i have found
 three principal advantages over the    
ordinary form4 ,first1 the dielectric   
strength of a given total width of air  
space is greater when a great many small
 air gaps are used instead of one1 which
 permits of working with a smaller      
length of air gap1 and that means       
smaller loss and less deterioration of  

the metal2 secondly by reason of        
splitting the arc up into smaller arcs1 
the polished surfaces are made to last  
much longer2 and1 thirdly1 the apparatus
 affords some gauge in the experiments4 
,i usually set the pieces by putting    
between them sheets of uniform thickness
 at a certain very small distance which 
is known from the experiments of ,sir   
,william ,thomson to require a certain  
electromotive force to be bridged by the
 spark4  ,it should1 of course1 be      
remembered that the sparking distance is
 much diminished as the frequency is    
increased4 ,by taking any number of     
spaces the experimenter has a rough idea
 of the electromotive force1 and he     
finds it easier to repeat an experiment1
 as he has not the trouble of setting   
the knobs again and again4 ,with this   
kind of discharger ,i have been able to 
maintain an oscillating motion without  
any spark being visible with the naked  
eye between the knobs1 and they would   
not show a very appreciable rise in     

temperature4 ,this form of discharge    
also lends itself to many arrangements  
of condensers and circuits which are    
often very convenient and time-saving4  
,i have used it preferably in a         
disposition similar to that indicated in
 ,fig4 #b1 when the currents forming the
 arc are small4  ,i may here mention    
that ,i have also used dischargers with 
single or multiple air gaps1 in which   
the discharge surfaces were rotated with
 great speed4 ,no particular advantage  
was1 however1 gained by this method1    
except in cases where the currents from 
the condenser were large and the keeping
 cool of the surfaces was necessary1 and
 in cases when1 the discharge not being 
oscillating of itself1 the arc as soon  
as established was broken by the air    
current1 thus starting the vibration at 
intervals in rapid succession4 ,i have  
also used mechanical interrupters in    
many ways4 ,to avoid the difficulties   
with frictional contacts1 the preferred 
plan adopted was to establish the arc   

and rotate through it at great speed a  
rim of mica provided with many holes and
 fastened to a steel plate4 ,it is      
understood1 of course1 that the         
employment of a magnet1 air current1 or 
other interrupter1 produces no effect   
worth noticing1 unless the              
self-induction1 capacity and resistance 
are so related that there are           
oscillations set up upon each           
interruption4  ,i will now endeavor to  
show you some of the most noteworthy of 
these discharge phenomena4  ,i have     
stretched across the room two ordinary  
cotton covered wires1 each about #g     
metres in length4 ,they are supported on
 insulating cords at a distance of about
 #cj centimetres4 ,i attach now to each 
of the terminals of the coil one of the 
wires and set the coil in action4 ,upon 
turning the lights off in the room you  
see the wires strongly illuminated by   
the streams issuing abundantly from     
their whole surface in spite of the     
cotton covering1 which may even be very 

thick4 ,when the experiment is performed
 under good conditions1 the light from  
the wires is sufficiently intense to    
allow distinguishing the objects in a   
room4 ,to produce the best result it is1
 of course1 necessary to adjust         
carefully the capacity of the jars1 the 
arc between the knobs and the length of 
the wires4 ,my experience is that       
calculation of the length of the wires  
leads1 in such case1 to no result       
whatever4 ,the experimenter will do best
 to take the wires at the start very    
long1 and then adjust by cutting off    
first long pieces1 and then smaller and 
smaller ones as he approaches the right 
length4  ,a convenient way is to use an 
oil condenser of very small capacity1   
consisting of two small adjustable metal
 plates1 in connection with this and    
similar experiments4 ,in such case ,i   
take wires rather short and set at the  
beginning the condenser plates at       
maximum distance4 ,if the streams for   
the wires increase by approach of the   

plates1 the length of the wires is about
 right2 if they diminish the wires are  
too long for that frequency and         
potential4 ,when a condenser is used in 
connection with experiments with such a 
coil1 it should be an oil condenser by  
all means1 as in using an air condenser 
considerable energy might be wasted4    
,the wires leading to the plates in the 
oil should be very thin1 heavily coated 
with some insulating compound1 and      
provided with a conducting              
covering--this preferably extending     
under the surface of the oil4 ,the      
conducting cover should not be too near 
the terminals1 or ends1 of the wire1 as 
a spark would be apt to jump from the   
wire to it4 ,the conducting coating is  
used to diminish the air losses1 in     
virtue of its action as an electrostatic
 screen4 ,as to the size of the vessel  
containing the oil1 and the size of the 
plates1 the experimenter gains at once  
an idea from a rough trial4 ,the size of
 the plates in oil is1 however1         

calculable1 as the dielectric losses are
 very small4  ,in the preceding         
experiment it is of considerable        
interest to know what relation the      
quantity of the light emitted bears to  
the frequency and potential of the      
electric impulses4 ,my opinion is that  
the heat as well as light effects       
produced should be proportionate1 under 
otherwise equal conditions of test1 to  
the product of frequency and square of  
potential1 but the experimental         
verification of the law1 whatever it may
 be1 would be exceedingly difficult4    
,one thing is certain1 at any rate1 and 
that is1 that in augmenting the         
potential and frequency we rapidly      
intensify the streams2 and1 though it   
may be very sanguine1 it is surely not  
altogether hopeless to expect that we   
may succeed in producing a practical    
illuminant on these lines4 ,we would    
then be simply using burners or flames1 
in which there would be no chemical     
process1 no consumption of material1 but

 merely a transfer of energy1 and which 
would1 in all probability emit more     
light and less heat than ordinary       
flames4  ,illustration3 ,,fig4          
#h4--;,,effect ,,produced ,,by          
,,concentrating ,,streams4  ,the        
luminous intensity of the streams is1 of
 course1 considerably increased when    
they are focused upon a small surface4  
,this may be shown by the following     
experiment3  ,i attach to one of the    
terminals of the coil a wire w 7,fig4   
#h71 bent in a circle of about #cj      
centimetres in diameter1 and to the     
other terminal ,i fasten a small brass  
sphere s1 the surface of the wire being 
preferably equal to the surface of the  
sphere1 and the centre of the latter    
being in a line at right angles to the  
plane of the wire circle and passing    
through its centre4 ,when the discharge 
is established under proper conditions1 
a luminous hollow cone is formed1 and in
 the dark one-half of the brass sphere  
is strongly illuminated1 as shown in the

 cut4  ,by some artifice or other1 it is
 easy to concentrate the streams upon   
small surfaces and to produce very      
strong light effects4 ,two thin wires   
may thus be rendered intensely luminous4
  ,in order to intensify the streams the
 wires should be very thin and short2   
but as in this case their capacity would
 be generally too small for the coil--at
 least1 for such a one as the           
present--it is necessary to augment the 
capacity to the required value1 while1  
at the same time1 the surface of the    
wires remains very small4 ,this may be  
done in many ways4  ,here1 for instance1
 ,i have two plates1 ,,rr1 of hard      
rubber 7,fig4 #i71 upon which ,i have   
glued two very thin wires ww1 so as to  
form a name4 ,the wires may be bare or  
covered with the best insulation--it is 
immaterial for the success of the       
experiment4 ,well insulated wires1 if   
anything1 are preferable4 ,on the back  
of each plate1 indicated by the shaded  
portion1 is a tinfoil coating tt4 ,the  

plates are placed in line at a          
sufficient distance to prevent a spark  
passing from one to the other wire4 ,the
 two tinfoil coatings ,i have joined by 
a conductor ,c1 and the two wires ,i    
presently connect to the terminals of   
the coil4 ,it is now easy1 by varying   
the strength and frequency of the       
currents through the primary1 to find a 
point at which1 the capacity of the     
system is best suited to the conditions1
 and the wires become so strongly       
luminous that1 when the light in the    
room is turned off the name formed by   
them appears in brilliant letters4      
,illustration3 ,,fig4 #i4--,,wires      
,,rendered ,,intensely ,,luminous4  ,it 
is perhaps preferable to perform this   
experiment with a coil operated from an 
alternator of high frequency1 as then1  
owing to the harmonic rise and fall1 the
 streams are very uniform1 though they  
are less abundant then when produced    
with such a coil as the present4 ,this  
experiment1 however1 may be performed   

with low frequencies1 but much less     
satisfactorily4  ,illustration3 ,,fig4  
#aj4--,,luminous ,,discs4  ,when two    
wires1 attached to the terminals of the 
coil1 are set at the proper distance1   
the streams between them may be so      
intense as to produce a continuous      
luminous sheet4 ,to show this phenomenon
 ,i have here two circles1 ,c and c     
7,fig4 #aj71 of rather stout wire1 one  
being about #hj centimetres and the     
other #cj centimetres in diameter4 ,to  
each of the terminals of the coil ,i    
attach one of the circles4 ,the         
supporting wires are so bent that the   
circles may be placed in the same plane1
 coinciding as nearly as possible4 ,when
 the light in the room is turned off and
 the coil set to work1 you see the whole
 space between the wires uniformly      
filled with streams1 forming a luminous 
disc1 which could be seen from a        
considerable distance1 such is the      
intensity of the streams4 ,the outer    
circle could have been much larger than 

the present one2 in fact1 with this coil
 ,i have used much larger circles1 and  
,i have been able to produce a strongly 
luminous sheet1 covering an area of more
 than one square metre1 which is a      
remarkable effect with this very small  
coil4 ,to avoid uncertainty1 the circle 
has been taken smaller1 and the area is 
now about #j4dc square metre4  ,the     
frequency of the vibration1 and the     
quickness of succession of the sparks   
between the knobs1 affect to a marked   
degree the appearance of the streams4   
,when the frequency is very low1 the air
 gives way in more or less the same     
manner1 as by a steady difference of    
potential1 and the streams consist of   
distinct threads1 generally mingled with
 thin sparks1 which probably correspond 
to the successive discharges occurring  
between the knobs4 ,but when the        
frequency is extremely high1 and the arc
 of the discharge produces a very loud  
but smooth sound--showing both that     
oscillation takes place and that the    

sparks succeed each other with great    
rapidity--then the luminous streams     
formed are perfectly uniform4 ,to reach 
this result very small coils and jars of
 small capacity should be used4 ,i take 
two tubes of thick ,bohemian glass1     
about #e centimetres in diameter and #bj
 centimetres long4 ,in each of the tubes
 ,i slip a primary of very thick copper 
wire4 ,on the top of each tube ,i wind a
 secondary of much thinner gutta-percha 
covered wire4 ,the two secondaries ,i   
connect in series1 the primaries        
preferably in multiple arc4 ,the tubes  
are then placed in a large glass vessel1
 at a distance of #aj to #ae centimetres
 from each other1 on insulating         
supports1 and the vessel is filled with 
boiled out oil1 the oil reaching about  
an inch above the tubes4 ,the free ends 
of the secondary are lifted out of the  
oil and placed parallel to each other at
 a distance of about #aj centimetres4   
,the ends which are scraped should be   
dipped in the oil4 ,two four-pint jars  

joined in series may be used to         
discharge through the primary4 ,when the
 necessary adjustments in the length and
 distance of the wires above the oil and
 in the arc of discharge are made1 a    
luminous sheet is produced between the  
wires which is perfectly smooth and     
textureless1 like the ordinary discharge
 through a moderately exhausted tube4   
,i have purposely dwelt upon this       
apparently insignificant experiment4 ,in
 trials of this kind the experimenter   
arrives at the startling conclusion     
that1 to pass ordinary luminous         
discharges through gases1 no particular 
degree of exhaustion is needed1 but that
 the gas may be at ordinary or even     
greater pressure4 ,to accomplish this1 a
 very high frequency is essential2 a    
high potential is likewise required1 but
 this is a merely incidental necessity4 
,these experiments teach us that1 in    
endeavoring to discover novel methods of
 producing light by the agitation of    
atoms1 or molecules1 of a gas1 we need  

not limit our research to the vacuum    
tube1 but may look forward quite        
seriously to the possibility of         
obtaining the light effects without the 
use of any vessel whatever1 with air at 
ordinary pressure4  ,such discharges of 
very high frequency1 which render       
luminous the air at ordinary pressures1 
we have probably often occasion to      
witness in ,nature4 ,i have no doubt    
that if1 as many believe1 the aurora    
borealis is produced by sudden cosmic   
disturbances1 such as eruptions at the  
sun's surface1 which set the            
electrostatic charge of the earth in an 
extremely rapid vibration1 the red glow 
observed is not confined to the upper   
rarefied strata of the air1 but the     
discharge traverses1 by reason of its   
very high frequency1 also the dense     
atmosphere in the form of a glow1 such  
as we ordinarily produce in a slightly  
exhausted tube4 ,if the frequency were  
very low1 or even more so1 if the charge
 were not at all vibrating1 the dense   

air would break down as in a lightning  
discharge4 ,indications of such breaking
 down of the lower dense strata of the  
air have been repeatedly observed at the
 occurrence of this marvelous           
phenomenon2 but if it does occur1 it can
 only be attributed to the fundamental  
disturbances1 which are few in number1  
for the vibration produced by them would
 be far too rapid to allow a disruptive 
break4 ,it is the original and irregular
 impulses which affect the instruments2 
the superimposed vibrations probably    
pass unnoticed4  ,when an ordinary low  
frequency discharge is passed through   
moderately rarefied air1 the air assumes
 a purplish hue4 ,if by some means or   
other we increase the intensity of the  
molecular1 or atomic1 vibration1 the gas
 changes to a white color4 ,a similar   
change occurs at ordinary pressures with
 electric impulses of very high         
frequency4 ,if the molecules of the air 
around a wire are moderately agitated1  
the brush formed is reddish or violet2  

if the vibration is rendered            
sufficiently intense1 the streams become
 white4 ,we may accomplish this in      
various ways4 ,in the experiment before 
shown with the two wires across the     
room1 ,i have endeavored to secure the  
result by pushing to a high value both  
the frequency and potential3 in the     
experiment with the thin wires glued on 
the rubber plate ,i have concentrated   
the action upon a very small surface--in
 other words1 ,i have worked with a     
great electric density4  ,a most curious
 form of discharge is observed with such
 a coil when the frequency and potential
 are pushed to the extreme limit4 ,to   
perform the experiment1 every part of   
the coil should be heavily insulated1   
and only two small spheres--or1 better  
still1 two sharp-edged metal discs 7dd1 
,fig4 #aa7 of no more than a few        
centimetres in diameter--should be      
exposed to the air4 ,the coil here used 
is immersed in oil1 and the ends of the 
secondary reaching out of the oil are   

covered with an air-tight cover of hard 
rubber of great thickness4 ,all cracks1 
if there are any1 should be carefully   
stopped up1 so that the brush discharge 
cannot form anywhere except on the small
 spheres or plates which are exposed to 
the air4 ,in this case1 since there are 
no large plates or other bodies of      
capacity attached to the terminals1 the 
coil is capable of an extremely rapid   
vibration4 ,the potential may be raised 
by increasing1 as far as the            
experimenter judges proper1 the rate of 
change of the primary current4 ,with a  
coil not widely differing from the      
present1 it is best to connect the two  
primaries in multiple arc2 but if the   
secondary should have a much greater    
number of turns the primaries should    
preferably be used in series1 as        
otherwise the vibration might be too    
fast for the secondary4 ,it occurs under
 these conditions that misty white      
streams break forth from the edges of   
the discs and spread out phantom-like   

into space4 ,with this coil1 when fairly
 well produced1 they are about #be to   
#cj centimetres long4 ,when the hand is 
held against them no sensation is       
produced1 and a spark1 causing a shock1 
jumps from the terminal only upon the   
hand being brought much nearer4 ,if the 
oscillation of the primary current is   
rendered intermittent by some means or  
other1 there is a corresponding         
throbbing of the streams1 and now the   
hand or other conducting object may be  
brought in still greater proximity to   
the terminal without a spark being      
caused to jump4  ,illustration3 ,,fig4  
#aa4--,,phantom ,,streams4  ,among the  
many beautiful phenomena which may be   
produced with such a coil ,i have here  
selected only those which appear to     
possess some features of novelty1 and   
lead us to some conclusions of interest4
 ,one will not find it at all difficult 
to produce in the laboratory1 by means  
of it1 many other phenomena which appeal
 to the eye even more than these here   

shown1 but present no particular feature
 of novelty4  ,early experimenters      
describe the display of sparks produced 
by an ordinary large induction coil upon
 an insulating plate separating the     
terminals4 ,quite recently ,siemens     
performed some experiments in which fine
 effects were obtained1 which were seen 
by many with interest4 ,no doubt large  
coils1 even if operated with currents of
 low frequencies1 are capable of        
producing beautiful effects4 ,but the   
largest coil ever made could not1 by    
far1 equal the magnificent display of   
streams and sparks obtained from such a 
disruptive discharge coil when properly 
adjusted4 ,to give an idea1 a coil such 
as the present one will cover easily a  
plate of #a metre in diameter completely
 with the streams4 ,the best way to     
perform such experiments is to take a   
very thin rubber or a glass plate and   
glue on one side of it a narrow ring of 
tinfoil of very large diameter1 and on  
the other a circular washer1 the centre 

of the latter coinciding with that of   
the ring1 and the surfaces of both being
 preferably equal1 so as to keep the    
coil well balanced4 ,the washer and ring
 should be connected to the terminals by
 heavily insulated thin wires4 ,it is   
easy in observing the effect of the     
capacity to produce a sheet of uniform  
streams1 or a fine network of thin      
silvery threads1 or a mass of loud      
brilliant sparks1 which completely cover
 the plate4  ,since ,i have advanced the
 idea of the conversion by means of the 
disruptive discharge1 in my paper before
 the ,american ,institute of ,electrical
 ,engineers at the beginning of the past
 year1 the interest excited in it has   
been considerable4 ,it affords us a     
means for producing any potentials by   
the aid of inexpensive coils operated   
from ordinary systems of distribution1  
and--what is perhaps more               
appreciated--it enables us to convert   
currents of any frequency into currents 
of any other lower or higher frequency4 

,but its chief value will perhaps be    
found in the help which it will afford  
us in the investigations of the         
phenomena of phosphorescence1 which a   
disruptive discharge coil is capable of 
exciting in innumerable cases where     
ordinary coils1 even the largest1 would 
utterly fail4  ,considering its probable
 uses for many practical purposes1 and  
its possible introduction into          
laboratories for scientific research1 a 
few additional remarks as to the        
construction of such a coil will perhaps
 not be found superfluous4  ,it is1 of  
course1 absolutely necessary to employ  
in such a coil wires provided with the  
best insulation4  ,good coils may be    
produced by employing wires covered with
 several layers of cotton1 boiling the  
coil a long time in pure wax1 and       
cooling under moderate pressure4 ,the   
advantage of such a coil is that it can 
be easily handled1 but it cannot        
probably give as satisfactory results as
 a coil immersed in pure oil4 ,besides1 

it seems that the presence of a large   
body of wax affects the coil            
disadvantageously1 whereas this does not
 seem to be the case with oil4 ,perhaps 
it is because the dielectric losses in  
the liquid are smaller4  ,i have tried  
at first silk and cotton covered wires  
with oil immersion1 but ,i have been    
gradually led to use gutta-percha       
covered wires1 which proved most        
satisfactory4 ,gutta-percha insulation  
adds1 of course1 to the capacity of the 
coil1 and this1 especially if the coil  
be large1 is a great disadvantage when  
extreme frequencies are desired2 but on 
the other hand1 gutta-percha will       
withstand much more than an equal       
thickness of oil1 and this advantage    
should be secured at any price4 ,once   
the coil has been immersed1 it should   
never be taken out of the oil for more  
than a few hours1 else the gutta-percha 
will crack up and the coil will not be  
worth half as much as before4           
,gutta-percha is probably slowly        

attacked by the oil1 but after an       
immersion of eight to nine months ,i    
have found no ill effects4  ,i have     
obtained in commerce two kinds of       
gutta-percha wire3 in one the insulation
 sticks tightly to the metal1 in the    
other it does not4 ,unless a special    
method is followed to expel all air1 it 
is much safer to use the first kind4 ,i 
wind the coil within an oil tank so that
 all interstices are filled up with the 
oil4 ,between the layers ,i use cloth   
boiled out thoroughly in oil1           
calculating the thickness according to  
the difference of potential between the 
turns4 ,there seems not to be a very    
great difference whatever kind of oil is
 used2 ,i use paraffine or linseed oil4 
,to exclude more perfectly the air1 an  
excellent way to proceed1 and easily    
practicable with small coils1 is the    
following3 ,construct a box of hard wood
 of very thick boards which have been   
for a long time boiled in oil4 ,the     
boards should be so joined as to safely 

withstand the external air pressure4    
,the coil being placed and fastened in  
position within the box1 the latter is  
closed with a strong lid1 and covered   
with closely fitting metal sheets1 the  
joints of which are soldered very       
carefully4 ,on the top two small holes  
are drilled1 passing through the metal  
sheet and the wood1 and in these holes  
two small glass tubes are inserted and  
the joints made air-tight4 ,one of the  
tubes is connected to a vacuum pump1 and
 the other with a vessel containing a   
sufficient quantity of boiled-out oil4  
,the latter tube has a very small hole  
at the bottom1 and is provided with a   
stopcock4 ,when a fairly good vacuum has
 been obtained1 the stopcock is opened  
and the oil slowly fed in4 ,proceeding  
in this manner1 it is impossible that   
any big bubbles1 which are the principal
 danger1 should remain between the      
turns4 ,the air is most completely      
excluded1 probably better than by       
boiling out1 which1 however1 when       

gutta-percha coated wires are used1 is  
not practicable4  ,for the primaries ,i 
use ordinary line wire with a thick     
cotton coating4 ,strands of very thin   
insulated wires properly interlaced     
would1 of course1 be the best to employ 
for the primaries1 but they are not to  
be had4  ,in an experimental coil the   
size of the wires is not of great       
importance4 ,in the coil here used the  
primary is ,no4 #ab and the secondary   
,no4 #bd ,brown  ,sharpe gauge wire2 but
 the sections may be varied             
considerably4 ,it would only imply      
different adjustments2 the results aimed
 at would not be materially affected4   
,i have dwelt at some length upon the   
various forms of brush discharge        
because1 in studying them1 we not only  
observe phenomena which please our eye1 
but also afford us food for thought1 and
 lead us to conclusions of practical    
importance4 ,in the use of alternating  
currents of very high tension1 too much 
precaution cannot be taken to prevent   

