,,the ,,telephone     ,by ,professor ,a4
 ,e4 ,dolbear   ,,the ,,telephone  ,with
 directions for making a ,speaking      
,telephone ,illustrated #ej cents       
,,the ,,art ,,of ,,projecting  ,a       
,manual of ,experimentation in ,physics1
 ,chemistry1 and ,natural ,history1 with
 the ,porte ,lumiere and ,magic ,lantern
 ,new ,edition ,revised ,illustrated    
#b4jj   ,,matter1 ,,ether1 ,,and        
,,motion  ,the ,factors and ,relations  
of ,physical ,science ,illustrated #a4ge
             ,lee and ,shepard          
,publishers ,boston     ,,the           
,,telephone3  ,,an ,,account ,,of ,,the 
,phenomena of ,electricity1 ,magnetism1 
and ,sound1  ,,as ,,involved ,,in ,,its 
,,action4  ,,with ,,directions ,,for    
,,making  ,a ,,speaking ,,telephone4    
,,by  ,,prof4 ,a4 ,e4 ,,dolbear1        
,,tufts ,,college1  ,,author ,,of ,,the 
,,art ,,of ,,projecting1 ,,etc4         
,,boston3           ,,lee  ,,shepard1   
,,publishers4               ,,copyright1
           #ahgg1           ,,by ,a4 ,e4

 ,,dolbear4     ,,preface4   ,,the      
popular exhibitions of the              
speaking-telephone during the past six  
months1 together with numerous newspaper
 articles1 have created a widespread    
interest in the instrument2 and it has  
been thought that a small book          
explanatory of its action would meet a  
public want4  ,it has seemed to be      
necessary to call attention to the      
various phenomena and inter-actions of  
the forces involved2 and hence the      
author has attempted to make plain and  
intelligible the phenomena of           
electricity1 magnetism1 and sound4 ,cuts
 have been inserted where they could be 
useful in making the mechanical         
conditions more intelligible2 and a     
table of tone-composition has been      
devised1 which shows at a glance the    
constituents of the sounds of various   
musical instruments4  ,as the           
speaking-telephone1 in which            
magneto-electric currents were utilized 
for the transmission of speech and other

 kinds of sounds1 was invented by me1 ,i
 have described at some length my first 
instrument1 and have also given explicit
 directions for making a                
speaking-telephone which ,i know1 by    
trial1 to be as efficient as any        
hitherto made2 but nothing in the book  
is to be taken as a dedication of the   
invention to the public1 as steps have  
already been taken to secure            
letters-patent according to the laws of 
the ,united ,states4                    
,a4 ,e4 ,,dolbear4  ,,college ,,hill1   
,,mass4     ,,the ,,telephone4          
,,electricity4  ,,some of the phenomena 
of electricity are manifested upon so   
large a scale as to be thrust upon the  
attention of everybody4 ,thus lightning1
 which accompanies so many showers in   
warm weather in almost every latitude1  
has always excited in some individuals a
 superstitious awe1 as being an         
exhibition of supernatural agency2 and  
probably every one feels more or less   
dread of it during a thunder-shower1 and

 this for the reason that it affects so 
many of the senses at the same time4    
,the flash may be blinding to the eyes  
if near to us2 the thunder may be       
deafening to the ears1 and so powerful  
as to shake the foundations of the      
hills1 and make the ground upon which we
 stand to sensibly move3 these with the 
remembered destructive effects that have
 been witnessed1 of buildings demolished
 and large trees torn to splinters in an
 instant1 are quite sufficient to raise 
a feeling of dread in the strongest     
mind4 ,in the polar regions1 both north 
and south1 where thunder-storms are less
 frequent1 the atmospheric electricity  
assumes the form called the aurora      
borealis1 or the aurora australis1      
according as it is seen north or south  
of the equator4  ,more than two thousand
 years ago it was noticed by the ,greeks
 that a certain kind of a mineral which 
was thrown up on the shores of the      
,mediterranean ,sea1 when rubbed would  
attract light bodies1 such as shreds of 

silk or linen and bits of paper4 ,to    
this substance they gave the name of    
,elektron1 and the property developed   
thus by friction was afterwards called  
electricity4 ,in #afjj ,dr4 ,gilbert1   
physician to ,queen ,elizabeth1         
published a book in which he described  
numerous experiments demonstrating that 
electricity could be developed by       
friction upon a great variety of        
substances1 such as stones1 gems1 and   
resins4 ,the first machine for          
developing electricity was made by ,otto
 von ,guericke of ,magdeburg1 about     
#afhj4 ,his machine consisted of a ball 
of sulphur about six inches in diameter1
 which could be rotated4 ,if the dry    
hand were held against the sulphur while
 it was being turned in a dark room1 the
 sphere appeared to emit light3 it also 
gave out a peculiar hissing or crackling
 sound4 ,newton experimented a little   
with electricity1 and noticed that the  
rubber was an important element in      
developing electricity4 ,he does not    

seem to have given to the subject the   
same attention that he gave to some     
other departments of science4 ,had he   
done so1 it is probable that he would   
have advanced the study a hundred years2
 that is to say1 he would probably have 
left it at the place where it actually  
was in #agij4 ,so great were his        
abilities that in one lifetime he made  
greater additions to human knowledge    
than all the rest of mankind had made   
during the preceding thousand years4 ,in
 the month of ,june1 #ageb1 ,franklin   
made that memorable experiment which    
immortalized him4 ,he flew his kite to  
the thunder-cloud1 practically asking   
the question of the lightning whether or
 not it was identical with electricity4 
,the lightning came down the wetted     
twine to his hand1 and proclaimed its   
identity4  ,for the next forty years the
 natural philosophers in both ,europe   
and ,america only rung the changes upon 
what was known4 ,they flew kites to the 
clouds2 they made and charged ,leyden   

jars1 and discharged them through wires 
and chains and circuits of clasped      
hands1 and studied the attractions and  
repulsions manifested by electrified    
bodies2 but they added nothing of       
importance in the way of experiments4   
,in #agia ,galvani1 a professor of      
anatomy at ,bologna1 announced a        
manifestation of electricity that was   
new and of a remarkable character1      
having its origin in the muscles of     
animals1 and so was called animal       
electricity4 ,he had some frogs' legs   
prepared for eating2 by chance they were
 placed near an electrical machine with 
which ,galvani was experimenting1 so    
that a spark would occasionally pass to 
the legs1 when they would contract as   
often as a spark passed to them4 ,the   
motion was first observed by his wife1  
who called his attention to the         
phenomenon2 and he very soon discovered 
that the thighs of a frog1 skinned and  
suspended1 made a very good             
electroscope4 ,while experimenting in   

this way he made another and more       
important discovery2 namely1 that1 when 
the muscles and nerves of the frog's leg
 were touched by pieces of two different
 metals1 the leg would contract as      
before4 ,alexander ,volta1 another      
,italian professor1 who had invented the
 electrophorus1 and was possessed of    
great experimental skill1 now turned his
 attention to the experiment of         
,galvani1 and very soon discovered that 
the origin of the electricity that moved
 the frogs' legs was not in the legs    
themselves1 but in the metals used4 ,the
 first form of the galvanic battery was 
the result of ,volta's investigations1  
and was called the ,voltaic pile4 ,this 
pile consisted of alternate disks of    
zinc1 flannel1 and copper1 piled one on 
top of the other in constant succession 
in that order4 ,the flannel was         
moistened with salt and water1 or with  
diluted sulphuric acid4 ,when the first 
zinc was connected with the last copper 
by means of a wire1 a powerful current  

of electricity was obtained4 ,this form 
of battery is not in use at all now1 as 
much more efficient means are known for 
producing electricity2 but this in      
#ahjj1 when it was first made known in  
,england1 was very startling1 and was   
one of those surprises which have been  
so frequent since then in the history of
 electricity4  ,surprising things were  
done by ,sir ,humphry ,davy1 with a     
large ,voltaic battery4 ,water was      
decomposed1 and the metals potassium and
 sodium were first separated from their 
compounds with oxygen4 ,bonaparte had   
offered a prize of sixty thousand francs
 to the person who by his experiments   
and discoveries should advance the      
knowledge of electricity and galvanism  
as much as ,franklin and ,volta did1 and
 of three thousand francs for the best  
experiments which should be made in each
 year on the galvanic fluid4 ,this      
latter prize was awarded to ,davy4      
,after ,davy's successes in #ahjf1 there
 was nothing of importance in an        

experimental way added to the knowledge 
of electricity1 until #ahbj1 when       
,oersted of ,copenhagen announced that  
the conducting wire of a ,voltaic       
circuit acts upon a magnetic needle1 and
 that the needle tends to set itself at 
right angles to the wire4 ,this was a   
kind of action altogether unexpected4   
,this observation was of the utmost     
importance2 and at once the philosophers
 in ,europe and ,america set themselves 
to inquire into the new phenomenon4 ,the
 laws of the motion of the magnetic     
needle when acted upon by a current of  
electricity traversing a wire were      
successfully investigated by ,m4 ,ampere
 of the ,french ,academy4 ,he observed  
that whenever a wire through which a    
current of electricity was passing was  
held over and parallel with a magnetic  
needle which was free to move1 and      
therefore pointed to the north1 if the  
current was moving towards the north1   
the north pole was deflected to the     
west2 if the current was moving towards 

the south1 the south pole of the magnet 
was deflected towards the west2 and that
 in all cases the magnet tended to set  
itself at right angles to the current2  
also that this angular displacement     
depended upon the strength of the       
current4 ,thus originated the           
galvanometer1 an instrument that not    
only detects the existence of an        
electric current1 but enables us to     
determine its direction and its         
strength4 ,our present knowledge of     
electrical laws is due1 in a very large 
measure1 to observations made with this 
instrument4 ,of course it has been very 
much modified1 and made almost          
incredibly sensitive3 yet1 in all       
galvanometers1 the fundamental principle
 involved in their structure is that of 
the action of a current of electricity  
upon a magnet1 which was first noticed  
by ,oersted4   ,,magnets4  ,it is       
related by ,nicander that among the     
shepherds who tended their flocks upon  
the sides of ,mount ,ida was one named  

,magnes1 who noticed1 that1 while taking
 his herds to pasture1 his shepherd's   
crook adhered to some of the rocks4     
,from this man's name some have supposed
 the name magnet to have been derived4  
,it is1 however1 generally believed to  
have received its name from the ancient 
city of ,magnesia in ,asia ,minor1 near 
which the loadstone or magnetic         
substance was found4 ,this rock1 which  
possesses the remarkable property of    
attracting and holding to itself small  
pieces of iron or steel1 is now known to
 be one of the ores of iron1 and is     
called magnetite by mineralogists4 ,the 
iron is chemically combined with oxygen1
 and forms #gb4e per cent of its weight4
 ,there is another ore of iron1 known as
 hematite1 which contains seventy per   
cent of iron2 but the difference of two 
and a half per cent of iron in the ore  
is enough to make the difference between
 a magnetically inert substance1 and one
 which may be able to lift a mass of    
iron equal to many times its own weight4

  ,sir ,isaac ,newton is said to have   
worn in a finger-ring a small loadstone 
weighing three grains1 which would lift 
seven hundred and fifty grains1 which is
 equal to two hundred and fifty times   
its own weight4 ,the most powerful      
magnet now known is owned by ,m4        
,obelliane of ,paris4 ,it can lift forty
 times its own weight4 ,large pieces1   
however1 do not support proportionally  
greater weights1 seldom more than one or
 two times their own weight4  ,there are
 in many places in the world immense    
beds of magnetic iron-ore4 ,such are to 
be found in the ,adirondack region in   
,northern ,new ,york1 and in ,chester   
,county1 ,pennsylvania4 ,the celebrated 
iron-mines of ,sweden consist of it1 and
 in ,lapland there are several large    
mountains of it4 ,it must not be        
inferred1 that1 because the mineral is  
called magnetite1 all specimens possess 
the property called magnetism4 ,the     
large masses seldom manifest any such   
force1 any more than ordinary pieces of 

iron or steel manifest it3 yet any of it
 will be attracted by a magnet in the   
same way as iron will be4 ,the most     
powerful native magnets are found in    
,siberia1 and in the ,hartz1 a range of 
mountains in ,northern ,germany4  ,when 
a piece of this magnetically endowed ore
 is placed in a mass of iron-filings1 it
 will be seen that the filings adhere to
 it in greatest quantity upon two       
opposite ends or sides1 and these are   
named the poles of the magnet4 ,if the  
piece be suspended by a string so as to 
turn freely1 it will invariably come to 
rest with the same pole turned towards  
the north2 and this pole is therefore   
called the north pole of the magnet1 and
 the action is called the directive     
action4 ,this directive action was known
 to the ,chinese more than three        
thousand years ago4 ,in traversing those
 vast steppes of ,tartary they employed 
magnetic cars1 in which was the figure  
of a man1 whose movable1 outstretched   
arm always pointed to the south4 ,dr4   

,gilbert affirms that the compass was   
brought from ,china to ,italy in #abfj1 
by a traveller named ,paulus ,venetus4  
,when a piece of hardened steel is      
rubbed upon a natural magnet1 it        
acquires the same directive property2   
and1 as the steel could be easily shaped
 into a convenient form for use1 a steel
 needle has generally been used for the 
needle of a compass4 ,the directive     
power of the magnet has been and still  
is of incalculable value to all         
civilized nations4 ,ocean navigation    
would be impossible without it1 and     
territorial boundaries are fixed by     
means of it2 but there are other        
properties and relations of a magnet1   
which have been discovered within the   
last fifty years1 which are destined to 
be as important to mankind as that of   
the compass has been4  ,in #ahbe        
,william ,sturgeon of ,woolwich1 ,eng41 
discovered that if a copper wire were   
wound around a piece of soft iron1 and a
 current of electricity sent through the

 wire1 the soft iron would become a     
magnet1 but would retain its magnetism  
no longer than while the current of     
electricity was passing through the     
coil4 ,the magnetism developed in this  
way was called electro-magnetism1 and   
the iron so wound was called an         
electro-magnet4 ,the first              
electro-magnet was made by winding bare 
wire upon the soft iron4 ,this method   
will not produce very strong magnets4   
,in #ahcj ,prof4 ,henry insulated the   
wire by covering it with silk1 and was  
the first to produce powerful magnets4  
,on a soft iron bar of fifty-nine pounds
 weight he used twenty-six coils of     
wire1 thirteen on each leg1 all joined  
to a common conductor by their opposite 
ends1 and having an aggregate length of 
seven hundred and twenty-eight feet4    
,this apparatus was found able to       
sustain a weight of twenty-five hundred 
pounds4 ,this electro-magnet is now     
owned by ,yale ,college4  ,the power of 
the electro-magnet is enormously greater

 than that of any permanent magnet4 ,a  
permanent magnet made by ,jamin of      
,paris1 which is made up of many strips 
of thin steel bound together1 and       
weighing four pounds1 is able to support
 a weight of one hundred pounds2 but    
,dr4 ,joule made an electro-magnet1 by  
arranging the coils to advantage1 that  
would support thirty-five hundred times 
its own weight1 or one hundred and forty
 times the proportionate load of ,sir   
,isaac ,newton's ring magnet4   ,,the   
,,galvanic ,,battery4  ,the original    
form of the galvanic battery as devised 
by ,volta1 and modified but little      
during thirty years1 consisted of a cell
 to contain a fluid1 which was usually  
dilute sulphuric acid1 in which two     
plates of different metals were         
immersed3 the metals used were generally
 plates of zinc and copper1 or zinc and 
silver4 ,such plates1 when first placed 
in the liquid1 will give a very good    
current of electricity2 but it will not 
last long4 ,the reason of this is easy  

