,,lightning1 ,,thunder      ,,and       
,,lightning ,,conductors4      ,,with   
,,an ,,appendix ,,on ,,the ,,recent     
,,controversy    ,,on ,,lightning       
,,conductors4      ,,by      ,,gerald   
,,molloy1 ,d4 ,d41 ,d4 ,sc4             
,,illustrated4      ,illustration       
,,new ,,york3      ,,the ,,humboldt     
,,publishing ,,co41      #bh ,,lafayette
 ,,place4          ,,lightning1         
,,thunder1 ,,and ,,lightning            
,,conductors4          ,,contents4      
,,lecture ,i4                           
,pages #e-bf      ,,lightning ,,and     
,,thunder4      ,identity of ,lightning 
and ,electricity--,franklin's           
,experiment--,fatal    ,experiment of   
,richman--,immediate ,cause of          
,lightning--,illustration from          
,electric ,spark--,what a ,flash of     
,lightning ,is--,duration of a ,flash of
    ,lightning--,experiments of         
,professor ,rood--,wheatstone's         
,experiments--,experiment with ,rotating
 ,disc--,brightness of a ,flash of      

,lightning--,various ,forms of          
,lightning--,forked ,lightning1 ,sheet  
,lightning1 ,globe ,lightning--,st4     
,elmo's ,fire--,experimental            
,illustration--,origin of               
,lightning--,length of a ,flash of      
,lightning--,physical ,cause of         
,thunder--,rolling of                   
,thunder--,succession    of             
,peals--,variation of                   
,intensity--,distance of a ,flash of    
,lightning        ,,lecture ,,ii4       
,pages #bf-ec      ,,lightning          
,,conductors4      ,destructive ,effects
 of ,lightning--,destruction of         
,buildings--,destruction of ,ships at   
,sea--,destruction of ,powder           
,magazines--,experimental               
,illustrations--,destruction of ,life by
    ,lightning--,the ,return            
,shock--,franklin's ,lightning          
,rods--,introduction    of ,lightning   
,rods into ,england--,the ,battle of    
,balls and    ,points--,functions of a  
,lightning ,conductor--,conditions of a 

,lightning    ,conductor--,mischief     
,done by ,bad ,conductors--,evil        
,effects of a ,bad    ,earth            
,contact--,danger from ,rival           
,conductors--,insulation of ,lightning  
,conductors--,personal ,safety in a     
,thunder ,storm--,practical             
,rules--,security ,afforded by          
,lightning ,rods        ,,appendix4     
,pages #ee-fb      ,,recent             
,,controversy ,,on ,,lightning          
,,conductors4      ,theory of ,lightning
 ,conductors ,challenged--,lectures of  
,professor    ,lodge--,short ,account of
 his ,views and ,arguments--,effect of  
,self-,induction on a ,lightning        
,rod--,experiment on the ,discharge of a
    ,leyden ,jar--,outer ,shell only of 
a ,lightning ,rod ,acts as a            
,conductor--,discussion at the ,meeting 
of the ,british ,association1           
,september1 #ahhh--,statement by ,mr4   
,preece--,lord ,rayleigh and ,sir       
,william ,thomson--,professor ,rowland  
and ,professor ,forbes--,m4 de          

,fonvielle1 ,sir ,james ,douglass1 and  
,mr4 ,symons--,reply of ,professor      
,lodge--,concluding ,remarks of         
,professor ,fitzgerald1 ,president    of
 the ,section--,summary ,showing the    
,present ,state of the ,question        
,,list ,,of ,,illustrations4            
,,page      ,,the ,,electric ,,spark3 ,a
 ,,type ,,of ,a ,,flash ,,of            
,,lightning1                  #h        
,,cardboard ,,disc ,,with ,,black ,,and 
,,white ,,sectors2 ,,as ,,seen ,,when   
,,at ,,rest1  #ab      ,,same ,,disc2   
,,as ,,seen ,,when ,,in ,,rapid         
,,rotation1                          #ab
      ,,the ,,brush ,,discharge1        
,,illustrating ,,st4 ,,elmo',s ,,fire1  
#ag      ,,origin ,,of ,,successive     
,,peals ,,of ,,thunder1                 
#bb      ,,variations ,,of ,,intensity  
,,in ,a ,,peal ,,of ,,thunder1          
#bd      ,,discharge ,,of ,,leyden ,,jar
 ,,battery ,,through ,,thin ,,wires1    
#bg      ,,glass ,,vessel ,,broken ,,by 
,,discharge ,,of ,,leyden ,,jar         

,,battery1             #cb      ,,gun   
,,cotton ,,set ,,on ,,fire ,,by         
,,electric ,,spark1                     
#cc      ,,volta',s ,,pistol2           
,,explosion ,,caused ,,by ,,electric    
,,spark1                 #cd      ,,the 
,,return ,,shock ,,illustrated1         
#ce      ,,protection ,,from ,,lightning
 ,,by ,a ,,closed ,,conductor1          
#dh      ,,induction ,,effect ,,of      
,,leyden ,,jar ,,discharge1             
#ef          ,,lecture ,i4              
,,lightning ,,and ,,thunder4      ,the  
electricity produced by an ordinary     
electric machine exhibits1  under       
certain conditions1 phenomena which bear
 a striking resemblance  to the         
phenomena attendant on lightning4 ,in   
both cases there is a flash  of light2  
in both there is a report1 which1 in the
 case of lightning1  we call thunder2   
and1 in both cases1 intense heat is     
developed1 which  is capable of setting 
fire to combustible bodies4 ,further1   
the spark  from an electric machine     

travels through space with extraordinary
  rapidity1 and so does a flash of      
lightning2 the spark follows a zig-zag  
course1 and so does a flash of          
lightning2 the spark moves silently and 
harmlessly through metal rods and stout 
wires1 while it forces its  way1 with   
destructive effect1 through bad         
conductors1 and it is so1  too1 with a  
flash of lightning4 ,lastly1 the        
electricity of a machine  is capable of 
giving a severe shock to the human body2
 and we know  that lightning gives a    
shock so severe as usually to cause     
immediate  death4 ,for these reasons it 
was long conjectured by scientific men  
that lightning is1 in its nature1       
identical with electricity2 and that  it
 differs from the electricity of our    
machines only in this1 that it  exists  
in a more powerful and destructive form4
      ,identity of ,lightning and       
,electricity4--,but it was reserved for 
the celebrated ,benjamin ,franklin to   
demonstrate the truth of this           

conjecture by direct experiment4 ,he    
first conceived the idea of drawing     
electricity from a thundercloud in the  
same way as it is drawn from  the       
conductor of an electric machine4 ,for  
this purpose he proposed  to place a    
kind of sentry-box on the summit of a   
lofty tower1 and to  erect1 on the      
sentry-box1 a metal rod1 projecting     
twenty or thirty  feet upward into the  
air1 pointed at the end1 and having no  
electrical  communication with the      
earth4 ,he predicted that when a        
thundercloud  would pass over the tower1
 the metal rod would become charged with
  electricity1 and that an observer1    
stationed in the sentry-box1 might  draw
 from it1 at pleasure1 a succession of  
electric sparks4    ,with the           
magnanimity of a really great man1      
,franklin published this  project to the
 world2 being more solicitous to extend 
the domain of  science by new           
discoveries1 than to secure for himself 
the glory  of having made them4 ,the    

project was set forth in a letter to    
,mr4  ,collinson1 of ,london1 which     
bears date ,july #bi1 #agej1 and which1 
in the  course of a year or two1 was    
translated into the principal languages 
of ,europe4 ,two years later the        
experiment suggested by ,franklin was   
made by ,monsieur ,dalibard1 a wealthy  
man of science1 at his villa near       
,marly-la-,ville1 a few miles from      
,paris4 ,in the middle of an elevated   
plain ,monsieur ,dalibard erected an    
iron rod1 forty feet in length1 one     
inch in diameter1 and ending above in a 
sharp steel point4 ,the iron rod  rested
 on an insulating support1 and was kept 
in position by means of  silk cords4    
,in the absence of ,monsieur ,dalibard1 
who was called by business to  ,paris1  
this apparatus was watched by an old    
dragoon1 named ,coiffier2  and on the   
afternoon of the tenth of ,may1 #ageb1  
he drew sparks from the  lower end of   
the rod at the time that a thundercloud 
was passing over  the neighborhood4     