the brush discharge4 ,in a main         
conveying such currents1 in an induction
 coil or transformer1 or in a condenser1
 the brush discharge is a source of     
great danger to the insulation4 ,in a   
condenser especially the gaseous matter 
must be most carefully expelled1 for in 
it the charged surfaces are near each   
other1 and if the potentials are high1  
just as sure as a weight will fall if   
let go1 so the insulation will give way 
if a single gaseous bubble of some size 
be present1 whereas1 if all gaseous     
matter were carefully excluded1 the     
condenser would safely withstand a much 
higher difference of potential4 ,a main 
conveying alternating currents of very  
high tension may be injured merely by a 
blow hole or small crack in the         
insulation1 the more so as a blowhole is
 apt to contain gas at low pressure2 and
 as it appears almost impossible to     
completely obviate such little          
imperfections1 ,i am led to believe that
 in our future distribution of          

electrical energy by currents of very   
high tension liquid insulation will be  
used4 ,the cost is a great drawback1 but
 if we employ an oil as an insulator the
 distribution of electrical energy with 
something like #ajj1jjj volts1 and even 
more1 become1 at least with higher      
frequencies1 so easy that they could be 
hardly called engineering feats4 ,with  
oil insulation and alternate current    
motors transmissions of power can be    
effected with safety and upon an        
industrial basis at distances of as much
 as a thousand miles4  ,a peculiar      
property of oils1 and liquid insulation 
in general1 when subjected to rapidly   
changing electric stresses1 is to       
disperse any gaseous bubbles which may  
be present1 and diffuse them through its
 mass1 generally long before any        
injurious break can occur4 ,this feature
 may be easily observed with an ordinary
 induction coil by taking the primary   
out1 plugging up the end of the tube    
upon which the secondary is wound1 and  

filling it with some fairly transparent 
insulator1 such as paraffine oil4 ,a    
primary of a diameter something like six
 millimetres smaller than the inside of 
the tube may be inserted in the oil4    
,when the coil is set to work one may   
see1 looking from the top through the   
oil1 many luminous points--air bubbles  
which are caught by inserting the       
primary1 and which are rendered luminous
 in consequence of the violent          
bombardment4 ,the occluded air1 by its  
impact against the oil1 heats it2 the   
oil begins to circulate1 carrying some  
of the air along with it1 until the     
bubbles are dispersed and the luminous  
points disappear4 ,in this manner1      
unless large bubbles are occluded in    
such way that circulation is rendered   
impossible1 a damaging break is averted1
 the only effect being a moderate       
warming up of the oil4 ,if1 instead of  
the liquid1 a solid insulation1 no      
matter how thick1 were used1 a breaking 
through and injury of the apparatus     

would be inevitable4  ,the exclusion of 
gaseous matter from any apparatus in    
which the dielectric is subjected to    
more or less rapidly changing electric  
forces is1 however1 not only desirable  
in order to avoid a possible injury of  
the apparatus1 but also on account of   
economy4 ,in a condenser1 for instance1 
as long as only a solid or only a liquid
 dielectric is used1 the loss is small2 
but if a gas under ordinary or small    
pressure be present the loss may be very
 great4 ,whatever the nature of the     
force acting in the dielectric may be1  
it seems that in a solid or liquid the  
molecular displacement produced by the  
force is small2 hence the product of    
force and displacement is insignificant1
 unless the force be very great2 but in 
a gas the displacement1 and therefore   
this product1 is considerable2 the      
molecules are free to move1 they reach  
high speeds1 and the energy of their    
impact is lost in heat or otherwise4 ,if
 the gas be strongly compressed1 the    

displacement due to the force is made   
smaller1 and the losses are reduced4    
,in most of the succeeding experiments  
,i prefer1 chiefly on account of the    
regular and positive action1 to employ  
the alternator before referred to4 ,this
 is one of the several machines         
constructed by me for the purposes of   
these investigations4 ,it has #chd pole 
projections1 and is capable of giving   
currents of a frequency of about #aj1jjj
 per second4 ,this machine has been     
illustrated and briefly described in my 
first paper before the ,american        
,institute of ,electrical ,engineers1   
,may #bj1 #ahia1 to which ,i have       
already referred4 ,a more detailed      
description1 sufficient to enable any   
engineer to build a similar machine1    
will be found in several electrical     
journals of that period4  ,the induction
 coils operated from the machine are    
rather small1 containing from #e1jjj to 
#ae1jjj turns in the secondary4 ,they   
are immersed in boiled-out linseed oil1 

contained in wooden boxes covered with  
zinc sheet4  ,i have found it           
advantageous to reverse the usual       
position of the wires1 and to wind1 in  
these coils1 the primaries on the top2  
this allowing the use of a much bigger  
primary1 which1 of course1 reduces the  
danger of overheating and increases the 
output of the coil4 ,i make the primary 
on each side at least one centimetre    
shorter than the secondary1 to prevent  
the breaking through on the ends1 which 
would surely occur unless the insulation
 on the top of the secondary be very    
thick1 and this1 of course1 would be    
disadvantageous4  ,when the primary is  
made movable1 which is necessary in some
 experiments1 and many times convenient 
for the purposes of adjustment1 ,i cover
 the secondary with wax1 and turn it off
 in a lathe to a diameter slightly      
smaller than the inside of the primary  
coil4 ,the latter ,i provide with a     
handle reaching out of the oil1 which   
serves to shift it in any position along

 the secondary4  ,i will now venture to 
make1 in regard to the general          
manipulation of induction coils1 a few  
observations bearing upon points which  
have not been fully appreciated in      
earlier experiments with such coils1 and
 are even now often overlooked4  ,the   
secondary of the coil possesses usually 
such a high self-induction that the     
current through the wire is             
inappreciable1 and may be so even when  
the terminals are joined by a conductor 
of small resistance4 ,if capacity is    
added to the terminals1 the             
self-induction is counteracted1 and a   
stronger current is made to flow through
 the secondary1 though its terminals are
 insulated from each other4 ,to one     
entirely unacquainted with the          
properties of alternating currents      
nothing will look more puzzling4 ,this  
feature was illustrated in the          
experiment performed at the beginning   
with the top plates of wire gauze       
attached to the terminals and the rubber

 plate4 ,when the plates of wire gauze  
were close together1 and a small arc    
passed between them1 the arc prevented a
 strong current from passing through the
 secondary1 because it did away with the
 capacity on the terminals2 when the    
rubber plate was inserted between1 the  
capacity of the condenser formed        
counteracted the self-induction of the  
secondary1 a stronger current passed    
now1 the coil performed more work1 and  
the discharge was by far more powerful4 
,the first thing1 then1 in operating the
 induction coil is to combine capacity  
with the secondary to overcome the      
self-induction4 ,if the frequencies and 
potentials are very high gaseous matter 
should be carefully kept away from the  
charged surfaces4 ,if ,leyden jars are  
used1 they should be immersed in oil1 as
 otherwise considerable dissipation may 
occur if the jars are greatly strained4 
,when high frequencies are used1 it is  
of equal importance to combine a        
condenser with the primary4 ,one may use

 a condenser connected to the ends of   
the primary or to the terminals of the  
alternator1 but the latter is not to be 
recommended1 as the machine might be    
injured4 ,the best way is undoubtedly to
 use the condenser in series with the   
primary and with the alternator1 and to 
adjust its capacity so as to annul the  
self-induction of both the latter4 ,the 
condenser should be adjustable by very  
small steps1 and for a finer adjustment 
a small oil condenser with movable      
plates may be used conveniently4  ,i    
think it best at this juncture to bring 
before you a phenomenon1 observed by me 
some time ago1 which to the purely      
scientific investigator may perhaps     
appear more interesting than any of the 
results which ,i have the privilege to  
present to you this evening4  ,it may be
 quite properly ranked among the brush  
phenomena--in fact1 it is a brush1      
formed at1 or near1 a single terminal in
 high vacuum4  ,in bulbs provided with a
 conducting terminal1 though it be of   

aluminium1 the brush has but an         
ephemeral existence1 and cannot1        
unfortunately1 be indefinitely preserved
 in its most sensitive state1 even in a 
bulb devoid of any conducting electrode4
 ,in studying the phenomenon1 by all    
means a bulb having no leading-in wire  
should be used4 ,i have found it best to
 use bulbs constructed as indicated in  
,figs4 #ab and #ac4  ,in ,fig4 #ab the  
bulb comprises an incandescent lamp     
globe ,l1 in the neck of which is sealed
 a barometer tube b1 the end of which is
 blown out to form a small sphere s4    
,this sphere should be sealed as closely
 as possible in the centre of the large 
globe4 ,before sealing1 a thin tube t1  
of aluminium sheet1 may be slipped in   
the barometer tube1 but it is not       
important to employ it4  ,the small     
hollow sphere s is filled with some     
conducting powder1 and a wire w is      
cemented in the neck for the purpose of 
connecting the conducting powder with   
the generator4  ,illustration3 ,,fig4   

#ab4 ,,fig4 #ac4 ,,bulbs ,,for          
,,producing ,,rotating ,,brush4  ,the   
construction shown in ,fig4 #ac was     
chosen in order to remove from the brush
 any conducting body which might        
possibly affect it4 ,the bulb consists  
in this case of a lamp globe ,l1 which  
has a neck n1 provided with a tube b and
 small sphere s1 sealed to it1 so that  
two entirely independent compartments   
are formed1 as indicated in the drawing4
 ,when the bulb is in use1 the neck n is
 provided with a tinfoil coating1 which 
is connected to the generator and acts  
inductively upon the moderately rarefied
 and highly conducting gas inclosed in  
the neck4 ,from there the current passes
 through the tube b into the small      
sphere s to act by induction upon the   
gas contained in the globe ,l4  ,it is  
of advantage to make the tube t very    
thick1 the hole through it very small1  
and to blow the sphere s very thin4 ,it 
is of the greatest importance that the  
sphere s be placed in the centre of the 

globe ,l4  ,illustration3 ,,fig4        
#ad4--;,,forms ,,and ,,phases ,,of ,,the
 ,,rotating ,,brush4  ,figs4 #ad1 #ae   
and #af indicate different forms1 or    
stages1 of the brush4 ,fig4 #ad shows   
the brush as it first appears in a bulb 
provided with a conducting terminal2    
but1 as in such a bulb it very soon     
disappears--often after a few           
minutes--,i will confine myself to the  
description of the phenomenon as seen in
 a bulb without conducting electrode4   
,it is observed under the following     
conditions3  ,when the globe ,l 7,figs4 
#ab and #ac7 is exhausted to a very high
 degree1 generally the bulb is not      
excited upon connecting the wire w      
7,fig4 #ab7 or the tinfoil coating of   
the bulb 7,fig4 #ac7 to the terminal of 
the induction coil4 ,to excite it1 it is
 usually sufficient to grasp the globe  
,l with the hand4 ,an intense           
phosphorescence then spreads at first   
over the globe1 but soon gives place to 
a white1 misty light4 ,shortly afterward

 one may notice that the luminosity is  
unevenly distributed in the globe1 and  
after passing the current for some time 
the bulb appears as in ,fig4 #ae4 ,from 
this stage the phenomenon will gradually
 pass to that indicated in ,fig4 #af1   
after some minutes1 hours1 days or      
weeks1 according as the bulb is worked4 
,warming the bulb or increasing the     
potential hastens the transit4          
,illustration3 ,,fig4 #ae4 ,,fig4 #af4  
,,forms ,,and ,,phases ,,of ,,the       
,,rotating ,,brush4  ,when the brush    
assumes the form indicated in ,fig4 #af1
 it maybe brought to a state of extreme 
sensitiveness to electrostatic and      
magnetic influence4 ,the bulb hanging   
straight down from a wire1 and all      
objects being remote from it1 the       
approach of the observer at a few paces 
from the bulb will cause the brush to   
fly to the opposite side1 and if he     
walks around the bulb it will always    
keep on the opposite side4 ,it may begin
 to spin around the terminal long before

 it reaches that sensitive stage4 ,when 
it begins to turn around principally1   
but also before1 it is affected by a    
magnet1 and at a certain stage it is    
susceptible to magnetic influence to an 
astonishing degree4 ,a small permanent  
magnet1 with its poles at a distance of 
no more than two centimetres1 will      
affect it visibly at a distance of two  
metres1 slowing down or accelerating the
 rotation according to how it is held   
relatively to the brush4 ,i think ,i    
have observed that at the stage when it 
is most sensitive to magnetic1 it is not
 most sensitive to electrostatic1       
influence4 ,my explanation is1 that the 
electrostatic attraction between the    
brush and the glass of the bulb1 which  
retards the rotation1 grows much quicker
 than the magnetic influence when the   
intensity of the stream is increased4   
,when the bulb hangs with the globe ,l  
down1 the rotation is always clockwise4 
,in the southern hemisphere it would    
occur in the opposite direction and on  

the equator the brush should not turn at
 all4 ,the rotation may be reversed by a
 magnet kept at some distance4 ,the     
brush rotates best1 seemingly1 when it  
is at right angles to the lines of force
 of the earth4 ,it very likely rotates1 
when at its maximum speed1 in           
synchronism with the alternations1 say  
#aj1jjj times a second4 ,the rotation   
can be slowed down or accelerated by the
 approach or receding of the observer1  
or any conducting body1 but it cannot be
 reversed by putting the bulb in any    
position4 ,when it is in the state of   
the highest sensitiveness and the       
potential or frequency be varied the    
sensitiveness is rapidly diminished4    
,changing either of these but little    
will generally stop the rotation4 ,the  
sensitiveness is likewise affected by   
the variations of temperature4 ,to      
attain great sensitiveness it is        
necessary to have the small sphere s in 
the centre of the globe ,l1 as otherwise
 the electrostatic action of the glass  

of the globe will tend to stop the      
rotation4 ,the sphere s should be small 
and of uniform thickness2 any           
dissymmetry of course has the effect to 
diminish the sensitiveness4  ,the fact  
that the brush rotates in a definite    
direction in a permanent magnetic field 
seems to show that in alternating       
currents of very high frequency the     
positive and negative impulses are not  
equal1 but that one always preponderates
 over the other4  ,of course1 this      
rotation in one direction may be due to 
the action of two elements of the same  
current upon each other1 or to the      
action of the field produced by one of  
the elements upon the other1 as in a    
series motor1 without necessarily one   
impulse being stronger than the other4  
,the fact that the brush turns1 as far  
as ,i could observe1 in any position1   
would speak for this view4 ,in such case
 it would turn at any point of the      
earth's surface4 ,but1 on the other     
hand1 it is then hard to explain why a  

permanent magnet should reverse the     
rotation1 and one must assume the       
preponderance of impulses of one kind4  
,as to the causes of the formation of   
the brush or stream1 ,i think it is due 
to the electrostatic action of the globe
 and the dissymmetry of the parts4 ,if  
the small bulb s and the globe ,l were  
perfect concentric spheres1 and the     
glass throughout of the same thickness  
and quality1 ,i think the brush would   
not form1 as the tendency to pass would 
be equal on all sides4 ,that the        
formation of the stream is due to an    
irregularity is apparent from the fact  
that it has the tendency to remain in   
one position1 and rotation occurs most  
generally only when it is brought out of
 this position by electrostatic or      
magnetic influence4 ,when in an         
extremely sensitive state it rests in   
one position1 most curious experiments  
may be performed with it4 ,for instance1
 the experimenter may1 by selecting a   
proper position1 approach the hand at a 

certain considerable distance to the    
bulb1 and he may cause the brush to pass
 off by merely stiffening the muscles of
 the arm4 ,when it begins to rotate     
slowly1 and the hands are held at a     
proper distance1 it is impossible to    
make even the slightest motion without  
producing a visible effect upon the     
brush4 ,a metal plate connected to the  
other terminal of the coil affects it at
 a great distance1 slowing down the     
rotation often to one turn a second4  ,i
 am firmly convinced that such a brush1 
when we learn how to produce it         
properly1 will prove a valuable aid in  
the investigation of the nature of the  
forces acting in an electrostatic or    
magnetic field4 ,if there is any motion 
which is measurable going on in the     
space1 such a brush ought to reveal it4 
,it is1 so to speak1 a beam of light1   
frictionless1 devoid of inertia4  ,i    
think that it may find practical        
applications in telegraphy4 ,with such a
 brush it would be possible to send     

dispatches across the ,atlantic1 for    
instance1 with any speed1 since its     
sensitiveness may be so great that the  
slightest changes will affect it4 ,if it
 were possible to make the stream more  
intense and very narrow1 its deflections
 could be easily photographed4  ,i have 
been interested to find whether there is
 a rotation of the stream itself1 or    
whether there is simply a stress        
traveling around in the bulb4 ,for this 
purpose ,i mounted a light mica fan so  
that its vanes were in the path of the  
brush4 ,if the stream itself was        
rotating the fan would be spun around4  
,i could produce no distinct rotation of
 the fan1 although ,i tried the         
experiment repeatedly2 but as the fan   
exerted a noticeable influence on the   
stream1 and the apparent rotation of the
 latter was1 in this case1 never quite  
satisfactory1 the experiment did not    
appear to be conclusive4  ,i have been  
unable to produce the phenomenon with   
the disruptive discharge coil1 although 

every other of these phenomena can be   
well produced by it--many1 in fact1 much
 better than with coils operated from an
 alternator4  ,it may be possible to    
produce the brush by impulses of one    
direction1 or even by a steady          
potential1 in which case it would be    
still more sensitive to magnetic        
influence4  ,in operating an induction  
coil with rapidly alternating currents1 
we realize with astonishment1 for the   
first time1 the great importance of the 
relation of capacity1 self-induction and
 frequency as regards the general       
result4 ,the effects of capacity are the
 most striking1 for in these            
experiments1 since the self-induction   
and frequency both are high1 the        
critical capacity is very small1 and    
need be but slightly varied to produce a
 very considerable change4 ,the         
experimenter may bring his body in      
contact with the terminals of the       
secondary of the coil1 or attach to one 
or both terminals insulated bodies of   

very small bulk1 such as bulbs1 and he  
may produce a considerable rise or fall 
of potential1 and greatly affect the    
flow of the current through the primary4
 ,in the experiment before shown1 in    
which a brush appears at a wire attached
 to one terminal1 and the wire is       
vibrated when the experimenter brings   
his insulated body in contact with the  
other terminal of the coil1 the sudden  
rise of potential was made evident4  ,i 
may show you the behavior of the coil in
 another manner which possesses a       
feature of some interest4 ,i have here a
 little light fan of aluminium sheet1   
fastened to a needle and arranged to    
rotate freely in a metal piece screwed  
to one of the terminals of the coil4    
,when the coil is set to work1 the      
molecules of the air are rhythmically   
attracted and repelled4 ,as the force   
with which they are repelled is greater 
than that with which they are attracted1
 it results that there is a repulsion   
exerted on the surfaces of the fan4 ,if 

the fan were made simply of a metal     
sheet1 the repulsion would be equal on  
the opposite sides1 and would produce no
 effect4 ,but if one of the opposing    
surfaces is screened1 or if1 generally  
speaking1 the bombardment on this side  
is weakened in some way or other1 there 
remains the repulsion exerted upon the  
other1 and the fan is set in rotation4  
,the screening is best effected by      
fastening upon one of the opposing sides
 of the fan insulated conducting        
coatings1 or1 if the fan is made in the 
shape of an ordinary propeller screw1 by
 fastening on one side1 and close to it1
 an insulated metal plate4 ,the static  
screen may1 however1 be omitted1 and    
simply a thickness of insulating        
material fastened to one of the sides of
 the fan4  ,to show the behavior of the 
coil1 the fan may be placed upon the    
terminal and it will readily rotate when
 the coil is operated by currents of    
very high frequency4 ,with a steady     
potential1 of course1 and even with     

alternating currents of very low        
frequency1 it would not turn1 because of
 the very slow exchange of air and1     
consequently1 smaller bombardment2 but  
in the latter case it might turn if the 
potential were excessive4 ,with a pin   
wheel1 quite the opposite rule holds    
good2 it rotates best with a steady     
potential1 and the effort is the smaller
 the higher the frequency4 ,now1 it is  
very easy to adjust the conditions so   
that the potential is normally not      
sufficient to turn the fan1 but that by 
connecting the other terminal of the    
coil with an insulated body it rises to 
a much greater value1 so as to rotate   
the fan1 and it is likewise possible to 
stop the rotation by connecting to the  
terminal a body of different size1      
thereby diminishing the potential4      
,instead of using the fan in this       
experiment1 we may use the electric     
radiometer with similar effect4 ,but in 
this case it will be found that the     
vanes will rotate only at high          

exhaustion or at ordinary pressures2    
they will not rotate at moderate        
pressures1 when the air is highly       
conducting4 ,this curious observation   
was made conjointly by ,professor       
,crookes and myself4 ,i attribute the   
result to the high conductivity of the  
air1 the molecules of which then do not 
act as independent carriers of electric 
charges1 but act all together as a      
single conducting body4 ,in such case1  
of course1 if there is any repulsion at 
all of the molecules from the vanes1 it 
must be very small4 ,it is possible1    
however1 that the result is in part due 
to the fact that the greater part of the
 discharge passes from the leading-in   
wire through the highly conducting gas1 
instead of passing off from the         
conducting vanes4  ,in trying the       
preceding experiment with the electric  
radiometer the potential should not     
exceed a certain limit1 as then the     
electrostatic attraction between the    
vanes and the glass of the bulb may be  