to understand4 ,whenever a current of   
electricity is generated by chemical    
action of a liquid upon two different   
metals1 there is always some            
decomposition of the liquid1 and this   
decomposition takes place upon the      
plates themselves2 and the liberated    
gases adhere to the plates1 and prevent 
further contact with the acid2 at the   
same time1 the gases themselves act upon
 the plates1 and generate a current of  
electricity in the opposite direction4  
,this will of course interfere with the 
first current2 and very soon the battery
 is useless until the plates have been  
withdrawn from the liquid4 ,this        
physico-chemical process that takes     
place in such a battery is called the   
polarization of the plates4             
,illustration3 ,,fig4 #a4  ,the         
accompanying figure will help one to    
understand the actions going on in a    
battery cell of the kind mentioned4 ,let
 ,pt represent a plate of platinum1 and 
,zn a plate of zinc1 both placed in a   

vessel containing hydrochloric acid1    
which is also represented by the symbols
 ,h,cl4 ,as such molecules are extremely
 minute1 there will of course be an     
immense number of them between the      
plates4 ,the plates are now to be       
connected by a wire running between them
 through the air4 ,as soon as these     
conditions are fulfilled1 a hissing     
sound will be heard coming from the     
cell1 and bubbles of gas will be seen to
 rise from the platinum plate3 these    
bubbles prove upon analysis to be       
bubbles of hydrogen4 ,at the same time  
the zinc will begin to dissolve1 forming
 what proves by analysis to be the      
chloride of zinc2 and at the same time a
 current of electricity travels through 
the wire from the platinum to the zinc4 
,the quantity of electricity that is    
thus generated is strictly proportionate
 to the quantity of hydrogen liberated1 
which is also proportionate to the      
weight of zinc dissolved2 and this1 in  
turn1 is proportionate to the surface of

 the metals exposed to the action of the
 acid4 ,now1 it happens under such      
circumstances as the above1 that the    
liberated hydrogen adheres very strongly
 to the platinum1 as there is nothing   
for it to unite with chemically2 and    
therefore the plate will very soon be   
visibly covered with bubbles1 which may 
be scraped off with a feather or a swab1
 but only to have the same thing        
repeated4  ,this coating of bubbles will
 prevent the acid from touching the     
plate1 and so practically diminishes the
 surface of it2 but the quantity of     
electricity generated being             
proportionate to the surface exposed to 
the chemical action1 it will be         
understood at once how such polarization
 of the plates must soon bring the      
battery to a standstill4  ,in #ahcf     
,prof4 ,j4 ,f4 ,daniell of ,london      
contrived a battery1 which has been     
called the ,daniell ,cell1 in which the 
metal 7copper7 that had the hydrogen    
liberated upon it was separated by a    

porous cell from the zinc4 ,the zinc was
 immersed in dilute sulphuric acid1 and 
the copper in an acid solution of blue  
vitriol 7copper sulphate74 ,the porous  
cup did not prevent the electricity from
 passing1 nor the decomposition from    
taking place2 but the hydrogen1 which in
 this case would have been liberated at 
the copper plate1 at once united with   
oxygen there1 which it got by           
decomposing the copper sulphate3 hence  
water was formed1 and copper was        
deposited upon the copper plate2 and1   
being an excellent conductor1 the       
battery would keep up a strong action   
for a long time4  ,mr4 ,grove1 also of  
,london1 in #ahci invented a battery    
which still goes by his name1 in which  
the hydrogen plate is of platinum       
immersed in strong nitric acid1 enclosed
 also in a porous earthen cell2 and     
this1 in turn1 is plunged into a vessel 
containing dilute sulphuric acid and the
 zinc4 ,in this case the liberated      
hydrogen immediately decomposes the     

nitric acid1 which readily parts with   
its oxygen2 water is the product1 as in 
the other case1 and the nitric acid     
loses strength4 ,strips of carbon have  
been substituted for the platinum1 and  
this is called the ,bunsen battery4 ,it 
is otherwise like the ,grove battery2 it
 gives a very powerful and constant     
current and it is by the use of one or  
the other of these batteries1 that most 
of the experiments in electricity are   
performed in institutions of learning1  
and1 until lately1 most in use for      
telegraphic purposes4     ,,other       
,,means ,,for ,,generating              
,,electricity4   ,,thermo-,,electricity4
  ,,if two strips of different metals1  
such as silver and iron1 be soldered    
together at one end1 and the other ends 
be connected with a galvanometer1 on    
heating the soldered junction of the    
metals it will be found that a current  
of electricity traverses the circuit    
from the iron to the silver4 ,if other  
metals be used1 having the same size1   

and the same degree of heat be applied1 
the current of electricity thus         
generated will give a greater or a less 
deflection1 which will be constant for  
the metals employed4 ,the two metals    
generally employed are bismuth and      
antimony1 in bars about an inch long and
 an eighth of an inch square4 ,these are
 soldered together in series so as to   
present for faces the ends of the bars1 
and these often number as many as fifty 
pairs4 ,such a series is called a       
thermo-pile4 ,this method of generating 
electricity was discovered by ,seebeck  
of ,berlin in #ahba1 but the thermo-pile
 so much in use now in heat             
investigations was invented by ,nobili  
in #ahce4 ,the strength of this current 
is not very great1 a single ,daniell    
cell being equal to nine pairs of the   
strongest combination yet discovered1   
namely1 the artificial sulphuret of     
copper with ,german silver4             
,,magneto-,,electricity4  ,illustration3
 ,,fig4 #b4  ,it has already been       

mentioned1 that ,oersted found that a   
magnet when free to turn tended to set  
itself at right angles to a wire in     
which a current of electricity was      
passing1 thus demonstrating some        
inter-action between electricity and    
magnetism2 but it remained for ,faraday 
to discover the converse fact1 namely1  
that a magnet moving across a wire1 the 
ends of which were connected with a     
galvanometer or otherwise closed1       
originated a current of electricity in  
the wire1 the direction of which        
depended upon the direction of the      
movement of the magnet4 ,if the wire was
 coiled into a hollow helix1 the magnet 
in moving through the helix moved       
across1 that is1 at right angles to all 
the turns of the helix2 and each        
complete turn added to the intensity of 
the current4 ,this will be understood by
 reference to the diagram1 ,fig4 #b4    
,let ,g be a galvanometer connected with
 the wires from a helix2 ,n ,s1 a       
permanent bar magnet4 ,if the magnet be 

thrust into the coil1 a current of      
electricity will traverse the helix1    
wire1 and galvanometer1 and the needle  
will indicate its direction4 ,if the    
magnet be now withdrawn1 a current will 
move in the opposite direction through  
the whole circuit4 ,the electricity that
 is thus originated is said to be       
induced4 ,the quantity of electricity   
that can be induced thus is almost      
unlimited1 depending upon the size and  
strength of the magnet1 the size of the 
wire1 and the length of wire in the     
coil4 ,there are now many forms of      
machines for developing electricity from
 the motion of coils of wire in front of
 the poles of permanent magnets4 ,they  
are generally called magneto-electric   
machines4 ,the action involved in these 
machines is so important in its bearing 
upon telephony as to necessitate a      
fuller description of them4   ,,magnetic
 ,,induction4  ,illustration3 ,,fig4 #c4
  ,let ,n ,s1 ,fig4 #c1 be a bar of     
hardened steel rendered permanently     

magnetic4 ,if now there be brought near 
to it a board-nail1 the latter will     
become a magnet through the inductive   
action of the first magnet4 ,this       
induced magnetism may be demonstrated by
 bringing a tack or other bit of iron to
 the end that is farthest from the      
permanent magnet2 the tack will adhere  
to the nail1 but will fall off when the 
nail is removed from the neighborhood of
 the magnet4 ,by testing the polarity of
 the nail1 it will be found that the end
 nearest the magnet will be a south pole
 if the magnet has its north pole       
towards it1 in all cases having a       
polarity opposite to that of the pole   
acting upon it4 ,the strength of this   
induced magnetism thus developed depends
 upon the distance apart of the magnet  
and the iron1 being at its maximum when 
the two touch4 ,but the tack itself is  
also made a magnet1 and will attract    
another tack1 and that one still        
another1 the number which can be thus   
supported being dependent upon the      

strength of the first or inducing       
magnet4  ,suppose now that we should    
wind a few feet of wire about the nail1 
and fasten the two ends of the wire to  
an ordinary galvanometer1 and then make 
the nail to approach the permanent      
magnet4 ,the galvanometer needle would  
be seen to move as the nail approached2 
and1 if the latter were allowed to touch
 the magnet1 the movement of the needle 
would suddenly be much hastened1 but    
would directly come to rest1 showing    
that1 so long as there is no motion of  
the nail towards or away from the       
magnet1 no electricity is moving in the 
wire1 although the nail is a strong     
magnet while it is in contact with the  
permanent magnet4 ,if the nail be now   
withdrawn1 the two phenomena happen as  
before3 that is to say1 as the nail     
recedes it loses its magnetism2 and the 
giving-up of its magnetism induces a    
current of electricity through the wire 
in the opposite direction to that it had
 when the nail approached4 ,the current 

of electricity in the opposite direction
 is indicated by the galvanometer       
needle1 which moves according to        
,ampere's law mentioned on a preceding  
page4  ,it may be noted here that we    
have an effect quite analogous to that  
already mentioned on page #ba as the    
experiment of ,faraday4 ,in one case a  
permanent magnet is thrust into a coil  
of wire1 and in the other a piece of    
iron is made a magnet while enclosed in 
a coil4 ,in each case there is generated
 a current of electricity which lasts no
 longer than the mechanical motion of   
the parts lasts4   ,,magneto-,,electric 
,,machines4  ,such transient currents   
are practically useless1 and several    
devices have been invented to make the  
flow continuous4 ,the common form of    
machine for doing this may be understood
 by reference to the diagram4           
,illustration3 ,,fig4 #d4  ,n ,s1 ,fig4 
#d1 is the permanent magnet1 which is   
bent into a ,u form in order to utilize 
both poles4 ,n' and ,s' are short rods  

of soft iron fastened into a yoke-piece 
,y1 also of soft iron4 ,coils of wire   
surround each of the rods as            
represented1 the ends of the wires      
connecting with each other and with what
 is called a pole-changer4 ,the whole of
 this part is capable of revolving upon 
an axis ,p ,y by a pulley at ,p4 ,the   
action is as follows3 ,from their       
position1 the soft-iron rods ,n' ,s'    
must be magnets through the inductive   
action of the permanent magnet1 just as 
the nail was made a magnet in like      
position4 ,so long as the parts have the
 relative position shown in the figure1 
and there is no motion1 no electricity  
can be developed2 but1 if the axis ,p ,y
 be turned1 ,s'1 which represents the   
polarity of the rod opposite ,n1 will be
 losing its induced magnetism2 and1 when
 half a revolution has been made1 that  
same pole will be where ,n' now is2 but 
it will then have ,n' polarity instead  
of ,s'2 that is1 it has been losing     
south polarity as it receded from ,n1   

and gaining north polarity as it        
approached ,s3 hence a current of       
electricity has steadily been flowing   
through the coil in one direction4 ,at  
the same time1 the other rod ,n' has    
passed through similar phases2 and its  
enveloping coil has had a current of    
electricity induced in it in the same   
direction as in the first coil4 ,this   
doubles the intensity of the current2   
and the whole is conducted by the       
connecting-wires where the current is   
wanted4 ,machines have been built upon  
this plan1 that contained fifty or sixty
 powerful compound permanent magnets1   
and as many wire coils1 needing a       
steam-engine of eight or ten horse-power
 to run them4  ,a less cumbersome and   
much more efficient magneto-electric    
machine has been made by changing the   
form of the soft iron armature to       
something like a shuttle1 and winding   
the wire inside of it4 ,this is called  
the ,siemen's ,armature4 ,the latest    
pattern of such machines is known as the

 ,gramme2 and its peculiarity consists  
in the substitution of a broad ring of  
soft iron for the armature4 ,about this 
ring a good many coils1 of equal        
lengths1 of insulated copper wire are   
wound in such a manner that one-half of 
any turn in the wire goes through the   
inside of the ring1 making the coils    
longitudinal4 ,the whole of the armature
 thus prepared is fixed upon a shaft1 so
 as to permit rotation1 and fixed       
between the poles of a powerful ,jamin  
magnet4 ,the ends of the coils are      
connected with conductors upon the axis2
 and1 when the armature thus constructed
 is rotated1 a very constant and        
powerful current of electricity flows in
 a single direction1 unlike the other   
forms4 ,it is stated1 that1 with        
one-horse power1 a light can be obtained
 equal to that from a battery of fifty  
,grove cells4   ,,secondary ,,currents4 
,so long ago as #ahcf it was noticed by 
,prof4 ,page of ,salem1 that1 whenever a
 current of electricity was made to flow

 in a coil of wire1 another current in  
the opposite direction was induced in a 
coil that was parallel with the first2  
and also1 when the current in the first 
was broken1 another current in the      
second coil would flow in the opposite  
direction to the former one4 ,these     
currents1 which are called secondary    
currents1 are very transient4 ,no       
current at all flows save at the instant
 of making or breaking the current4 ,in 
this respect1 we are reminded of the    
behavior of the soft iron within the    
coil1 which gives origin to a current of
 electricity when it is made to approach
 a magnet or recede from it1 but gives  
no current so long as it is still4      
,these secondary currents were          
investigated by ,prof4 ,henry1 resulting
 in the discovery of many curious and   
interesting phenomena4 ,it will be      
sufficient here for me to refer to what 
are called induction coils1 which are   
developments of the principles involved 
in electro-magnetism and                

electro-induction4 ,imagine a rod of    
soft iron of any size to be wound with a
 coil of wire1 the ends of the wire to  
be so left that they may be connected   
with a galvanic battery4 ,around this   
coil let another coil be wound of very  
fine and well-insulated wire2 the       
terminal wires of it to be left         
adjustable to any distance from each    
other4 ,now1 upon making connection with
 a battery to the primary coil1 there   
will be two results produced            
simultaneously4 ,first1 the soft iron   
will be rendered magnetic2 and1 second1 
a current of electricity will be        
generated in the secondary coil2 and the
 strength of this secondary current is  
very much increased by the inductive    
action of the soft iron that has been   
made a magnet4 ,when the battery current
 is broken1 the iron loses its          
magnetism1 and a current of electricity 
is again started in the secondary coil  
in the opposite direction4 ,the energy  
of this derived current is so great that

 it will jump some distance through the 
air1 and thus is apparently unlike the  
electricity that originates in a        
battery4 ,an induction coil made by ,mr4
 ,ritchie for the ,stevens ,institute at
 ,hoboken1 ,n4,j41 has a primary coil of
 #aie feet of ,no4 #f wire4 ,the        
secondary coil is over fifty miles in   
length1 and is made of ,no4 #cf wire1   
which is but 4#jje of an inch in        
diameter4 ,this instrument has given a  
spark twenty-one inches in length1 with 
three large cells of a bichromate       
battery4  ,mr4 ,spottiswood of ,london  
has just had completed for him the      
largest induction coil ever made4 ,it   
has two primary coils1 one containing   
sixty-seven pounds of wire1 and the     
other eighty-four pounds1 the wire being
 4#jif inch in diameter4 ,the secondary 
coil is two hundred and eighty miles    
long1 and has #cha1hej turns4 ,this coil
 is made in three parts1 the diameter of
 the wire in the first part being 4#jjie
 inch2 of the second part1 4#jae2 and   