,conscious of the importance that would 
be attached to  this phenomenon1 the old
 dragoon summoned1 in all haste1 the    
prior of  ,marly to come and witness it4
 ,the prior came without delay1 and he  
was  followed by some of the principal  
inhabitants of the village4 ,in the     
presence of the little group1 thus      
gathered together1 the experiment  was  
repeated--electric sparks were again    
drawn1 in rapid succession1  from the   
iron rod2 the prediction of ,franklin   
was fulfilled to the  letter2 and the   
identity of lightning and electricity   
was1 for the  first time1 demonstrated  
to the world4      ,franklin's          
,experiment4--,meanwhile ,franklin had  
been waiting1 with  impatience1 for the 
completion of the tower of              
,christchurch1 in  ,philadelphia1 on    
which he intended to make the experiment
 himself4  ,he even collected money1 it 
is said1 to hasten on the building4     
,but1 notwithstanding his exertions1 the
 progress of the tower was  slow2 and   

his active mind1 which could ill brook  
delay1 hit upon  another expedient1     
remarkable alike for its simplicity and 
for its  complete success4 ,he          
constructed a boy's kite1 using1        
however1 a silk  pockethandkerchief1    
instead of paper1 that it might not be  
damaged by  rain4 ,to the top of the    
kite he attached a pointed iron wire    
about a  foot long1 and he provided a   
roll of hempen twine1 which he knew to  
be  a conductor of electricity1 for     
flying it4 ,this was the apparatus with 
which he proposed to explore the nature 
of a thundercloud4    ,the thundercloud 
came late in the afternoon of the fourth
 of ,july1  #ageb1 and ,franklin sallied
 out with his kite1 accompanied by his  
son1  and taking with him a common      
door-key and a ,leyden jar4 ,the kite   
was soon high in air1 and the           
philosopher awaited the result of his   
experiment1 standing1 with his son1     
under the lee of a cowshed1 partly  to  
protect himself from the rain that was  

coming1 and partly1 it is  said1 to     
shield himself from the ridicule of     
passers-by1 who1 having  no sympathy    
with his philosophical speculations1    
might be inclined to  regard him as a   
lunatic4 ,to guard against the danger of
 receiving a  flash of lightning through
 his body1 he held the kite by means of 
a  silk ribbon1 which was tied to the   
door-key1 the door-key being itself     
attached to the lower end of the hempen 
string4    ,a flash of lightning soon   
came from the cloud1 and a second1 and a
  third2 but no sign of electricity     
could be observed in the kite1 or  the  
hempen cord1 or the key4 ,franklin was  
almost beginning to despair  of success1
 when suddenly he noticed that the      
little fibres of the  cord began to     
bristle up1 just as they would if it    
were placed near an  electric machine in
 action4 ,he presented the door-key to  
the knob of  the ,leyden jar1 and a     
spark passed between them4 ,presently a 
shower  began to fall2 the cord1 wetted 

by the rain1 became a better conductor  
than it had been before1 and sparks came
 more freely4 ,with these sparks  he now
 charged the ,leyden jar1 and found1 to 
his intense delight1 that  he could     
exhibit all the phenomena of electricity
 by means of the  lightning he had drawn
 from the clouds4    ,in the following  
year a similar experiment1 with even    
more striking  results1 was carried out1
 in ,france1 by de ,romas4 ,though it is
 said he  had no knowledge of what      
,franklin had done in ,america1 he1 too1
 used  a kite2 and1 with a view of      
making the string a better conductor1 he
  interlaced with it a thin copper wire4
 ,then1 flying his kite in the  ordinary
 way1 when it had risen to a height of  
about #eej feet1 he drew  sparks from it
 which1 we are told1 were upwards of    
nine feet long1 and  emitted a sound    
like the report of a pistol4      ,fatal
 ,experiment of ,richman4--,there can be
 no doubt that experiments  of this     
kind1 made with the electricity of a    

thundercloud1 were  extremely dangerous2
 and this was soon proved by a fatal    
accident4  ,professor ,richman1 of ,st4 
,petersburgh1 had erected on the roof of
 his  house a pointed iron rod1 the     
lower end of which passed into a glass  
vessel1 intended1 as we are informed1 to
 measure the strength of the  charge    
which he expected to receive from the   
clouds4 ,on the sixth of  ,august1      
#agec1 observing the approach of a      
thunderstorm1 he hastened  to his       
apparatus2 and as he stood near it1 with
 his head bent down1  to watch the      
effect1 a flash of lightning passed     
through his body and  killed him on the 
spot4 ,this catastrophe served to fix   
public attention  on the danger of such 
experiments1 and gave occasion to the   
saying of  ,voltaire3 8,there are some  
great lords whom we should always       
approach  with extreme precaution1 and  
lightning is one of them40#a ,from this 
time the practice of making experiments 
directly with the lightning of  the     

clouds seems to have been1 by common    
consent1 abandoned4      ,immediate     
,cause of ,lightning4--,and now1 having 
set before you some  of the most        
memorable experiments by which the      
identity of lightning  and electricity  
has been demonstrated1 ,i will try to   
give you a clear  conception regarding  
the immediate cause of lightning1 so far
 as the  subject is understood at the   
present day by scientific men4 ,you know
  that there are two kinds of           
electricity1 which are called positive  
and negative2 and that each of them     
repels electricity of the same  kind as 
itself1 while it attracts electricity of
 the opposite kind4  ,now1 every        
thundercloud is charged with electricity
 of one kind or  the other1 positive or 
negative2 and1 as it hovers over the    
earth1 it  develops1 by what is called  
induction1 or influence1 electricity  of
 the opposite kind in that part of the  
earth which is immediately  under it4   
,thus we have two bodies--the cloud and 

the earth--charged  with opposite kinds 
of electricity1 and separated by a      
stratum of the  atmosphere4 ,the two    
opposite electricities powerfully       
attract each  other2 but for a time they
 are prevented from rushing together by 
the  intervening stratum of air1 which  
is a non-conductor of electricity1  and 
acts as a barrier between them4 ,as the 
electricity1 however1  continues to     
accumulate1 the attraction becomes      
stronger and stronger1  until at length 
it is able to overcome the resistance of
 this barrier2  a violent disruptive    
discharge then takes place between the  
cloud  and the earth1 and the flash of  
lightning is the consequence of the     
discharge4    ,illustration3 ,,the      
,,electric ,,spark2 ,a ,,type ,,of ,a   
,,flash ,,of ,,lightning4    ,the whole 
phenomenon may be illustrated1 on a     
small scale1 by means  of this electric 
machine of ,carr's which you see before 
you4 ,when  my assistant turns the      
handle of the machine negative          

electricity is  developed in that large 
brass cylinder1 which in our experiment 
will  represent the thundercloud4 ,at a 
distance of five or six inches from  the
 cylinder ,i hold a brass ball1 which is
 in electrical communication  with the  
earth through my body4 ,the electrified 
brass cylinder acts  by induction1 or   
influence on the brass ball1 and        
develops in it1 as  well as in my body1 
a charge of positive electricity4 ,now1 
the positive  electricity of the ball   
and the negative electricity of the     
cylinder  are mutually attracting each  
other1 but the intervening stratum of   
air  offers a resistance which prevents 
a discharge from taking place4 ,my      
assistant1 however1 continues to work   
the machine2 the two opposite           
electricities rapidly accumulate on the 
cylinder and the ball2 at  length their 
mutual attraction is strong enough to   
overcome the  resistance interposed     
between them2 a disruptive discharge    
follows1  and at the same moment a spark