so great as to stop the rotation4  ,a   
most curious feature of alternate       
currents of high frequencies and        
potentials is that they enable us to    
perform many experiments by the use of  
one wire only4 ,in many respects this   
feature is of great interest4  ,in a    
type of alternate current motor invented
 by me some years ago ,i produced       
rotation by inducing1 by means of a     
single alternating current passed       
through a motor circuit1 in the mass or 
other circuits of the motor1 secondary  
currents1 which1 jointly with the       
primary or inducing current1 created a  
moving field of force4 ,a simple but    
crude form of such a motor is obtained  
by winding upon an iron core a primary1 
and close to it a secondary coil1       
joining the ends of the latter and      
placing a freely movable metal disc     
within the influence of the field       
produced by both4 ,the iron core is     
employed for obvious reasons1 but it is 
not essential to the operation4 ,to     

improve the motor1 the iron core is made
 to encircle the armature4 ,again to    
improve1 the secondary coil is made to  
overlap partly the primary1 so that it  
cannot free itself from a strong        
inductive action of the latter1 repel   
its lines as it may4 ,once more to      
improve1 the proper difference of phase 
is obtained between the primary and     
secondary currents by a condenser1      
self-induction1 resistance or equivalent
 windings4  ,i had discovered1 however1 
that rotation is produced by means of a 
single coil and core2 my explanation of 
the phenomenon1 and leading thought in  
trying the experiment1 being that there 
must be a true time lag in the          
magnetization of the core4 ,i remember  
the pleasure ,i had when1 in the        
writings of ,professor ,ayrton1 which   
came later to my hand1 ,i found the idea
 of the time lag advocated4 ,whether    
there is a true time lag1 or whether the
 retardation is due to eddy currents    
circulating in minute paths1 must remain

 an open question1 but the fact is that 
a coil wound upon an iron core and      
traversed by an alternating current     
creates a moving field of force1 capable
 of setting an armature in rotation4 ,it
 is of some interest1 in conjunction    
with the historical ,arago experiment1  
to mention that in lag or phase motors  
,i have produced rotation in the        
opposite direction to the moving field1 
which means that in that experiment the 
magnet may not rotate1 or may even      
rotate in the opposite direction to the 
moving disc4 ,here1 then1 is a motor    
7diagrammatically illustrated in ,fig4  
#ag71 comprising a coil and iron core1  
and a freely movable copper disc in     
proximity to the latter4  ,illustration3
 ,,fig4 #ag4--,,single ,,wire ,,and     
,,no-,,wire ,,motor4  ,to demonstrate a 
novel and interesting feature1 ,i have1 
for a reason which ,i will explain1     
selected this type of motor4 ,when the  
ends of the coil are connected to the   
terminals of an alternator the disc is  

set in rotation4 ,but it is not this    
experiment1 now well known1 which ,i    
desire to perform4 ,what ,i wish to show
 you is that this motor rotates with one
 single connection between it and the   
generator2 that is to say1 one terminal 
of the motor is connected to one        
terminal of the generator--in this case 
the secondary of a high-tension         
induction coil--the other terminals of  
motor and generator being insulated in  
space4 ,to produce rotation it is       
generally 7but not absolutely7 necessary
 to connect the free end of the motor   
coil to an insulated body of some size4 
,the experimenter's body is more than   
sufficient4 ,if he touches the free     
terminal with an object held in the     
hand1 a current passes through the coil 
and the copper disc is set in rotation4 
,if an exhausted tube is put in series  
with the coil1 the tube lights          
brilliantly1 showing the passage of a   
strong current4 ,instead of the         
experimenter's body1 a small metal sheet

 suspended on a cord may be used with   
the same result4 ,in this case the plate
 acts as a condenser in series with the 
coil4 ,it counteracts the self-induction
 of the latter and allows a strong      
current to pass4 ,in such a combination1
 the greater the self-induction of the  
coil the smaller need be the plate1 and 
this means that a lower frequency1 or   
eventually a lower potential1 is        
required to operate the motor4 ,a single
 coil wound upon a core has a high      
self-induction2 for this reason         
principally1 this type of motor was     
chosen to perform the experiment4 ,were 
a secondary closed coil wound upon the  
core1 it would tend to diminish the     
self-induction1 and then it would be    
necessary to employ a much higher       
frequency and potential4 ,neither would 
be advisable1 for a higher potential    
would endanger the insulation of the    
small primary coil1 and a higher        
frequency would result in a materially  
diminished torque4  ,it should be       

remarked that when such a motor with a  
closed secondary is used1 it is not at  
all easy to obtain rotation with        
excessive frequencies1 as the secondary 
cuts off almost completely the lines of 
the primary--and this1 of course1 the   
more1 the higher the frequency--and     
allows the passage of but a minute      
current4 ,in such a case1 unless the    
secondary is closed through a condenser1
 it is almost essential1 in order to    
produce rotation1 to make the primary   
and secondary coils overlap each other  
more or less4  ,but there is an         
additional feature of interest about    
this motor1 namely1 it is not necessary 
to have even a single connection between
 the motor and generator1 except1       
perhaps1 through the ground3 for not    
only is an insulated plate capable of   
giving off energy into space1 but it is 
likewise capable of deriving it from an 
alternating electrostatic field1 though 
in the latter case the available energy 
is much smaller4 ,in this instance one  

of the motor terminals is connected to  
the insulated plate or body located     
within the alternating electrostatic    
field1 and the other terminal preferably
 to the ground4  ,it is quite possible1 
however1 that such no-wire motors1 as   
they might be called1 could be operated 
by conduction through the rarefied air  
at considerable distances4 ,alternate   
currents1 especially of high            
frequencies1 pass with astonishing      
freedom through even slightly rarefied  
gases4 ,the upper strata of the air are 
rarefied4 ,to reach a number of miles   
out into space requires the overcoming  
of difficulties of a merely mechanical  
nature4 ,there is no doubt that with the
 enormous potentials obtainable by the  
use of high frequencies and oil         
insulation luminous discharges might be 
passed through many miles of rarefied   
air1 and that1 by thus directing the    
energy of many hundreds or thousands of 
horse-power1 motors or lamps might be   
operated at considerable distances from 

stationary sources4 ,but such schemes   
are mentioned merely as possibilities4  
,we shall have no need to transmit power
 in this way4 ,we shall have no need to 
transmit power at all4 ,ere many        
generations pass1 our machinery will be 
driven by a power obtainable at any     
point of the universe4 ,this idea is not
 novel4 ,men have been led to it long   
ago by instinct or reason4 ,it has been 
expressed in many ways1 and in many     
places1 in the history of old and new4  
,we find it in the delightful myth of   
,antheus1 who derives power from the    
earth2 we find it among the subtile     
speculations of one of your splendid    
mathematicians1 and in many hints and   
statements of thinkers of the present   
time4 ,throughout space there is energy4
 ,is this energy static or kinetic8 ,if 
static our hopes are in vain2 if        
kinetic--and this we know it is1 for    
certain--then it is a mere question of  
time when men will succeed in attaching 
their machinery to the very wheelwork of

 nature4 ,of all1 living or dead1       
,crookes came nearest to doing it4 ,his 
radiometer will turn in the light of day
 and in the darkness of the night2 it   
will turn everywhere where there is     
heat1 and heat is everywhere4 ,but1     
unfortunately1 this beautiful little    
machine1 while it goes down to posterity
 as the most interesting1 must likewise 
be put on record as the most inefficient
 machine ever invented6  ,the preceding 
experiment is only one of many equally  
interesting experiments which may be    
performed by the use of only one wire   
with alternate currents of high         
potential and frequency4 ,we may connect
 an insulated line to a source of such  
currents1 we may pass an inappreciable  
current over the line1 and on any point 
of the same we are able to obtain a     
heavy current1 capable of fusing a thick
 copper wire4 ,or we may1 by the help of
 some artifice1 decompose a solution in 
any electrolytic cell by connecting only
 one pole of the cell to the line or    

source of energy4 ,or we may1 by        
attaching to the line1 or only bringing 
into its vicinity1 light up an          
incandescent lamp1 an exhausted tube1 or
 a phosphorescent bulb4  ,however       
impracticable this plan of working may  
appear in many cases1 it certainly seems
 practicable1 and even recommendable1 in
 the production of light4 ,a perfected  
lamp would require but little energy1   
and if wires were used at all we ought  
to be able to supply that energy without
 a return wire4  ,it is now a fact that 
a body may be rendered incandescent or  
phosphorescent by bringing it either in 
single contact or merely in the vicinity
 of a source of electric impulses of the
 proper character1 and that in this     
manner a quantity of light sufficient to
 afford a practical illuminant may be   
produced4 ,it is1 therefore1 to say the 
least1 worth while to attempt to        
determine the best conditions and to    
invent the best appliances for attaining
 this object4  ,some experiences have   

already been gained in this direction1  
and ,i will dwell on them briefly1 in   
the hope that they might prove useful4  
,the heating of a conducting body       
inclosed in a bulb1 and connected to a  
source of rapidly alternating electric  
impulses1 is dependent on so many things
 of a different nature1 that it would be
 difficult to give a generally          
applicable rule under which the maximum 
heating occurs4 ,as regards the size of 
the vessel1 ,i have lately found that at
 ordinary or only slightly differing    
atmospheric pressures1 when air is a    
good insulator1 and hence practically   
the same amount of energy by a certain  
potential and frequency is given off    
from the body1 whether the bulb be small
 or large1 the body is brought to a     
higher temperature if inclosed in a     
small bulb1 because of the better       
confinement of heat in this case4  ,at  
lower pressures1 when air becomes more  
or less conducting1 or if the air be    
sufficiently warmed as to become        

conducting1 the body is rendered more   
intensely incandescent in a large bulb1 
obviously because1 under otherwise equal
 conditions of test1 more energy may be 
given off from the body when the bulb is
 large4  ,at very high degrees of       
exhaustion1 when the matter in the bulb 
becomes radiant1 a large bulb has still 
an advantage1 but a comparatively slight
 one1 over the small bulb4  ,finally1 at
 excessively high degrees of exhaustion1
 which cannot be reached except by the  
employment of special means1 there seems
 to be1 beyond a certain and rather     
small size of vessel1 no perceptible    
difference in the heating4  ,these      
observations were the result of a number
 of experiments1 of which one1 showing  
the effect of the size of the bulb at a 
high degree of exhaustion1 may be       
described and shown here1 as it presents
 a feature of interest4 ,three spherical
 bulbs of #b inches1 #c inches and #d   
inches diameter were taken1 and in the  
centre of each was mounted an equal     

length of an ordinary incandescent lamp 
filament of uniform thickness4 ,in each 
bulb the piece of filament was fastened 
to the leading-in wire of platinum1     
contained in a glass stem sealed in the 
bulb2 care being taken1 of course1 to   
make everything as nearly alike as      
possible4 ,on each glass stem in the    
inside of the bulb was slipped a highly 
polished tube made of aluminium sheet1  
which fitted the stem and was held on it
 by spring pressure4 ,the function of   
this aluminium tube will be explained   
subsequently4 ,in each bulb an equal    
length of filament protruded above the  
metal tube4 ,it is sufficient to say now
 that under these conditions equal      
lengths of filament of the same         
thickness--in other words1 bodies of    
equal bulk--were brought to             
incandescence4 ,the three bulbs were    
sealed to a glass tube1 which was       
connected to a ,sprengel pump4 ,when a  
high vacuum had been reached1 the glass 
tube carrying the bulbs was sealed off4 

,a current was then turned on           
successively on each bulb1 and it was   
found that the filaments came to about  
the same brightness1 and1 if anything1  
the smallest bulb1 which was placed     
midway between the two larger ones1 may 
have been slightly brighter4 ,this      
result was expected1 for when either of 
the bulbs was connected to the coil the 
luminosity spread through the other two1
 hence the three bulbs constituted      
really one vessel4 ,when all the three  
bulbs were connected in multiple arc to 
the coil1 in the largest of them the    
filament glowed brightest1 in the next  
smaller it was a little less bright1 and
 in the smallest it only came to        
redness4 ,the bulbs were then sealed off
 and separately tried4 ,the brightness  
of the filaments was now such as would  
have been expected on the supposition   
that the energy given off was           
proportionate to the surface of the     
bulb1 this surface in each case         
representing one of the coatings of a   

condenser4 ,accordingly1 time was less  
difference between the largest and the  
middle sized than between the latter and
 the smallest bulb4  ,an interesting    
observation was made in this experiment4
 ,the three bulbs were suspended from a 
straight bare wire connected to a       
terminal of the coil1 the largest bulb  
being placed at the end of the wire1 at 
some distance from it the smallest bulb1
 and an equal distance from the latter  
the middle-sized one4 ,the carbons      
glowed then in both the larger bulbs    
about as expected1 but the smallest did 
not get its share by far4 ,this         
observation led me to exchange the      
position of the bulbs1 and ,i then      
observed that whichever of the bulbs was
 in the middle it was by far less bright
 than it was in any other position4     
,this mystifying result was1 of course1 
found to be due to the electrostatic    
action between the bulbs4 ,when they    
were placed at a considerable distance1 
or when they were attached to the       

corners of an equilateral triangle of   
copper wire1 they glowed about in the   
order determined by their surfaces4  ,as
 to the shape of the vessel1 it is also 
of some importance1 especially at high  
degrees of exhaustion4 ,of all the      
possible constructions1 it seems that a 
spherical globe with the refractory body
 mounted in its centre is the best to   
employ4 ,in experience it has been      
demonstrated that in such a globe a     
refractory body of a given bulk is more 
easily brought to incandescence than    
when otherwise shaped bulbs are used4   
,there is also an advantage in giving to
 the incandescent body the shape of a   
sphere1 for self-evident reasons4 ,in   
any case the body should be mounted in  
the centre1 where the atoms rebounding  
from the glass collide4 ,this object is 
best attained in the spherical bulb2 but
 it is also attained in a cylindrical   
vessel with one or two straight         
filaments coinciding with its axis1 and 
possibly also in parabolical or         

spherical bulbs with the refractory body
 or bodies placed in the focus or foci  
of the same2 though the latter is not   
probable1 as the electrified atoms      
should in all cases rebound normally    
from the surface they strike1 unless the
 speed were excessive1 in which case    
they would probably follow the general  
law of reflection4 ,no matter what shape
 the vessel may have1 if the exhaustion 
be low1 a filament mounted in the globe 
is brought to the same degree of        
incandescence in all parts2 but if the  
exhaustion be high and the bulb be      
spherical or pear-shaped1 as usual1     
focal points form and the filament is   
heated to a higher degree at or near    
such points4  ,to illustrate the effect1
 ,i have here two small bulbs which are 
alike1 only one is exhausted to a low   
and the other to a very high degree4    
,when connected to the coil1 the        
filament in the former glows uniformly  
throughout all its length2 whereas in   
the latter1 that portion of the filament

 which is in the centre of the bulb     
glows far more intensely than the rest4 
,a curious point is that the phenomenon 
occurs even if two filaments are mounted
 in a bulb1 each being connected to one 
terminal of the coil1 and1 what is still
 more curious1 if they be very near     
together1 provided the vacuum be very   
high4 ,i noted in experiments with such 
bulbs that the filaments would give way 
usually at a certain point1 and in the  
first trials ,i attributed it to a      
defect in the carbon4 ,but when the     
phenomenon occurred many times in       
succession ,i recognized its real cause4
  ,in order to bring a refractory body  
inclosed in a bulb to incandescence1 it 
is desirable1 on account of economy1    
that all the energy supplied to the bulb
 from the source should reach without   
loss the body to be heated2 from there1 
and from nowhere else1 it should be     
radiated4 ,it is1 of course1 out of the 
question to reach this theoretical      
result1 but it is possible by a proper  

construction of the illuminating device 
to approximate it more or less4  ,for   
many reasons1 the refractory body is    
placed in the centre of the bulb1 and it
 is usually supported on a glass stem   
containing the leading-in wire4 ,as the 
potential of this wire is alternated1   
the rarefied gas surrounding the stem is
 acted upon inductively1 and the glass  
stem is violently bombarded and heated4 
,in this manner by far the greater      
portion of the energy supplied to the   
bulb--especially when exceedingly high  
frequencies are used--may be lost for   
the purpose contemplated4 ,to obviate   
this loss1 or at least to reduce it to a
 minimum1 ,i usually screen the rarefied
 gas surrounding the stem from the      
inductive action of the leading-in wire 
by providing the stem with a tube or    
coating of conducting material4 ,it     
seems beyond doubt that the best among  
metals to employ for this purpose is    
aluminium1 on account of its many       
remarkable properties4 ,its only fault  

is that it is easily fusible1 and1      
therefore1 its distance from the        
incandescing body should be properly    
estimated4 ,usually1 a thin tube1 of a  
diameter somewhat smaller than that of  
the glass stem1 is made of the finest   
aluminium sheet1 and slipped on the     
stem4 ,the tube is conveniently prepared
 by wrapping around a rod fastened in a 
lathe a piece of aluminium sheet of the 
proper size1 grasping the sheet firmly  
with clean chamois leather or blotting  
paper1 and spinning the rod very fast4  
,the sheet is wound tightly around the  
rod1 and a highly polished tube of one  
or three layers of the sheet is         
obtained4 ,when slipped on the stem1 the
 pressure is generally sufficient to    
prevent it from slipping off1 but1 for  
safety1 the lower edge of the sheet may 
be turned inside4 ,the upper inside     
corner of the sheet--that is1 the one   
which is nearest to the refractory      
incandescent body--should be cut out    
diagonally1 as it often happens that1 in

 consequence of the intense heat1 this  
corner turns toward the inside and comes
 very near to1 or in contact with1 the  
wire1 or filament1 supporting the       
refractory body4 ,the greater part of   
the energy supplied to the bulb is then 
used up in heating the metal tube1 and  
the bulb is rendered useless for the    
purpose4 ,the aluminium sheet should    
project above the glass stem more or    
less--one inch or so--or else1 if the   
glass be too close to the incandescing  
body1 it may be strongly heated and     
become more or less conducting1         
whereupon it may be ruptured1 or may1 by
 its conductivity1 establish a good     
electrical connection between the metal 
tube and the leading-in wire1 in which  
case1 again1 most of the energy will be 
lost in heating the former4 ,perhaps the
 best way is to make the top of the     
glass tube1 for about an inch1 of a much
 smaller diameter4 ,to still further    
reduce the danger arising from the      
heating of the glass stem1 and also with

 the view of preventing an electrical   
connection between the metal tube and   
the electrode1 ,i preferably wrap the   
stem with several layers of thin mica1  
which extends at least as far as the    
metal tube4 ,in some bulbs ,i have also 
used an outside insulating cover4  ,the 
preceding remarks are only made to aid  
the experimenter in the first trials1   
for the difficulties which he encounters
 he may soon find means to overcome in  
his own way4  ,to illustrate the effect 
of the screen1 and the advantage of     
using it1 ,i have here two bulbs of the 
same size1 with their stems1 leading-in 
wires and incandescent lamp filaments   
tied to the latter1 as nearly alike as  
possible4 ,the stem of one bulb is      
provided with an aluminium tube1 the    
stem of the other has none4 ,originally 
the two bulbs were joined by a tube     
which was connected to a ,sprengel pump4
 ,when a high vacuum had been reached1  
first the connecting tube1 and then the 
bulbs1 were sealed off2 they are        

therefore of the same degree of         
exhaustion4 ,when they are separately   
connected to the coil giving a certain  
potential1 the carbon filament in the   
bulb provided with the aluminium screen 
is rendered highly incandescent1 while  
the filament in the other bulb may1 with
 the same potential1 not even come to   
redness1 although in reality the latter 
bulb takes generally more energy than   
the former4 ,when they are both         
connected together to the terminal1 the 
difference is even more apparent1       
showing the importance of the screening4
 ,the metal tube placed on the stem     
containing the leading-in wire performs 
really two distinct functions3 ,first3  
it acts more or less as an electrostatic
 screen1 thus economizing the energy    
supplied to the bulb2 and1 second1 to   
whatever extent it may fail to act      
electrostatically1 it acts mechanically1
 preventing the bombardment1 and        
consequently intense heating and        
possible deterioration of the slender   

support of the refractory incandescent  
body1 or of the glass stem containing   
the leading-in wire4 ,i say slender     
support1 for it is evident that in order
 to confine the heat more completely to 
the incandescing body its support should
 be very thin1 so as to carry away the  
smallest possible amount of heat by     
conduction4 ,of all the supports used ,i
 have found an ordinary incandescent    
lamp filament to be the best1           
principally because among conductors it 
can withstand the highest degrees of    
heat4  ,the effectiveness of the metal  
tube as an electrostatic screen depends 
largely on the degree of exhaustion4    
,at excessively high degrees of         
exhaustion--which are reached by using  
great care and special means in         
connection with the ,sprengel pump--when
 the matter in the globe is in the      
ultra-radiant state1 it acts most       
perfectly4 ,the shadow of the upper edge
 of the tube is then sharply defined    
upon the bulb4  ,at a somewhat lower    

degree of exhaustion1 which is about the
 ordinary non-striking vacuum1 and      
generally as long as the matter moves   
predominantly in straight lines1 the    
screen still does well4 ,in elucidation 
of the preceding remark it is necessary 
to state that what is a non-striking    
vacuum for a coil operated1 as          
ordinarily1 by impulses1 or currents1 of
 low-frequency1 is not1 by far1 so when 
the coil is operated by currents of very
 high frequency4 ,in such case the      
discharge may pass with great freedom   
through the rarefied gas through which a
 low-frequency discharge may not pass1  
even though the potential be much       
higher4 ,at ordinary atmospheric        
pressures just the reverse rule holds   
good3 the higher the frequency1 the less
 the spark discharge is able to jump    
between the terminals1 especially if    
they are knobs or spheres of some size4 
,finally1 at very low degrees of        
exhaustion1 when the gas is well        
conducting1 the metal tube not only does

 not act as an electrostatic screen1 but
 even is a drawback1 aiding to a        
considerable extent the dissipation of  
the energy laterally from the leading-in
 wire4 ,this1 of course1 is to be       
expected4 ,in this case1 namely1 the    
metal tube is in good electrical        
connection with the leading-in wire1 and
 most of the bombardment is directed    
upon the tube4 ,as long as the          
electrical connection is not good1 the  
conducting tube is always of some       
advantage1 for although it may not      
greatly economize energy1 still it      
protects the support of the refractory  
button1 and is a means for concentrating
 more energy upon the same4  ,to        
whatever extent the aluminium tube      
performs the function of a screen1 its  
usefulness is therefore limited to very 
high degrees of exhaustion when it is   
insulated from the electrode--that is1  
when the gas as a whole is              
non-conducting1 and the molecules1 or   
atoms1 act as independent carriers of   