the third part1 4#jaa4 ,with five ,grove
 cells this induction coil has given a  
spark forty-two inches long1 and has    
perforated glass three inches thick4    
,the electricity thus developed in      
secondary coils is of the same character
 as that developed by friction2 and all 
of the experiments usually performed    
with the latter may be repeated with the
 former1 many of them being greatly     
heightened in beauty and interest4      
,such1 for instance1 are the discharges 
in vacuo in ,geisler tubes1 exhibiting  
stratifications1 fluorescence1          
phosphorescence1 the production of ozone
 in great quantity1 decomposition of    
chemical compounds1 c4  ,the electricity
 developed by friction upon glass1 wax1 
resin1 and other so-called              
non-conductors1 has heretofore been     
called static electricity1 for the      
reason that when it was once originated 
upon a surface it would remain upon it  
for an indefinite time1 or until some   
conducting body touched it1 and thus    

gave it a way of escape4 ,thus1 a cake  
of wax if rubbed with a piece of        
flannel1 or struck with a cat-skin or a 
fox-tail becomes highly electrified1 and
 in a dry atmosphere will remain so for 
months4 ,common air has1 however1 always
 a notable quantity of moisture in it2  
and1 as water is a conductor of         
electricity1 such damp air moving over  
the electrified surface will carry off  
very soon all the electricity4  ,again1 
the electricity developed through       
chemical action in a battery and through
 the inter-action of magnets and coils  
of wire has been called dynamic         
electricity1 inasmuch as it never       
appeared to exist save when it was in   
motion in a completed circuit4 ,this1   
however1 is not true2 for if one of the 
wires from a galvanic battery be        
connected with the earth1 and the other 
wire be attached to a delicate          
electrometer1 it will be found that the 
latter gives evidence of electrical     
excitement in the same manner as it does

 for the electricity developed by       
friction in another body4 ,this is      
sometimes called tension1 and is very   
slight for a single cell2 but in a      
series of cells it becomes noticeable in
 other ways4 ,thus when the terminals of
 a single cell are taken in the hands1  
no effect is perceived3 if1 however1 the
 terminals of a battery consisting of   
forty or fifty cells be thus taken1 a   
decided shock is felt1 not to be        
compared though with the shock that     
would be felt from the discharge of a   
very small ,leyden jar4 ,the shock from 
several hundred cells would be very     
dangerous4  ,it was formerly doubted    
that the electricity would pass between 
the terminals of a battery without      
actual contact of the terminals4        
,gassiot first showed that the spark    
would jump between the wires of a       
battery of a large number of cells      
before actual contact was made4         
,latterly ,mr4 ,de ,la ,rue has been    
measuring the distance across which the 

spark would jump1 using a battery of a  
large number of cells4  ,i give his     
table as taken from the ,proceedings of 
the ,royal ,society3--                  
,cells4   ,striking distance4           
#fjj     4#jjcc inch4            #a1bjj 
4#jacj               #a1hjj     4#jcde  
#b1djj     4#jece     ,this table shows 
that the striking distance is very      
nearly as the square of the number of   
cells4 ,thus1 with #fjj cells the spark 
jumped 4#jjcc inch2 and with double the 
number of cells1 #a1bjj1 the spark      
jumped 4#jacj inch1 or within 4#jjjb of 
an inch as far as four times the first  
distance4  ,this leads one to ask how   
big a battery would be needed to give a 
spark of any given length1 say like a   
flash of lightning4 ,one cell would give
 a spark 4#jjjjjjja inch long1 and a    
hundred thousand would give a spark #ib 
inches long4 ,a million cells would give
 a spark #gfd feet long1 a veritable    
flash of lightning4 ,it is hardly       
probable that so many as a million cells

 will ever be made into one connected   
battery1 but it is not improbable that a
 hundred thousand cells may be4 ,de ,la 
,rue has since completed #h1jdj cells1  
and finds that the striking distance of 
that number is #j4cde inch1 a little    
more than one-third of an inch4 ,he also
 states that the striking distance      
increases faster than the above         
indicated ratio1 as determined by       
experimenting with a still larger number
 of cells4  ,these experiments and many 
others show that there is no essential  
difference between the so-called static 
and dynamic electricity4 ,in the one    
case it is developed upon a surface     
which has such a molecular character    
that it cannot be conducted away1 every 
surface molecule being practically a    
little battery cell with one terminal   
free in the air1 so that when a proper  
conductor approaches the surface it     
receives the electricity from millions  
of cells1 and therefore becomes strongly
 electrified so that a spark may at once

 be drawn from it4     ,,what ,,is      
,,electricity8   ,,theories4  ,,numerous
 attempts have been made to explain the 
phenomena of electricity4 ,as a general 
thing1 these phenomena are so utterly   
unlike other phenomena that have been   
explained and are easily intelligible1  
that it has quite generally been taken  
for granted1 until lately1 that         
something very different from ordinary  
matter and the laws of forces applicable
 to it must be involved in the phenomena
 themselves4 ,consequently the term     
imponderable was applied to             
it1--something that was matter minus    
some of the essentials of matter2 and as
 it was apparent that1 whatever it was1 
it moved1 apparently flowed1 from one   
place to another1 the term fluid was    
applied to it1 a term descriptive of a  
certain form of matter4 ,imponderable   
fluid was the descriptive name applied  
to electricity4 ,newton supposed that an
 excited body emitted such a fluid that 
could penetrate glass4 ,when the two    

facts of electrical attraction and      
repulsion had to be accounted for1 two  
theories were propounded1--one by       
,benjamin ,franklin1 the other by       
,dufay4 ,franklin supposed that         
electricity was a subtle1 imponderable  
fluid1 of which all bodies contained a  
certain normal quantity4 ,by friction or
 otherwise this normal quantity was     
disturbed4 ,if a body received more than
 its due share1 it was said to be       
positively electrified3 if it had less  
than its normal quantity1 it was said to
 be negatively electrified4 ,franklin   
supposed this electric fluid to be      
highly self-repulsive1 and that it      
powerfully attracted the particles of   
matter4  ,according to ,dufay1 there are
 two electric fluids1 opposite in       
tendency but equal in amount4 ,when     
associated together in equal quantities1
 they neutralize each other completely4 
,a portion of this neutral compound     
fluid pervades all matter in its        
unexcited state4 ,by friction or        

otherwise this compound fluid is        
decomposed1 the rubber and the body     
rubbed exchanging equal quantities of   
opposite kinds with each other1 leaving 
one of them positively1 the other       
negatively electrified4 ,these two      
fluids were supposed to be              
self-repulsive1 but to attract each     
other3 so that1 if two bodies be charged
 with either positive or negative       
electricity1 such bodies would mutually 
repel each other2 but if one was charged
 with positive1 while the other was     
charged with negative electricity1 the  
two bodies would mutually attract each  
other4  ,either of these two theories   
may be used to illustrate the phenomena1
 and so have done good service in       
systematizing the facts4 ,it is evident 
that both of them cannot be true1 and it
 is in the highest degree probable that 
neither of them is true4  ,some have    
supposed that there was a kind of       
electric atmosphere about every atom of 
matter2 and still another theory1 now   

advocated by ,edlund of ,stockholm1     
assumes that electricity is identical   
with the ether by which radiant energy1 
light and heat1 is transmitted4  ,before
 a correct judgment can be formed of the
 nature of any force1 it is necessary to
 know what it can do1 what kind of      
phenomena it can produce4 ,let us1 then1
 take a brief survey of what electricity
 can do4  #ast1 ,it can directly produce
 motion1 through the attractions and    
repulsions of electrified bodies1--as   
indicated by electrometers1 the rotation
 of the fly-wheel1 the deflection of the
 galvanometer needle4 ,it has been      
proved by the mathematical labors of    
,clausius1 and confirmed by experiment1 
that1 when electricity performs any     
mechanical work1 so much electricity is 
lost1 annihilated as electricity4  #b;d1
 ,it can directly produce heat1 as shown
 by passing a sufficient quantity of    
electricity through a fine platinum     
wire3 the wire becomes heated1 and      
glows1 and it may even be fused by the  

intensity of the heat4 ,the heat        
developed in the so-called electric arc 
is so great as to fuse the most         
refractory substances4 ,if a current of 
electricity from a battery be sent      
through a thermo-pile1 one of the faces 
of the pile will be heated4 ,the heat of
 the spark from a ,leyden jar may be    
made to ignite gunpowder1 and dissipate 
gold into vapor4 ,the heat produced by  
lightning is seen when a live tree is   
struck by a powerful flash3 the sap of  
the tree is instantly converted into    
steam of so high a tension as to explode
 the tree1 scattering it in small       
fragments over a wide area4 ,the tips of
 lightning-rods often exhibit this      
heating effect1 being fused by the      
passage of too great a quantity of      
electricity4  ,in the early part of the 
present century it was demonstrated by  
,count ,rumford1 and also by ,sir       
,humphry ,davy1 that heat was but a form
 of molecular motion4 ,since then the   
exact relations between the motion of a 

mass of matter and the equivalent heat  
have been experimentally determined by  
,joule1 so that the unit of heat may be 
expressed in the motion of a mass of    
matter4 ,this is deducible from a more  
general law1 known as the conservation  
of energy4 ,the application in this     
place is1 that whenever heat appears    
through electric action1 as in the      
above-mentioned places1 we know that it 
still is only motion that is the        
product1 only that this motion is now   
among the molecules of the body1 instead
 of the motion of the whole body in     
space1 as when a pith-ball moves1 or a  
galvanometer-needle turns4  #c;d1 ,it   
can directly produce light4 ,this is    
seen in every spark from an electric    
machine1 in the flash of lightning1 and 
in the electric light4  ,it has been    
shown in numberless ways1 that there is 
no essential difference between light   
and heat1 and that what we call light is
 only the active relation which certain 
rays of radiant energy have to the eyes4

 ,in order to make this plain1 suppose  
that a beam of light1 say from the sun1 
be permitted to fall upon a triangular  
prism of glass3 at once it is seen that 
the beam is deflected1 and instead of   
appearing a spot of white light1 as it  
did before it was deflected1 it now     
appears as a brilliant band of colors1  
which is called the solar spectrum4 ,if 
now this spectrum be examined as to the 
distribution of heat1 by moving a       
thermo-pile through it from the blue end
 towards the red end1 it will be noticed
 that the galvanometer-needle will be   
but slightly deflected at the blue end2 
but1 as the thermo-pile is moved1 the   
deflections are greater until it is past
 the red end1 where the heat is         
greatest4 ,on this account it has been  
customary to say that the red end of the
 spectrum was the heating end4 ,with    
various pieces of mechanism the rays may
 be separated from each other1 and      
measured2 and then it appears that a red
 ray of light has a wave length of about

 #a_/cgjjj in41 and the violet ray about
 #a_/fjjjj in4 ,the rays beyond the red 
have also been measured1 and found to be
 greater in length uniformly as one     
recedes from the visible part of the    
spectrum4  ,in like manner1 beyond the  
blue end the wave lengths become shorter
 and shorter2 and in each of these      
directions the spectrum that is         
invisible is much longer than the       
visible one4 ,now1 it has also been     
found that where a prism of glass or    
other material is used to produce a     
spectrum1 it distributes the rays very  
unevenly2 that is1 towards the red end  
of the spectrum they are very much      
crowded1 while towards the blue end they
 are more dispersed4 ,hence1 if one were
 measuring the heating power of such a  
spectrum1 many more rays would fall upon
 an equal surface of the thermo-pile at 
the red end than at the blue end2       
therefore the indications of the        
galvanometer would be fallacious4       
,before any thing definite could be     

known about the matter1 it would plainly
 be necessary to work with an equal     
dispersion of all the rays4 ,this was   
effected a few years ago by ,dr4 ,draper
 of ,new ,york4 ,he took the spectrum   
produced by diffraction instead of      
refraction1 and measured that4 ,in that 
way it was found that the heating power 
of the spectrum is equal in every part  
of it2 and hence the pictures in        
treatises on physics that represent the 
heating power of the spectrum to be     
concentrated at the red end is not true 
save where the spectrum is irregularly  
produced4 ,as for vision1 the mechanical
 structure of the eye is such that      
radiant vibrations having a wave length 
between #a_/cgjjj in4 and #a_/fjjjj in4 
can affect it1 while longer or shorter  
wave lengths can not4 ,such waves we    
call light1 but it is not at all        
improbable that some animals and insects
 have eyes adapted to either longer or  
shorter wave-lengths2 in which case1    
what would be perfectly dark to us would

 be light to them4 ,it is a familiar    
enough fact1 that many animals1 such as 
dogs1 cats1 rats1 and mice1 can see in  
the night4 ,some horses may be trusted  
to keep in the road in a dark night1    
when the driver cannot see even the     
horse itself4 ,this has usually been    
accounted for by saying that their eyes 
are constructed so as to collect a      
greater number of luminous rays4 ,it is 
much better explained by supposing their
 eyes to be constructed to respond to   
wave-lengths either greater or less than
 those of mankind4  ,a ray of light1    
then1 consists of a single line of      
undulations of a definite wave length1  
such that if it falls upon the eye it   
will produce sight2 if it falls upon a  
thermo-pile it heats it by just the same
 quantity that another wave-length would
 heat it2 if it falls upon matter in    
unstable chemical relations1 it will do 
chemical work1 depending upon the kinds 
of matter4 ,a red ray is as effective   
for some substances as a violet ray is  

for others4 ,the statement1 then1 so    
often lately made to do certain         
analogical work1 namely1 that a ray of  
light consists of three distinct parts1 
which may be separated from each other1 
and are called heat1 light1 and chemical
 properties1 is simply untrue4 ,what a  
ray will do1 depends upon what kind of a
 structure it falls on2 and when it has 
done that work1 of whatever kind it may 
be1 it ceases to exist as a ray4  ,if1  
therefore1 electricity can directly     
produce light1 it is simply producing   
motion1 as in the case of heat1 the     
motion being of such a sort that the    
eyes of men are affected by it4  #dth1  
,it can produce magnetism4 ,a current of
 electricity passing through a coil of  
wire makes such a coil a magnet1 which  
will set itself in the direction of the 
magnetic meridian of the earth2 and1 if 
a bar of soft iron be placed in the     
coil1 it becomes the familiar           
electro-magnet2 and1 if hardened steel  
be put in it1 it becomes a permanent    

magnet4  ,this leads to the inquiry as  
to what magnetism is4 ,we know that it  
can produce motion by its moving at a   
distance a piece of iron or another     
magnet4 ,it will also sustain a mass of 
matter against gravity or some other    
contrary force4 ,through such mechanism 
as magneto-electric machines it produces
 electricity in great abundance1 which  
again can be used to produce any of the 
effects of electricity1--moving bodies  
by attraction or repulsion1 generating  
heat or light1 or again making a magnet4
 ,but as all of these are but varied    
forms of motion1 either of a mass as a  
whole1 or molecular1 can it be doubted  
for an instant1 that what we call       
magnetism is but some form of motion8   
,must it not be either some form of     
matter1 or some form of motion8 ,if it  
were a form of matter1 then a magnet    
would only be permanent so long as it   
was not used2 for use implies           
consumption of the force2 and1 if this  
be matter in any form1 then in a given  