 is seen to pass1 accompanied by a sharp
  snapping report4    ,this spark is a  
miniature flash of lightning2 and the   
snapping report  is a diminutive peal of
 thunder4 ,furthermore1 at the moment   
the spark  passes you may observe a     
slight convulsive movement in my hand   
and  wrist4 ,this convulsive movement   
represents1 on a small scale1 the       
violent shock1 generally fatal to life1 
which is produced by a flash of         
lightning when it passes through the    
body4    ,i can continue to take sparks 
from the conductor as long as the       
machine  is worked2 and it is           
interesting to observe that these sparks
 follow  an irregular zig-zag course1   
just as lightning does4 ,the reason is  
the  same in both cases3 a discharge    
between two electrified bodies takes    
place along the line of least           
resistance2 and1 owing to the varying   
condition of the atmosphere1 as well as 
of the minute particles of  matter      
floating in it1 the line of least       

resistance is almost always a  zig-zag  
line4      ,what a ,flash of ,lightning 
is4--,lightning1 then1 may be conceived 
as  an electrical discharge1 sudden and 
violent in its character1 which  takes  
place1 through the atmosphere1 between  
two bodies highly charged  with opposite
 kinds of electricity4 ,sometimes this  
electrical discharge  passes1 as ,i have
 said1 between a cloud and the earth2   
sometimes it  passes between one cloud  
and another2 sometimes1 on a smaller    
scale1  it takes place1 between the     
great mass of a cloud and its outlying  
fragments4    ,but1 if you ask me in    
what the discharge itself consists1 ,i  
am utterly  unable to tell you4 ,it is  
usual to speak and write on this subject
 as  if electricity were a material     
substance1 a very subtle fluid1 and as  
if1 at the moment the discharge takes   
place1 this fluid passes like a  rapid  
stream1 from the body that is positively
 electrified to the body  that is       
negatively electrified4 ,but we must    

always remember that this  is only a    
conventional mode of expression1        
intended chiefly to assist  our         
conceptions1 and to help us to talk     
about the phenomena4 ,it does  not even 
profess to represent the objective      
truth4 ,all that we know  for certain is
 this3 that immediately before the      
discharge the two  bodies are highly    
electrified with opposite kinds of      
electricity2 and1  that immediately     
after the discharge1 they are found to  
have returned  to their ordinary        
condition1 or1 at least1 to have become 
less highly  electrified than they were 
before4    ,the flash of light that     
accompanies an electric discharge is    
often  supposed to be the electricity   
itself1 passing from one body to  the   
other4 ,but it is not2 it is simply an  
effect produced by the  discharge4 ,heat
 is generated by the expenditure of     
electrical energy1  in overcoming the   
resistance offered by the atmosphere2   
and this heat  is so intense1 that it   

produces a brilliant incandescence along
 the  path of the discharge4 ,when a    
spark appears1 for example1 between the 
conductor of the machine and this brass 
ball1 it can be shown1 by very          
satisfactory evidence1 that minute      
particles of these solid bodies are     
first converted into vapor1 and then    
made to glow with intense heat4  ,the   
gases1 too1 of which the air is         
composed1 and the solid particles       
floating in the air1 are likewise raised
 to incandescence4 ,so1 too1  with      
lightning2 the flash of light is due to 
the intense heat generated  by the      
electrical discharge1 and owes its      
character to the composition  and the   
density of the atmosphere through which 
the discharge passes4      ,duration of 
a ,flash of ,lightning4--,how long does 
a flash of lightning  last8 ,you are    
aware1 ,i dare say1 that when an        
impression of light is  made on the eye1
 the impression remains for a sensible  
interval of  time1 not less than the    

tenth of a second1 after the source of  
light  has been extinguished or removed4
 ,hence we continue1 in fact1 to see    
the light1 for at least the tenth of a  
second1 after the light has  ceased4    
,now1 if you reflect how brief is the   
moment for which a flash  of lightning  
is visible1 and if you deduct the tenth 
of a second from  that brief moment1 you
 will see1 at once1 that the period of  
its actual  duration must be very short 
indeed4    ,the exact duration of a     
flash of lightning is a question on     
which no  settled opinion has yet been  
accepted generally by scientific men4   
,indeed1 the most widely different      
statements have been made on the        
subject1 quite recently1 by the highest 
authorities1 each speaking  apparently  
with unhesitating confidence4 ,thus1 for
 example1 ,professor  ,mascart describes
 an experiment1 which he says was made  
by ,wheatstone1  and which showed that a
 flash of lightning lasts for less than 
one-thousandth of a second2#b ,professor

 ,everett describes the same            
experiment1 without saying by whom it   
was made1 and gives1 as the  result1    
that 8the duration of the illumination  
produced by lightning  is certainly less
 than the ten-thousandth of a second20#c
 ,professor  ,tyndall1 in his own       
picturesque way1 tells us that 8a flash 
of  lightning cleaves a cloud1 appearing
 and disappearing in less than the      
hundred-thousandth of a second20#d and  
according to ,professor ,tait1  of      
,edinburgh1 8,wheatstone has shown that 
lightning certainly lasts less  than the
 millionth of a second40#e              
,experiments of ,professor ,rood4--,i   
cannot say which of these  statements is
 best supported by actual observation2  
for none of the  writers ,i have quoted 
gives any reference to the original     
memoir from  which his statement is     
derived4 ,as far as my own reading goes1
 ,i have  only come across one original 
record of experiments1 made directly on 
the flash of lightning itself1 with a   

view to determine the period of  its    
duration4 ,these experiments were       
carried out by ,professor ,ogden  ,rood1
 of ,columbia ,college1 ,new ,york1     
between the years #ahgj and #ahgc1  and 
are recorded in the ,american ,journal  
of ,science and ,arts4#f    ,for the    
description of his apparatus1 and for   
the details of his  observations1 ,i    
must refer you to the memoir itself2 but
 ,i may tell you  briefly that the      
results at which he arrived1 if they be 
accepted1 must  lead to a considerable  
modification of the views previously    
entertained  on the subject4 ,in the    
first place1 he satisfied himself that  
what  appears to the eye a single flash 
of lightning is usually1 if not  always1
 multiple in its character2 consisting1 
in fact1 of a succession  of distinct   
flashes1 which follow one another with  
such rapidity as  to make a continuous  
impression on the retina4 ,next1 he     
proceeded to  measure approximately the 
duration of these several component     

flashes2  and he found that it varied   
over a wide range1 amounting sometimes  
to  fully the twentieth of a second1 and
 being sometimes less than the          
sixteen-hundredth of a second4          
,wheatstone's ,experiments4--,these     
results are extremely interesting2  but 
we can hardly regard them as finally    
established1 until they have  been      
confirmed by other observers4 ,i may    
remark1 however1 that they  fit in very 
well with the experiments made by       
,professor ,wheatstone1  many years ago1
 on the duration of the electric spark1 
which1 as ,i told  you1 is a miniature  
flash of lightning4 ,in these classical 
experiments1  which leave nothing to be 
desired in point of accuracy1 ,professor
  ,wheatstone showed that a spark taken 
directly from a ,leyden jar1 or a  spark
 taken from the conductor of a powerful 
electric machine1 that is1  just such a 
spark as you have seen here to-day1     
lasts for less than the  millionth of a 
second4    ,but he also showed that the 