electric charges4  ,in addition to      
acting as a more or less effective      
screen1 in the true meaning of the word1
 the conducting tube or coating may also
 act1 by reason of its conductivity1 as 
a sort of equalizer or dampener of the  
bombardment against the stem4 ,to be    
explicit1 ,i assume the action as       
follows3 ,suppose a rhythmical          
bombardment to occur against the        
conducting tube by reason of its        
imperfect action as a screen1 it        
certainly must happen that some         
molecules1 or atoms1 strike the tube    
sooner than others4 ,those which come   
first in contact with it give up their  
superfluous charge1 and the tube is     
electrified1 the electrification        
instantly spreading over its surface4   
,but this must diminish the energy lost 
in the bombardment for two reasons3     
first1 the charge given up by the atoms 
spreads over a great area1 and hence the
 electric density at any point is small1
 and the atoms are repelled with less   

energy than they would be if they would 
strike against a good insulator3        
secondly1 as the tube is electrified by 
the atoms which first come in contact   
with it1 the progress of the following  
atoms against the tube is more or less  
checked by the repulsion which the      
electrified tube must exert upon the    
similarly electrified atoms4 ,this      
repulsion may perhaps be sufficient to  
prevent a large portion of the atoms    
from striking the tube1 but at any rate 
it must diminish the energy of their    
impact4 ,it is clear that when the      
exhaustion is very low1 and the rarefied
 gas well conducting1 neither of the    
above effects can occur1 and1 on the    
other hand1 the fewer the atoms1 with   
the greater freedom they move2 in other 
words1 the higher the degree of         
exhaustion1 up to a limit1 the more     
telling will be both the effects4  ,what
 ,i have just said may afford an        
explanation of the phenomenon observed  
by ,prof4 ,crookes1 namely1 that a      

discharge through a bulb is established 
with much greater facility when an      
insulator than when a conductor is      
present in the same4 ,in my opinion1 the
 conductor acts as a dampener of the    
motion of the atoms in the two ways     
pointed out2 hence1 to cause a visible  
discharge to pass through the bulb1 a   
much higher potential is needed if a    
conductor1 especially of much surface1  
be present4  ,for the sake of clearness 
of some of the remarks before made1 ,i  
must now refer to ,figs4 #ah1 #ai and   
#bj1 which illustrate various           
arrangements with a type of bulb most   
generally used4  ,illustration3 ,,fig4  
#ah4--;,,bulb ,,with ,,mica ,,tube ,,and
 ,,aluminium ,,screen4  ,illustration3  
,,fig4 #ai4--;,,improved ,,bulb ,,with  
,,socket ,,and ,,screen4  ,fig4 #ah is a
 section through a spherical bulb ,l1   
with the glass stem s1 containing the   
leading-in wire w2 which has a lamp     
filament l fastened to it1 serving to   
support the refractory button m in the  

centre4 ,m is a sheet of thin mica wound
 in several layers around the stem s1   
and a is the aluminium tube4  ,fig4 #ai 
illustrates such a bulb in a somewhat   
more advanced stage of perfection4 ,a   
metallic tube ,s is fastened by means of
 some cement to the neck of the tube4   
,in the tube is screwed a plug ,p1 of   
insulating material1 in the centre of   
which is fastened a metallic terminal t1
 for the connection to the leading-in   
wire w4 ,this terminal must be well     
insulated from the metal tube ,s1       
therefore1 if the cement used is        
conducting--and most generally it is    
sufficiently so--the space between the  
plug ,p and the neck of the bulb should 
be filled with some good insulating     
material1 as mica powder4               
,illustration3 ,,fig4 #bj4--;,,bulb     
,,for ,,experiments ,,with ,,conducting 
,,tube4  ,fig4 #bj shows a bulb made for
 experimental purposes4 ,in this bulb   
the aluminium tube is provided with an  
external connection1 which serves to    

investigate the effect of the tube under
 various conditions4 ,it is referred to 
chiefly to suggest a line of experiment 
followed4  ,since the bombardment       
against the stem containing the         
leading-in wire is due to the inductive 
action of the latter upon the rarefied  
gas1 it is of advantage to reduce this  
action as far as practicable by         
employing a very thin wire1 surrounded  
by a very thick insulation of glass or  
other material1 and by making the wire  
passing through the rarefied gas as     
short as practicable4 ,to combine these 
features ,i employ a large tube ,t      
7,fig4 #ba71 which protrudes into the   
bulb to some distance1 and carries on   
the top a very short glass stem s1 into 
which is sealed the leading-in wire w1  
and ,i protect the top of the glass stem
 against the heat by a small1 aluminium 
tube a and a layer of mica underneath   
the same1 as usual4 ,the wire w1 passing
 through the large tube to the outside  
of the bulb1 should be well             

insulated--with a glass tube1 for       
instance--and the space between ought to
 be filled out with some excellent      
insulator4 ,among many insulating       
powders ,i have tried1 ,i have found    
that mica powder is the best to employ4 
,if this precaution is not taken1 the   
tube ,t1 protruding into the bulb1 will 
surely be cracked in consequence of the 
heating by the brushes which are apt to 
form in the upper part of the tube1 near
 the exhausted globe1 especially if the 
vacuum be excellent1 and therefore the  
potential necessary to operate the lamp 
very high4  ,fig4 #bb illustrates a     
similar arrangement1 with a large tube  
,t protruding in to the part of the bulb
 containing the refractors button m4 ,in
 this case the wire leading from the    
outside into the bulb is omitted1 the   
energy required being supplied through  
condenser coatings ,,cc4 ,the insulating
 packing ,p should in this construction 
be tightly fitting to the glass1 and    
rather wide1 or otherwise the discharge 

might avoid passing through the wire w1 
which connects the inside condenser     
coating to the incandescent button m4   
,the molecular bombardment against the  
glass stem in the bulb is a source of   
great trouble4 ,as illustration ,i will 
cite a phenomenon only too frequently   
and unwillingly observed4 ,a bulb1      
preferably a large one1 may be taken1   
and a good conducting body1 such as a   
piece of carbon1 may be mounted in it   
upon a platinum wire sealed in the glass
 stem4 ,the bulb may be exhausted to a  
fairly high degree1 nearly to the point 
when phosphorescence begins to appear4  
,illustration3 ,,fig4 #ba4--;,,improved 
,,bulb ,,with ,,non-,,conducting        
,,button4  ,illustration3 ,,fig4        
#bb4--,,type ,,of ,,bulb ,,without      
,,leading-,,in ,,wire4  ,when the bulb  
is connected with the coil1 the piece of
 carbon1 if small1 may become highly    
incandescent at first1 but its          
brightness immediately diminishes1 and  
then the discharge may break through the

 glass somewhere in the middle of the   
stem1 in the form of bright sparks1 in  
spite of the fact that the platinum wire
 is in good electrical connection with  
the rarefied gas through the piece of   
carbon or metal at the top4 ,the first  
sparks are singularly bright1 recalling 
those drawn from a clear surface of     
mercury4 ,but1 as they heat the glass   
rapidly1 they1 of course1 lose their    
brightness1 and cease when the glass at 
the ruptured place becomes incandescent1
 or generally sufficiently hot to       
conduct4 ,when observed for the first   
time the phenomenon must appear very    
curious1 and shows in a striking manner 
how radically different alternate       
currents1 or impulses1 of high frequency
 behave1 as compared with steady        
currents1 or currents of low frequency4 
,with such currents--namely1 the        
latter--the phenomenon would of course  
not occur4 ,when frequencies such as are
 obtained by mechanical means are used1 
,i think that the rupture of the glass  

is more or less the consequence of the  
bombardment1 which warms it up and      
impairs its insulating power2 but with  
frequencies obtainable with condensers  
,i have no doubt that the glass may give
 way without previous heating4 ,although
 this appears most singular at first1 it
 is in reality what we might expect to  
occur4 ,the energy supplied to the wire 
leading into the bulb is given off      
partly by direct action through the     
carbon button1 and partly by inductive  
action through the glass surrounding the
 wire4 ,the case is thus analogous to   
that in which a condenser shunted by a  
conductor of low resistance is connected
 to a source of alternating currents4   
,as long as the frequencies are low1 the
 conductor gets the most1 and the       
condenser is perfectly safe3 but when   
the frequency becomes excessive1 the    
role of the conductor may become quite  
insignificant4 ,in the latter case the  
difference of potential at the terminals
 of the condenser may become so great as

 to rupture the dielectric1             
notwithstanding the fact that the       
terminals are joined by a conductor of  
low resistance4  ,illustration3 ,,fig4  
#bc4--;,,effect ,,produced ,,by ,a      
,,ruby ,,drop4  ,it is1 of course1 not  
necessary1 when it is desired to produce
 the incandescence of a body inclosed in
 a bulb by means of these currents1 that
 the body should be a conductor1 for    
even a perfect non-conductor may be     
quite as readily heated4 ,for this      
purpose it is sufficient to surround a  
conducting electrode with a             
non-conducting material1 as1 for        
instance1 in the bulb described before  
in ,fig4 #ba1 in which a thin           
incandescent lamp filament is coated    
with a non-conductor1 and supports a    
button of the same material on the top4 
,at the start the bombardment goes on by
 inductive action through the           
non-conductor1 until the same is        
sufficiently heated to become           
conducting1 when the bombardment        

continues in the ordinary way4  ,a      
different arrangement used in some of   
the bulbs constructed is illustrated in 
,fig4 #bc4 ,in this instance a          
non-conductor m is mounted in a piece of
 common arc light carbon so as to       
project some small distance above the   
latter4 ,the carbon piece is connected  
to the leading-in wire passing through a
 glass stem1 which is wrapped with      
several layers of mica4 ,an aluminium   
tube a is employed as usual for         
screening4 ,it is so arranged that it   
reaches very nearly as high as the      
carbon and only the non-conductor m     
projects a little above it4 ,the        
bombardment goes at first against the   
upper surface of carbon1 the lower parts
 being protected by the aluminium tube4 
,as soon1 however1 as the non-conductor 
m is heated it is rendered good         
conducting1 and then it becomes the     
centre of the bombardment1 being most   
exposed to the same4  ,i have also      
constructed during these experiments    

many such single-wire bulbs with or     
without internal electrode1 in which the
 radiant matter was projected against1  
or focused upon1 the body to be rendered
 incandescent4 ,fig4 #bd illustrates one
 of the bulbs used4 ,it consists of a   
spherical globe ,l1 provided with a long
 neck n1 on the top1 for increasing the 
action in some cases by the application 
of an external conducting coating4 ,the 
globe ,l is blown out on the bottom into
 a very small bulb b1 which serves to   
hold it firmly in a socket ,s of        
insulating material into which it is    
cemented4 ,a fine lamp filament f1      
supported on a wire w1 passes through   
the centre of the globe ,l4 ,the        
filament is rendered incandescent in the
 middle portion1 where the bombardment  
proceeding from the lower inside surface
 of the globe is most intense4 ,the     
lower portion of the globe1 as far as   
the socket ,s reaches1 is rendered      
conducting1 either by a tinfoil coating 
or otherwise1 and the external electrode

 is connected to a terminal of the coil4
  ,the arrangement diagrammatically     
indicated in ,fig4 #bd was found to be  
an inferior one when it was desired to  
render incandescent a filament or button
 supported in the centre of the globe1  
but it was convenient when the object   
was to excite phosphorescence4  ,in many
 experiments in which bodies of a       
different kind were mounted in the bulb 
as1 for instance1 indicated in ,fig4    
#bc1 some observations of interest were 
made4  ,it was found1 among other       
things1 that in such cases1 no matter   
where the bombardment began1 just as    
soon as a high temperature was reached  
there was generally one of the bodies   
which seemed to take most of the        
bombardment upon itself1 the other1 or  
others1 being thereby relieved4 ,this   
quality appeared to depend principally  
on the point of fusion1 and on the      
facility with which the body was        
evaporated1 or1 generally speaking1     
disintegrated--meaning by the latter    

term not only the throwing off of atoms1
 but likewise of larger lumps4 ,the     
observation made was in accordance with 
generally accepted notions4 ,in a highly
 exhausted bulb electricity is carried  
off from the electrode by independent   
carriers1 which are partly the atoms1 or
 molecules1 of the residual atmosphere1 
and partly the atoms1 molecules1 or     
lumps thrown off from the electrode4 ,if
 the electrode is composed of bodies of 
different character1 and if one of these
 is more easily disintegrated than the  
others1 most of the electricity supplied
 is carried off from that body1 which is
 then brought to a higher temperature   
than the others1 and this the more1 as  
upon an increase of the temperature the 
body is still more easily disintegrated4
  ,it seems to me quite probable that a 
similar process takes place in the bulb 
even with a homogeneous electrode1 and  
,i think it to be the principal cause of
 the disintegration4 ,there is bound to 
be some irregularity1 even if the       

surface is highly polished1 which1 of   
course1 is impossible with most of the  
refractory bodies employed as           
electrodes4 ,assume that a point of the 
electrode gets hotter1 instantly most of
 the discharge passes through that      
point1 and a minute patch is probably   
fused and evaporated4 ,it is now        
possible that in consequence of the     
violent disintegration the spot attacked
 sinks in temperature1 or that a counter
 force is created1 as in an arc2 at any 
rate1 the local tearing off meets with  
the limitations incident to the         
experiment1 whereupon the same process  
occurs on another place4 ,to the eye the
 electrode appears uniformly brilliant1 
but there are upon it points constantly 
shifting and wandering around1 of a     
temperature far above the mean1 and this
 materially hastens the process of      
deterioration4 ,that some such thing    
occurs1 at least when the electrode is  
at a lower temperature1 sufficient      
experimental evidence can be obtained in

 the following manner3 ,exhaust a bulb  
to a very high degree1 so that with a   
fairly high potential the discharge     
cannot pass--that is1 not a luminous    
one1 for a weak invisible discharge     
occurs always1 in all probability4 ,now 
raise slowly and carefully the          
potential1 leaving the primary current  
on no more than for an instant4 ,at a   
certain point1 two1 three1 or half a    
dozen phosphorescent spots will appear  
on the globe4 ,these places of the glass
 are evidently more violently bombarded 
than others1 this being due to the      
unevenly distributed electric density1  
necessitated1 of course1 by sharp       
projections1 or1 generally speaking1    
irregularities of the electrode4 ,but   
the luminous patches are constantly     
changing in position1 which is          
especially well observable if one       
manages to produce very few1 and this   
indicates that the configuration of the 
electrode is rapidly changing4  ,from   
experiences of this kind ,i am led to   

infer that1 in order to be most durable1
 the refractory button in the bulb      
should be in the form of a sphere with a
 highly polished surface4 ,such a small 
sphere could be manufactured from a     
diamond or some other crystal1 but a    
better way would be to fuse1 by the     
employment of extreme degrees of        
temperature1 some oxide--as1 for        
instance1 zirconia--into a small drop1  
and then keep it in the bulb at a       
temperature somewhat below its point of 
fusion4  ,interesting and useful results
 can no doubt be reached in the         
direction of extreme degrees of heat4   
,how can such high temperatures be      
arrived at8 ,how are the highest degrees
 of heat reached in nature8 ,by the     
impact of stars1 by high speeds and     
collisions4 ,in a collision any rate of 
heat generation may be attained4 ,in a  
chemical process we are limited4 ,when  
oxygen and hydrogen combine1 they fall1 
metaphorically speaking1 from a definite
 height4 ,we cannot go very far with a  

blast1 nor by confining heat in a       
furnace1 but in an exhausted bulb we can
 concentrate any amount of energy upon a
 minute button4 ,leaving practicability 
out of consideration1 this1 then1 would 
be the means which1 in my opinion1 would
 enable us to reach the highest         
temperature4 ,but a great difficulty    
when proceeding in this way is          
encountered1 namely1 in most cases the  
body is carried off before it can fuse  
and form a drop4 ,this difficulty exists
 principally with an oxide such as      
zirconia1 because it cannot be          
compressed in so hard a cake that it    
would not be carried off quickly4 ,i    
endeavored repeatedly to fuse zirconia1 
placing it in a cup or arc light carbon 
as indicated in ,fig4 #bc4 ,it glowed   
with a most intense light1 and the      
stream of the particles projected out of
 the carbon cup was of a vivid white3   
but whether it was compressed in a cake 
or made into a paste with carbon1 it was
 carried off before it could be fused4  

,the carbon cup containing the zirconia 
had to be mounted very low in the neck  
of a large bulb1 as the heating of the  
glass by the projected particles of the 
oxide was so rapid that in the first    
trial the bulb was cracked almost in an 
instant when the current was turned on4 
,the heating of the glass by the        
projected particles was found to be     
always greater when the carbon cup      
contained a body which was rapidly      
carried off--,i presume because in such 
cases1 with the same potential1 higher  
speeds were reached1 and also because1  
per unit of time1 more matter was       
projected--that is1 more particles would
 strike the glass4  ,the before         
mentioned difficulty did not exist1     
however1 when the body mounted in the   
carbon cup offered great resistance to  
deterioration4 ,for instance1 when an   
oxide was first fused in an oxygen blast
 and then mounted in the bulb1 it melted
 very readily into a drop4  ,generally  
during the process of fusion magnificent

 light effects were noted1 of which it  
would be difficult to give an adequate  
idea4 ,fig4 #bc is intended to          
illustrate the effect observed with a   
ruby drop4 ,at first one may see a      
narrow funnel of white light projected  
against the top of the globe1 where it  
produces an irregularly outlined        
phosphorescent patch4 ,when the point of
 the ruby fuses the phosphorescence     
becomes very powerful2 but as the atoms 
are projected with much greater speed   
from the surface of the drop1 soon the  
glass gets hot and tired1 and now only  
the outer edge of the patch glows4 ,in  
this manner an intensely phosphorescent1
 sharply defined line1 l1 corresponding 
to the outline of the drop1 is produced1
 which spreads slowly over the globe as 
the drop gets larger4 ,when the mass    
begins to boil1 small bubbles and       
cavities are formed1 which cause dark   
colored spots to sweep across the globe4
 ,the bulb may be turned downward       
without fear of the drop falling off1 as

 the mass possesses considerable        
viscosity4  ,i may mention here another 
feature of some interest1 which ,i      
believe to have noted in the course of  
these experiments1 though the           
observations do not amount to a         
certitude4 ,it appeared that under the  
molecular impact caused by the rapidly  
alternating potential the body was fused
 and maintained in that state at a lower
 temperature in a highly exhausted bulb 
than was the case at normal pressure and
 application of heat in the ordinary    
way--that is1 at least1 judging from the
 quantity of the light emitted4 ,one of 
the experiments performed may be        
mentioned here by way of illustration4  
,a small piece of pumice stone was stuck
 on a platinum wire1 and first melted to
 it in a gas burner4 ,the wire was next 
placed between two pieces of charcoal   
and a burner applied so as to produce an
 intense heat1 sufficient to melt down  
the pumice stone into a small glass-like
 button4 ,the platinum wire had to be   

taken of sufficient thickness to prevent
 its melting in the fire4 ,while in the 
charcoal fire1 or when held in a burner 
to get a better idea of the degree of   
heat1 the button glowed with great      
brilliancy4 ,the wire with the button   
was then mounted in a bulb1 and upon    
exhausting the same to a high degree1   
the current was turned on slowly so as  
to prevent the cracking of the button4  
,the button was heated to the point of  
fusion1 and when it melted it did not1  
apparently1 glow with the same          
brilliancy as before1 and this would    
indicate a lower temperature4 ,leaving  
out of consideration the observer's     
possible1 and even probable1 error1 the 
question is1 can a body under these     
conditions be brought from a solid to a 
liquid state with evolution of less     
light8  ,when the potential of a body is
 rapidly alternated it is certain that  
the structure is jarred4 ,when the      
potential is very high1 although the    
vibrations may be few--say #bj1jjj per  

second--the effect upon the structure   
may be considerable4 ,suppose1 for      
example1 that a ruby is melted into a   
drop by a steady application of energy4 
,when it forms a drop it will emit      
visible and invisible waves1 which will 
be in a definite ratio1 and to the eye  
the drop will appear to be of a certain 
brilliancy4 ,next1 suppose we diminish  
to any degree we choose the energy      
steadily supplied1 and1 instead1 supply 
energy which rises and falls according  
to a certain law4 ,now1 when the drop is
 formed1 there will be emitted from it  
three different kinds of vibrations--the
 ordinary visible1 and two kinds of     
invisible waves3 that is1 the ordinary  
dark waves of all lengths1 and1 in      
addition1 waves of a well defined       
character4 ,the latter would not exist  
by a steady supply of the energy2 still 
they help to jar and loosen the         
structure4 ,if this really be the case1 
then the ruby drop will emit relatively 
less visible and more invisible waves   

than before4 ,thus it would seem that   
when a platinum wire1 for instance1 is  
fused by currents alternating with      
extreme rapidity1 it emits at the point 
of fusion less light and more invisible 
radiation than it does when melted by a 
steady current1 though the total energy 
used up in the process of fusion is the 
same in both cases4 ,or1 to cite another
 example1 a lamp filament is not capable
 of withstanding as long with currents  
of extreme frequency as it does with    
steady currents1 assuming that it be    
worked at the same luminous intensity4  
,this means that for rapidly alternating
 currents the filament should be shorter
 and thicker4 ,the higher the           
frequency--that is1 the greater the     
departure from the steady flow--the     
worse it would be for the filament4 ,but
 if the truth of this remark were       
demonstrated1 it would be erroneous to  
conclude that such a refractory button  
as used in these bulbs would be         
deteriorated quicker by currents of     

extremely high frequency than by steady 
or low frequency currents4 ,from        
experience ,i may say that just the     
opposite holds good3 the button         
withstands the bombardment better with  
currents of very high frequency4 ,but   
this is due to the fact that a high     
frequency discharge passes through a    
rarefied gas with much greater freedom  
than a steady or low frequency          
discharge1 and this will say that with  
the former we can work with a lower     
potential or with a less violent impact4
 ,as long1 then1 as the gas is of no    
consequence1 a steady or low frequency  
current is better2 but as soon as the   
action of the gas is desired and        
important1 high frequencies are         
preferable4  ,in the course of these    
experiments a great many trials were    
made with all kinds of carbon buttons4  
,electrodes made of ordinary carbon     
buttons were decidedly more durable when
 the buttons were obtained by the       
application of enormous pressure4       