mass of matter there can be but a       
definite quantity of such magnetic      
matter1 and consumption must lessen that
 quantity4 ,as a matter of fact1 there  
is no perceptible lessening of the power
 of a magnet when it is properly used4  
,it is also a matter of fact1 that      
neither motion of a mass1 nor electrical
 effects1 nor any other1 can be produced
 by the action of a magnet alone4 ,it is
 only when some form of motion has been 
added to its own property1 that we get  
any kind of an effect from it3 hence all
 effects due to its action are          
resultants of two forces1 one of them   
being common motion of a mass of matter1
 and the other the energy of the magnet4
 ,hence we infer that a magnet is a     
mechanism of such a structure as to     
change the direction and character of   
the motion which acts upon it4 ,when the
 wheel of a common electrical machine is
 turned1 the product is electricity1--a 
force very different from that which    
originates it4 ,ordinary mechanical     

motion goes in2 electricity comes out1  
the latter being a modified motion due  
to the physical structure of the        
machine4 ,in like manner1 a magnet may  
be considered as a machine by means of  
which mechanical motion may be converted
 into some other form of motion4 ,it is 
evident that molecular structure is     
chiefly concerned in this4 ,if a bar of 
iron that exhibits no evidence of       
magnetism whatever be subjected to      
torsion1 it will immediately become a   
magnet with poles dependent upon the    
direction of the twist4 ,this developed 
magnetism will re-act upon a coil of    
wire1 and so move a galvanometer needle4
 ,if the bar be permitted to recover its
 original condition1 it will lose its   
magnetism1 which will at once re-appear 
upon twisting the rod again4 ,now1 when 
the rod is twisted1 it is evident that  
there is a molecular strain in certain  
directions throughout the mass4 ,the    
converse experiment illustrates the same
 thing4 ,it has been found1 that when a 

rod of iron is made magnetic by the     
action of a current of electricity      
circulating about it1 and at the same   
time passing longitudinally through it1 
the rod is slightly lengthened and      
twisted in a direction that depends upon
 the direction of the current4          
,moreover1 if a permanent magnet be     
heated to a red heat1 its magnetism is  
destroyed2 for such a heat allows the   
molecules to freely arrange themselves  
without any external constraint4 ,also1 
if a permanent magnet be suspended so as
 to give out a musical sound when it is 
struck1 the magnetism will be much      
weakened by making it thus to vibrate4  
,in this case1 as in the other1 the     
vibrations affect every molecule1 and so
 enable them to re-adjust themselves to 
the positions they held before being    
magnetized4 ,the same thing happens when
 a bar of iron is made magnetic through 
the inductive action of the earth4 ,when
 this bar is held in the direction of   
the magnetic dip1 it becomes but very   

slightly magnetized2 but1 if it be so   
held that when it is struck with a      
hammer it will ring1 that is1 give out a
 musical sound1 it will at once become  
decidedly magnetic4 ,evidently the      
earth's action tends to set the         
molecules of the mass in a new position1
 but cohesion prevents them from        
assuming it4 ,when the molecules are    
made to vibrate1 they can assume such   
new positions more readily4 ,the        
molecules of a magnet1 then1 are        
differently arranged from those in an   
unmagnetized piece of iron or steel2    
and1 for every new arrangement of the   
molecules of a mass of any kind1 we     
always have some new physical property  
developed4 ,the same identical substance
 may appear as charcoal1 coke1 plumbago1
 anthracite coal1 and diamond4 ,hence a 
magnet is a machine in which other      
forces acting upon it are transformed in
 character1 and re-appear as attractions
 and repulsions of other kinds of       
matter3 this transformation cannot take 

place1 and hence magnetism cannot become
 apparent1 only upon the condition of   
another force acting in concert with it2
 and1 if at any time it may seem to be  
acting without such external force1 it  
is done at the expense of the heat it   
has absorbed1 and therefore the magnet  
must at such time be losing temperature 
proportional to the work done4 ,this ,i 
have discovered to be true by making a  
magnet to exert its force in front of a 
thermo-pile1 which uniformly exhibits a 
cooled face under such conditions4 ,what
 the particular form of the motion may  
be that we call magnetism1 is not yet   
made out2 but that it is some form of   
motion1 is very evident4 ,the following 
experiments may throw some light upon   
it4 ,last ,august ,mr4 ,kerr read a     
paper before the ,british ,association  
of ,science1 in which was detailed the  
following experiment3 ,the pole of an   
electro-magnet was nicely polished so as
 to reflect light like a mirror4 ,a beam
 of sunlight was permitted to fall upon 

it1 and be reflected to a convenient    
place for examination4 ,a current of    
electricity was sent through the coil1  
which of course rendered the iron       
magnetic2 and it was noticed that the   
light that was reflected from the pole  
was circularly polarized3 that is1 the  
motion of a ray1 instead of being a     
simple undulatory movement1 was now made
 to assume such a motion as the water   
from a garden-hose has when the nozzle  
is swung round in a circle while the    
water is escaping from it4 ,after       
reading the account of it1 it occurred  
to me that the converse experiment might
 be tried2 that is to say1 the effect of
 a circularly polarized beam of light   
upon a piece of steel4 ,by concentrating
 a large beam of ordinary plane         
polarized light with a quartz lens1 and 
passing it through a quarter wave-plate 
at the proper angle1 a powerful beam of 
circularly polarized light was obtained4
 ,at the focus of this beam a fine      
cambric needle without magnetism was    

placed so that the light passed it      
longitudinally4 ,ten minutes' exposure  
was sufficient to make it decidedly     
magnetic4 ,hence ,i infer that the      
motions which we call magnetic          
attractions and repulsions may be quite 
analogous to such helical motions2 also1
 that these motions exist in ether1 and 
evidently may be either right-handed or 
left-handed4 ,wind up on a pencil a     
piece of wire twelve or fifteen inches  
long1 making a loose spiral4 ,bring the 
two ends of the spiral together2 and    
note first that one is twisted to the   
right1 the other to the left4 ,if they  
be twisted into each other1 they will   
advance very easily2 but if a           
right-handed spiral were to be          
interlocked with another like it1 and   
both turned in the direction of their   
spiral1 they would separate rapidly4    
,applying this conception to a magnet1  
we might suppose that such spiral       
motions will be set up in the ether by  
the magnet1 and that such motions       

re-acting upon ordinary matter affect it
 as attraction and repulsion2 and thus  
we should have at least a conceivable   
mechanical explanation of the           
phenomenon4  ,illustration3 ,,fig4 #e4  
,there are numberless experiments which 
might be given to further exhibit the   
relation of mass motion to magnetism1   
but a single one more must suffice4 ,no 
rotation of a magnet upon its own axis  
can produce any effects upon a current  
that is exterior to it2 but if a loop of
 wire be kept stationary adjacent to a  
magnet1 as in ,fig4 #e1 while the magnet
 revolves1 a current of electricity is  
produced2 and if the magnet be kept     
stationary1 and the loop revolves1 a    
current will also be produced1 but in   
the opposite direction4 ,here1 as in all
 the other cases1 no electricity is     
originated1 save when motion is imparted
 to one or other of the parts4 ,this    
experiment is due to ,faraday4  ,from   
all these cases we can come to but one  
conclusion1 that both electricity and   

magnetism are but forms of motion2      
electricity being a form of motion in   
ordinary matter1 for it cannot be made  
to pass through a vacuum1 while         
magnetism must be a form of motion      
induced in the ether1 for it is as      
effective in a vacuum as out of it2     
electricity always needing some material
 conductor1 magnetism needing no more   
than do radiant heat and light4         
,,velocity4  ,measurements have been    
made of the velocity of electricity2    
both that of high tension1 such as the  
spark from a ,leyden jar1 and also that 
from a battery4 ,the former was found to
 have a velocity over #bjj1jjj miles a  
second1 while the electricity from a    
battery may move as slowly as #ae1jjj or
 #bj1jjj miles a second2 but this is    
very largely a matter of conductors4    
,its velocity is seldom above #cj1jjj   
miles a second on ordinary telegraphic  
lines4 ,if the electricity be used to   
give signals1 as in ordinary telegraphy1
 the time required varies nearly as the 

length of the line1 and in any case is a
 much greater quantity4 ,prescott in his
 work on the telegraph states that the  
time required to produce a signal on the
 electro-magnet at the extremity of a   
line of #cjj miles of ,no4 #h iron wire 
is about 4#ja seconds1 and that this    
time increases in a greater proportion  
than the length of the line2 for        
example1 on a line #fjj miles in length 
it amounts to about 4#jc seconds4 ,he   
also states that it varies much with the
 kind of magnet used1 some forms of     
magnets being much more sensitive than  
others for this work4  ,wheatstone      
proved a good many years ago that the   
duration of the electric spark was less 
than one millionth of a second4 ,when a 
swiftly moving body can only be seen by 
an electric spark1 or flash of          
lightning1 it looks as if it were       
quiescent4 ,thus a train of cars rushing
 along at the rate of forty or fifty    
miles per hour appears sharply          
defined1--even the driving-wheels of the

 locomotive can be seen in detail1 which
 is impossible in continuous light1--and
 all seems to be standing still4 ,in    
like manner will the sails of a         
windmill1 which may be turning at a     
rapid rate1 be seen apparently at rest4 
,this is because in the short time      
during which they are illuminated they  
do not appreciably move4  ,i am not     
aware that any attempt has been made to 
measure the velocity of magnetism4 ,if1 
however1 it be a form of motion in      
ether1 it is probable that the velocity 
is comparable to the velocity of radiant
 energy1 light1 which is equal to about 
#ahf1jjj miles a second4     ,,sound4   
,,before explaining the relation that   
sound has to telephony1 it will be      
necessary to make quite plain what sound
 is1 and how it affects the substance of
 the body through which it moves4 ,if ,i
 strike my pencil upon the table1 ,i    
hear a snap that appears to the ear to  
be simultaneous with the stroke3 if1    
however1 ,i see a man upon a somewhat   

distant hill strike a tree with an axe1 
the sound does not reach me until some  
appreciable time has passed2 and it is  
noted1 that1 the farther away the place 
where a so-called sound originates1 the 
longer time does it take to reach any   
listener4 ,hence sound has in air a     
certain velocity which has been very    
accurately measured1 and found to be    
#a1jic feet per second when the         
temperature of the air is at the        
freezing point of water4 ,as the        
temperature increases1 the velocity of  
sound will increase a little more than  
one foot for every ,fahrenheit degree2  
so that at #fj deg4 the velocity is     
#a1abe feet per second4 ,this is the    
velocity in air4 ,in water the velocity 
is about four times greater1 in steel   
sixteen times1 in pine-wood about ten   
times4   ,,constitution ,,of ,a ,,single
 ,,sound-,,wave4  ,if a person stands at
 the distance of fifteen or twenty rods 
from a cannon that is fired1 he will    
first see the flash1 then the cloud of  

smoke that rushes from the cannon's     
mouth1 then the ground will be felt to  
tremble1 and lastly the sound will reach
 his ear at the same time that a strong 
puff of air will be felt4 ,this puff of 
air is the sound-wave itself1 travelling
 at the rate of eleven hundred feet or  
more per second4 ,at the instant of     
explosion of the gunpowder1 the air in  
front of the cannon is very much        
compressed2 and this compression at once
 begins to move outwards in every       
direction1 so as to be a kind of a      
spherical shell of air constantly       
increasing in diameter2 and1 whenever it
 reaches an ear1 the sound is perceived4
 ,whenever such a sound-wave strikes    
upon a solid surface1 as upon a cliff or
 a building1 it is turned back1 and the 
reflected wave may be heard2 in which   
case we call it an echo4 ,when a cannon 
is fired1 we generally hear the sound   
repeated1 so that it apparently lasts   
for a second or more2 but when1 as in   
the first case1 we hear the sound of a  

pencil struck upon the table1 but a     
single short report is noticed1 and     
this1 as may be supposed1 consists of a 
single wave of condensed air4           
,illustration3 ,,fig4 #f4               
,illustration3 ,,fig4 #g4  ,imagine a   
tuning-fork that is made to vibrate4    
,each of the prongs beats the air in    
opposite directions at the same time4   
,look at the physical condition of the  
air in front of one of these prongs4 ,as
 the latter strikes outwards1 the air in
 front of it will be driven outwards1   
condensed2 and1 on account of the       
elasticity of the air1 the condensation 
will at once start to travel outwards in
 every direction1--a wave of denser air2
 but directly the prong recedes1 beating
 the air back in the contrary direction1
 which will obviously rarefy the air on 
the first side4 ,but the disturbance we 
call rarefaction moves in air with the  
same velocity as a condensation4 ,we    
must therefore remember1 that just      
behind the wave of condensation is the  

wave of rarefaction1 both travelling    
with the same velocity1 and therefore   
always maintaining the same relative    
position to each other4 ,now1 the fork  
vibrates a great many times in a second1
 and will consequently generate as many 
of these waves1 all of them constituted 
alike1 and having the same length2 by   
length meaning the sum of the           
thicknesses of the condensation and the 
rarefaction4 ,suppose a fork to make one
 hundred vibrations per second3 at the  
end of the second1 the wave generated by
 the vibration at the beginning of the  
second would have travelled1 say1 eleven
 hundred feet2 and evenly distributed   
between the fork and the outer limit1   
would be ranged the intermediate waves  
occupying the whole distance3 that is to
 say1 in eleven hundred feet there would
 be one hundred sound-waves1 each of    
them evidently being eleven feet long4  
,if the fork made eleven hundred        
vibrations per second1 each of these    
waves would be one foot long2 for       

sound-waves of all lengths travel in air
 with the same rapidity4 ,some late     
experiments seem to show that the actual
 amplitude of motion of the air1 when   
moved by such a high sound as that from 
a small whistle1 is less than the       
millionth of an inch4   ,,pitch4  ,the  
pitch of a sound depends wholly upon the
 number of vibrations per second that   
produce it2 and if one of two sounds    
consists of twice as many vibrations per
 second as the other one1 they differ in
 pitch by the interval called in music  
an octave1 this latter term merely      
signifying the number of intervals into 
which the larger interval is divided for
 the ordinary musical scale4 ,the       
difference between a high and a low     
sound is simply in the number of        
vibrations of the air reaching the ear  
in a given time4 ,the smaller intervals 
into which the octave is divided stand  
in mathematical relations to each other 
when they are properly produced1 and are
 represented by the following           

fractions3--        ,c     ,d     ,e    
,f     ,g     ,a     ,b     ,c       #a 
#i_/h   #e_/d   #d_/c   #c_/b   #e_/c   
#ae_/h   #b  ,illustration  ,these      
numbers are to be interpreted thus3     
,suppose that we have a tuning-fork     
giving #bef vibrations per second3 the  
sound will be that of the standard or   
concert pitch for the ,c on the added   
line as shown on the staff4 ,now1 ,d    
when properly tuned will make #i        
vibrations while ,c makes but #h2 but1  
as ,c in this case makes #bef1 ,d must  
make #befx#i_/hbhh4 ,in like manner ,g  
is produced by #befx#c_/bchd1 and ,c    
above by #befx#beab1 and so on for any  
of the others4 ,if other sounds are used
 in the octave above or below this one1 
the number of vibrations of any given   
note may be found by either doubling or 
halving the number for the corresponding
 note in the given octave4 ,thus ,g     
below will consist of #chd_/baib1 and ,g
 above of #chdx#bgfh4  ,during the past 
century there has been a quite steady   