duration of the spark is greatly        
increased1  when a resisting wire is    
introduced into the path of the         
discharge4  ,thus1 for example1 when the
 discharge from a ,leyden jar was made  
to  pass through half a mile of copper  
wire1 with breaks at intervals1 the     
sparks that appeared at these breaks    
were found to last for   of a second4#g 
,hence we should naturally expect that  
the period of  illumination would be    
still further increased1 in the case of 
a flash  of lightning1 where the        
resistance interposed is enormously     
greater  than in either of the          
experiments made by ,wheatstone4#h      
,experiment of the ,rotating ,disk4--,it
 would be tedious1 on an occasion  like 
the present1 to enter into an account of
 ,wheatstone's beautiful  and ingenious 
method of investigation1 by which the   
above facts have  been established2 but 
,i will show you a much more simple     
experiment  which brings home very      
forcibly to the mind how exceedingly    

short  must be the duration of the      
electric spark4 ,here is a circular disk
  of cardboard1 the outer part of which1
 as you see1 is divided into  sectors1  
black and white alternately1 while the  
space about the centre  is entirely     
white4 ,the disk is mounted on a stand1 
by means of which  ,i can make it rotate
 with great velocity4 ,when it is put in
 rotation1  the effect on the eye is    
very striking--the central space remains
 white  as before1 but in the outer rim 
the distinction of black and white      
absolutely disappears and gives place to
 a uniform gray4 ,this color is  due to 
the blending together of black and white
 in equal proportions2  the blending    
being effected1 not on the cardboard    
disk1 but on the  retina of the eye4    
,illustration3 ,,cardboard ,,disk ,,as  
,,seen ,,when ,,at ,,rest4              
,illustration3 ,,same ,,disk ,,as ,,seen
 ,,when ,,in ,,rapid ,,rotation4    ,i  
mentioned just now that an impression   
made on the retina lasts for  the tenth 

of a second after the cause of it has   
been removed4 ,now1 when  this disk is  
in rotation1 the sectors follow one     
another so rapidly  that the particular 
part of space occupied at any moment by 
a white  sector will be occupied by a   
black sector within a time much less    
than  the tenth of a second4 ,it follows
 that the impression made by each  white
 sector remains on the retina until the 
following black sector  comes into the  
same position2 and1 in like manner1 the 
impression made  by each black sector   
remains until the following white sector
 takes up  the position of the black4   
,therefore1 the impression made by the  
whole  outer rim is the impression of   
black and white combined--that is1 the  
impression of gray4    ,so far1 ,i dare 
say1 the phenomenon is already familiar 
to you all4  ,but ,i propose now to show
 you the revolving disk illuminated by  
the electric spark2 and you will observe
 that1 at the moment of  illumination1  
the black and white sectors come out as 

clearly and  distinctly as if the disk  
were standing still4    ,for the success
 of this experiment it is desirable1 not
 only to have  a brilliant spark in     
order to secure a good illumination of  
the disk1  but also to have a succession
 of such sparks1 that you may see the   
phenomenon frequently repeated1 and thus
 be able to observe it at your  leisure4
 ,to attain these two objects1 ,i have  
made the arrangement which  is here     
before you4    ,in front of the disk is 
a large and very powerful ,leyden jar4  
,the  rod connected with the inner      
coating rises well above the mouth of   
the jar1 and ends in a brass ball nearly
 opposite the centre of the  disk4      
,connected with the outer coating of the
 jar is another rod  which likewise ends
 in a brass ball1 and which is so       
adjusted that  the distance between the 
two balls is about an inch4 ,the two    
rods are  connected respectively with   
the two conductors of a ,holtz machine1 
so  that1 when the machine is worked1   

the jar is first quickly charged1  and  
then it discharges itself1 with a       
brilliant spark1 between the  two brass 
balls4 ,thus1 by continuing to work the 
machine1 we can get1  as long as we     
choose1 a succession of sparks following
 one another at  short and regular      
intervals right in front of the disk4   
,everything being now ready1 and the    
room partially darkened1 the  disk is   
put in rapid rotation2 and you can see1 
by the twilight that  remains1 the outer
 rim a uniform gray1 and the central    
space white4  ,but when my assistant    
begins to turn the ,holtz machine1 and  
brilliant  sparks leap out at intervals1
 the revolving disk1 illuminated for a  
moment at each discharge1 seems to be   
standing still1 and shows the  black and
 white sectors distinctly visible4      
,the reason of this is clear3 ,so brief 
is the moment for which the spark       
endures1 that the disk1 though in rapid 
motion1 makes no sensible  advance      
during that small fraction of time2     

therefore1 in the image on  the retina1 
the impression made by the white sectors
 remains distinct  from the impression  
made by the black1 and the eye sees the 
disk as it  really is4    ,i may notice1
 in passing1 a very interesting         
consideration1 suggested  by this       
experiment4 ,a cannon ball is now       
commonly discharged with a  velocity of 
about #a1fjj feet a second4 ,moving with
 this velocity it  is1 as you know1     
under ordinary circumstances1 altogether
 invisible to  the eye4 ,but suppose it 
were illuminated1 in the darkness of    
night1  by this electric spark1 which   
lasts1 we will say1 for the millionth   
of a second4 ,during the moment of      
illumination1 the cannon ball moves     
through the millionth part of #a1fjj    
feet1 which is a little less than  the  
fiftieth of an inch4 ,practically1 we   
may say that the cannon ball  does not  
sensibly change its place while the     
spark lasts4 ,further1 the  impression  
it makes on the eye1 from the position  

it occupies at the  moment of           
illumination1 remains on the retina for 
at least the tenth  of a second4        
,therefore1 if we are looking toward    
that particular part  of space where the
 cannon ball happens to be at the moment
 the spark  passes1 we must see the     
cannon ball hanging motionless in the   
air1  though we know it is traveling at 
the rate of #a1fjj feet a second1 or    
about #a1jjj miles an hour4             
,brightness of a ,flash of              
,lightning4--,i should like to say one  
word  about the brightness of a flash of
 lightning4 ,somewhat more than  thirty 
years ago1 ,professor ,swan1 of         
,edinburgh1 showed that the eye         
requires a sensible time--about the     
tenth of a second--to perceive  the full
 brightness of a luminous object4       
,further1 he proved1 by a  series of    
interesting experiments1 that when a    
flash of light lasts  for less than the 
tenth of a second1 its apparent         
brilliancy to the  eye is proportional  

to the time of its duration4#i ,now     
consider the  consequence of these facts
 in reference to the brightness of our  
electric spark4 ,if the spark lasted for
 the tenth of a second1 we  should      
perceive its full brightness2 if it     
lasted for the tenth part of  that time1
 we should see only the tenth part of   
its brightness2 if it  lasted for the   
hundredth part1 we should see only the  
hundredth part  of its brightness2 and  
so on4 ,but we know1 in point of fact1  
that it  lasts for less than the        
millionth of a second1 that is1 less    
than the  hundred-thousandth part of the
 tenth of a second4 ,therefore we see   
only  the hundred-thousandth part of its
 real brightness4    ,here is a         
startling conclusion1 and one1 ,i may   
say1 fully justified  by scientific     
evidence4 ,that electric spark1         
brilliant as it appears  to us1 is      
really a hundred thousand times as      
bright as it seems to  be4 ,we cannot   
speak with the same precision of a flash

 of lightning2  because its duration has
 not yet been so exactly determined4    
,but if we  suppose that a flash of     
lightning1 in a particular case1 lasts  
for the  thousandth of a second1 it     
would follow1 from the above            
experiments1  that the flash is a       
hundred times as bright1 in fact1 as it 
appears to  the eye4      ,various      
,forms of ,lightning4--,the lightning of
 which ,i have spoken  hitherto is      
commonly called forked lightning2 a name
 which seems  to have been derived from 
the zig-zag line of light it presents to
  the eye4 ,but there are other forms   
under which the electricity of the      
clouds often makes itself manifest2 and 
to these ,i would now invite  your      
attention for a few moments4 ,the most  
common of them all1 at least  in this   
country1 is that which is familiarly    
known by the name of  sheet lightning4  
,this is1 probably1 nothing else than   
the lighting up  of the atmosphere1 or  
of the clouds1 by forked lightning1     