,electrodes prepared by depositing      
carbon in well known ways did not show  
up well2 they blackened the globe very  
quickly4 ,from many experiences ,i      
conclude that lamp filaments obtained in
 this manner can be advantageously used 
only with low potentials and low        
frequency currents4 ,some kinds of      
carbon withstand so well that1 in order 
to bring them to the point of fusion1 it
 is necessary to employ very small      
buttons4 ,in this case the observation  
is rendered very difficult on account of
 the intense heat produced4             
,nevertheless there can be no doubt that
 all kinds of carbon are fused under the
 molecular bombardment1 but the liquid  
state must be one of great instability4 
,of all the bodies tried there were two 
which withstood best--diamond and       
carborundum4 ,these two showed up about 
equally1 but the latter was preferable1 
for many reasons4 ,as it is more than   
likely that this body is not yet        
generally known1 ,i will venture to call

 your attention to it4  ,it has been    
recently produced by ,mr4 ,e4,g4        
,acheson1 of ,monongahela ,city1 ,pa41  
,u4,s4,a4 ,it is intended to replace    
ordinary diamond powder for polishing   
precious stones1 etc41 and ,i have been 
informed that it accomplishes this      
object quite successfully4 ,i do not    
know why the name carborundum has been  
given to it1 unless there is something  
in the process of its manufacture which 
justifies this selection4 ,through the  
kindness of the inventor1 ,i obtained a 
short while ago some samples which ,i   
desired to test in regard to their      
qualities of phosphorescence and        
capability of withstanding high degrees 
of heat4  ,carborundum can be obtained  
in two forms--in the form of crystals   
and of powder4 ,the former appear to the
 naked eye dark colored1 but are very   
brilliant2 the latter is of nearly the  
same color as ordinary diamond powder1  
but very much finer4 ,when viewed under 
a microscope the samples of crystals    

given to me did not appear to have any  
definite form1 but rather resembled     
pieces of broken up egg coal of fine    
quality4 ,the majority were opaque1 but 
there were some which were transparent  
and colored4 ,the crystals are a kind of
 carbon containing some impurities2 they
 are extremely hard1 and withstand for a
 long time even an oxygen blast4 ,when  
the blast is directed against them they 
at first form a cake of some            
compactness1 probably in consequence of 
the fusion of impurities they contain4  
,the mass withstands for a very long    
time the blast without further fusion2  
but a slow carrying off1 or burning1    
occurs1 and1 finally1 a small quantity  
of a glass-like residue is left1 which1 
,i suppose1 is melted alumina4 ,when    
compressed strongly they conduct very   
well1 but not as well as ordinary       
carbon4 ,the powder1 which is obtained  
from the crystals in some way1 is       
practically non-conducting4 ,it affords 
a magnificent polishing material for    

stones4  ,the time has been too short to
 make a satisfactory study of the       
properties of this product1 but enough  
experience has been gained in a few     
weeks ,i have experimented upon it to   
say that it does possess some remarkable
 properties in many respects4 ,it       
withstands excessively high degrees of  
heat1 it is little deteriorated by      
molecular bombardment1 and it does not  
blacken the globe as ordinary carbon    
does4 ,the only difficulty which ,i have
 found in its use in connection with    
these experiments was to find some      
binding material which would resist the 
heat and the effect of the bombardment  
as successfully as carborundum itself   
does4  ,i have here a number of bulbs   
which ,i have provided with buttons of  
carborundum4 ,to make such a button of  
carborundum crystals ,i proceed in the  
following manner3 ,i take an ordinary   
lamp filament and dip its point in tar1 
or some other thick substance or paint  
which may be readily carbonized4 ,i next

 pass the point of the filament through 
the crystals1 and then hold it          
vertically over a hot plate4 ,the tar   
softens and forms a drop on the point of
 the filament1 the crystals adhering to 
the surface of the drop4 ,by regulating 
the distance from the plate the tar is  
slowly dried out and the button becomes 
solid4 ,i then once more dip the button 
in tar and hold it again over a plate   
until the tar is evaporated1 leaving    
only a hard mass which firmly binds the 
crystals4 ,when a larger button is      
required ,i repeat the process several  
times1 and ,i generally also cover the  
filament a certain distance below the   
button with crystals4 ,the button being 
mounted in a bulb1 when a good vacuum   
has been reached1 first a weak and then 
a strong discharge is passed through the
 bulb to carbonize the tar and expel all
 gases1 and later it is brought to a    
very intense incandescence4  ,when the  
powder is used ,i have found it best to 
proceed as follows3 ,i make a thick     

paint of carborundum and tar1 and pass a
 lamp filament through the paint4       
,taking then most of the paint off by   
rubbing the filament against a piece of 
chamois leather1 ,i hold it over a hot  
plate until the tar evaporates and the  
coating becomes firm4 ,i repeat this    
process as many times as it is necessary
 to obtain a certain thickness of       
coating4 ,on the point of the coated    
filament ,i form a button in the same   
manner4  ,there is no doubt that such a 
button--properly prepared under great   
pressure--of carborundum1 especially of 
powder of the best quality1 will        
withstand the effect of the bombardment 
fully as well as anything we know4 ,the 
difficulty is that the binding material 
gives way1 and the carborundum is slowly
 thrown off after some time4 ,as it does
 not seem to blacken the globe in the   
least1 it might be found useful for     
coating the filaments of ordinary       
incandescent lamps1 and ,i think that it
 is even possible to produce thin       

threads or sticks of carborundum which  
will replace the ordinary filaments in  
an incandescent lamp4 ,a carborundum    
coating seems to be more durable than   
other coatings1 not only because the    
carborundum can withstand high degrees  
of heat1 but also because it seems to   
unite with the carbon better than any   
other material ,i have tried4 ,a coating
 of zirconia or any other oxide1 for    
instance1 is far more quickly destroyed4
 ,i prepared buttons of diamond dust in 
the same manner as of carborundum1 and  
these came in durability nearest to     
those prepared of carborundum1 but the  
binding paste gave way much more quickly
 in the diamond buttons3 this1 however1 
,i attributed to the size and           
irregularity of the grains of the       
diamond4  ,it was of interest to find   
whether carborundum possesses the       
quality of phosphorescence4 ,one is1 of 
course1 prepared to encounter two       
difficulties3 first1 as regards the     
rough product1 the crystals1 they are   

good conducting1 and it is a fact that  
conductors do not phosphoresce2 second1 
the powder1 being exceedingly fine1     
would not be apt to exhibit very        
prominently this quality1 since we know 
that when crystals1 even such as diamond
 or ruby1 are finely powdered1 they lose
 the property of phosphorescence to a   
considerable degree4  ,the question     
presents itself here1 can a conductor   
phosphoresce8 ,what is there in such a  
body as a metal1 for instance1 that     
would deprive it of the quality of      
phosphorescence1 unless it is that      
property which characterizes it as a    
conductor8 for it is a fact that most of
 the phosphorescent bodies lose that    
quality when they are sufficiently      
heated to become more or less           
conducting4 ,then1 if a metal be in a   
large measure1 or perhaps entirely1     
deprived of that property1 it should be 
capable of phosphorescence4 ,therefore  
it is quite possible that at some       
extremely high frequency1 when behaving 

practically as a non-conductor1 a metal 
or any other conductor might exhibit the
 quality of phosphorescence1 even though
 it be entirely incapable of            
phosphorescing under the impact of a    
low-frequency discharge4 ,there is1     
however1 another possible way how a     
conductor might at least appear to      
phosphoresce4  ,considerable doubt still
 exists as to what really is            
phosphorescence1 and as to whether the  
various phenomena comprised under this  
head are due to the same causes4        
,suppose that in an exhausted bulb1     
under the molecular impact1 the surface 
of a piece of metal or other conductor  
is rendered strongly luminous1 but at   
the same time it is found that it       
remains comparatively cool1 would not   
this luminosity be called               
phosphorescence8 ,now such a result1    
theoretically at least1 is possible1 for
 it is a mere question of potential or  
speed4 ,assume the potential of the     
electrode1 and consequently the speed of

 the projected atoms1 to be sufficiently
 high1 the surface of the metal piece   
against which the atoms are projected   
would be rendered highly incandescent1  
since the process of heat generation    
would be incomparably faster than that  
of radiating or conducting away from the
 surface of the collision4 ,in the eye  
of the observer a single impact of the  
atoms would cause an instantaneous      
flash1 but if the impacts were repeated 
with sufficient rapidity they would     
produce a continuous impression upon his
 retina4 ,to him then the surface of the
 metal would appear continuously        
incandescent and of constant luminous   
intensity1 while in reality the light   
would be either intermittent or at least
 changing periodically in intensity4    
,the metal piece would rise in          
temperature until equilibrium was       
attained--that is until the energy      
continuously radiated would equal that  
intermittently supplied4 ,but the       
supplied energy might under such        

conditions not be sufficient to bring   
the body to any more than a very        
moderate mean temperature1 especially if
 the frequency of the atomic impacts be 
very low--just enough that the          
fluctuation of the intensity of the     
light emitted could not be detected by  
the eye4 ,the body would now1 owing to  
the manner in which the energy is       
supplied1 emit a strong light1 and yet  
be at a comparatively very low mean     
temperature4 ,how could the observer    
call the luminosity thus produced8 ,even
 if the analysis of the light would     
teach him something definite1 still he  
would probably rank it under the        
phenomena of phosphorescence4 ,it is    
conceivable that in such a way both     
conducting and non-conducting bodies may
 be maintained at a certain luminous    
intensity1 but the energy required would
 very greatly vary with the nature and  
properties of the bodies4  ,these and   
some foregoing remarks of a speculative 
nature were made merely to bring out    

curious features of alternate currents  
or electric impulses4 ,by their help we 
may cause a body to emit more light1    
while at a certain mean temperature1    
than it would emit if brought to that   
temperature by a steady supply2 and1    
again1 we may bring a body to the point 
of fusion1 and cause it to emit less    
light than when fused by the application
 of energy in ordinary ways4 ,it all    
depends on how we supply the energy1 and
 what kind of vibrations we set up3 in  
one case the vibrations are more1 in the
 other less1 adapted to affect our sense
 of vision4  ,some effects1 which ,i had
 not observed before1 obtained with     
carborundum in the first trials1 ,i     
attributed to phosphorescence1 but in   
subsequent experiments it appeared that 
it was devoid of that quality4 ,the     
crystals possess a noteworthy feature4  
,in a bulb provided with a single       
electrode in the shape of a small       
circular metal disc1 for instance1 at a 
certain degree of exhaustion the        

electrode is covered with a milky film1 
which is separated by a dark space from 
the glow filling the bulb4 ,when the    
metal disc is covered with carborundum  
crystals1 the film is far more intense1 
and snow-white4 ,this ,i found later to 
be merely an effect of the bright       
surface of the crystals1 for when an    
aluminium electrode was highly polished 
it exhibited more or less the same      
phenomenon4 ,i made a number of         
experiments with the samples of crystals
 obtained1 principally because it would 
have been of special interest to find   
that they are capable of                
phosphorescence1 on account of their    
being conducting4 ,i could not produce  
phosphorescence distinctly1 but ,i must 
remark that a decisive opinion cannot be
 formed until other experimenters have  
gone over the same ground4  ,the powder 
behaved in some experiments as though it
 contained alumina1 but it did not      
exhibit with sufficient distinctness the
 red of the latter4 ,its dead color     

brightens considerably under the        
molecular impact1 but ,i am now         
convinced it does not phosphoresce4     
,still1 the tests with the powder are   
not conclusive1 because powdered        
carborundum probably does not behave    
like a phosphorescent sulphide1 for     
example1 which could be finely powdered 
without impairing the phosphorescence1  
but rather like powdered ruby or        
diamond1 and therefore it would be      
necessary1 in order to make a decisive  
test1 to obtain it in a large lump and  
polish up the surface4  ,if the         
carborundum proves useful in connection 
with these and similar experiments1 its 
chief value will be found in the        
production of coatings1 thin conductors1
 buttons1 or other electrodes capable of
 withstanding extremely high degrees of 
heat4  ,the production of a small       
electrode capable of withstanding       
enormous temperatures ,i regard as of   
the greatest importance in the          
manufacture of light4 ,it would enable  

us to obtain1 by means of currents of   
very high frequencies1 certainly #bj    
times1 if not more1 the quantity of     
light which is obtained in the present  
incandescent lamp by the same           
expenditure of energy4 ,this estimate   
may appear to many exaggerated1 but in  
reality ,i think it is far from being   
so4 ,as this statement might be         
misunderstood ,i think it necessary to  
expose clearly the problem with which in
 this line of work we are confronted1   
and the manner in which1 in my opinion1 
a solution will be arrived at4  ,any one
 who begins a study of the problem will 
be apt to think that what is wanted in a
 lamp with an electrode is a very high  
degree of incandescence of the          
electrode4 ,there he will be mistaken4  
,the high incandescence of the button is
 a necessary evil1 but what is really   
wanted is the high incandescence of the 
gas surrounding the button4 ,in other   
words1 the problem in such a lamp is to 
bring a mass of gas to the highest      

possible incandescence4 ,the higher the 
incandescence1 the quicker the mean     
vibration1 the greater is the economy of
 the light production4 ,but to maintain 
a mass of gas at a high degree of       
incandescence in a glass vessel1 it will
 always be necessary to keep the        
incandescent mass away from the glass2  
that is1 to confine it as much as       
possible to the central portion of the  
globe4  ,in one of the experiments this 
evening a brush was produced at the end 
of a wire4 ,this brush was a flame1 a   
source of heat and light4 ,it did not   
emit much perceptible heat1 nor did it  
glow with an intense light2 but is it   
the less a flame because it does not    
scorch my hand8 ,is it the less a flame 
because it does not hurt my eye by its  
brilliancy8 ,the problem is precisely to
 produce in the bulb such a flame1 much 
smaller in size1 but incomparably more  
powerful4 ,were there means at hand for 
producing electric impulses of a        
sufficiently high frequency1 and for    

transmitting them1 the bulb could be    
done away with1 unless it were used to  
protect the electrode1 or to economize  
the energy by confining the heat4 ,but  
as such means are not at disposal1 it   
becomes necessary to place the terminal 
in a bulb and rarefy the air in the     
same4 ,this is done merely to enable the
 apparatus to perform the work which it 
is not capable of performing at ordinary
 air pressure4 ,in the bulb we are able 
to intensify the action to any          
degree--so far that the brush emits a   
powerful light4  ,the intensity of the  
light emitted depends principally on the
 frequency and potential of the         
impulses1 and on the electric density of
 the surface of the electrode4 ,it is of
 the greatest importance to employ the  
smallest possible button1 in order to   
push the density very far4 ,under the   
violent impact of the molecules of the  
gas surrounding it1 the small electrode 
is of course brought to an extremely    
high temperature1 but around it is a    

mass of highly incandescent gas1 a flame
 photosphere1 many hundred times the    
volume of the electrode4 ,with a        
diamond1 carborundum or zirconia button 
the photosphere can be as much as one   
thousand times the volume of the button4
 ,without much reflecting one would     
think that in pushing so far the        
incandescence of the electrode it would 
be instantly volatilized4 ,but after a  
careful consideration he would find     
that1 theoretically1 it should not      
occur1 and in this fact--which1 however1
 is experimentally demonstrated--lies   
principally the future value of such a  
lamp4  ,at first1 when the bombardment  
begins1 most of the work is performed on
 the surface of the button1 but when a  
highly conducting photosphere is formed 
the button is comparatively relieved4   
,the higher the incandescence of the    
photosphere the more it approaches in   
conductivity to that of the electrode1  
and the more1 therefore1 the solid and  
the gas form one conducting body4 ,the  

consequence is that the further is      
forced the incandescence the more work1 
comparatively1 is performed on the gas1 
and the less on the electrode4 ,the     
formation of a powerful photosphere is  
consequently the very means for         
protecting the electrode4 ,this         
protection1 of course1 is a relative    
one1 and it should not be thought that  
by pushing the incandescence higher the 
electrode is actually less deteriorated4
 ,still1 theoretically1 with extreme    
frequencies1 this result must be        
reached1 but probably at a temperature  
too high for most of the refractory     
bodies known4 ,given1 then1 an electrode
 which can withstand to a very high     
limit the effect of the bombardment and 
outward strain1 it would be safe no     
matter how much it is forced beyond that
 limit4 ,in an incandescent lamp quite  
different considerations apply4 ,there  
the gas is not at all concerned3 the    
whole of the work is performed on the   
filament2 and the life of the lamp      

diminishes so rapidly with the increase 
of the degree of incandescence that     
economical reasons compel us to work it 
at a low incandescence4 ,but if an      
incandescent lamp is operated with      
currents of very high frequency1 the    
action of the gas cannot be neglected1  
and the rules for the most economical   
working must be considerably modified4  
,in order to bring such a lamp with one 
or two electrodes to a great perfection1
 it is necessary to employ impulses of  
very high frequency4 ,the high frequency
 secures1 among others1 two chief       
advantages1 which have a most important 
bearing upon the economy of the light   
production4 ,first1 the deterioration of
 the electrode is reduced by reason of  
the fact that we employ a great many    
small impacts1 instead of a few violent 
ones1 which shatter quickly the         
structure2 secondly1 the formation of a 
large photosphere is facilitated4  ,in  
order to reduce the deterioration of the
 electrode to the minimum1 it is        

desirable that the vibration be         
harmonic1 for any suddenness hastens the
 process of destruction4 ,an electrode  
lasts much longer when kept at          
incandescence by currents1 or impulses1 
obtained from a high-frequency          
alternator1 which rise and fall more or 
less harmonically1 than by impulses     
obtained from a disruptive discharge    
coil4 ,in the latter case there is no   
doubt that most of the damage is done by
 the fundamental sudden discharges4     
,one of the elements of loss in such a  
lamp is the bombardment of the globe4   
,as the potential is very high1 the     
molecules are projected with great      
speed2 they strike the glass1 and       
usually excite a strong phosphorescence4
 ,the effect produced is very pretty1   
but for economical reasons it would be  
perhaps preferable to prevent1 or at    
least reduce to the minimum1 the        
bombardment against the globe1 as in    
such case it is1 as a rule1 not the     
object to excite phosphorescence1 and as

 some loss of energy results from the   
bombardment4 ,this loss in the bulb is  
principally dependent on the potential  
of the impulses and on the electric     
density on the surface of the electrode4
 ,in employing very high frequencies the
 loss of energy by the bombardment is   
greatly reduced1 for1 first1 the        
potential needed to perform a given     
amount of work is much smaller2 and1    
secondly1 by producing a highly         
conducting photosphere around the       
electrode1 the same result is obtained  
as though the electrode were much       
larger1 which is equivalent to a smaller
 electric density4 ,but be it by the    
diminution of the maximum potential or  
of the density1 the gain is effected in 
the same manner1 namely1 by avoiding    
violent shocks1 which strain the glass  
much beyond its limit of elasticity4 ,if
 the frequency could be brought high    
enough1 the loss due to the imperfect   
elasticity of the glass would be        
entirely negligible4 ,the loss due to   

bombardment of the globe may1 however1  
be reduced by using two electrodes      
instead of one4 ,in such case each of   
the electrodes may be connected to one  
of the terminals2 or else1 if it is     
preferable to use only one wire1 one    
electrode may be connected to one       
terminal and the other to the ground or 
to an insulated body of some surface1   
as1 for instance1 a shade on the lamp4  
,in the latter case1 unless some        
judgment is used1 one of the electrodes 
might glow more intensely than the      
other4  ,but on the whole ,i find it    
preferable when using such high         
frequencies to employ only one electrode
 and one connecting wire4 ,i am         
convinced that the illuminating device  
of the near future will not require for 
its operation more than one lead1 and1  
at any rate1 it will have no leading-in 
wire1 since the energy required can be  
as well transmitted through the glass4  
,in experimental bulbs the leading-in   
wire is most generally used on account  

of convenience1 as in employing         
condenser coatings in the manner        
indicated in ,fig4 #bb1 for example1    
there is some difficulty in fitting the 
parts1 but these difficulties would not 
exist if a great many bulbs were        
manufactured2 otherwise the energy can  
be conveyed through the glass as well as
 through a wire1 and with these high    
frequencies the losses are very small4  
,such illuminating devices will         
necessarily involve the use of very high
 potentials1 and this1 in the eyes of   
practical men1 might be an objectionable
 feature4 ,yet1 in reality1 high        
potentials are not                      
objectionable--certainly not in the     
least as far as the safety of the       
devices is concerned4  ,there are two   
ways of rendering an electric appliance 
safe4 ,one is to use low potentials1 the
 other is to determine the dimensions of
 the apparatus so that it is safe no    
matter how high a potential is used4 ,of
 the two the latter seems to me the     

better way1 for then the safety is      
absolute1 unaffected by any possible    
combination of circumstances which might
 render even a low-potential appliance  
dangerous to life and property4 ,but the
 practical conditions require not only  
the judicious determination of the      
dimensions of the apparatus2 they       
likewise necessitate the employment of  
energy of the proper kind4 ,it is easy1 
for instance1 to construct a transformer
 capable of giving1 when operated from  
an ordinary alternate current machine of
 low tension1 say #ej1jjj volts1 which  
might be required to light a highly     
exhausted phosphorescent tube1 so that1 
in spite of the high potential1 it is   
perfectly safe1 the shock from it       
producing no inconvenience4 ,still1 such
 a transformer would be expensive1 and  
in itself inefficient2 and1 besides1    
what energy was obtained from it would  
not be economically used for the        
production of light4 ,the economy       
demands the employment of energy in the 