rise in the standard pitch1 and this has
 been brought about in a very curious   
and unsuspected way4 ,the tuning-fork   
has been the instrument to preserve the 
pitch1 as it is the best available      
instrument for such a purpose1 it being 
convenient to use1 and does not vary as 
most other musical instruments do4 ,but 
a tuning-fork is brought to its pitch   
with a file1 which warms it somewhat1 so
 that at the moment when it is in tune  
with the standard that is being         
duplicated it is above its normal       
temperature2 and when it cools its tone 
rises4 ,when another is made of like    
pitch with this one1 the same thing is  
repeated2 and so it has continued until 
the standard pitch has risen nearly a   
tone higher than it was in ,haendel's   
time4  ,the common ,a and ,c            
tuning-forks to be had in music stores1 
often vary a great deal from the        
accepted concert pitch4 ,such as the    
writer has measured have been generally 
too high2 sometimes being ten or more   

vibrations per second beyond the proper 
number4 ,the tuning-forks made by ,m4   
,koeenig of ,paris are accurate within  
the tenth of one vibration1 the ,c      
making #bef vibrations in one second4   
,,limits ,,of ,,audibility4  ,numerous  
experiments have been made to determine 
the limits of audible sounds2 and here  
it is found that there is a very great  
difference in individuals in their      
ability to perceive sounds4 ,helmholtz  
states that about #bc vibrations per    
second is the fewest in number that can 
be heard as continuous sound2 if they   
are fewer in number than that1 the      
vibrations are heard as separate        
distinct noises1 as when one knocks upon
 a door four or five times a second4 ,if
 one could knock evenly #bc times per   
second1 he would be making a continuous 
musical sound of a very low pitch4 ,but 
this limit of #bc is not the limit for  
all3 some can hear a continuous sound   
with as few as #af or #ah vibrations per
 second1 while others are as far above  

the medium as this is below it4 ,the    
limits of sound in musical instruments  
are about all included in the range of a
 #g-octave pianoforte from ,f to ,f1 say
 from #db to #e1dfj vibrations per      
second4 ,but this high number is not    
anywhere near the upper limit of audible
 sounds for man4  ,very many of the     
familiar sounds of insects1 such as     
crickets and mosquitoes1 have a much    
higher pitch4 ,helmholtz puts this upper
 limit at #ch1jjj vibrations per second1
 and ,despraetz at #cf1hej4 ,the        
discrepancy of results is due solely to 
the marked difference in individuals as 
to acoustic perception4  ,for the       
production of high musical tones1       
,koeenig of ,paris makes a set of steel 
rods4 ,a steel rod of a certain length1 
diameter1 and temper1 will give a       
musical sound which may be determined4  
,the proper length for other rods for   
giving higher tones may be determined by
 the rule that the number of vibrations 
is inversely proportional to the square 

of the length of the rod4  ,the         
dimensions of these rods when made #b c4
 m4 in diameter are as follows3--       
,length4       ,vibrations4             
#ff4b m4 m4      #bj1jjj                
#ei4a          #be1jjj            #ec4h 
#cj1jjj            #ej4a                
#ce1jjj            #dg4e                
#dj1jjj  ,these rods need to be         
suspended upon loops of silk1 and they  
are struck with a piece of steel so     
short as to be wholly beyond the ability
 of any ear to hear its ring4 ,nothing  
but a short thud is to be heard from it 
when it strikes1 while from the others  
comes a distinct ringing sound4 ,in     
experimenting with such a set of steel  
rods ,i have not found any one yet who  
could hear as many as #be1jjj per       
second1 my own limit being about        
#ba1jjj4 ,but it has been experimentally
 found that children and youth have a   
perceptive power for high sounds        
considerably above adults4 ,dr4         
,clarence ,blake of ,boston reports a   

case in his aural practice1 of a woman  
whose hearing had been gradually        
diminishing for some years until she    
could not hear at all with one ear1 and 
the ticking of a watch could only be    
heard with the other when the watch was 
held against the ear4 ,after treatment  
it was discovered that the sensibility  
to high sounds was very great1 and that 
she could hear the steel rod having a   
tone of #dj1jjj vibrations4  ,last year 
,mr4 ,f4 ,galton1 ,f4,r4,s41 exhibited  
before the ,science ,conference an      
instrument in the shape of a very small 
whistle1 which he had devised for       
producing a very high sound4 ,the       
whistle had a diameter less than the one
 twenty-fifth of an inch4 ,the length   
could be varied by moving a plug at the 
end of the whistle4 ,it was easy to make
 a sound upon such an instrument that   
was altogether out of hearing-range of  
any person4 ,mr4 ,galton tried some very
 interesting experiments upon animals1  
by using these whistles4 ,he went       

through the ,zooelogical ,gardens1 and  
produced such high sounds near the ears 
of all the animals4 ,some of them would 
prick up their ears1 showing that they  
heard the sound2 while others apparently
 could not hear it4 ,he declares that   
among all the animals the cat was found 
to hear the sharpest sound4 ,small dogs 
can also hear very shrill notes1 while  
larger ones can not4 ,cattle were found 
to hear higher sounds than horses4 ,the 
squeak of bats and of mice cannot be    
heard by many persons who can hear      
ordinary sounds as well as any2         
sharpness of hearing having nothing to  
do with the limits of hearing4          
,,effects ,,of ,,sound ,,upon ,,other   
,,bodies4  ,if a vibrating tuning-fork  
be held close to a delicately suspended 
body1 the latter will approach the fork1
 as if impelled by some attractive      
force4 ,the experiment can be made by   
fastening a bit of paper about an inch  
square to a straw five or six inches    
long1 and then suspending the straw to a

 thread1 so that it is balanced         
horizontally4 ,bring the vibrating      
tuning-fork within a quarter of an inch 
of the paper4 ,in this case the motion  
of approach is due to the fact that the 
pressure of the air is less close to a  
vibrating body than at a distance from  
it2 there is therefore a slightly       
greater pressure on the side of the     
paper away from the fork than on the    
side next to it4  ,if a vibrating       
tuning-fork be held near to the ear1 and
 turned around1 there may be found four 
places in one rotation where the sound  
will be heard but very faintly1 while in
 every other position it can be heard   
plainly enough4 ,the extinction of the  
sound is due to what is called          
interference4 ,each of the prongs of the
 fork is giving out a sound-wave at the 
same time1 but in opposite directions1  
each wave advancing outwards in every   
direction4 ,where the rarefied part of  
one wave exactly balances the condensed 
part of the other1 there of course the  

sound will be extinguished2 and these   
lines of interference are found to be   
hyperbolas1 or1 if considered with      
reference to both entire waves1 two     
hyperbolic surfaces4   ,,sympathetic    
,,vibrations4  ,when it is once         
understood that a musical sound is      
caused by the vibrations more or less   
frequent which only make the difference 
we call pitch1 it might at once be      
inferred1 that if we have a body that is
 capable of vibrating say a hundred     
times a second1 and it receives a       
hundred pulses or pushes a second1 it   
would in this way be made to vibrate4   
,suppose1 then1 that we take two        
tuning-forks1 each capable of vibrating 
#bef times a second3 if one be struck   
while the other is left free1 the former
 one will be giving to the air #bef     
impulses per second1 which will reach   
the other fork1 each pulse tending to   
move it a little1 the cumulative result 
being to make it move perceptibly1 that 
is1 to give out a sound4 ,the principle 

is just the same as that employed in the
 common swing4 ,one push makes the swing
 to move a little1 upon its return      
another is given1 in like manner a      
third1 and so on until a person may be  
swung many feet high4 ,if a glass       
tumbler be struck1 it gives out a       
musical sound of a certain pitch1 which 
will set a piano-string sounding that is
 tuned to the same pitch1 provided that 
the damper be raised4 ,it is said that  
some persons' voices have broken        
tumblers by singing powerfully near them
 the same note which the tumblers could 
give out1 the vibrations of the tumblers
 being so great as to overcome cohesion 
of the molecules4  ,there are very many 
interesting effects due to sympathetic  
vibrations4  ,large trees are sometimes 
uprooted by wind that comes in gusts    
timed to the rate of vibration of the   
tree4 ,when troops of soldiers are to   
cross a bridge1 the music ceases1 and   
the ranks are broken1 lest the          
accumulated strain of timed vibrations  

should break the structure2 indeed1 such
 accidents have several times occurred4 
,there is not so much danger to a bridge
 when it is heavily loaded with men or  
with cattle1 as when a few men go       
marching over it4 ,when the iron bridge 
at ,colebrooke ,dale was building1 a    
fiddler came along1 and said to the     
workmen that he could fiddle their      
bridge down4 ,the builders thought this 
boast a fiddle-de-dee1 and invited the  
musician to fiddle away to his heart's  
content4 ,one note after another was    
struck upon the strings1 until one was  
found with which the bridge was in      
sympathy4 ,when the bridge began to     
shake violently1 the workmen were       
alarmed at the unexpected result1 and   
ordered the fiddler to stop4  ,some     
halls and churches are wretchedly       
adapted to hear either speaking or      
singing in4 ,if wires be stretched      
across such halls1 between the speaker's
 stand and the opposite end1 they will  
absorb the passing sound-waves1 and will

 be made to sympathetically vibrate1    
thus preventing in a good degree the    
interfering echoes4 ,the wire should be 
rather fine piano-wire1 and it should be
 stretched so tightly as to give out a  
low musical sound when plucked with the 
fingers4 ,in a large hall there should  
be twenty or more such wires4           
,,resonance4  ,when a tuning-fork is    
struck1 and held out in the air1 the    
vibrations can be felt for a time by the
 fingers2 but the sound is hardly       
audible unless the fork be placed close 
to the ear4 ,let the stem of the fork   
rest upon the table1 a chair1 or any    
solid body of considerable size1 and the
 sound is so much increased in loudness 
as to be heard in every part of a large 
room4 ,the reason appears to be1 that in
 the first case the vibrations are so   
slight that the air is not much         
affected4 ,most of the force of the     
vibration is absorbed by the hand that  
holds it2 but when the stem rests upon a
 hard body of considerable extent1 the  

vibrations are given up to it1 and every
 part of its surface is giving off the  
vibrations to the air4 ,in other words1 
it is a much larger body that is now    
vibrating1 and consequently the air is  
receiving the amplified sound-waves4    
,if the stem of the fork had been made  
to rest upon a bit of rubber1 the sound 
would not only not have been re-enforced
 in such a way1 but the fork would very 
soon have been brought to rest2 for     
,india rubber absorbs sound vibrations1 
and converts them into heat vibrations1 
as is proved by placing such a          
combination upon the face of a          
thermo-pile4  ,if one will but put his  
hand upon a table or a chair-back in any
 room where a piano or an organ is being
 played1 or where voices are singing1   
especially in church1 he cannot fail to 
feel the sound2 and if he notices       
carefully he will perceive that some    
sounds make such table or seat to shake 
much more vigorously than others1--a    
genuine case of sympathetic vibrations4 

,it is for this reason that special     
materials and shapes are given to parts 
of musical instruments1 so that they may
 respond to the various vibrations of   
the strings or reeds4 ,for instance1 the
 piano has an extensive thin board of   
spruce underneath all the strings1 which
 is called the sounding-board4 ,this    
board takes up the vibrations of the    
strings2 but1 unlike the rubber1 gives  
them all out to the air1 greatly        
re-enforcing their strength1 and        
changing somewhat their quality4 ,but   
the air itself may act in like manner4  
,in almost any room or hall not more    
than fifteen or twenty feet long1 a     
person can find some tone of the voice  
that will seem to meet some response    
from the room4 ,some short tunnels will 
from certain positions yield very       
powerful1 responsive1 resonant tones4   
,there is certainly one such in ,central
 ,park1 ,new ,york4 ,it is forty or     
fifty feet long4 ,to a person standing  
in the middle of this1 and speaking or  

making any kind of a noise on a certain 
pitch1 the resonance is almost          
deafening4 ,it is easy to understand4   
,when a column of air enclosed in a tube
 is made to vibrate by any sound whose  
wave-length is twice the length of the  
tube1 we have such column of air now    
filled with the condensed part of the   
wave1 and now with the rarefied part2   
and as these motions cannot be conducted
 laterally1 but must move in the        
direction of the length of the tube1 the
 air has a very great amplitude of      
motion1 and the sound is very loud4 ,if 
one end of the tube be closed1 then the 
length must be but one-fourth of the    
wave-length of the sound4 ,take a       
tuning-fork of any convenient pitch1 say
 a ,c of #eab vibrations per second3    
hold it while vibrating over a vertical 
test-tube about eight inches long4 ,no  
response will be heard2 but1 if a little
 water be carefully poured into the tube
 to the depth of about two inches1 the  
tube will respond loudly1 so that it    

might be heard over a large hall4 ,in   
this case the length of the air-column  
that was responding1 being one-fourth   
the wave-length1 would give twenty-four 
inches as the wave-length of that fork4 
,it is easy in this way to measure      
approximately the number of vibrations  
made by a fork4        ,letting l  depth
 of tube1                d  diameter of 
tube1                v  velocity of     
sound reduced for temperature1          
,n  number of vibrations1               
,then ,n     v                          
------------                            
7#d7ld774  ,when a vibrating tuning-fork
 is placed opposite the embouchure of an
 organ-pipe of the same pitch1 the pipe 
will resound to it1 giving quite a      
volume of sound4 ,in #ahgb it occurred  
to me1 that the action of an organ-pipe 
might be quite like that of a vibrating 
reed in front of the embouchure4 ,as the
 air is driven past it from the bellows1
 the form of the escaping air will      
evidently be like a thin1 elastic strip2

 and1 having considerable velocity1 it  
will carry off by friction a little of  
the air in the tube3 this will of course
 rarefy the air in the tube somewhat1   
and a wave of condensation will travel  
down the tube4 ,at the bottom1 being    
suddenly stopped1 its re-action will be 
partly outwards1 and so will drive the  
strip of air away from the tube4 ,after 
this will follow1 for a like reason1 the
 other phase of the wave1 the           
rarefaction1 which will swing the strip 
of air towards the tube4 ,this theory ,i
 verified by filling the bellows with   
smoke1 and watching the motion of the   
escaping air and smoke with a           
stroboscope4 ,this view is now advocated
 by an organ-builder in ,england1       
,herman ,smith2 but whether he          
discovered it before or after me1 ,i do 
not know4  ,when a membrane vibrates1   
its motion is generally perceptible to  
the eye2 and it may have a very great   
amplitude of motion1 as in the case of  
the drum2 and various instruments have  