which is not  itself directly visible4  
,generally speaking1 after a flash of   
sheet lightning1 we hear the  rolling of
 distant thunder4 ,but it sometimes     
happens1 especially in  summer time1    
that the atmosphere is again and again  
lit up by a sudden  glow of light1 and  
yet no thunder is heard4 ,this          
phenomenon is commonly  called summer   
lightning1 or heat lightning4 ,it is    
probably due1  in many cases1 to        
electrical discharges in the higher     
regions of the  atmosphere1 where the   
air is greatly rarified2 and1 in these  
cases1 it  would seem to resemble the   
discharges obtained by means of an      
induction  coil in glass tubes          
containing rarified gases4 ,but there is
 little  doubt that in many cases1 too1 
summer lightning1 like ordinary sheet   
lightning1 is due to forked lightning1  
which is so remote that we can  neither 
see the flash itself directly1 nor hear 
the rolling of the  thunder4    ,perhaps
 the most distinct and satisfactory     

evidence on this subject1  derived from 
actual observation1 is contained in the 
following letter  of ,professor         
,tyndall1 written in ,may1 #ahhc3       
8,looking to the south  and south-east  
from the ,bel ,alp1 the play of silent  
lightning among  the clouds and         
mountains is sometimes very wonderful4  
,it may be seen  palpitating for hours1 
with a barely appreciable interval      
between  the thrills4 ,most of those who
 see it regard it as lightning without  
thunder--,blitz ohne ,donner1           
,wetterleuchten1 ,i have heard it named 
by  ,german visitors4 ,the ,monte       
,generoso1 overlooking the ,lake of     
,lugano1 is  about fifty miles from the 
,bel ,alp1 as the crow flies4 ,the two  
points  are connected by telegraph2 and 
frequently when the ,wetterleuchten1  as
 seen from the ,bel ,alp1 was in full   
play1 ,i have telegraphed to the        
proprietor of the ,monte ,generoso      
,hotel and learned1 in every instance1  
that our silent lightning co-existed in 

time with a thunderstorm more  or less  
terrific in upper ,italy40#aj           
,another form of lightning1 described by
 many writers1 is called globe          
lightning4 ,it is said to appear as a   
ball of fire1 about the size of  a      
child's head1 or even larger1 which     
moves for a time slowly about1  and     
then1 after the lapse of several        
seconds1 explodes with a terrific       
noise1 sending forth flashes of fire in 
all directions1 which burn  whatever    
they strike4 ,many accounts are on      
record of such phenomena2  but they are 
derived1 for the most part1 from the    
evidence of persons  who were not       
specially competent to observe1 and to  
describe with  precision1 the facts that
 fell under their observation4 ,hence   
these  accounts1 while they are accepted
 by some1 are rejected by others2  and  
it seems to me1 in the present state of 
the question1 that the  existence of    
globe lightning can hardly be regarded  
as a demonstrated  fact4 ,at all events1

 if phenomena of this kind have really  
occurred1 ,i  can only say that nothing 
we know about electricity1 at present1  
will  enable us to account for them4#aa 
,st4 ,elmo's ,fire4--,a much more       
authentic and1 at the same time1 very   
interesting form1 under which the       
electricity of the clouds sometimes     
manifests its presence1 is known by the 
name of ,st4 ,elmo's fire4 ,this        
phenomenon at one time presents the     
appearance of a star1 shining at  the   
points of the lances or bayonets of a   
company of soldiers2 at  another1 it    
takes the form of a tuft of bluish      
light1 which seems to  stream away from 
the masts and spars of a ship at sea1 or
 from the  pointed spire of a church4   
,it was well known to the ancients4     
,csar1  in his ,commentaries1 tells us  
that1 after a stormy night1 the iron    
points of the javelins of the fifth     
legion seemed to be on fire2 and  ,pliny
 says that he saw lights1 like stars1   
shining on the lances of  the soldiers1 

keeping watch by night upon the         
ramparts4 ,when two  such lights        
appeared at once1 on the masts of a     
ship1 they were  called ,castor and     
,pollux1 and were regarded by sailors as
 a sign of a  prosperous voyage4 ,when  
only one appeared1 it was called ,helen1
 and was  taken as an unfavorable omen4 
,in modern times ,st4 ,elmo's fire has  
been witnessed by a host of  observers1 
and all its various phases have been    
repeatedly described4  ,in the memoirs  
of ,forbin we read that1 when he was    
sailing once1 in  #afif1 among the      
,balearic ,islands1 a sudden storm came 
on during the  night1 accompanied by    
lightning and thunder4 8,we saw on the  
vessel10 he  says1 8more than thirty    
,st4 ,elmo's fires4 ,among the rest     
there was one  on the vane of the       
mainmast more than a foot and a half    
high4 ,i sent a  man up to fetch it     
down4 ,when he was aloft he cried out   
that it made  a noise like wetted       
gunpowder set on fire4 ,i told him to   

take off the  vane and come down2 but1  
scarcely had he removed it from its     
place1  when the fire left it and       
reappeared at the end of the mast1 so   
that  it was impossible to take it away4
 ,it remained for a long time1 and      
gradually went out40    ,on the #adth of
 ,january1 #ahbd1 ,monsieur ,maxadorf   
happened to look at a  load of straw in 
the middle of a field just under a dense
 black cloud4  ,the straw seemed        
literally on fire--a streak of light    
went forth from  every blade2 even the  
driver's whip shone with a pale-blue    
flame4 ,as  the black cloud passed away1
 the light gradually disappeared1 after 
having lasted about ten minutes4 ,again1
 it is related that on the #hth  of     
,may1 #ahca1 in ,algiers1 as the ,french
 artillery officers were walking  out   
after sunset without their caps1 each   
one saw a tuft of blue light  on his    
neighbor's head2 and1 when they         
stretched out their hands1 a  tuft of   
light was seen at the end of every      

finger4 ,not infrequently a  traveler in
 the ,alps sees the same luminous tuft  
on the point of his  alpenstock4 ,and   
quite recently1 during a thunderstorm1 a
 whole forest  was observed to become   
luminous just before each flash of      
lightning1  and to become dark again at 
the moment of the discharge4#ab    ,this
 phenomenon may be easily explained4 ,it
 consists in a gradual and              
comparatively silent electrical         
discharge between the earth and the     
cloud2 and generally1 but not always1 it
 has the effect of preventing  such an  
accumulation of electricity as would be 
necessary to produce  a flash of        
lightning4 ,i can illustrate this kind  
of discharge with  the aid of our       
machine4 ,if ,i hold a pointed metal rod
 toward the  large conductor1 you can   
see1 when the machine is worked and the 
room  darkened1 how the point of the rod
 becomes luminous and shines like a     
faint blue star4 ,i substitute for the  
pointed rod the blunt handles of  a pair

 of pliers1 and a tuft of blue light is 
at once developed at the  end of each   
handle1 and seems to stream away with a 
hissing noise4 ,i  now put aside the    
pliers1 and open out my hand under the  
conductor--and  observe how ,i can set  
up1 at pleasure1 a luminous tuft at the 
tips  of my fingers4 ,now and then a    
spark passes1 giving me a smart shock1  
and showing how the electricity may     
sometimes accumulate so fast that  it   
cannot be sufficiently discharged by the
 luminous tuft4 ,lastly1 ,i  present a  
small bushy branch of a tree to the     
conductor1 and all its  leaves and twigs
 are aglow with bluish light1 which     
ceases for a moment  when a spark       
escapes1 to be again renewed when       
electricity is again  developed by the  
working of the machine4                 
,illustration3 ,,the ,,brush            
,,discharge1 ,,illustrating ,,st4       
,,elmo',s ,,fire4    ,now1 if you put a 
thundercloud in the place of that       
conductor1 you can  easily realize how1 