form of extremely rapid vibrations4 ,the
 problem of producing light has been    
likened to that of maintaining a certain
 high-pitch note by means of a bell4 ,it
 should be said a barely audible note2  
and even these words would not express  
it1 so wonderful is the sensitiveness of
 the eye4 ,we may deliver powerful blows
 at long intervals1 waste a good deal of
 energy1 and still not get what we want2
 or we may keep up the note by          
delivering frequent gentle taps1 and get
 nearer to the object sought by the     
expenditure of much less energy4 ,in the
 production of light1 as far as the     
illuminating device is concerned1 there 
can be only one rule--that is1 to use as
 high frequencies as can be obtained2   
but the means for the production and    
conveyance of impulses of such character
 impose1 at present at least1 great     
limitations4 ,once it is decided to use 
very high frequencies1 the return wire  
becomes unnecessary1 and all the        
appliances are simplified4 ,by the use  

of obvious means the same result is     
obtained as though the return wire were 
used4 ,it is sufficient for this purpose
 to bring in contact with the bulb1 or  
merely in the vicinity of the same1 an  
insulated body of some surface4 ,the    
surface need1 of course1 be the smaller1
 the higher the frequency and potential 
used1 and necessarily1 also1 the higher 
the economy of the lamp or other device4
  ,this plan of working has been        
resorted to on several occasions this   
evening4 ,so1 for instance1 when the    
incandescence of a button was produced  
by grasping the bulb with the hand1 the 
body of the experimenter merely served  
to intensify the action4 ,the bulb used 
was similar to that illustrated in ,fig4
 #ai1 and the coil was excited to a     
small potential1 not sufficient to bring
 the button to incandescence when the   
bulb was hanging from the wire2 and     
incidentally1 in order to perform the   
experiment in a more suitable manner1   
the button was taken so large that a    

perceptible time had to elapse before1  
upon grasping the bulb1 it could be     
rendered incandescent4 ,the contact with
 the bulb was1 of course1 quite         
unnecessary4 ,it is easy1 by using a    
rather large bulb with an exceedingly   
small electrode1 to adjust the          
conditions so that the latter is brought
 to bright incandescence by the mere    
approach of the experimenter within a   
few feet of the bulb1 and that the      
incandescence subsides upon his         
receding4  ,illustration3 ,,fig4        
#bd4--;,,bulb ,,without ,,leading-,,in  
,,wire1 ,,showing ,,effect ,,of         
,,projected ,,matter4  ,in another      
experiment1 when phosphorescence was    
excited1 a similar bulb was used4 ,here 
again1 originally1 the potential was not
 sufficient to excite phosphorescence   
until the action was intensified--in    
this case1 however1 to present a        
different feature1 by touching the      
socket with a metallic object held in   
the hand4 ,the electrode in the bulb was

 a carbon button so large that it could 
not be brought to incandescence1 and    
thereby spoil the effect produced by    
phosphorescence4  ,illustration3 ,,fig4 
#be4--;,,improved ,,experimental ,,bulb4
  ,again1 in another of the early       
experiments1 a bulb was used as         
illustrated in ,fig4 #ab4 ,in this      
instance1 by touching the bulb with one 
or two fingers1 one or two shadows of   
the stem inside were projected against  
the glass1 the touch of the finger      
producing the same result as the        
application of an external negative     
electrode under ordinary circumstances4 
,in all these experiments the action was
 intensified by augmenting the capacity 
at the end of the lead connected to the 
terminal4 ,as a rule1 it is not         
necessary to resort to such means1 and  
would be quite unnecessary with still   
higher frequencies2 but when it is      
desired1 the bulb1 or tube1 can be      
easily adapted to the purpose4          
,illustration3 ,,fig4 #bf4--;,,improved 

,,bulb ,,with ,,intensifying            
,,reflector4  ,in ,fig4 #bd1 for        
example1 an experimental bulb ,l is     
shown1 which is provided with a neck n  
on the top for the application of an    
external tinfoil coating1 which may be  
connected to a body of larger surface4  
,such a lamp as illustrated in ,fig4 #be
 may also be lighted by connecting the  
tinfoil coating on the neck n to the    
terminal1 and the leading-in wire w to  
an insulated plate4 ,if the bulb stands 
in a socket upright1 as shown in the    
cut1 a shade of conducting material may 
be slipped in the neck n1 and the action
 thus magnified4  ,a more perfected     
arrangement used in some of these bulbs 
is illustrated in ,fig4 #bf4 ,in this   
case the construction of the bulb is as 
shown and described before1 when        
reference was made to ,fig4 #ai4 ,a zinc
 sheet ,z1 with a tubular extension ,t1 
is slipped over the metallic socket ,s4 
,the bulb hangs downward from the       
terminal t1 the zinc sheet ,z1          

performing the double office of         
intensifier and reflector4 ,the         
reflector is separated from the terminal
 t by an extension of the insulating    
plug ,p4  ,illustration3 ,,fig4         
#bg4--,,phosphorescent ,,tube ,,with    
,,intensifying ,,reflector4  ,a similar 
disposition with a phosphorescent tube  
is illustrated in ,fig4 #bg4 ,the tube  
,t is prepared from two short tubes of a
 different diameter1 which are sealed on
 the ends4 ,on the lower end is placed  
an outside conducting coating ,c1 which 
connects to the wire w4 ,the wire has a 
hook on the upper end for suspension1   
and passes through the centre of the    
inside tube1 which is filled with some  
good and tightly packed insulator4 ,on  
the outside of the upper end of the tube
 ,t is another conducting coating ,c#a  
upon which is slipped a metallic        
reflector ,z1 which should be separated 
by a thick insulation from the end of   
wire w4  ,the economical use of such a  
reflector or intensifier would require  

that all energy supplied to an air      
condenser should be recoverable1 or1 in 
other words1 that there should not be   
any losses1 neither in the gaseous      
medium nor through its action elsewhere4
 ,this is far from being so1 but1       
fortunately1 the losses may be reduced  
to anything desired4 ,a few remarks are 
necessary on this subject1 in order to  
make the experiences gathered in the    
course of these investigations perfectly
 clear4  ,suppose a small helix with    
many well insulated turns1 as in        
experiment ,fig4 #ag1 has one of its    
ends connected to one of the terminals  
of the induction coil1 and the other to 
a metal plate1 or1 for the sake of      
simplicity1 a sphere1 insulated in      
space4 ,when the coil is set to work1   
the potential of the sphere is          
alternated1 and the small helix now     
behaves as though its free end were     
connected to the other terminal of the  
induction coil4 ,if an iron rod be held 
within the small helix it is quickly    

brought to a high temperature1          
indicating the passage of a strong      
current through the helix4 ,how does the
 insulated sphere act in this case8 ,it 
can be a condenser1 storing and         
returning the energy supplied to it1 or 
it can be a mere sink of energy1 and the
 conditions of the experiment determine 
whether it is more one or the other4    
,the sphere being charged to a high     
potential1 it acts inductively upon the 
surrounding air1 or whatever gaseous    
medium there might be4 ,the molecules1  
or atoms1 which are near the sphere are 
of course more attracted1 and move      
through a greater distance than the     
farther ones4 ,when the nearest         
molecules strike the sphere they are    
repelled1 and collisions occur at all   
distances within the inductive action of
 the sphere4 ,it is now clear that1 if  
the potential be steady1 but little loss
 of energy can be caused in this way1   
for the molecules which are nearest to  
the sphere1 having had an additional    

charge imparted to them by contact1 are 
not attracted until they have parted1 if
 not with all1 at least with most of the
 additional charge1 which can be        
accomplished only after a great many    
collisions4 ,from the fact that with a  
steady potential there is but little    
loss in dry air1 one must come to such a
 conclusion4 ,when the potential of the 
sphere1 instead of being steady1 is     
alternating1 the conditions are entirely
 different4 ,in this case a rhythmical  
bombardment occurs1 no matter whether   
the molecules after coming in contact   
with the sphere lose the imparted charge
 or not2 what is more1 if the charge is 
not lost1 the impacts are only the more 
violent4 ,still if the frequency of the 
impulses be very small1 the loss caused 
by the impacts and collisions would not 
be serious unless the potential were    
excessive4 ,but when extremely high     
frequencies and more or less high       
potentials are used1 the loss may be    
very great4 ,the total energy lost per  

unit of time is proportionate to the    
product of the number of impacts per    
second1 or the frequency and the energy 
lost in each impact4 ,but the energy of 
an impact must be proportionate to the  
square of the electric density of the   
sphere1 since the charge imparted to the
 molecule is proportionate to that      
density4 ,i conclude from this that the 
total energy lost must be proportionate 
to the product of the frequency and the 
square of the electric density2 but this
 law needs experimental confirmation4   
,assuming the preceding considerations  
to be true1 then1 by rapidly alternating
 the potential of a body immersed in an 
insulating gaseous medium1 any amount of
 energy may be dissipated into space4   
,most of that energy then1 ,i believe1  
is not dissipated in the form of long   
ether waves1 propagated to considerable 
distance1 as is thought most generally1 
but is consumed--in the case of an      
insulated sphere1 for example--in impact
 and collisional losses--that is1 heat  

vibrations--on the surface and in the   
vicinity of the sphere4 ,to reduce the  
dissipation it is necessary to work with
 a small electric density--the smaller  
the higher the frequency4  ,but since1  
on the assumption before made1 the loss 
is diminished with the square of the    
density1 and since currents of very high
 frequencies involve considerable waste 
when transmitted through conductors1 it 
follows that1 on the whole1 it is better
 to employ one wire than two4           
,therefore1 if motors1 lamps1 or devices
 of any kind are perfected1 capable of  
being advantageously operated by        
currents of extremely high frequency1   
economical reasons will make it         
advisable to use only one wire1         
especially if the distances are great4  
,when energy is absorbed in a condenser 
the same behaves as though its capacity 
were increased4 ,absorption always      
exists more or less1 but generally it is
 small and of no consequence as long as 
the frequencies are not very great4 ,in 

using extremely high frequencies1 and1  
necessarily in such case1 also high     
potentials1 the absorption--or1 what is 
here meant more particularly by this    
term1 the loss of energy due to the     
presence of a gaseous medium--is an     
important factor to be considered1 as   
the energy absorbed in the air condenser
 may be any fraction of the supplied    
energy4 ,this would seem to make it very
 difficult to tell from the measured or 
computed capacity of an air condenser   
its actual capacity or vibration period1
 especially if the condenser is of very 
small surface and is charged to a very  
high potential4 ,as many important      
results are dependent upon the          
correctness of the estimation of the    
vibration period1 this subject demands  
the most careful scrutiny of other      
investigators4 ,to reduce the probable  
error as much as possible in experiments
 of the kind alluded to1 it is advisable
 to use spheres or plates of large      
surface1 so as to make the density      

exceedingly small4 ,otherwise1 when it  
is practicable1 an oil condenser should 
be used in preference4 ,in oil or other 
liquid dielectrics there are seemingly  
no such losses as in gaseous media4 ,it 
being impossible to exclude entirely the
 gas in condensers with solid           
dielectrics1 such condensers should be  
immersed in oil1 for economical reasons 
if nothing else2 they can then be       
strained to the utmost and will remain  
cool4 ,in ,leyden jars the loss due to  
air is comparatively small1 as the      
tinfoil coatings are large1 close       
together1 and the charged surfaces not  
directly exposed2 but when the          
potentials are very high1 the loss may  
be more or less considerable at1 or     
near1 the upper edge of the foil1 where 
the air is principally acted upon4 ,if  
the jar be immersed in boiled-out oil1  
it will be capable of performing four   
times the amount of work which it can   
for any length of time when used in the 
ordinary way1 and the loss will be      

inappreciable4  ,it should not be       
thought that the loss in heat in an air 
condenser is necessarily associated with
 the formation of visible streams or    
brushes4 ,if a small electrode1 inclosed
 in an unexhausted bulb1 is connected to
 one of the terminals of the coil1      
streams can be seen to issue from the   
electrode and the air in the bulb is    
heated2 if1 instead of a small          
electrode1 a large sphere is inclosed in
 the bulb1 no streams are observed1     
still the air is heated4  ,nor should it
 be thought that the temperature of an  
air condenser would give even an        
approximate idea of the loss in heat    
incurred1 as in such case heat must be  
given off much more quickly1 since there
 is1 in addition to the ordinary        
radiation1 a very active carrying away  
of heat by independent carriers going   
on1 and since not only the apparatus1   
but the air at some distance from it is 
heated in consequence of the collisions 
which must occur4  ,owing to this1 in   

experiments with such a coil1 a rise of 
temperature can be distinctly observed  
only when the body connected to the coil
 is very small4 ,but with apparatus on a
 larger scale1 even a body of           
considerable bulk would be heated1 as1  
for instance1 the body of a person2 and 
,i think that skilled physicians might  
make observations of utility in such    
experiments1 which1 if the apparatus    
were judiciously designed1 would not    
present the slightest danger4  ,a       
question of some interest1 principally  
to meteorologists1 presents itself here4
 ,how does the earth behave8 ,the earth 
is an air condenser1 but is it a perfect
 or a very imperfect one--a mere sink of
 energy8 ,there can be little doubt that
 to such small disturbance as might be  
caused in an experiment the earth       
behaves as an almost perfect condenser4 
,but it might be different when its     
charge is set in vibration by some      
sudden disturbance occurring in the     
heavens4 ,in such case1 as before       

stated1 probably only little of the     
energy of the vibrations set up would be
 lost into space in the form of long    
ether radiations1 but most of the       
energy1 ,i think1 would spend itself in 
molecular impacts and collisions1 and   
pass off into space in the form of short
 heat1 and possibly light1 waves4 ,as   
both the frequency of the vibrations of 
the charge and the potential are in all 
probability excessive1 the energy       
converted into heat may be considerable4
 ,since the density must be unevenly    
distributed1 either in consequence of   
the irregularity of the earth's surface1
 or on account of the condition of the  
atmosphere in various places1 the effect
 produced would accordingly vary from   
place to place4 ,considerable variations
 in the temperature and pressure of the 
atmosphere may in this manner be caused 
at any point of the surface of the      
earth4 ,the variations may be gradual or
 very sudden1 according to the nature of
 the general disturbance1 and may       

produce rain and storms1 or locally     
modify the weather in any way4  ,from   
the remarks before made one may see what
 an important factor of loss the air in 
the neighborhood of a charged surface   
becomes when the electric density is    
great and the frequency of the impulses 
excessive4 ,but the action as explained 
implies that the air is insulating--that
 is1 that it is composed of independent 
carriers immersed in an insulating      
medium4 ,this is the case only when the 
air is at something like ordinary or    
greater1 or at extremely small1         
pressure4 ,when the air is slightly     
rarefied and conducting1 then true      
conduction losses occur also4 ,in such  
case1 of course1 considerable energy may
 be dissipated into space even with a   
steady potential1 or with impulses of   
low frequency1 if the density is very   
great4  ,when the gas is at very low    
pressure1 an electrode is heated more   
because higher speeds can be reached4   
,if the gas around the electrode is     

strongly compressed1 the displacements1 
and consequently the speeds1 are very   
small1 and the heating is insignificant4
 ,but if in such case the frequency     
could be sufficiently increased1 the    
electrode would be brought to a high    
temperature as well as if the gas were  
at very low pressure2 in fact1          
exhausting the bulb is only necessary   
because we cannot produce 7and possibly 
not convey7 currents of the required    
frequency4  ,returning to the subject of
 electrode lamps1 it is obviously of    
advantage in such a lamp to confine as  
much as possible the heat to the        
electrode by preventing the circulation 
of the gas in the bulb4 ,if a very small
 bulb be taken1 it would confine the    
heat better than a large one1 but it    
might not be of sufficient capacity to  
be operated from the coil1 or1 if so1   
the glass might get too hot4 ,a simple  
way to improve in this direction is to  
employ a globe of the required size1 but
 to place a small bulb1 the diameter of 

which is properly estimated1 over the   
refractory button contained in the      
globe4 ,this arrangement is illustrated 
in ,fig4 #bh4  ,illustration3 ,,fig4    
#bh4--,,lamp ,,with ,,auxiliary ,,bulb  
,,for ,,confining ,,the ,,action ,,to   
,,the ,,centre4  ,the globe ,l has in   
this case a large neck n1 allowing the  
small bulb b to slip through4 ,otherwise
 the construction is the same as shown  
in ,fig4 #ah1 for example4 ,the small   
bulb is conveniently supported upon the 
stem s1 carrying the refractory button  
m4 ,it is separated from the aluminium  
tube a by several layers of mica ,m1 in 
order to prevent the cracking of the    
neck by the rapid heating of the        
aluminium tube upon a sudden turning on 
of the current4 ,the inside bulb should 
be as small as possible when it is      
desired to obtain light only by         
incandescence of the electrode4 ,if it  
is desired to produce phosphorescence1  
the bulb should be larger1 else it would
 be apt to get too hot1 and the         

phosphorescence would cease4 ,in this   
arrangement usually only the small bulb 
shows phosphorescence1 as there is      
practically no bombardment against the  
outer globe4 ,in some of these bulbs    
constructed as illustrated in ,fig4 #bh 
the small tube was coated with          
phosphorescent paint1 and beautiful     
effects were obtained4 ,instead of      
making the inside bulb large1 in order  
to avoid undue heating1 it answers the  
purpose to make the electrode m larger4 
,in this case the bombardment is        
weakened by reason of the smaller       
electric density4  ,many bulbs were     
constructed on the plan illustrated in  
,fig4 #bi4 ,here a small bulb b1        
containing the refractory button m1 upon
 being exhausted to a very high degree  
was sealed in a large globe ,l1 which   
was then moderately exhausted and sealed
 off4 ,the principal advantage of this  
construction was that it allowed of     
reaching extremely high vacua1 and1 at  
the same time use a large bulb4 ,it was 

found1 in the course of experiences with
 bulbs such as illustrated in ,fig4 #bi1
 that it was well to make the stem s    
near the seal at e very thick1 and the  
leading-in wire w thin1 as it occurred  
sometimes that the stem at e was heated 
and the bulb was cracked4 ,often the    
outer globe ,l was exhausted only just  
enough to allow the discharge to pass   
through1 and the space between the bulbs
 appeared crimson1 producing a curious  
effect4 ,in some cases1 when the        
exhaustion in globe ,l was very low1 and
 the air good conducting1 it was found  
necessary1 in order to bring the button 
m to high incandescence1 to place1      
preferably on the upper part of the neck
 of the globe1 a tinfoil coating which  
was connected to an insulated body1 to  
the ground1 or to the other terminal of 
the coil1 as the highly conducting air  
weakened the effect somewhat1 probably  
by being acted upon inductively from the
 wire w1 where it entered the bulb at e4
 ,another difficulty--which1 however1 is

 always present when the refractory     
button is mounted in a very small       
bulb--existed in the construction       
illustrated in ,fig4 #bi1 namely1 the   
vacuum in the bulb b would be impaired  
in a comparatively short time4          
,illustration3 ,,fig4 #bi4--,,lamp      
,,with ,,independent ,,auxiliary ,,bulb4
  ,the chief idea in the two last       
described constructions was to confine  
the heat to the central portion of the  
globe by preventing the exchange of air4
 ,an advantage is secured1 but owing to 
the heating of the inside bulb and slow 
evaporation of the glass the vacuum is  
hard to maintain1 even if the           
construction illustrated in ,fig4 #bh be
 chosen1 in which both bulbs            
communicate4  ,but by far the better    
way--the ideal way--would be to reach   
sufficiently high frequencies4 ,the     
higher the frequency the slower would be
 the exchange of the air1 and ,i think  
that a frequency may be reached at which
 there would be no exchange whatever of 

the air molecules around the terminal4  
,we would then produce a flame in which 
there would be no carrying away of      
material1 and a queer flame it would be1
 for it would be rigid6 ,with such high 
frequencies the inertia of the particles
 would come into play4 ,as the brush1 or
 flame1 would gain rigidity in virtue of
 the inertia of the particles1 the      
exchange of the latter would be         
prevented4 ,this would necessarily      
occur1 for1 the number of the impulses  
being augmented1 the potential energy of
 each would diminish1 so that finally   
only atomic vibrations could be set up1 
and the motion of translation through   
measurable space would cease4 ,thus an  
ordinary gas burner connected to a      
source of rapidly alternating potential 
might have its efficiency augmented to a
 certain limit1 and this for two        
reasons--because of the additional      
vibration imparted1 and because of a    
slowing down of the process of carrying 
off4 ,but the renewal being rendered    

difficult1 and renewal being necessary  
to maintain the burner1 a continued     
increase of the frequency of the        
impulses1 assuming they could be        
transmitted to and impressed upon the   
flame1 would result in the extinction of
 the latter1 meaning by this term only  
the cessation of the chemical process4  
,i think1 however1 that in the case of  
an electrode immersed in a fluid        
insulating medium1 and surrounded by    
independent carriers of electric        
charges1 which can be acted upon        
inductively1 a sufficiently high        
frequency of the impulses would probably
 result in a gravitation of the gas all 
around toward the electrode4 ,for this  
it would be only necessary to assume    
that the independent bodies are         
irregularly shaped2 they would then turn
 toward the electrode their side of the 
greatest electric density1 and this     
would be a position in which the fluid  
resistance to approach would be smaller 
than that offered to the receding4  ,the

 general opinion1 ,i do not doubt1 is   
that it is out of the question to reach 
any such frequencies as might--assuming 
some of the views before expressed to be
 true--produce any of the results which 
,i have pointed out as mere             
possibilities4 ,this may be so1 but in  
the course of these investigations1 from
 the observation of many phenomena ,i   
have gained the conviction that these   
frequencies would be much lower than one
 is apt to estimate at first4 ,in a     
flame we set up light vibrations by     
causing molecules1 or atoms1 to collide4
 ,but what is the ratio of the frequency
 of the collisions and that of the      
vibrations set up8 ,certainly it must be
 incomparably smaller than that of the  
knocks of the bell and the sound        
vibrations1 or that of the discharges   
and the oscillations of the condenser4  
,we may cause the molecules of the gas  
to collide by the use of alternate      
electric impulses of high frequency1 and
 so we may imitate the process in a     