been devised for the study of           
vibrations1 using membranes like rubber1
 gold-beater's skin1 or even tissue     
paper1 to receive the vibrations4 ,one  
of the musical instruments of a former  
generation of boys was the comb4 ,a     
strip of paper was placed in front of   
it1 and placed at the mouth1 and sung   
through1 the paper responding to the    
pitch with a loose nasal sound4 ,koeenig
 fixed a membrane across a small        
capsule1 one side of which was connected
 by a tube to any source of sound1 and  
the other side to a gas-pipe and a small
 burner4 ,a sound made in the tube would
 shake the flame1 and a mirror moving in
 front of the flame would show a zigzag 
outline corresponding to the sound      
vibrations4  ,in like manner if a thin  
rubber be stretched over the end of a   
tube one or two inches in diameter and  
four or five inches long1 and a bit of  
looking-glass one-fourth of an inch     
square be made fast to the middle of the
 membrane1 the motions of the latter can

 be seen by letting a beam of sunlight  
fall upon the mirror so as to be        
reflected upon a white wall or screen a 
few feet away4 7,fig4 #h47              
,illustration3 ,,fig4 #h4  ,when a sound
 is made in this tube1 the spot of light
 will at once assume some peculiar      
form1--either a straight line with some 
knots of light in it1 or some curve     
simple or compound1 and such as are     
known as ,lissajous curves4 ,if1 while  
some of these forms are upon the screen1
 the instrument be moved sideways1 the  
forms will change to undulating lines   
with or without loops1 varying with the 
pitch and intensity1 but being alike for
 the same pitch and intensity4 7,fig4   
#i7  ,this instrument ,i called the     
opeidoscope4  ,illustration3 ,,fig4 #i4 
,the vibration of a membrane and that of
 a solid differ chiefly in the amplitude
 of such vibration4 ,the scratch of a   
pin at one end of a long log can be     
heard by an ear applied to the other end
 of the log2 but every molecule in the  

log must move slightly2 and there are   
all degrees of movement between that    
visible to the eye1 which we call mass  
motion1 and that called molecular simply
 because we cannot measure the amplitude
 of the motion4 ,we may1 then1 roughly  
divide all bodies into two classes1 as  
to their relations to sound1--such as   
re-enforce it1 and such as distribute   
it3 the first depending upon the form of
 the body1 as related to a particular   
sound2 the second independent of form1  
and responding to all orders of         
vibrations4 ,air1 wood1 and metals      
belong in this latter class4 ,the common
 toy-string telegraph1 or lovers'       
telegraph1 is an example of this class4 
,two tin boxes are connected by a string
 passing through the middle of the      
bottom of each4 ,when the string is     
stretched1 and a person speaks in one   
box1 what is said can be heard by an ear
 applied at the other4 ,if the          
speaking-tubes be made about four inches
 in diameter1 and about four inches     

deep1 they are capable of doing much    
more service than is generally supposed 
to be possible4 ,i know of two lines1   
one of five hundred feet and the other  
of a thousand feet in length1 over which
 one can talk1 and be heard with        
distinctness4 ,in the line of a thousand
 feet1 the end of the tube is made of   
sheepskin tightly stretched1 and the    
line is made of ,no4 #h cotton thread4  
,the greater the tension1 the better is 
the sound transmitted4 ,the thread is   
supported at intervals by running       
through a loop on the ends of cords not 
less than three feet long1 attached to  
supports4 ,the thread pierces the       
membrane1 and is attached to a small    
button which is in contact with the     
membrane4 ,wind and rain affect this    
line disadvantageously4 ,the other line 
of five hundred feet1 between a         
passenger and a freight depot1 has the  
tube end covered with stretched         
calfskin4 ,instead of thread1 a         
copper-relay wire is employed 7any small

 uninsulated wire will do as well74     
,this permits a good tension1 and is    
unaffected by the weather4 ,one may     
stand in front of it about three feet1  
and converse with ease1 and in an       
ordinary tone4 ,the wire is supported in
 loops of string1 as in the other4      
,musicians have in all times employed   
various instruments for the production  
of musical effects4 ,whistles made of   
bone were used by pre-historic men1 some
 of them having finger-holes so that    
different tones could be produced4 ,a   
stag-horn that was blown like a         
flageolet1 and having three             
finger-holes1 has also been found2 while
 on the old monuments of ,egypt are     
pictured harps1 pipes with seven        
finger-holes1 a kind of flute1 drums1   
tambourines1 cymbals1 and trumpets4 ,in 
later times these primeval forms have   
been modified into the various          
instruments in use in the modern        
orchestra4 ,it seems as if no musician  
had ever been interested in the question

 as to why one instrument should give   
out a sound so different from another   
one1 even though it was sounding upon   
the same pitch4 ,no one can ever mistake
 the sound of a violin1 or a horn1 or a 
piano1 for any other instrument2 and no 
two persons have voices alike4 ,this    
difference in tone1 which enables us to 
identify an instrument by its sound or a
 friend by his voice1 is called quality 
of tone1 or timbre4  ,about twenty years
 ago1 that great ,german physicist      
,helmholtz undertook the investigation  
of this subject1 and succeeded in       
unravelling the whole mystery of the    
qualities of sound4  ,he discovered     
first1 that a musical sound is very     
rarely a simple tone1 but is made up of 
several tones1 sometimes as many as ten 
or fifteen1 having different degrees of 
intensity and pitch4 ,the lowest sound1 
which is also the strongest1 is called  
the fundamental2 and it is this tone we 
mean when we speak of the pitch of a    
sound1 as the pitch of middle ,c upon a 

piano1 or the pitch of the ,a string on 
a violin4 ,the higher sounds that       
accompany the fundamental are called    
sometimes harmonics1 sometimes upper    
partial tones1 but generally overtones4 
,the character or quality of a sound    
depends altogether upon the number and  
intensity of these overtones associated 
with the fundamental4 ,if a sound can be
 made upon a pipe and a violin1 that    
consists wholly of the fundamental with 
no overtones1 the two instruments sound 
absolutely alike4 ,it is exceedingly    
difficult to do this2 and such sound    
when produced is smooth1 but without    
character1 and unpleasing4  ,second1    
,helmholtz discovered that the overtones
 always stand in the simplest           
mathematical relation to the fundamental
 tone1--in fact1 are simple multiples of
 that tone1 being two1 three1 four1 and 
so on1 times the number of vibrations of
 it4  ,this will be readily understood  
by considering the position of such     
related sounds when they are written    

upon the staff4  ,illustration  ,if we  
start with ,c in the bass as indicated  
in the staff1 calling that the          
fundamental1 then the notes that will   
represent the above ratios are those    
indicated by smaller notes1 which are   
the overtones up to the ninth4 ,the     
first overtone1 being produced by twice 
the number of vibrations1 must be the   
octave2 the second1 the fifth of the    
second octave2 the third will be two    
octaves from the first1 and so on3 the  
number of vibrations of each of these   
notes being the number of the           
fundamental multiplied by its order in  
the series4  ,taking ,c with #abh       
vibrations1 we have for this series3--  
#abh x  #a    #abh  ,c fundamental4     
#abh x  #b    #bef  ,c'4           #abh 
x  #c    #chd  ,g'4           #abh x  #d
    #eab  ,c''4           #abh x  #e    
#fdj  ,e''4           #abh x  #f    #gfh
  ,g''4           #abh x  #g    #hif    
,b''flat4           #abh x  #h  #a1jbd  
,c'''4           #abh x  #i  #a1aeb     

,d'''4           #abh x #aj  #a1bhj     
,e'''4  ,this series is continued up to 
the limits of hearing4 ,now1 it appears 
that all instruments do not give the    
complete series3 indeed1 it is not      
possible to obtain them all upon some   
instruments4 ,each of them1 however1    
when present helps in the general effect
 which we call quality4 ,sometimes the  
overtones are more prominent than the   
fundamental1 as when a piano-wire is    
struck with a nail4 ,it has always been 
noticed that it does not give out the   
sound that is wanted when it is struck  
in this way4 ,hence it is the art of an 
instrument-maker to so construct the    
instrument as to develop and re-enforce 
such tones as are pleasing1 and to      
suppress the interfering and            
disagreeable overtones4 ,piano-makers   
learned by trial where was the proper   
place to strike the stretched wire in   
order to develop the most musical sound 
upon it2 but no reason could be given   
until it was observed that striking it  

at a point about one-seventh or         
one-ninth its length from either end    
prevented the development of the        
objectionable overtones1 the seventh and
 the ninth4 ,hence they can scarcely be 
heard in a properly constructed         
instrument4 ,these overtones are very   
discordant with the lower sounds4       
,organ-pipes have their specific        
qualities given to them by making them  
wide-mouthed1 narrow-mouthed1 conical1  
and so on2 shapes which experience has  
determined give pleasing sounds with    
different qualities4  ,the violin is an 
instrument that seems to puzzle makers  
more than almost any other4 ,some of the
 old violins made two hundred years ago 
by the ,amati family at ,cremona are    
worth many times their weight in gold4  
,recent makers have tried in vain to    
equal them2 but1 when their ingenuity   
and skill have failed1 they declare that
 age has much to do with such           
instruments1 that age mellows the       
sounding quality of the violin4 ,but the

 ,cremona violins were just as          
extraordinary instruments when they left
 the hands of the makers as they are    
now2 and the fame of the ,amati family  
as violin-makers was over all ,europe   
while they were living4  ,a good violin 
when well played gives an exquisite     
musical effect1 and on account of its   
range and quality of tones it is the    
leading orchestral instrument1 always   
pleasing and satisfying2 but in         
unskilled hands even the best ,cremona  
will give forth sounds that make one    
grieve that it was ever invented4       
,overtones of all sorts and with all    
degrees of prominence may be easily     
developed upon it3 therefore the skilful
 player draws the bow at such a place   
upon the strings as to develop the      
overtones he wants1 and suppress the    
ones not wanted4 ,the usual rule is to  
draw the bow about an inch below the    
bridge2 but the place for the bow       
depends upon where the fingers are that 
stop the strings1 and also the pressure 

upon it4 ,it requires an almost         
incredible amount of practice to be able
 to play a violin very well4  ,in the   
accompanying table will be found the    
component parts of tones upon a few     
instruments in common use4   ,,tone     
,,composition4  ,the components of the  
tones are indicated by lines in the     
column underneath the figures           
representing the series4 ,thus the      
narrow-stopped organ-pipe gives a sound 
composed of a fundamental1 and overtones
 three1 five1 seven1 and nine times the 
number of vibrations of it4  ,,tone     
,,composition4                          
----------------------------------------
----------------   ,,instruments4       
#a  #b  #c  #d  #e  #f  #g  #h  #i  #aj 
----------------------------------------
----------------           _/ ,wide     
stopped     _/                          
------------------------------          
,narrow          _/     _/     _/     _/
     _/                                 
------------------------------          

,narrow cylinder  _/  _/  _/  _/  _/  _/
             ,,organ                    
------------------------------          
,,pipes4   ,principal       _/  _/  _/  
7,wood7                                 
------------------------------          
,conically       _/           _/  _/  _/
                   narrow at top4       
------------------------------   ,flute 
_/  _/  _/  _/                          
------------------------------   ,violin
                     _/  _/  _/  _/  _/ 
_/  _/  _/  _/  _/                      
------------------------------   ,piano 
_/  _/  _/  _/  _/  _/  _/  _/          
------------------------------   ,bell  
_/  _/  _/  _/  _/  _/  _/              
------------------------------          
,clarionet                  _/     _/   
_/     _/     _/                        
------------------------------          
,bassoon                    _/  _/  _/  
_/  _/  _/  _/                          
------------------------------   ,oboe  
_/  _/  _/  _/  _/  _/  _/              

----------------------------------------
----------------  ,it must not be       
inferred that all of the overtones are  
of equal strength3 they are very far    
from that2 but these differ in different
 instruments1 and it is this that       
constitutes the difference between a    
good instrument and a poor one of the   
same name4  ,in a few of the spaces very
 light lines are made for the purpose of
 indicating that such overtones are     
quite weak4 ,for instance3 the piano has
 the sixth1 seventh1 and eighth thus    
marked2 these tones being suppressed by 
the mechanism1 as described on a former 
page4  ,only a few of the many forms of 
organ-pipes are given2 but these are    
sufficient to show what a physical      
difference there is between the musical 
tones in such pipes4  ,as for the human 
voice1 it is very rich in overtones2 but
 no two voices are alike1 therefore it  
would be impossible to tabulate the     
components of it in the manner they are 
tabulated for musical instruments4  ,in 

,helmholtz's experiments in the analysis
 of sounds1 use was made of the         
principle of resonance of a body of air 
enclosed in a vessel4 ,in the experiment
 with the tuning-fork to determine the  
wave-length1 p4 #gh1 it is remarked that
 no response came until the volume of   
the air in the tube was reduced to a    
certain length1 which depended upon the 
vibration number of the fork4 ,if       
instead of a test-tube a bottle had been
 taken1 the result would have been the  
same4 ,every kind of a vessel can       
respond to some tone of a definite      
wave-length1 and a sphere has been found
 to give the best results4 ,these are   
made with a hole on one side for the    
sound-wave to enter1 and a projection on
 the opposite side1 through which a hole
 about the one-eighth of an inch is     
made1 this to be placed in the ear4 ,any
 sound that is made in front of the     
large orifice will not meet any         
response1 unless it be that particular  
one which the globe can naturally       

re-enforce1 when it will be plainly     
heard4 ,suppose1 then1 one has a series 
of twenty or more of these1 graduated to
 the proper size for re-enforcing sounds
 in the ratio of one1 two1 three1 four1 
and so on4 ,take any instrument1 say a  
flute3 have one to blow it upon the     
proper pitch to respond to the largest  
sphere1 then take each of the spheres in
 their order1 applying them to the ear  
while the flute is being sounded4 ,when 
the overtones are present they will be  
heard plainly and distinct from the     
fundamental sound4 ,in like manner any  
or all other sounds may be studied4     
,but ,helmholtz did not stop after      
analyzing sounds of so many kinds3 he   
invented a method of synthesis1 by which
 the sounds of any kind of an instrument
 could be imitated4 ,a tuning-fork1 when
 made to vibrate by an electric current1
 gives out a tone without harmonics or  
overtones4 ,so if a series of forks with
 vibration periods equal to the numbers 
of the series of overtones given on p4  

#hf be so arranged that any of them may 
be made to vibrate at will1 it is       
evident that the resulting compound tone
 would be comparable with that from an  
instrument having such overtones4 ,thus1
 if with a tuning-fork giving a         
fundamental ,c1 other forks giving two1 
three1 and four times the number of the 
fundamental were associated1 each one   
giving a simple tone1 we should have for
 a resultant the tone of a flute1 as    
shown on p4 #ia4 ,if one1 three1 five1  
seven1 and nine1 were all sounded1 the  
resulting tone would be that of the     
clarionet1 and so on4 ,this he actually 
accomplished1 and now makers of physical
 apparatus advertise just such          
instruments4  ,helmholtz also contrived 
a set of tuning-forks1 which1 when      
bowed1 will give out the vowel sounds   
like the voice4  ,it was remarked upon  
p4 #hi that it has generally been       
considered that age has a mellowing     
effect upon the sound of a violin4 ,once
 in possession of the facts concerning  

sound that have been alluded to on the  
preceding pages1 it is easy to see how  
such an opinion should arise1 and also  
the fallacy of it4 ,it is proved        
conclusively that the ability to hear   
high sounds decreases as one grows      
older4 ,as the violin gives a very great
 number of overtones1 even up to the    
limits of audibility1 it is plain that  
if such an instrument should not change 
in its quality of tone in the least     
degree1 yet to a man who played upon it 
for a number of years it would seem to  
change by subtracting some of the higher
 overtones from the sound2 that is1 it  
would seem to become mellower4 ,there is
 no evidence that such a physical change
 takes place in the instrument4 ,it is  
not here affirmed that no change does   
take place4 ,it may be probable2 but all
 the evidence we have is the opinions of
 individuals whose hearing we know does 
change2 and this change is competent to 
modify the judgment as to the quality of
 the sound in the same direction4       