through its influence1 the lance and    
bayonet of  the soldier1 the alpenstock 
of the traveler1 the pointed spire of a 
church1 the masts of a ship at sea1 the 
trees of a forest1 can all be  made to  
glow with a silent electrical discharge 
which may or may not1  according to     
circumstances1 culminate at intervals in
 a genuine flash  of lightning4         
,origin of ,lightning4--,when we seek to
 account for the origin of  lightning1  
we are confronted at once with two      
questions of great  interest and        
importance--first1 ,what are the sources
 from which the  electricity of the     
thundercloud is derived8 and1 secondly1 
,how does  this electricity come to be  
developed in a form which so far        
transcends  in power the electricity of 
our machines8 ,these questions have long
  engaged the attention of scientific   
men1 but ,i cannot say that they  have  
yet received a perfectly satisfactory   
solution4 ,nevertheless1  some facts of 
great scientific value have been        

established1 and some  speculations have
 been put forward1 which are well       
deserving of  consideration4    ,in the 
first place1 it is quite certain that   
the atmosphere which  surrounds our     
globe is almost always in a state of    
electrification4  ,further1 the         
electrical condition of the atmosphere  
would seem to be  as variable as the    
wind4 ,it changes with the change of    
season2 it  changes from day to day2 it 
changes from hour to hour4 ,the charge  
of  electricity is sometimes positive1  
sometimes negative2 sometimes it  is    
strong1 sometimes feeble2 and the       
transition from one condition to        
another is sometimes slow and gradual1  
sometimes sudden and violent4    ,as a  
general rule1 in fine1 clear weather1   
the electricity of the  atmosphere is   
positive1 and not very strongly         
developed4 ,in wet weather  the charge  
may be either positive or negative1 and 
is generally  strong1 especially when   
there are sudden heavy showers4 ,in fog 

it is  also strong1 and almost always   
positive4 ,in a snowstorm it is very    
strong1 and most frequently positive4   
,finally1 in a thunderstorm it is       
extremely strong1 and generally         
negative2 but it is subject to a sudden 
change of sign1 when a flash of         
lightning passes or when rain begins to 
fall4    ,so far ,i have simply stated  
facts1 which have been ascertained  by  
careful observations1 made at different 
stations by competent  observers1 and   
extending over a period of many years4  
,but as regards  the process by which   
the electricity of the atmosphere is    
developed1 we  have1 up to the present  
time1 no certain knowledge4 ,it has been
 said  that electricity may be generated
 in the atmosphere by the friction of   
the air itself1 and of the minute       
particles floating in it1 against  the  
surface of the earth1 against trees and 
buildings1 against rocks1  cliffs1 and  
mountains4 ,but this opinion1 however   
probable it may be1  has not yet been   

confirmed by any direct experimental    
investigation4    ,the second theory is 
that the electricity of the atmosphere  
is due1 in  great part at least1 to the 
evaporation of salt water4 ,many years  
ago1  ,pouillet1 a ,french philosopher1 
made a series of experiments in the     
laboratory1 which seemed to show that   
evaporation is generally attended  with 
the development of electricity2 and1 in 
particular1 he satisfied  himself that  
the vapor which passes off from the     
surface of salt water  is always        
positively electrified4 ,now1 the       
atmosphere is everywhere  charged1 more 
or less1 with vapor which comes1 almost 
entirely1 from  the salt water of the   
ocean4 ,hence ,pouillet inferred that   
the chief  source of atmospheric        
electricity is the evaporation of sea   
water4  ,this explanation would         
certainly go far to account for the     
presence  of electricity in the         
atmosphere1 if the fact on which it     
rests were  established beyond dispute4 

,but there is some reason to doubt      
whether  the development of electricity1
 in the experiments of ,pouillet1 was   
due  simply to the process of           
evaporation1 and not rather to other    
causes1  the influence of which he did  
not sufficiently take into account4     
,a conjecture has recently been started 
that electricity may be  generated by   
the mere impact of minute particles of  
water vapor against  minute particles of
 air4#ac ,if this conjecture could be   
established as  a fact1 it would be     
amply sufficient to account for all the 
electricity  of the atmosphere4 ,from   
the very nature of a gas1 the molecules 
of  which it is composed are forever    
flying about with incredible velocity2  
and therefore the particles of water    
vapor and the particles of air1  which  
exist together in the atmosphere1 must  
be incessantly coming  into collision4  
,hence1 however small may be the charge 
of electricity  developed at each       
individual impact1 the total amount     

generated over  any considerable area1  
in a single day1 must be very great     
indeed4  ,it is evident1 however1 that  
this method of explaining the origin of 
atmospheric electricity can only be     
regarded as1 at best1 a probable        
hypothesis1 until the assumption on     
which it rests is supported by the      
evidence of observation or experiment4  
,length of a ,flash of ,lightning4--,it 
would seem1 then1 that we are  not yet  
in a position to indicate with certainty
 the sources from  which the electricity
 of the atmosphere is derived4 ,but     
whatever  these sources may be1 there   
can be little doubt that the electricity
  of the atmosphere is intimately       
associated with the minute particles  of
 water vapor of which the thundercloud  
is eventually built up4  ,this          
consideration is of great importance    
when we come to consider  the special   
properties of lightning1 as compared    
with other forms of  electricity4 ,the  
most striking characteristic of         

lightning is the  wonderful power it    
possesses of forcing its way through the
 resisting  medium of the air4 ,in this 
respect it incomparably surpasses all   
forms  of electricity that have hitherto
 been produced by artificial means4     
,the spark of an ordinary electric      
machine can leap across a space of      
three or four inches2 the machine we    
have employed in our experiments  to-day
 can give1 under favorable              
circumstances1 a spark of nine or ten   
inches2 the longest electric spark ever 
yet produced artificially is  probably  
the spark of ,mr4 ,spottiswoode's       
gigantic induction coil2 and  it does   
not exceed three feet six inches4 ,but  
the length of a flash of  lightning is  
not to be measured in inches1 or in feet
 or in yards2 it  varies from one or two
 miles1 for ordinary flashes1 to eight  
or ten  miles in exceptional cases4     
,this power of discharging itself       
violently through a resisting  medium1  
in which the thundercloud so far        

transcends the conductor of  an electric
 machine1 is due to the property        
commonly known among  scientific men as 
electrical potential4 ,the greater the  
distance to  which an electrified body  
can shoot its flashes through the air1  
the  higher must be its potential4      
,hence the potential of a thundercloud  
must be exceedingly high1 since its     
flashes can pierce the air to a         
distance of several miles4 ,and what ,i 
want to point out is1 that we  are able 
to account for this exceedingly high    
potential1 if we may  only assume that  
the minute particles of water vapor in  
the atmosphere  have1 from any cause1   
received ever so small a charge of      
electricity4  ,the number of such       
particles that go to make up an ordinary
 drop of  rain are to be counted by     
millions of millions2 and it is capable 
of  scientific proof that1 as each new  
particle is added1 in the building  up  
of the drop1 a rise of potential is     
necessarily produced4 ,it is  clear1    

therefore1 that there is practically no 
limit to the potential  that may be     
developed by the simple agglomeration of
 very small cloud  particles1 each      
carrying a very small charge of         
electricity4#ad    ,this explanation1   
which traces the exceedingly high       
potential of  lightning to the building 
up of rain drops in the thundercloud1   
suggests a reason why it so often       
happens that immediately after a  flash 
of lightning 8the big rain comes dancing
 to the earth40 ,the  potential has been
 steadily rising as the drops have been 
getting  larger and larger1 until at    
length the potential has become so high 
that the thundercloud is able to        
discharge itself1 and almost at the     
same moment the drops have become so    
large that they can no longer be  held  
aloft against the attracting force of   
gravity4      ,physical ,cause of       
,thunder4--,let us now proceed to       
consider the  phenomenon of thunder1    
which is so intimately associated with  