flame2 and from experiments with        
frequencies which we are now able to    
obtain1 ,i think that the result is     
producible with impulses which are      
transmissible through a conductor4  ,in 
connection with thoughts of a similar   
nature1 it appeared to me of great      
interest to demonstrate the rigidity of 
a vibrating gaseous column4 ,although   
with such low frequencies as1 say       
#aj1jjj per second1 which ,i was able to
 obtain without difficulty from a       
specially constructed alternator1 the   
task looked discouraging at first1 ,i   
made a series of experiments4 ,the      
trials with air at ordinary pressure led
 to no result1 but with air moderately  
rarefied ,i obtain what ,i think to be  
an unmistakable experimental evidence of
 the property sought for4 ,as a result  
of this kind might lead able            
investigators to conclusions of         
importance ,i will describe one of the  
experiments performed4  ,it is well     
known that when a tube is slightly      

exhausted the discharge may be passed   
through it in the form of a thin        
luminous thread4 ,when produced with    
currents of low frequency1 obtained from
 a coil operated as usual1 this thread  
is inert4 ,if a magnet be approached to 
it1 the part near the same is attracted 
or repelled1 according to the direction 
of the lines of force of the magnet4 ,it
 occurred to me that if such a thread   
would be produced with currents of very 
high frequency1 it should be more or    
less rigid1 and as it was visible it    
could be easily studied4 ,accordingly ,i
 prepared a tube about #a inch in       
diameter and #a metre long1 with outside
 coating at each end4 ,the tube was     
exhausted to a point at which by a      
little working the thread discharge     
could be obtained4 ,it must be remarked 
here that the general aspect of the     
tube1 and the degree of exhaustion1 are 
quite different than when ordinary low  
frequency currents are used4 ,as it was 
found preferable to work with one       

terminal1 the tube prepared was         
suspended from the end of a wire        
connected to the terminal1 the tinfoil  
coating being connected to the wire1 and
 to the lower coating sometimes a small 
insulated plate was attached4 ,when the 
thread was formed it extended through   
the upper part of the tube and lost     
itself in the lower end4 ,if it         
possessed rigidity it resembled1 not    
exactly an elastic cord stretched tight 
between two supports1 but a cord        
suspended from a height with a small    
weight attached at the end4 ,when the   
finger or a magnet was approached to the
 upper end of the luminous thread1 it   
could be brought locally out of position
 by electrostatic or magnetic action2   
and when the disturbing object was very 
quickly removed1 an analogous result was
 produced1 as though a suspended cord   
would be displaced and quickly released 
near the point of suspension4 ,in doing 
this the luminous thread was set in     
vibration1 and two very sharply marked  

nodes1 and a third indistinct one1 were 
formed4 ,the vibration1 once set up1    
continued for fully eight minutes1 dying
 gradually out4 ,the speed of the       
vibration often varied perceptibly1 and 
it could be observed that the           
electrostatic attraction of the glass   
affected the vibrating thread2 but it   
was clear that the electrostatic action 
was not the cause of the vibration1 for 
the thread was most generally           
stationary1 and could always be set in  
vibration by passing the finger quickly 
near the upper part of the tube4 ,with a
 magnet the thread could be split in two
 and both parts vibrated4 ,by           
approaching the hand to the lower       
coating of the tube1 or insulated plate 
if attached1 the vibration was          
quickened2 also1 as far as ,i could see1
 by raising the potential or frequency4 
,thus1 either increasing the frequency  
or passing a stronger discharge of the  
same frequency corresponded to a        
tightening of the cord4 ,i did not      

obtain any experimental evidence with   
condenser discharges4 ,a luminous band  
excited in a bulb by repeated discharges
 of a ,leyden jar must possess rigidity1
 and if deformed and suddenly released  
should vibrate4 ,but probably the amount
 of vibrating matter is so small that in
 spite of the extreme speed the inertia 
cannot prominently assert itself4       
,besides1 the observation in such a case
 is rendered extremely difficult on     
account of the fundamental vibration4   
,the demonstration of the fact--which   
still needs better experimental         
confirmation--that a vibrating gaseous  
column possesses rigidity1 might greatly
 modify the views of thinkers4 ,when    
with low frequencies and insignificant  
potentials indications of that property 
may be noted1 how must a gaseous medium 
behave under the influence of enormous  
electrostatic stresses which may be     
active in the interstellar space1 and   
which may alternate with inconceivable  
rapidity8 ,the existence of such an     

electrostatic1 rhythmically throbbing   
force--of a vibrating electrostatic     
field--would show a possible way how    
solids might have formed from the       
ultra-gaseous uterus1 and how transverse
 and all kinds of vibrations may be     
transmitted through a gaseous medium    
filling all space4 ,then1 ether might be
 a true fluid1 devoid of rigidity1 and  
at rest1 it being merely necessary as a 
connecting link to enable interaction4  
,what determines the rigidity of a body8
 ,it must be the speed and the amount of
 moving matter4 ,in a gas the speed may 
be considerable1 but the density is     
exceedingly small2 in a liquid the speed
 would be likely to be small1 though the
 density may be considerable2 and in    
both cases the inertia resistance       
offered to displacement is practically  
nil4 ,but place a gaseous 7or liquid7   
column in an intense1 rapidly           
alternating electrostatic field1 set the
 particles vibrating with enormous      
speeds1 then the inertia resistance     

asserts itself4 ,a body might move with 
more or less freedom through the        
vibrating mass1 but as a whole it would 
be rigid4  ,there is a subject which ,i 
must mention in connection with these   
experiments3 it is that of high vacua4  
,this is a subject the study of which is
 not only interesting1 but useful1 for  
it may lead to results of great         
practical importance4 ,in commercial    
apparatus1 such as incandescent lamps1  
operated from ordinary systems of       
distribution1 a much higher vacuum than 
obtained at present would not secure a  
very great advantage4 ,in such a case   
the work is performed on the filament   
and the gas is little concerned2 the    
improvement1 therefore1 would be but    
trifling4 ,but when we begin to use very
 high frequencies and potentials1 the   
action of the gas becomes all important1
 and the degree of exhaustion materially
 modifies the results4 ,as long as      
ordinary coils1 even very large ones1   
were used1 the study of the subject was 

limited1 because just at a point when it
 became most interesting it had to be   
interrupted on account of the           
non-striking vacuum being reached4 ,but 
presently we are able to obtain from a  
small disruptive discharge coil         
potentials much higher than even the    
largest coil was capable of giving1 and1
 what is more1 we can make the potential
 alternate with great rapidity4 ,both of
 these results enable us now to pass a  
luminous discharge through almost any   
vacua obtainable1 and the field of our  
investigations is greatly extended4     
,think we as we may1 of all the possible
 directions to develop a practical      
illuminant1 the line of high vacua seems
 to be the most promising at present4   
,but to reach extreme vacua the         
appliances must be much more improved1  
and ultimate perfection will not be     
attained until we shall have discarded  
the mechanical and perfected an         
electrical vacuum pump4 ,molecules and  
atoms can be thrown out of a bulb under 

the action of an enormous potential3    
this will be the principle of the vacuum
 pump of the future4 ,for the present1  
we must secure the best results we can  
with mechanical appliances4 ,in this    
respect1 it might not be out of the way 
to say a few words about the method of1 
and apparatus for1 producing excessively
 high degrees of exhaustion of which ,i 
have availed myself in the course of    
these investigations4 ,it is very       
probable that other experimenters have  
used similar arrangements2 but as it is 
possible that there may be an item of   
interest in their description1 a few    
remarks1 which will render this         
investigation more complete1 might be   
permitted4  ,illustration3 ,,fig4       
#cj4--;,,apparatus ,,used ,,for         
,,obtaining ,,high ,,degrees ,,of       
,,exhaustion4  ,the apparatus is        
illustrated in a drawing shown in ,fig4 
#cj4 ,s represents a ,sprengel pump1    
which has been specially constructed to 
better suit the work required4 ,the     

stop-cock which is usually employed has 
been omitted1 and instead of it a hollow
 stopper s has been fitted in the neck  
of the reservoir ,r4 ,this stopper has a
 small hole h1 through which the mercury
 descends2 the size of the outlet o     
being properly determined with respect  
to the section of the fall tube t1 which
 is sealed to the reservoir instead of  
being connected to it in the usual      
manner4 ,this arrangement overcomes the 
imperfections and troubles which often  
arise from the use of the stopcock on   
the reservoir and the connection of the 
latter with the fall tube4  ,the pump is
 connected through a ,u-shaped tube t to
 a very large reservoir ,r#a4 ,especial 
care was taken in fitting the grinding  
surfaces of the stoppers p and p#a1 and 
both of these and the mercury caps above
 them were made exceptionally long4     
,after the ,u-shaped tube was fitted and
 put in place1 it was heated1 so as to  
soften and take off the strain resulting
 from imperfect fitting4 ,the ,u-shaped 

tube was provided with a stopcock ,c1   
and two ground connections g and        
g#a--one for a small bulb b1 usually    
containing caustic potash1 and the other
 for the receiver r1 to be exhausted4   
,the reservoir ,r#a was connected by    
means of a rubber tube to a slightly    
larger reservoir ,r#b1 each of the two  
reservoirs being provided with a        
stopcock ,c#a and ,c#b1 respectively4   
,the reservoir ,r#b could be raised and 
lowered by a wheel and rack1 and the    
range of its motion was so determined   
that when it was filled with mercury and
 the stopcock ,c#b closed1 so as to form
 a ,torricellian vacuum in it when      
raised1 it could be lifted so high that 
the mercury in reservoir ,r#a would     
stand a little above stopcock ,c#a2 and 
when this stopcock was closed and the   
reservoir ,r#b descended1 so as to form 
a ,torricellian vacuum in reservoir     
,r#a1 it could be lowered so far as to  
completely empty the latter1 the mercury
 filling the reservoir ,r#b up to a     

little above stopcock ,c#b4  ,the       
capacity of the pump and of the         
connections was taken as small as       
possible relatively to the volume of    
reservoir ,r#a1 since1 of course1 the   
degree of exhaustion depended upon the  
ratio of these quantities4  ,with this  
apparatus ,i combined the usual means   
indicated by former experiments for the 
production of very high vacua4 ,in most 
of the experiments it was convenient to 
use caustic potash4 ,i may venture to   
say1 in regard to its use1 that much    
time is saved and a more perfect action 
of the pump insured by fusing and       
boiling the potash as soon as1 or even  
before1 the pump settles down4 ,if this 
course is not followed the sticks1 as   
ordinarily employed1 may give moisture  
off at a certain very slow rate1 and the
 pump may work for many hours without   
reaching a very high vacuum4 ,the potash
 was heated either by a spirit lamp or  
by passing a discharge through it1 or by
 passing a current through a wire       

contained in it4 ,the advantage in the  
latter case was that the heating could  
be more rapidly repeated4  ,generally   
the process of exhaustion was the       
following3--,at the start1 the          
stop-cocks ,c and ,c#a being open1 and  
all other connections closed1 the       
reservoir ,r#b was raised so far that   
the mercury filled the reservoir ,r#a   
and a part of the narrow connecting     
,u-shaped tube4 ,when the pump was set  
to work1 the mercury would1 of course1  
quickly rise in the tube1 and reservoir 
,r#b was lowered1 the experimenter      
keeping the mercury at about the same   
level4 ,the reservoir ,r#b was balanced 
by a long spring which facilitated the  
operation1 and the friction of the parts
 was generally sufficient to keep it    
almost in any position4 ,when the       
,sprengel pump had done its work1 the   
reservoir ,r#b was further lowered and  
the mercury descended in ,r#a and filled
 ,r#b1 whereupon stopcock ,c#b was      
closed4 ,the air adhering to the walls  

of ,r#a and that absorbed by the mercury
 was carried off1 and to free the       
mercury of all air the reservoir ,r#b   
was for a long time worked up and down4 
,during this process some air1 which    
would gather below stopcock ,c#b1 was   
expelled from ,r#b by lowering it far   
enough and opening the stopcock1 closing
 the latter again before raising the    
reservoir4 ,when all the air had been   
expelled from the mercury1 and no air   
would gather in ,r#b when it was        
lowered1 the caustic potash was resorted
 to4 ,the reservoir ,r#b was now again  
raised until the mercury in ,r#a stood  
above stopcock ,c#a4 ,the caustic potash
 was fused and boiled1 and the moisture 
partly carried off by the pump and      
partly re-absorbed2 and this process of 
heating and cooling was repeated many   
times1 and each time1 upon the moisture 
being absorbed or carried off1 the      
reservoir ,r#b was for a long time      
raised and lowered4 ,in this manner all 
the moisture was carried off from the   

mercury1 and both the reservoirs were in
 proper condition to be used4 ,the      
reservoir ,r#b was then again raised to 
the top1 and the pump was kept working  
for a long time4 ,when the highest      
vacuum obtainable with the pump had been
 reached the potash bulb was usually    
wrapped with cotton which was sprinkled 
with ether so as to keep the potash at a
 very low temperature1 then the         
reservoir ,r#b was lowered1 and upon    
reservoir ,r#a being emptied the        
receiver r was quickly sealed up4  ,when
 a new bulb was put on1 the mercury was 
always raised above stopcock ,c#a which 
was closed1 so as to always keep the    
mercury and both the reservoirs in fine 
condition1 and the mercury was never    
withdrawn from ,r#a except when the pump
 had reached the highest degree of      
exhaustion4 ,it is necessary to observe 
this rule if it is desired to use the   
apparatus to advantage4  ,by means of   
this arrangement ,i was able to proceed 
very quickly1 and when the apparatus was

 in perfect order it was possible to    
reach the phosphorescent stage in a     
small bulb in less than #ae minutes1    
which is certainly very quick work for a
 small laboratory arrangement requiring 
all in all about #ajj pounds of mercury4
 ,with ordinary small bulbs the ratio of
 the capacity of the pump1 receiver1 and
 connections1 and that of reservoir ,r  
was about #a-bj1 and the degrees of     
exhaustion reached were necessarily very
 high1 though ,i am unable to make a    
precise and reliable statement how far  
the exhaustion was carried4  ,what      
impresses the investigator most in the  
course of these experiences is the      
behavior of gases when subjected to     
great rapidly alternating electrostatic 
stresses4 ,but he must remain in doubt  
as to whether the effects observed are  
due wholly to the molecules1 or atoms1  
of the gas which chemical analysis      
discloses to us1 or whether there enters
 into play another medium of a gaseous  
nature1 comprising atoms1 or molecules1 

immersed in a fluid pervading the space4
 ,such a medium surely must exist1 and  
,i am convinced that1 for instance1 even
 if air were absent1 the surface and    
neighborhood of a body in space would be
 heated by rapidly alternating the      
potential of the body2 but no such      
heating of the surface or neighborhood  
could occur if all free atoms were      
removed and only a homogeneous1         
incompressible1 and elastic fluid--such 
as ether is supposed to be--would       
remain1 for then there would be no      
impacts1 no collisions4 ,in such a case1
 as far as the body itself is concerned1
 only frictional losses in the inside   
could occur4  ,it is a striking fact    
that the discharge through a gas is     
established with ever increasing freedom
 as the frequency of the impulses is    
augmented4 ,it behaves in this respect  
quite contrarily to a metallic          
conductor4 ,in the latter the impedance 
enters prominently into play as the     
frequency is increased1 but the gas acts

 much as a series of condensers would3  
the facility with which the discharge   
passes through seems to depend on the   
rate of change of potential4 ,if it act 
so1 then in a vacuum tube even of great 
length1 and no matter how strong the    
current1 self-induction could not assert
 itself to any appreciable degree4 ,we  
have1 then1 as far as we can now see1 in
 the gas a conductor which is capable of
 transmitting electric impulses of any  
frequency which we may be able to       
produce4 ,could the frequency be brought
 high enough1 then a queer system of    
electric distribution1 which would be   
likely to interest gas companies1 might 
be realized3 metal pipes filled with    
gas--the metal being the insulator1 the 
gas the conductor--supplying            
phosphorescent bulbs1 or perhaps devices
 as yet uninvented4 ,it is certainly    
possible to take a hollow core of       
copper1 rarefy the gas in the same1 and 
by passing impulses of sufficiently high
 frequency through a circuit around it1 

bring the gas inside to a high degree of
 incandescence2 but as to the nature of 
the forces there would be considerable  
uncertainty1 for it would be doubtful   
whether with such impulses the copper   
core would act as a static screen4 ,such
 paradoxes and apparent impossibilities 
we encounter at every step in this line 
of work1 and therein lies1 to a great   
extent1 the claim of the study4  ,i have
 here a short and wide tube which is    
exhausted to a high degree and covered  
with a substantial coating of bronze1   
the coating allowing barely the light to
 shine through4 ,a metallic clasp1 with 
a hook for suspending the tube1 is      
fastened around the middle portion of   
the latter1 the clasp being in contact  
with the bronze coating4 ,i now want to 
light the gas inside by suspending the  
tube on a wire connected to the coil4   
,any one who would try the experiment   
for the first time1 not having any      
previous experience1 would probably take
 care to be quite alone when making the 

trial1 for fear that he might become the
 joke of his assistants4 ,still1 the    
bulb lights in spite of the metal       
coating1 and the light can be distinctly
 perceived through the latter4 ,a long  
tube covered with aluminium bronze      
lights when held in one hand--the other 
touching the terminal of the coil--quite
 powerfully4 ,it might be objected that 
the coatings are not sufficiently       
conducting2 still1 even if they were    
highly resistant1 they ought to screen  
the gas4 ,they certainly screen it      
perfectly in a condition of rest1 but   
not by far perfectly when the charge is 
surging in the coating4 ,but the loss of
 energy which occurs within the tube1   
notwithstanding the screen1 is          
occasioned principally by the presence  
of the gas4 ,were we to take a large    
hollow metallic sphere and fill it with 
a perfect incompressible fluid          
dielectric1 there would be no loss      
inside of the sphere1 and consequently  
the inside might be considered as       

perfectly screened1 though the potential
 be very rapidly alternating4 ,even were
 the sphere filled with oil1 the loss   
would be incomparably smaller than when 
the fluid is replaced by a gas1 for in  
the latter case the force produces      
displacements2 that means impact and    
collisions in the inside4  ,no matter   
what the pressure of the gas may be1 it 
becomes an important factor in the      
heating of a conductor when the electric
 density is great and the frequency very
 high4 ,that in the heating of          
conductors by lightning discharges air  
is an element of great importance1 is   
almost as certain as an experimental    
fact4 ,i may illustrate the action of   
the air by the following experiment3 ,i 
take a short tube which is exhausted to 
a moderate degree and has a platinum    
wire running through the middle from one
 end to the other4 ,i pass a steady or  
low frequency current through the wire1 
and it is heated uniformly in all parts4
 ,the heating here is due to conduction1

 or frictional losses1 and the gas      
around the wire has--as far as we can   
see--no function to perform4 ,but now   
let me pass sudden discharges1 or a high
 frequency current1 through the wire4   
,again the wire is heated1 this time    
principally on the ends and least in the
 middle portion2 and if the frequency of
 the impulses1 or the rate of change1 is
 high enough1 the wire might as well be 
cut in the middle as not1 for           
practically all the heating is due to   
the rarefied gas4 ,here the gas might   
only act as a conductor of no impedance 
diverting the current from the wire as  
the impedance of the latter is          
enormously increased1 and merely heating
 the ends of the wire by reason of their
 resistance to the passage of the       
discharge4 ,but it is not at all        
necessary that the gas in the tube      
should he conducting2 it might be at an 
extremely low pressure1 still the ends  
of the wire would be heated--as1        
however1 is ascertained by              

experience--only the two ends would in  
such1 case not be electrically connected
 through the gaseous medium4 ,now what  
with these frequencies and potentials   
occurs in an exhausted tube occurs in   
the lightning discharges at ordinary    
pressure4 ,we only need remember one of 
the facts arrived at in the course of   
these investigations1 namely1 that to   
impulses of very high frequency the gas 
at ordinary pressure behaves much in the
 same manner as though it were at       
moderately low pressure4 ,i think that  
in lightning discharges frequently wires
 or conducting objects are volatilized  
merely because air is present and that1 
were the conductor immersed in an       
insulating liquid1 it would be safe1 for
 then the energy would have to spend    
itself somewhere else4 ,from the        
behavior of gases to sudden impulses of 
high potential ,i am led to conclude    
that there can be no surer way of       
diverting a lightning discharge than by 
affording it a passage through a volume 

of gas1 if such a thing can be done in a
 practical manner4  ,there are two more 
features upon which ,i think it         
necessary to dwell in connection with   
these experiments--the radiant state and
 the non-striking vacuum4  ,any one who 
has studied ,crookes' work must have    
received the impression that the radiant
 state is a property of the gas         
inseparably connected with an extremely 
high degree of exhaustion4 ,but it      
should be remembered that the phenomena 
observed in an exhausted vessel are     
limited to the character and capacity of
 the apparatus which is made use of4 ,i 
think that in a bulb a molecule1 or     
atom1 does not precisely move in a      
straight line because it meets no       
obstacle1 but because the velocity      
imparted to it is sufficient to propel  
it in a sensibly straight line4 ,the    
mean free path is one thing1 but the    
velocity--the energy associated with the
 moving body--is another1 and under     
ordinary circumstances ,i believe that  

it is a mere question of potential or   
speed4 ,a disruptive discharge coil1    
when the potential is pushed very far1  
excites phosphorescence and projects    
shadows1 at comparatively low degrees of
 exhaustion4 ,in a lightning discharge1 
matter moves in straight lines as       
ordinary pressure when the mean free    
path is exceedingly small1 and          
frequently images of wires or other     
metallic objects have been produced by  
the particles thrown off in straight    
lines4  ,illustration3 ,,fig4           
#ca4--;,,bulb ,,showing ,,radiant ,,lime
 ,,stream ,,at ,,low ,,exhaustion4  ,i  
have prepared a bulb to illustrate by an
 experiment the correctness of these    
assertions4 ,in a globe ,l 7,fig4 #ca7  
,i have mounted upon a lamp filament f a
 piece of lime l4 ,the lamp filament is 
connected with a wire which leads into  
the bulb1 and the general construction  
of the latter is as indicated in ,fig4  
#ai1 before described4 ,the bulb being  
suspended from a wire connected to the  

terminal of the coil1 and the latter    
being set to work1 the lime piece l and 
the projecting parts of the filament f  
are bombarded4 ,the degree of exhaustion
 is just such that with the potential   
the coil is capable of giving           
phosphorescence of the glass is         
produced1 but disappears as soon as the 
vacuum is impaired4 ,the lime containing
 moisture1 and moisture being given off 
as soon as heating occurs1 the          
phosphorescence lasts only for a few    
moments4 ,when the lime has been        
sufficiently heated1 enough moisture has
 been given off to impair materially the
 vacuum of the bulb4 ,as the bombardment
 goes on1 one point of the lime piece is
 more heated than other points1 and the 
result is that finally practically all  
the discharge passes through that point 
which is intensely heated1 and a white  
stream of lime particles 7,fig4 #ca7    
then breaks forth from that point4 ,this
 stream is composed of radiant matter1  
yet the degree of exhaustion is low4    