,before it can be affirmed that such a  
physical change does take place in the  
violin as to make a perceptible         
difference in the quality of its tone1  
it will be needful to determine         
accurately the number and intensity of  
the overtones at intervals during many  
years1 and then to compare them4 ,this  
has not yet been done4   ,,form ,,of ,a 
,,compound ,,sound-,,wave ,,in ,,air4   
,upon p4 #fc is given a picture of the  
form of a simple sound-wave in air1     
which1 as described1 consists of two    
parts1 a condensation and a rarefaction4
 ,all simple sound-waves have such a    
form2 but when two or more sound-waves  
that stand in some simple ratio to each 
other1 as do the sounds of musical      
instruments1 are formed in air1 the     
resulting wave is more or less complex  
in structure2 and where there are many  
components1 as there are where a number 
of different kinds of instruments are   
all sounding at once1 it is well-nigh   
impossible to figure even approximately 

the form of such wave-combinations4 ,it 
is generally given in treatises upon    
sound with ordinates representing the   
factors with their relative intensities4
 ,when the extremities of the ordinates 
are connected1 there is drawn a curved  
line with regularly recurring loops4    
,this cannot give a correct idea of the 
form of the wave1 because the motion of 
a particle of air is not up and down    
like a floating body upon waving water1 
but it is forward and back1 in the      
direction of the motion of the wave4    
,in ,fig4 #aj three simple sound-waves  
are thus represented at #a1 #b1 and #c1 
these having the wave-length #a1 #b1 and
 #c4 ,in #d1 the three are combined into
 one compound wave1 and better show the 
form of a transverse section of such a  
sound-wave in the air4 ,the organ-pipe  
called the principal gives out such a   
compound wave as is seen by referring to
 the table on p4 #ia4 ,the second       
overtone1 however1 is quite weak in that
 pipe1 which would so modify the form as

 to lessen somewhat the density at b1   
and increase it at a4  ,illustration3   
,,fig4 #aj4  ,in like manner the space  
in the length of the fundamental sound1 
whatever it may be1 is divided up into a
 number of minor condensations and      
rarefactions1 which may strengthen each 
other1 or so interfere as to change the 
position of both2 as is seen in the     
figure at b1 where the condensation due 
to wave #b interferes with the          
rarefaction of #c4     ,,correlation4   
,,having treated at some length of the  
three factors involved in               
telephony1--namely1 electricity1        
magnetism1 and sound1--it remains to    
follow up the various steps that have   
led to the actual transmission of       
musical sounds and speech over an       
ordinary electric circuit4  ,it is      
stated upon p4 #ca1 that1 when a current
 of electricity is passed through a coil
 of wire that surrounds a rod of soft   
iron1 the latter is made a temporary    
magnet3 it loses its magnetic property  

the instant that the current ceases4 ,if
 the rod be of considerable size1 say a 
foot or more in length1 and half an inch
 or more in diameter1 and the current be
 strong enough to make a powerful magnet
 of it1 whenever the current from the   
battery is broken1 the bar may be heard 
to give out a single click4 ,this will  
happen as often as the current is       
broken4 ,this is occasioned by a        
molecular movement which results in a   
change of length of the bar4 ,when it is
 made a magnet1 it elongates about      
#a_/bejjj of its length2 and1 when it   
loses its magnetism1 it suddenly regains
 its original length2 and this change is
 accompanied with the sound4 ,this sound
 was first noticed by ,prof4 ,c4 ,g4    
,page of ,salem1 ,mass41 in #ahcg4 ,if  
some means be devised for breaking such 
a circuit more than fifteen or sixteen  
times a second1 we shall have a         
continuous sound with a pitch depending 
upon the number of clicks per second4   
,such a device was first invented by the

 same man1 and was accomplished by      
fixing the armature of an electro-magnet
 to a spring which was in the circuit   
when the spring was pressing against a  
metallic knob1 at which time the current
 made the circuit in the coil of the    
electro-magnet4 ,the magnet attracting  
the armature away from the button broke 
the circuit1 which of course destroyed  
the magnetism of the magnet1 and allowed
 the spring to fly back against the     
button1 to complete the circuit and     
reproduce the same series of changes4   
,the rapidity with which the current may
 be broken in this way is only limited  
by the strength of both spring and      
current4 ,the greater the tension of the
 spring with a given current1 the       
greater number of vibrations will it    
make4  ,illustration3 ,,fig4 #aa4       
,suppose such an intermittent current to
 pass through the coil surrounding the  
soft iron rod1 #bef times per second2   
then the rod would evidently give #bef  
clicks per second1 which would have the 

pitch of ,c4 ,when these clicks are     
produced in the rod hold in the hand1   
the sound is hardly perceptible1 being  
like that of a sounding tuning-fork when
 held thus4 ,in order to strengthen it1 
it is necessary to place it on some     
resonant surface4 ,it is customary to   
mount it upon an oblong box with one or 
two holes in its upper surface1 inasmuch
 as such a form is found to give a      
louder response than any other1 and is  
the shape usually given to ,a,eolian    
harps4 ,the accompanying cut shows the  
combination of battery ,b1 the          
circuit-breaker1 and the rod mounted    
upon the box4 ,the wire ,w may evidently
 be of any length1 the magnetized rod   
and box responding to the number of     
vibrations of the spring ,s1 how long   
soever the circuit may be4              
,,helmholtz' ,,electric ,,interruptor4  
,in some of ,helmholtz' experiments1 it 
was essential to maintain the vibrations
 of a tuning-fork for a considerable    
time4 ,he effected this by placing a    

short electro-magnet between the prongs 
of the fork1 and affixing a platinum    
point at the end of one prong in such a 
manner1 that1 as the prong descended in 
its vibration1 the platinum point dipped
 into a small cup of mercury that       
completed the circuit4 ,when the prong  
receded1 it was of course withdrawn from
 the mercury1 and the current was       
broken4 ,as it is not possible for a    
tuning-fork to vibrate in more than one 
period1 such an arrangement would       
evidently make and break the current as 
many times per second as the fork       
vibrated4 ,when1 therefore1 such an     
interruptor is inserted in the circuit  
with the click-rod on its resonant box1 
the latter must give out just such a    
sound as the fork is giving4 ,with such 
a device1 it is possible to reproduce at
 almost any distance in a telegraphic   
circuit1 a sound of a given pitch4 ,it  
is therefore a true telephone4          
,,reiss' ,,telephone4  ,the ease with   
which membranes are thrown into         

vibrations corresponding in period to   
that of the sounding body has already   
been alluded to on p4 #hj2 and several  
attempts have been made1 at different   
times1 to make membranes available in   
telephony4 ,the first of these attempts 
was made by ,philip ,reiss of           
,friedrichsdorf1 ,germany1 in #ahfa4    
,his apparatus consisted of a hollow    
box1 with two apertures3 one in front1  
in which was inserted a short tube for  
producing the sound in1 and indicated by
 the arrow in the cut1 ,fig4 #ab2 the   
other on the top4 ,this was covered with
 the membrane m1--a piece of bladder    
stretched tight over it4 ,upon the      
middle of the membrane1 a thin piece of 
platinum was glued2 and this piece of   
platinum was connected by a wire to a   
screw-cup from which another wire went  
to a battery4  ,illustration3 ,,fig4    
#ab4  ,a platinum finger1 ,s1 rested    
upon the strip of platinum1 but was made
 fast at one end to the screw-cup that  
connected with the other wire from the  

battery4 ,now1 when a sound is made in  
the box1 the membrane is made to vibrate
 powerfully3 this makes the platinum    
strip to strike as often upon the       
platinum finger1 and as often to bound  
away from it1 thus making and breaking  
the current the same number of times per
 second4 ,if1 then1 a person sings into 
this box while it is in circuit with the
 afore-mentioned click-rod and box1 the 
latter will evidently change its pitch  
as often as it is changed by the voice4 
,in this apparatus we have a telephone  
with which a melody may be reproduced at
 a distance with distinctness4 ,but the 
sounds are not loud1 and they have a    
tin-trumpet quality4 ,if one reflects   
upon the possibilities of such a        
mechanism1 and upon the conditions      
necessary to produce a sound of any     
given quality1 as that of the voice or  
of a musical instrument as described in 
preceding pages1 he will understand that
 it can reproduce only pitch4 ,it might 
here be inferred that something more    

than a single pitch is transmitted if   
the sound is like that of a tin trumpet 
as stated3 but the reason of this is    
that1 whenever a current is passing     
between two surfaces that can move only 
slightly on each other1 there is always 
an irregularity in the conduction1 so as
 to produce a kind of scratching sound2 
and it is this1 combined with the other1
 the true pitch1 that gives the         
character to the sound of this          
instrument4  ,dr4 ,wright found that a  
sound of considerable intensity could be
 obtained by passing the interrupted    
current through the primary wire of a   
small induction coil1 and placing a     
conductor made of two sheets of silvered
 paper placed back to back in the       
secondary circuit4 ,the silvered paper  
becomes rapidly charged and discharged1 
making a sound that can be heard over a 
large hall1 and having the same pitch as
 the sending instrument4   ,,gray',s    
,,telephones4  ,in #ahgc ,mr4 ,elisha   
,gray of ,chicago discovered that if an 

induction coil be made to operate by the
 current from any automatic             
circuit-breaker1 and one of the wires   
from the secondary circuit be held in   
the hand while the dry finger of the    
same hand is rubbed upon a sonorous     
metallic plate1 the other wire being in 
connection with the plate1 a musical    
sound would be given out by the plate1  
appearing to come from the point of     
contact of the finger with the plate4   
,he therefore contrived a musical       
instrument with a range of two octaves1 
in which the reeds were made to vibrate 
by electro magnets1 the current entering
 any one by depressing the appropriate  
key4 ,this circuit is sent through the  
primary wire of an induction coil while 
one of the terminals of the secondary   
coil is connected with the thin sheet   
metal that forms one head of a shallow  
wooden drum about eight inches in       
diameter1 which is so fixed as to be    
rotated like a pulley4 ,the other       
terminal is held in the hand while one  

finger of the same hand rests upon the  
metallic surface4 ,while the drum is    
turned with the other hand1 the sounds  
given out have considerable intensity4  
,the faster the drum is turned1 the     
louder do the sounds become1 though the 
pitch remains the same4  ,in this case1 
as in the case mentioned on p4 #aje1 we 
have an electric current passing between
 two surfaces that are moving upon each 
other2 the contact not being uniform1   
the current is varying as well as       
intermittent4  ,mr4 ,gray has also      
invented a musical telephone by means of
 which many musical sounds may be       
simultaneously transmitted and          
reproduced4 ,the actual mechanism used  
is quite complex1 and requires          
considerable familiarity with electrical
 science in order to understand it2 but 
the fundamental principle involved is   
not difficult to one who has            
comprehended the preceding descriptions4
  ,suppose that we have a series of four
 steel reeds1 each one fixed at one end 

to one pole of a short electro-magnet1  
while the other end is left free to     
vibrate over the other pole of the      
magnet and not quite touching it4 ,each 
of the reeds is to be tuned to a        
different pitch1 say the #a1 #c1 #e1 and
 #h of the scale4 ,these electro-magnets
 with their attached vibrators are to be
 attached each to a resonant box 7see p4
 #ic71 which can respond to that        
particular number of vibrations per     
second4 ,this is the receiving          
instrument4 ,the sender consists of a   
like set of reeds tuned to the same     
pitch1 which can be made to vibrate at  
will by pressing a key which sends the  
current of electricity through its      
electro-magnet1 which makes and breaks  
the current4 ,imagine one of these keys 
to be pressed down so as to make the    
circuit complete3 the sending instrument
 then has one of its reeds1 let it be   
the #a of the scale1 set in vibration2  
the intermittent current traverses the  
whole line1 going through all four of   

the receiving instruments4 ,now1 we know
 from the study of the action of        
sounding bodies1 that only one of the   
four receivers is competent to vibrate  
in consonance with this tone1 and this  
one will respond2 that is1 the          
vibrations are truly sympathetic        
vibrations4 ,if1 instead of making the  
#a of the scale in the                  
sending-instrument1 the #c had been     
made1 the current would have gone       
through all of the receiving instruments
 just the same as before1 but only one  
of them could take up that vibratory    
movement3 three of them would remain at 
rest1 the #c responding loudly4 ,in like
 manner1 any number of vibrating reeds  
in the sending instrument can make a    
corresponding number of reeds in the    
receiving instrument to vibrate1        
provided the latter be exactly tuned    
with the former4 ,each transmitter is   
connected with but a part of the        
battery1 so that several tones may be   
transmitted at the same time4 ,if the   

performer plays a piece of music in its 
various parts1 every part will be       
reproduced3 thus we have a compound or  
multiple telephone4 ,this instrument has
 been used during the past winter to    
give concerts in cities when the        
performer was in a distant place4  ,it  
has also been used as a multiple        
telegraph2 as many as eight operators   
sending messages simultaneously over the
 same wire1--four in each               
direction1--without the slightest       
interference4   ,,bell',s ,,telephone4  
,prof4 ,a4 ,graham ,bell of ,boston     
independently discovered the same means 
for producing multiple effects over the 
same wire2 but it appears he did not    
practically work it out as completely as
 did ,mr4 ,gray4 ,but while the latter  
was chiefly employed in perfecting the  
method as a telegraphic system1 ,prof4  
,bell had set before himself the more   
difficult problem of transmitting       
speech4 ,this he has actually           
accomplished1 as we have so often been  

reminded during the past year4          
,thoroughly conversant with the acoustic
 researches of ,helmholtz1 and keeping  
in mind the complex form of the air     
vibrations produced by the human voice1 
he attempted to make these vibrations   
produce corresponding pulsations in an  
electric current in the manner analogous
 to the electric interrupter4           
,observing that membranes when properly 
stretched can vibrate to any kind of a  
sound1 he sought to utilize them for    
this purpose4 ,so did ,reiss2 but ,reiss
 inserted the vibrating membrane into   
the circuit1 and it was quite evident   
that such a plan would not answer1      
therefore the current must not be       
broken2 but could an electric current be
 interfered with without breaking the   
connections8  ,the well-known re-actions
 of magnets upon electrical currents1   
first noted by ,oersted1 and fully      
developed by ,faraday1 gave the clew to 
the solution4 ,a piece of iron should be
 made to vibrate by means of sound      