lightning1 and which1 though perfectly  
harmless in itself1 and though  never   
heard until the real danger is past1    
often excites more terror  in the mind  
than the lightning flash itself4 ,the   
sound of thunder1  like that of the     
electric spark1 is due to a disturbance 
caused in  the air by the electric      
discharge4 ,the air is first expanded by
 the  intense heat that is developed    
along the line of discharge1 and then it
  rushes back again to fill up the      
partial vacuum which its expansion has  
produced4 ,this sudden movement gives   
rise to a series of sound waves1  which 
reach the ear in the form of thunder4   
,but there are certain  peculiar        
characteristics of thunder which are    
deserving of special  consideration4    
,rolling of ,thunder4--,they may be     
classified1 ,i think1 under two  heads4 
,first1 the sound of thunder is not an  
instantaneous report  like the sound of 
the electric spark--it is a prolonged   
peal lasting1  sometimes1 for several   

seconds4 ,secondly1 each flash of       
lightning gives  rise1 not to one peal  
only1 but to a succession of peals      
following  one another at irregular     
intervals4 ,these two phenomena1 taken  
together1 produce that peculiar effect  
on the ear which is commonly  described 
as the rolling of thunder2 and both of  
them1 ,i think1 may  be sufficiently    
accounted for in accordance with the    
well-established  properties of sound4  
,to understand why the sound of thunder 
reaches the ear as a prolonged  peal1 we
 have only to remember that sound takes 
time to travel4 ,since a  flash of      
lightning is practically instantaneous1 
we may assume that the  sound is        
produced at the same moment all along   
the line of discharge4  ,but the sound  
waves1 setting out at the same moment   
from all points  along the line of      
discharge1 must reach the ear in        
successive instants  of time1 arriving  
first from that point which is nearest  
to the  observer1 and last from that    

point which is most distant4 ,suppose1  
for  example1 that the nearest point of 
the flash is a mile distant from the    
observer1 and the farthest point two    
miles--the sound will take about  five  
seconds to come from the nearest point1 
and about ten seconds to  come from the 
farthest point2 and moreover1 in each   
successive instant  from the time the   
first sound reaches the ear1 sound will 
continue  to arrive from the successive 
points between4 ,therefore the thunder1 
though instantaneous in its origin1 will
 reach the ear as a prolonged  peal     
extending over a period of five seconds4
      ,succession of ,peals4--,the      
succession of peals produced by a single
  flash of lightning is due to several  
causes1 each one of which may           
contribute more or less1 according to   
circumstances1 toward the general       
effect4 ,first1 if we accept the results
 arrived at by ,professor ,ogden  ,rood1
 of ,columbia ,college1 what appears to 
the eye as a single flash  of lightning1

 consists1 in fact1 as a general rule1  
of a succession  of flashes1 each one of
 which must naturally produce its own   
peal of  thunder2 and although the      
several flashes1 if they follow one     
another  at intervals of the tenth of a 
second1 will make one continuous        
impression on the eye1 the several peals
 of thunder1 under the same  conditions1
 will impress the ear as so many        
distinct peals4    ,the next cause that 
,i would mention is the zigzag path of  
the lightning  discharge4 ,to make clear
 to you the influence of this           
circumstance1 ,i  must ask your         
attention for a moment to the diagram on
 next page4 ,let  the broken line       
represent the path of a flash of        
lightning1 and let ,o  represent the    
position of an observer4 ,the sound will
 reach him first  from the point ,a1    
which is nearest to him1 and then it    
will continue to  arrive in successive  
instants from the successive points     
along the line  ,a ,n and along the line

 ,a ,m1 thus producing the effect of a  
continuous  peal4 ,meanwhile the sound  
waves have been traveling from the point
 ,b1  and in due time will reach the    
observer at ,o4 ,coming as they do in a 
different direction from the former1    
they will strike the ear as the         
beginning of a new peal which1 in its   
turn1 will be prolonged by the  sound   
waves arriving1 in successive instants1 
from the successive  points along the   
line ,b ,m and ,b ,h4 ,a little later1  
the sound will  arrive from the more    
distant point ,c1 and a third peal will 
begin4 ,and  so there will be several   
distinct peals proceeding1 so to speak1 
from  several distinct points in the    
path of the lightning flash4            
,illustration3 ,,origin ,,of            
,,successive ,,peals ,,of ,,thunder4    
,a third cause to which the succession  
of peals may be referred is to  be found
 in the minor electrical discharges that
 must often take place  within the      
thundercloud itself4 ,a thundercloud is 

not a continuous mass  like the metal   
cylinder of this electric machine--it   
has many outlying  fragments1 more or   
less imperfectly connected with the     
principal body4  ,moreover1 the material
 of which the cloud is composed is only 
a very  imperfect conductor as compared 
with our brass cylinder4 ,for these  two
 reasons it must often happen1 about the
 time a flash of lightning  passes1 that
 different parts of the cloud will be in
 such different  electrical conditions  
as to give rise to electrical discharges
 within  the cloud itself4 ,each of     
these discharges produces its own peal  
of  thunder2 and thus we may have a     
number of minor peals1 sometimes        
preceding and sometimes following the   
great crash which is due to the         
principal discharge4    ,lastly1 the    
influence of echo has often a           
considerable share in  multiplying the  
number of peals of thunder4 ,the waves  
of sound1 going  forth in all           
directions1 are reflected from the      

surfaces of mountains1  forests1 clouds1
 and buildings1 and coming back from    
different  quarters1 and with varying   
intensity1 reach the ear like the roar  
of  distant artillery4 ,the striking    
effect of these reverberations in a     
mountain district has been described by 
a great poet in words which1 ,i         
daresay1 are familiar to most of you3   
8,far along1    ,from peak to peak1 the 
rattling crags among1      ,leaps the   
live thunder6 ,not from one lone cloud1 
,but every mountain now has found a     
tongue1      ,and ,jura answers from her
 misty shroud      ,back to the joyous  
,alps1 that call to her aloud60         
,variations of ,intensity in            
,thunder4--,from what has been said1 it 
is easy to understand how the general   
roar of thunder is subject to  great    
changes of intensity1 during the time it
 lasts1 according to  the number of     
peals that may be arriving at the ear of
 an observer in  each particular moment4
 ,but every one must have observed that 

even an  individual peal of thunder     
often undergoes similar changes1        
swelling  out at one moment with great  
power1 and the next moment rapidly      
dying away4 ,to account for this        
phenomenon1 ,i would observe1 first1    
that there is no reason to suppose that 
the disturbance caused by  lightning is 
of exactly the same magnitude at every  
point of its path4  ,on the contrary1 it
 would seem very probable that the      
amount of this  disturbance is1 in some 
way1 dependent on the resistance which  
the  discharge encounters4 ,hence the   
intensity of the sound waves sent forth 
by a flash of lightning is probably very
 different at different parts  of its   
course2 and each individual peal will   
swell out on the ear or  die away1      
according to the greater or less        
intensity of the sound waves  that reach
 the ear in each successive moment of   
time4    ,but there is another influence
 at work which must produce variations  
in the loudness of a peal of thunder1   

even though the sound waves1 set  in    
motion by the lightning1 were everywhere
 of equal intensity4 ,this  influence   
depends on the position of the observer 
in relation to the  path of the         
lightning flash4 ,at one part of its    
course the lightning  may follow a path 
which remains for a certain length at   
nearly the  same distance from the      
observer2 then all the sound produced   
along  this length will reach the       
observer nearly at the same moment1 and 
will burst upon the ear with great      
intensity4 ,at another part1 the        
lightning may for an equal length go    
right away from the observer2 and  it is
 evident that the sound produced along  
this length will reach the  observer in 
successive instants1 and consequently   
produce an effect  comparatively feeble4
    ,with a view to investigate this    
interesting question a little more      
closely1 let me suppose the position of 
the observer taken as a  centre1 and a  
number of concentric circles drawn1     