,but the particles move in straight     
lines because the velocity imparted to  
them is great1 and this is due to three 
causes--to the great electric density1  
the high temperature of the small point1
 and the fact that the particles of the 
lime are easily torn and thrown off--far
 more easily than those of carbon4 ,with
 frequencies such as we are able to     
obtain1 the particles are bodily thrown 
off and projected to a considerable     
distance2 but with sufficiently high    
frequencies no such thing would occur3  
in such case only a stress would spread 
or a vibration would be propagated      
through the bulb4 ,it would be out of   
the question to reach any such frequency
 on the assumption that the atoms move  
with the speed of light2 but ,i believe 
that such a thing is impossible2 for    
this an enormous potential would be     
required4 ,with potentials which we are 
able to obtain1 even with a disruptive  
discharge coil1 the speed must be quite 
insignificant4  ,as to the non-striking 

vacuum1 the point to be noted is that it
 can occur only with low frequency      
impulses1 and it is necessitated by the 
impossibility of carrying off enough    
energy with such impulses in high vacuum
 since the few atoms which are around   
the terminal upon coming in contact with
 the same are repelled and kept at a    
distance for a comparatively long period
 of time1 and not enough work can be    
performed to render the effect          
perceptible to the eye4 ,if the         
difference of potential between the     
terminals is raised1 the dielectric     
breaks down4 ,but with very high        
frequency impulses there is no necessity
 for such breaking down1 since any      
amount of work can be performed by      
continually agitating the atoms in the  
exhausted vessel1 provided the frequency
 is high enough4 ,it is easy to         
reach--even with frequencies obtained   
from an alternator as here used--a stage
 at which the discharge does not pass   
between two electrodes in a narrow tube1

 each of these being connected to one of
 the terminals of the coil1 but it is   
difficult to reach a point at which a   
luminous discharge would not occur      
around each electrode4  ,a thought which
 naturally presents itself in connection
 with high frequency currents1 is to    
make use of their powerful              
electro-dynamic inductive action to     
produce light effects in a sealed glass 
globe4 ,the leading-in wire is one of   
the defects of the present incandescent 
lamp1 and if no other improvement were  
made1 that imperfection at least should 
be done away with4 ,following this      
thought1 ,i have carried on experiments 
in various directions1 of which some    
were indicated in my former paper4 ,i   
may here mention one or two more lines  
of experiment which have been followed  
up4  ,many bulbs were constructed as    
shown in ,fig4 #cb and ,fig4 #cc4  ,in  
,fig4 #cb a wide tube ,t was sealed to a
 smaller ,w-shaped tube ,u1 of          
phosphorescent glass4 ,in the tube ,t   

was placed a coil ,c of aluminium wire1 
the ends of which were provided with    
small spheres t and t#a of aluminium1   
and reached into the ,u tube4 ,the tube 
,t was slipped into a socket containing 
a primary coil through which usually the
 discharges of ,leyden jars were        
directed1 and the rarefied gas in the   
small ,u tube was excited to strong     
luminosity by the high-tension currents 
induced in the coil ,c4 ,when ,leyden   
jar discharges were used to induce      
currents in the coil ,c1 it was found   
necessary to pack the tube ,t tightly   
with insulating powder1 as a discharge  
would occur frequently between the turns
 of the coil1 especially when the       
primary was thick and the air gap1      
through which the jars discharged1      
large1 and no little trouble was        
experienced in this way4  ,illustration3
 ,,fig4 #cb4--;,,electro-,,dynamic      
,,induction ,,tube4  ,illustration3     
,,fig4 #cc--;,,electro-,,dynamic        
,,induction ,,lamp4  ,in ,fig4 #cc is   

illustrated another form of the bulb    
constructed4 ,in this case a tube ,t is 
sealed to a globe ,l4 ,the tube contains
 a coil ,c1 the ends of which pass      
through two small glass tubes t and t#a1
 which are sealed to the tube ,t4 ,two  
refractory buttons m and m#a are mounted
 on lamp filaments which are fastened to
 the ends of the wires passing through  
the glass tubes t and t#a4 ,generally in
 bulbs made on this plan the globe ,l   
communicated with the tube ,t4 ,for this
 purpose the ends of the small tubes t  
and t#a were just a trifle heated in the
 burner1 merely to hold the wires1 but  
not to interfere with the communication4
 ,the tube ,t1 with the small tubes1    
wires through the same1 and the         
refractory buttons m and m#a1 was first 
prepared1 and then sealed to globe ,l1  
whereupon the coil ,c was slipped in and
 the connections made to its ends4 ,the 
tube was then packed with insulating    
powder1 jamming the latter as tight as  
possible up to very nearly the end1 then

 it was closed and only a small hole    
left through which the remainder of the 
powder was introduced1 and finally the  
end of the tube was closed4 ,usually in 
bulbs constructed as shown in ,fig4 #cc 
an aluminium tube a was fastened to the 
upper end s of each of the tubes t and  
t#a1 in order to protect that end       
against the heat4 ,the buttons m and m#a
 could be brought to any degree of      
incandescence by passing the discharges 
of ,leyden jars around the coil ,c4 ,in 
such bulbs with two buttons a very      
curious effect is produced by the       
formation of the shadows of each of the 
two buttons4  ,another line of          
experiment1 which has been assiduously  
followed1 was to induce by              
electro-dynamic induction a current or  
luminous discharge in an exhausted tube 
or bulb4 ,this matter has received such 
able treatment at the hands of ,prof4   
,j4,j4 ,thomson that ,i could add but   
little to what he has made known1 even  
had ,i made it the special subject of   

this lecture4 ,still1 since experiences 
in this line have gradually led me to   
the present views and results1 a few    
words must be devoted here to this      
subject4  ,it has occurred1 no doubt1 to
 many that as a vacuum tube is made     
longer the electromotive force per unit 
length of the tube1 necessary to pass a 
luminous discharge through the latter1  
gets continually smaller2 therefore1 if 
the exhausted tube be made long enough1 
even with low frequencies a luminous    
discharge could be induced in such a    
tube closed upon itself4 ,such a tube   
might be placed around a ball or on a   
ceiling1 and at once a simple appliance 
capable of giving considerable light    
would be obtained4 ,but this would be an
 appliance hard to manufacture and      
extremely unmanageable4 ,it would not do
 to make the tube up of small lengths1  
because there would be with ordinary    
frequencies considerable loss in the    
coatings1 and besides1 if coatings were 
used1 it would be better to supply the  

current directly to the tube by         
connecting the coatings to a            
transformer4 ,but even if all objections
 of such nature were removed1 still1    
with low frequencies the light          
conversion itself would be inefficient1 
as ,i have before stated4 ,in using     
extremely high frequencies the length of
 the secondary--in other words1 the size
 of the vessel--can be reduced as far as
 desired1 and the efficiency of the     
light conversion is increased1 provided 
that means are invented for efficiently 
obtaining such high frequencies4 ,thus  
one is led1 from theoretical and        
practical considerations1 to the use of 
high frequencies1 and this means high   
electromotive forces and small currents 
in the primary4 ,when he works with     
condenser charges--and they are the only
 means up to the present known for      
reaching these extreme frequencies--he  
gets to electromotive forces of several 
thousands of volts per turn of the      
primary4 ,he cannot multiply the        

electro-dynamic inductive effect by     
taking more turns in the primary1 for he
 arrives at the conclusion that the best
 way is to work with one single         
turn--though he must sometimes depart   
from this rule--and he must get along   
with whatever inductive effect he can   
obtain with one turn4 ,but before he has
 long experimented with the extreme     
frequencies required to set up in a     
small bulb an electromotive force of    
several thousands of volts he realizes  
the great importance of electrostatic   
effects1 and these effects grow         
relatively to the electro-dynamic in    
significance as the frequency is        
increased4  ,now1 if anything is        
desirable in this case1 it is to        
increase the frequency1 and this would  
make it still worse for the             
electro-dynamic effects4 ,on the other  
hand1 it is easy to exalt the           
electrostatic action as far as one likes
 by taking more turns on the secondary1 
or combining self-induction and capacity

 to raise the potential4 ,it should also
 be remembered that1 in reducing the    
current to the smallest value and       
increasing the potential1 the electric  
impulses of high frequency can be more  
easily transmitted through a conductor4 
,these and similar thoughts determined  
me to devote more attention to the      
electrostatic phenomena1 and to endeavor
 to produce potentials as high as       
possible1 and alternating as fast as    
they could be made to alternate4 ,i then
 found that ,i could excite vacuum tubes
 at considerable distance from a        
conductor connected to a properly       
constructed coil1 and that ,i could1 by 
converting the oscillatory current of a 
condenser to a higher potential1        
establish electrostatic alternating     
fields which acted through the whole    
extent of a room1 lighting up a tube no 
matter where it was held in space4 ,i   
thought ,i recognized that ,i had made a
 step in advance1 and ,i have persevered
 in this line2 but ,i wish to say that  

,i share with all lovers of science and 
progress the one and only desire--to    
reach a result of utility to men in any 
direction to which thought or experiment
 may lead me4 ,i think that this        
departure is the right one1 for ,i      
cannot see1 from the observation of the 
phenomena which manifest themselves as  
the frequency is increased1 what there  
would remain to act between two circuits
 conveying1 for instance1 impulses of   
several hundred millions per second1    
except electrostatic forces4 ,even with 
such trifling frequencies the energy    
would be practically all potential1 and 
my conviction has grown strong that1 to 
whatever kind of motion light may be    
due1 it is produced by tremendous       
electrostatic stresses vibrating with   
extreme rapidity4  ,of all these        
phenomena observed with currents1 or    
electric impulses1 of high frequency1   
the most fascinating for an audience are
 certainly those which are noted in an  
electrostatic field acting through      

considerable distance1 and the best an  
unskilled lecturer can do is to begin   
and finish with the exhibition of these 
singular effects4 ,i take a tube in the 
hand and move it about1 and it is       
lighted wherever ,i may hold it2        
throughout space the invisible forces   
act4 ,but ,i may take another tube and  
it might not light1 the vacuum being    
very high4 ,i excite it by means of a   
disruptive discharge coil1 and now it   
will light in the electrostatic field4  
,i may put it away for a few weeks or   
months1 still it retains the faculty of 
being excited4 ,what change have ,i     
produced in the tube in the act of      
exciting it8 ,if a motion imparted to   
the atoms1 it is difficult to perceive  
how it can persist so long without being
 arrested by frictional losses2 and if a
 strain exerted in the dielectric1 such 
as a simple electrification would       
produce1 it is easy to see how it may   
persist indefinitely1 but very difficult
 to understand why such a condition     

should aid the excitation when we have  
to deal with potentials which are       
rapidly alternating4  ,since ,i have    
exhibited these phenomena for the first 
time1 ,i have obtained some other       
interesting effects4 ,for instance1 ,i  
have produced the incandescence of a    
button1 filament1 or wire enclosed in a 
tube4 ,to get to this result it was     
necessary to economize the energy which 
is obtained from the field and direct   
most of it on the small body to be      
rendered incandescent4 ,at the beginning
 the task appeared difficult1 but the   
experiences gathered permitted me to    
reach the result easily4 ,in ,fig4 #cd  
and ,fig4 #ce two such tubes are        
illustrated which are prepared for the  
occasion4 ,in ,fig4 #cd a short tube    
,t#a1 sealed to another long tube ,t1 is
 provided with a stem s1 with a platinum
 wire sealed in the latter4 ,a very thin
 lamp filament l is fastened to this    
wire1 and connection to the outside is  
made through a thin copper wire w4 ,the 

tube is provided with outside and inside
 coatings1 ,c and ,c#a respectively1 and
 is filled as far as the coatings reach 
with conducting1 and the space above    
with insulating powder4 ,these coatings 
are merely used to enable me to perform 
two experiments with the tube--namely1  
to produce the effect desired either by 
direct connection of the body of the    
experimenter or of another body to the  
wire w1 or by acting inductively through
 the glass4 ,the stem s is provided with
 an aluminium tube a1 for purposes      
before explained1 and only a small part 
of the filament reaches out of this     
tube4 ,by holding the tube ,t#a anywhere
 in the electrostatic field the filament
 is rendered incandescent4              
,illustration3 ,,fig4 #cd4--,,tube      
,,with ,,filament ,,rendered            
,,incandescent ,,in ,,an ,,electrostatic
 ,,field4  ,illustration3 ,,fig4        
#ce4--;,,crookes' ,,experiment ,,in     
,,electrostatic ,,field4  ,a more       
interesting piece of apparatus is       

illustrated in ,fig4 #ce4 ,the          
construction is the same as before1 only
 instead of the lamp filament a small   
platinum wire p1 sealed in a stem s1 and
 bent above it in a circle1 is connected
 to the copper wire w1 which is joined  
to an inside coating ,c4 ,a small stem  
s#a is provided with a needle1 on the   
point of which is arranged to rotate    
very freely a very light fan of mica v4 
,to prevent the fan from falling out1 a 
thin stem of glass g is bent properly   
and fastened to the aluminium tube4     
,when the glass tube is held anywhere in
 the electrostatic field the platinum   
wire becomes incandescent1 and the mica 
vanes are rotated very fast4  ,intense  
phosphorescence may be excited in a bulb
 by merely connecting it to a plate     
within the field1 and the plate need not
 be any larger than an ordinary lamp    
shade4 ,the phosphorescence excited with
 these currents is incomparably more    
powerful than with ordinary apparatus4  
,a small phosphorescent bulb1 when      

attached to a wire connected to a coil1 
emits sufficient light to allow reading 
ordinary print at a distance of five to 
six paces4 ,it was of interest to see   
how some of the phosphorescent bulbs of 
,professor ,crookes would behave with   
these currents1 and he has had the      
kindness to lend me a few for the       
occasion4 ,the effects produced are     
magnificent1 especially by the sulphide 
of calcium and sulphide of zinc4 ,from  
the disruptive discharge coil they glow 
intensely merely by holding them in the 
hand and connecting the body to the     
terminal of the coil4  ,to whatever     
results investigations of this kind may 
lead1 their chief interest lies for the 
present in the possibilities they offer 
for the production of an efficient      
illuminating device4 ,in no branch of   
electric industry is an advance more    
desired than in the manufacture of      
light4 ,every thinker1 when considering 
the barbarous methods employed1 the     
deplorable losses incurred in our best  

systems of light production1 must have  
asked himself1 ,what is likely to be the
 light of the future8 ,is it to be an   
incandescent solid1 as in the present   
lamp1 or an incandescent gas1 or a      
phosphorescent body1 or something like a
 burner1 but incomparably more          
efficient8  ,there is little chance to  
perfect a gas burner2 not1 perhaps1     
because human ingenuity has been bent   
upon that problem for centuries without 
a radical departure having been         
made--though this argument is not devoid
 of force-but because in a burner the   
higher vibrations can never be reached  
except by passing through all the low   
ones4 ,for how is a flame produced      
unless by a fall of lifted weights8     
,such process cannot be maintained      
without renewal1 and renewal is repeated
 passing from low to high vibrations4   
,one way only seems to be open to       
improve a burner1 and that is by trying 
to reach higher degrees of              
incandescence4 ,higher incandescence is 

equivalent to a quicker vibration2 that 
means more light from the same material1
 and that1 again1 means more economy4   
,in this direction some improvements    
have been made1 but the progress is     
hampered by many limitations4           
,discarding1 then1 the burner1 there    
remain the three ways first mentioned1  
which are essentially electrical4       
,suppose the light of the immediate     
future to be a solid rendered           
incandescent by electricity4 ,would it  
not seem that it is better to employ a  
small button than a frail filament8     
,from many considerations it certainly  
must be concluded that a button is      
capable of a higher economy1 assuming1  
of course1 the difficulties connected   
with the operation of such a lamp to be 
effectively overcome4 ,but to light such
 a lamp we require a high potential2 and
 to get this economically we must use   
high frequencies4  ,such considerations 
apply even more to the production of    
light by the incandescence of a gas1 or 

by phosphorescence4 ,in all cases we    
require high frequencies and high       
potentials4 ,these thoughts occurred to 
me a long time ago4  ,incidentally we   
gain1 by the use of very high           
frequencies1 many advantages1 such as a 
higher economy in the light production1 
the possibility of working with one     
lead1 the possibility of doing away with
 the leading-in wire1 etc4  ,the        
question is1 how far can we go with     
frequencies8 ,ordinary conductors       
rapidly lose the facility of            
transmitting electric impulses when the 
frequency is greatly increased4 ,assume 
the means for the production of impulses
 of very great frequency brought to the 
utmost perfection1 every one will       
naturally ask how to transmit them when 
the necessity arises4 ,in transmitting  
such impulses through conductors we must
 remember that we have to deal with     
pressure and flow1 in the ordinary      
interpretation of these terms4 ,let the 
pressure increase to an enormous value1 

and let the flow correspondingly        
diminish1 then such impulses--variations
 merely of pressure1 as it were--can no 
doubt be transmitted through a wire even
 if their frequency be many hundreds of 
millions per second4 ,it would1 of      
course1 be out of question to transmit  
such impulses through a wire immersed in
 a gaseous medium1 even if the wire were
 provided with a thick and excellent    
insulation for most of the energy would 
be lost in molecular bombardment and    
consequent heating4 ,the end of the wire
 connected to the source would be       
heated1 and the remote end would receive
 but a trifling part of the energy      
supplied4 ,the prime necessity1 then1 if
 such electric impulses are to be used1 
is to find means to reduce as much as   
possible the dissipation4  ,the first   
thought is1 employ the thinnest possible
 wire surrounded by the thickest        
practicable insulation4 ,the next       
thought is to employ electrostatic      
screens4 ,the insulation of the wire may

 be covered with a thin conducting      
coating and the latter connected to the 
ground4 ,but this would not do1 as then 
all the energy would pass through the   
conducting coating to the ground and    
nothing would get to the end of the     
wire4 ,if a ground connection is made it
 can only be made through a conductor   
offering an enormous impedance1 or      
though a condenser of extremely small   
capacity4 ,this1 however1 does not do   
away with other difficulties4  ,if the  
wave length of the impulses is much     
smaller than the length of the wire1    
then corresponding short waves will be  
sent up in the conducting coating1 and  
it will be more or less the same as     
though the coating were directly        
connected to earth4 ,it is therefore    
necessary to cut up the coating in      
sections much shorter than the wave     
length4 ,such an arrangement does not   
still afford a perfect screen1 but it is
 ten thousand times better than none4 ,i
 think it preferable to cut up the      

conducting coating in small sections1   
even if the current waves be much longer
 than the coating4  ,if a wire were     
provided with a perfect electrostatic   
screen1 it would be the same as though  
all objects were removed from it at     
infinite distance4 ,the capacity would  
then be reduced to the capacity of the  
wire itself1 which would be very small4 
,it would then be possible to send over 
the wire current vibrations of very high
 frequencies at enormous distance       
without affecting greatly the character 
of the vibrations4 ,a perfect screen is 
of course out of the question1 but ,i   
believe that with a screen such as ,i   
have just described telephony could be  
rendered practicable across the         
,atlantic4 ,according to my ideas1 the  
gutta-percha covered wire should be     
provided with a third conducting coating
 subdivided in sections4 ,on the top of 
this should be again placed a layer of  
gutta-percha and other insulation1 and  
on the top of the whole the armor4 ,but 

such cables will not be constructed1 for
 ere long intelligence--transmitted     
without wires--will throb through the   
earth like a pulse through a living     
organism4 ,the wonder is that1 with the 
present state of knowledge and the      
experiences gained1 no attempt is being 
made to disturb the electrostatic or    
magnetic condition of the earth1 and    
transmit1 if nothing else1 intelligence4
  ,it has been my chief aim in          
presenting these results to point out   
phenomena or features of novelty1 and to
 advance ideas which ,i am hopeful will 
serve as starting points of new         
departures4 ,it has been my chief desire
 this evening to entertain you with some
 novel experiments4 ,your applause1 so  
frequently and generously accorded1 has 
told me that ,i have succeeded4  ,in    
conclusion1 let me thank you most       
heartily for your kindness and          
attention1 and assure you that the honor
 ,i have had in addressing such a       
distinguished audience1 the pleasure ,i 

have had in presenting these results to 
a gathering of so many able men--and    
among them also some of those in whose  
work for many years past ,i have found  
enlightenment and constant pleasure--,i 
shall never forget4    ,transcriber's   
note3 ,corrected the following          
typesetting errors3      #a7 'preceived'
 to 'perceived'1 page #af4      #b7     
'disharging' to 'discharging'1 page #cj4
      #c7 'park' to 'spark'1 page #cc4  
#d7 'pssition' to 'position'1 page #ej4 
#e7 'to th opposite side' to 'to the    
opposite side'1 page #ef4      #f7 's   
resses' to 'stresses'1 page #adg4