vibrations1 so as to affect an          
electro-magnet and induce corresponding 
electrical pulsations4   ,,first ,,form 
,,of ,,speaking-,,telephone4  ,a        
membrane of gold-beater's skin was      
tightly stretched over the end of a     
speaking-tube or funnel2 on the middle  
of this membrane a piece of iron1 ,n ,s1
 ,fig4 #ac1 was glued4 ,in front of this
 piece of iron an electro-magnet ,m is  
so situated that its poles are opposite 
to it1 but not quite touching it4 ,one  
of the terminal wires of the            
electro-magnet goes to the battery ,b2  
the other goes to the receiving         
instrument ,r1 which consists of a      
tubular electro-magnet1 the coil being  
enclosed in a short tube of soft iron2  
the wire thence goes to the plate ,e'1  
which is sunk in the earth4 ,on the top 
of ,r1 at ,p1 is a rather loose1 thin   
disk of iron1 which acts as an armature 
to the electro-magnet below it4         
,illustration3 ,,fig4 #ac4  ,supposing  
that all the parts are thus properly    

connected1 the current of electricity   
from the battery makes both ,m and ,r   
magnetic2 the electro-magnet ,m will    
inductively make the piece of iron ,n   
,s1 a magnet1 with its poles unlike     
those of the inducing electro-magnet2   
and the two will mutually attract each  
other4 ,if now this piece of iron ,n ,s 
be made to move toward ,m1 a current of 
electricity will be induced in the      
coils1 which will traverse the whole    
circuit4 ,this induced electricity will 
consist of a single wave or pulse1 and  
its force will depend upon the velocity 
of the approach of ,n ,s to ,m4 ,a like 
pulse of electricity will be induced in 
the coils when ,n ,s is made to move    
away from ,m2 but this current will move
 through the circuit in the opposite    
direction1 so that whether the pulsation
 goes from ,m to ,r1 or from ,r to ,m1  
depends simply upon the direction of the
 motion of ,n ,s4  ,the electricity thus
 generated in the wire by such vibratory
 movements varies in strength           

proportional to the movement of the     
armature2 therefore the line wire       
between two places will be filled with  
electrical pulsation exactly like the   
aerial pulsations in structure4 ,fig4   
#aj1 p4 #ih1 may be used to illustrate  
the condition of the wire through which 
the currents pass4 ,the dark part may   
represent the strongest part of the     
wave1 while the lighter part would show 
the weaker part of the wave4 ,the chief 
difference would be1 that electricity   
travels so fast1 that what is there     
represented as one wave in air with a   
length of two feet would1 in an electric
 wave1 be more than fifty miles long4   
,these induced electric currents are but
 very transient 7see p4 #ca72 and their 
effect upon the receiver ,r is to either
 increase or decrease the power of the  
magnet there1 as they are in one        
direction or the other1 and consequently
 to vary the attractive power exercised 
upon the iron plate armature4  ,let a   
simple sound be now made in the tube1   

consisting of #bef vibrations per       
second3 the membrane carrying the iron  
will vibrate as many times1 and so many 
pulses of induced electricity will be   
imposed upon the constant current1 which
 will each act upon the receiver1 and   
cause so many vibrations of the armature
 upon it2 and an ear held at ,p will    
hear the sound with the same pitch as   
that at the sending instrument4 ,if two 
or more sound-waves act simultaneously  
upon the membrane1 its motions must     
correspond with such combined motions2  
that is1 its motions will be the        
resultant of all the sound-waves1 and   
the corresponding pulsations in the     
current must reproduce at ,r the same   
effect4 ,now1 when a person speaks in   
the tube1 the membrane is thrown into   
vibrations more complex in structure    
than those just mentioned1 differing    
only in number and intensity4 ,the      
magnet will cause responses from even   
the minutest motion2 and therefore an   
ear at ,r will hear what is said at the 

tube4 ,this was the instrument exhibited
 at the ,centennial ,exposition at      
,philadelphia1 and concerning which ,sir
 ,william ,thompson said on his return  
to ,england1 ,this is the greatest by   
far of all the marvels of the electric  
telegraph4  ,the popular impression has 
been1 concerning the telephone1 that the
 sound was in some way conveyed over the
 wire4 ,it will be obvious to every one 
who may read this1 that such is very far
 from being the case4 ,the fact is1 it  
is a beautiful example of the           
convertibility of forces from one form  
to another4 ,there is first the initial 
vibratory mechanical motion of the air1 
which is imparted to the membrane       
carrying the iron4 ,this motion is      
converted into electricity in the coil  
of wire surrounding the electro-magnet1 
and at the receiving-end is first       
effective as magnetism1 which is again  
converted into vibratory motion of the  
iron armature1 which motion is imparted 
to the air1 and so becomes again a      

sound-wave in air like the original one4
  ,this was the first speaking-telephone
 that was ever constructed1 so far as   
the writer is aware1 but it was not a   
practicable instrument4 ,many sounds    
were not reproduced at all1 and1        
according to the report of the judges at
 the ,philadelphia ,exposition1 one     
needed to shout himself hoarse in order 
that he might be heard at all4   ,,the  
,,author',s ,,telephone4  ,for several  
years past my regularly recurring duties
 have taken me over the various subjects
 treated of in this book1 and each one  
has been extensively illustrated in an  
experimental way1 and a considerable    
number of new pieces of apparatus and   
new experiments to exhibit their        
phenomena have been devised by me4      
,among these1 ,i would mention the      
following3--             #a4            
,measurement of the elongation of a     
magnetized               bar4           
#b4 ,a magneto-electric telegraph4      
#c4 ,an electro-magnetic instrument for 

demonstrating the rotation of the earth4
             #d4 ,the permanent         
magnetism of the magnetic               
phantom4             #e4 ,the           
convertibility of sound into            
electricity4             #f4 ,the       
induction of a vibrating magnet upon an 
electric circuit4             #g4 ,the  
origination of electric waves in a      
circuit               by a sounding     
magnet4             #h4 ,the discovery  
of the action of the air in a           
sounding organ-pipe4             #i4    
,two or three methods for studying the  
vibrations of membranes4            #aj4
 ,lissajous forks for enlarged          
projections of               sound      
vibrations4  ,as soon1 therefore1 as ,i 
gave attention to the subject of        
telephony1 ,i was able1 with a few      
preliminary experiments1 to determine   
the proper conditions for the           
transmission of speech in an electric   
circuit2 and1 without the slightest     
knowledge of the mechanism which ,prof4 

,bell had used1 ,i devised the following
 arrangement for a speaking-telephone4  
,illustration3 ,,fig4 #ad4--,,my ,,first
 ,,speaking ,,telephone4  ,illustration3
 ,,fig4 #ad4--;,,end ,,view4  ,my first 
speaking-telephone1 ,fig4 #ad1 consisted
 of a magnet made out of half-inch round
 steel bent into a ,u form1 having the  
poles about two inches apart4 ,over     
these were slipped two bobbins taken    
from an old telegraph register1 and were
 already fitted to a half-inch core4    
,these bobbins1 two inches and a half   
long1 were wound with cotton-covered    
copper wire1 ,no4 #bc1 each bobbin      
containing about #aej feet4 ,this       
magnet1 with the bobbins slipped upon   
its poles1 was made fast to a post two  
or three inches high4 ,the steel was    
made as strongly magnetic as was        
possible1 and would hold up three or    
four times its own weight4 ,in front of 
the poles1 a sheet of thin steel1       
one-fiftieth of an inch thick1 was made 
fast to an upright board having a hole  

cut through it three and a half inches  
in diameter 7,fig4 #ad1 end view72 the  
plate was screwed tightly to this board1
 so as to cover the hole2 and the middle
 of the hole was at the same height as  
the two poles of the magnet4 ,the wires 
from the two bobbins were connected1 as 
if to make an electro-magnet2 while the 
two free terminals were to be connected 
with the line-wires4 ,of course there   
were two of these instruments1 both     
alike2 and talking and singing were     
reproduced with these4  ,a very great   
number of experiments have been made to 
determine the best conditions for each  
of the essential parts1--the size and   
strength of the magnet1 the size of the 
bobbins1 as to length and fineness of   
wire1 the best thickness for the plate  
for absorbing the vibrations1 c42 and it
 is really surprising1 how little is the
 difference between very wide limits4   
,the following directions will enable   
any one to construct a                  
speaking-telephone with which good      

results may be obtained4 ,the           
specifications will be for only one     
instrument2 though of course two        
instruments made alike will be necessary
 for any purposes of speaking or other  
signals4  ,illustration3 ,,fig4 #ae4    
,illustration3 ,,fig4 #af4  ,procure    
three common horse-shoe magnets about   
six inches long1 all of the same size2  
these retail in the market at about a   
dollar apiece4 ,they should be strong   
enough to hold up several times their   
own weight each4 ,next1 have turned out 
of good hard wood1--such as maple or    
boxwood1--two spools not over half an   
inch long and an inch and a half broad1 
the sides cut square both inside and    
out1 as shown at ,s1 ,fig4 #ae2 a hole  
the third of an inch in diameter is to  
be made through the spool4 ,into this   
hole is to be fitted a short rod of soft
 iron1 ,i1 about an inch long1 which    
should be a little rounded at the outer 
end4 ,the bobbins may be wound with as  
much insulated copper wire as they will 

hold4 ,the wire may be from the         
one-fortieth to the one-fiftieth of an  
inch in diameter1 as is most convenient 
to obtain1 the latter size being        
preferable4 ,the resistance of such     
bobbins will probably be from two to    
three ohms each4 ,the soft-iron core ,i 
must project backwards far enough to be 
clamped between the two outer magnets #a
 and #c1 while the inner one1 #b1 is    
drawn back4 ,when the bobbins are in    
their places1 and are clamped between   
the upper and lower magnets1 they will  
stand as shown in ,fig4 #af1 where the  
view is from above2 the magnets being   
buttoned down to the block they rest on 
7see ,fig4 #ag71 which at the same time 
holds the soft-iron rods with the       
bobbins upon them4 ,the wires on these  
coils must be connected in the same way 
they would be in order to make opposite 
poles of their outer ends1 if a current 
of electricity were to be sent through  
the coils4 ,an upright board ,b 7,fig4  
#ag7 six or seven inches square1 having 

a round hole four inches in diameter cut
 out from the middle of it1 must be     
fixed near the end of the base-board2   
and over this hole is to be screwed     
tightly a piece of thin sheet iron or   
steel2 it may be from the one-twentieth 
to the one-fiftieth of an inch in       
thickness4 ,it does not seem to make    
much difference about the thickness of  
this plate4 ,i have generally got the   
best results from a plate one-fiftieth  
of an inch thick4 ,the upright board    
carrying this plate must be very rigid1 
otherwise the plate will be kept tight  
to the magnets all the time2 and one of 
the conditions of success in working is1
 that this plate shall be as close as   
possible to the magnet-ends1 but not to 
touch3 therefore fix the board tight1   
and adjust the magnets by means of the  
button shown on top of them in the      
perspective figure4  ,illustration3     
,,fig4 #ag4  ,the sounds to be          
transmitted1 of whatever sort they may  
be1 are to be made on the side ,p1 ,fig4

 #af2 and likewise1 when the instrument 
is used as a receiver1 the ear is to be 
applied at the same place4 ,a tube about
 two inches in diameter may be made fast
 to the front of the board1 in a line   
with the centre of the plate2 this will 
aid somewhat in hearing4 ,when two or   
three persons are to sing1 it will be   
best to have each one supplied with a   
tube to sing through2 one end of the    
tube to be placed close to the front of 
the plate4 ,the sound of musical        
instruments1 such as the flute and the  
cornet1 will be reproduced much louder1 
if the front of such instrument be      
allowed to rest upon the rim of the hole
 in the board1 just in front of the     
plate4  ,it is noticeable that low      
talking can be heard more distinctly    
than when a great effort is made2 but   
the sounds though distinct are not      
strong at any time1 and other sounds    
seriously interfere with hearing4 ,it is
 probable that some way will hereafter  
be devised for increasing the usefulness

 of the invention by increasing the     
volume of sound4 ,on account of the     
weakness of the sound it becomes        
necessary to provide a call to attract  
the attention of one in the room4 ,this 
may be accomplished by having a small   
electric bell worked by a one or two    
cell battery4 ,another way which ,i have
 found to be quite as efficient is to   
have a rod of iron or steel about a foot
 long1 and half an inch in diameter1    
bent into a ,u form4 ,when this is held 
by the bend1 and struck upon the floor  
or with a stick1 it vibrates powerfully2
 and if one of its prongs be permitted  
to strike against the plate ,p1 ,fig4   
#af1 the sound will be reproduced loud  
enough to hear over a large room4 ,i    
have never failed to call with this when
 any one was in the same room with the  
telephone4  ,wherever a telephone       
circuit has been made upon telegraph    
poles having other wires upon them1 the 
inductive actions of the currents upon  
the other wires has been found to       

seriously interfere with the action of  
the telephones1 inasmuch as the latter  
reproduce every other message4 ,one     
skilled in reading by sound in the      
ordinary way can read through the       
telephone what message is travelling in 
a neighboring wire4 ,messages may be    
thus read upon wires as far distant as  
ten feet from the telephone circuit4 ,it
 there fore seems to be essential that  
each telephone circuit should be        
isolated from every other one1 else     
there can be no secrecy in messages4  ,a
 very interesting effect was noticed one
 night when there was a bright aurora   
display4 ,there was a continuous current
 through the wires1 accompanied with    
sounds which increased in intensity as  
the bright streamers passed by4 ,this   
will probably lead to some important    
results in science4  ,in all probability
 the telephone is as much in its infancy
 as was ordinary telegraphy in #ahdj4   
,since that time the sciences of        
electricity and magnetism have had the  

most of their growth1 and telegraphy has
 kept pace with the advancing knowledge 
until its commercial importance is      
second to no other agency4 ,very many   
important principles that are invaluable
 in telegraphy to-day were wholly       
unknown in #ahdj2 but it may here be    
noted that in the telephone1 as it now  
is1 there is not a single principle that
 was not well enough known in #ahdj4    
,this will be apparent to one who       
follows out the phenomena from the      
sender to the receiver4 ,first1 the     
sound in air causing a corresponding    
movement in a solid body1 iron4 ,this   
iron1 acting inductively upon a magnet1 
originates magneto-electric currents in 
a wire helix about it2 and these travel 
to another helix1 and1 re-acting upon   
the magnet in it1 have electro-magnetic 
effects1 and increase and decrease the  
strength of the magnet2 and this        
variable magnetism affects the plate of 
iron in front of that magnet1 and makes 
it to vibrate in a corresponding manner1

 and thus to restore to the air in one  
place the vibrations absorbed from the  
air in another place4 ,to some it may   
seem strange that a simple thing as the 
telephone is1 involving nothing but     
principles familiar enough to every one 
interested in physical science1 should  
have waited nearly forty years to be    
invented4 ,the reason is probably this3 
,men of science1 as a rule1 do not feel 
called upon to apply the principles     
which they may discover4 ,they are      
content to be discovering1 not          
inventing4 ,now1 the schools of the     
country ought to make the youth quite   
familiar with the general principles of 
physical science1 that the inventive    
ones--and there are many such--may apply
 them intelligently4 ,mechanism is all  
that stands between us and aerial       
navigation2 all that is necessary to    
reproduce human speech in writing2 and  
all that is needed to realize completely
 the prophetic picture of the ,graphic1 
of the orator who shall at the same     

instant address an audience in every    
city in the world4         99       99  
99       99       99  ,transcriber's    
,notes3  ,the musical flat symbol is    
represented in the text by flat4  ,page 
#ag1 propererties changed to properties 
7there are other properties7  ,page #db1
 muturally changed to mutually 7bodies  
would mutually7  ,page #ajf1 outby      
changed to out by 7given out by the7