cutting the path of  the lightning      
flash1 and separated from one another by
 a distance of  #aaj feet1 measured     
along the direction of the radius4 ,it  
is evident  that all the sound produced 
between any two consecutive circles will
  reach the ear within a period which   
must be measured by the time that  sound
 takes to travel #aaj feet1 that is1    
within the tenth of a second4  ,hence1  
in order to determine the quantity of   
sound that reaches the  ear in          
successive periods of one-tenth of a    
second1 we have only to  observe how    
much is produced between each two       
consecutive circles4  ,but on the       
supposition that the sound waves1 set in
 motion by the  flash of lightning1 are 
of equal intensity at every point of its
 path1  it is clear that the quantity of
 sound developed between each two       
consecutive circles will be simply      
proportional to the length of the  path 
enclosed between them4    ,with these   
principles established1 let us now      

follow the course of a  peal of thunder1
 in the diagram before us4 ,this broken 
line1 drawn  almost at random1          
represents the path of a flash of       
lightning2 the  observer is supposed to 
be placed at ,o1 which is the centre of 
the  concentric circles2 these circles  
are separated from one another by a     
distance of #aaj feet1 measured in the  
direction of the radius2 and we  want to
 consider how any one peal of thunder   
may vary in loudness in  the successive 
periods of one-tenth of a second4       
,illustration3 ,,variations ,,of        
,,intensity ,,in ,a ,,peal ,,of         
,,thunder4    ,let us take1 for example1
 the peal which begins when the sound   
waves  reach the ear from the point ,a4 
,in the first unit of time the sound    
that reaches the ear is the sound       
produced along the lines ,a ,b and ,a   
,c2 in the second unit1 the sound       
produced along the lines ,b ,d and ,c   
,e2  in the third unit1 the sound       
produced along ,d ,f and ,e ,g4 ,so far 

the  peal has been fairly uniform in its
 intensity2 though there has been a     
slight falling off in the second and    
third units of time1 as compared  with  
the first4 ,but in the fourth unit there
 is a considerable falling  away of the 
sound2 for the line ,f ,k is only about 
one-third as long  as ,d ,f and ,e ,g   
taken together2 therefore the quantity  
of sound that  reaches the ear in the   
fourth unit of time is only one-third of
 that  which reaches it in each of the  
three preceding units2 and consequently 
the sound is only one-third as loud4 ,in
 the fifth unit1 however1 the  peal must
 rise to a sudden crash2 for the portion
 of the lightning path  inclosed between
 the fifth and sixth circles is about   
six times as  great as that between the 
fourth and fifth2 therefore the         
intensity of  the sound will be suddenly
 increased about six-fold4 ,after this  
sudden  crash1 the sound as suddenly    
dies away in the sixth unit of time2 it 
continues feeble as the path of the     

lightning goes nearly straight  away    
from the observer2 it swells again      
slightly in the ninth unit of  time2 and
 then continues without much variation  
to the end4 ,this is  only a single     
illustration1 but it seems quite        
sufficient to show that  the changes of 
intensity in a peal of thunder must be  
largely due to  the position of the     
spectator in relation to the several    
parts of the  lightning flash4          
,distance of a ,flash of ,lightning4--,i
 need hardly remind you that1 by        
observing the interval that elapses     
between the flash of lightning and  the 
peal of thunder that follows it1 we may 
estimate approximately the  distance of 
the nearest point of the discharge4     
,light travels with such  amazing       
velocity that we may assume1 without any
 sensible error1 that  we see the flash 
of lightning at the very moment in which
 the discharge  takes place4 ,but sound1
 as we have seen1 takes a sensible time 
to  travel even short distances2 and    

therefore a measurable interval almost  
always elapses between the moment in    
which the flash is seen and the  moment 
in which the peal of thunder first      
reaches the ear4 ,and the  distance     
through which sound travels in this     
interval will be the  distance of the   
nearest point through which the         
discharge has passed4  ,now1 the        
velocity of sound in air varies slightly
 with the temperature2  but1 at the     
ordinary temperature of our climate1 we 
shall not be far  astray if we allow    
#a1ajj feet for every second1 or about  
one mile for  every five seconds4       
,you will observe also that1 by         
repeating this observation1 we can      
determine whether the thundercloud is   
coming toward us1 or going away  from   
us4 ,so long as the interval between    
each successive flash and the           
corresponding peal of thunder1 continues
 to get shorter and shorter1  the       
thundercloud is approaching2 when the   
interval begins to increase1  the       

thundercloud is receding from us1 and   
the danger is passed4    ,the crash of  
thunder is terrific when the lightning  
is close at hand2  but it is a curious  
fact1 that the sound does not seem to   
travel as  far as the report of an      
ordinary cannon4 ,we have no authentic  
record  of thunder having been heard at 
a greater distance than from twelve to  
fifteen miles1 whereas the report of a  
single cannon has been heard  at five   
times that distance2 and the roar of    
artillery1 in battle1  at a greater     
distance still4 ,on the occasion of the 
,queen's visit to  ,cherbourg1 in       
,august1 #aheh1 the salute fired in     
honor of her arrival  was heard at      
,bonchurch1 in the ,isle of ,wight1 a   
distance of sixty  miles4 ,it was also  
heard at ,lyme ,regis1 in ,dorsetshire1 
which is  eighty-five miles from        
,cherbourg1 as the crow flies2 and we   
are told  that1 not only was it audible 
in its general effect1 but the report of
  individual guns was distinctly        

recognized4 ,the artillery of ,waterloo 
is  said to have been heard at the town 
of ,creil1 in ,france1 #aae miles from  
the field of battle2 and the cannonading
 at the siege of ,valenciennes1  in     
#agic1 was heard1 from day to day1 at   
,deal1 on the coast of ,england1  a     
distance of #abj miles4#ae    ,so far1  
,i have endeavored to set forth some    
general ideas on the nature  and origin 
of lightning1 and of the thunder that   
accompanies it4 ,in  my next ,lecture ,i
 propose to give a short account of the 
destructive  effects of lightning1 and  
to consider how these effects may best  
be  averted by means of lightning       
conductors4      ,,note ,,to ,,page #bj4
    ,,on ,,the ,,high ,,potential ,,of  
,a ,,flash ,,of ,,lightning4    ,the    
potential of an electrified sphere is   
equal to the quantity of  electricity   
with which the sphere is charged1       
divided by the radius  of the sphere4   
,now the minute cloud particles1 which  
go to make up  a drop of rain1 may be   

taken to be very small spheres2 and if v
  represent the potential of each one1 q
 the quantity of electricity  with which
 it is charged1 and r the radius of the 
sphere1 we have v   q_/r4 ,suppose      
#a1jjj of these cloud particles to unite
 into one2  the quantity of electricity 
in the drop1 thus formed1 will be       
#a1jjjq2  and the radius1 which         
increases in the ratio of the cube root 
of the  volume1 will be #ajr4 ,therefore
 the potential of the new sphere will   
be #ajjjq_/#ajr1 or #ajjq_/r2 that is to
 say1 it will be #ajj times as  great as
 the potential of each of the cloud     
particles which compose  it4 ,when a    
million of cloud particles are blended  
into a single drop1  the same process   
will show that the potential has been   
increased ten  thousandfold2 and when a 
drop is produced by the agglomeration of
 a  million of millions of cloud        
particles1 the potential of the drop    
will be a hundred million times as great
 as that of the individual              

particles4#af      ,,footnotes3    #a   
8,il y a des grands seigneurs dont il ne
 faut approcher qu'avec  d'extrmes      
prcautions4 ,le tonnerre est de ce      
nombre40--,dict4 ,philos4  art4 ,foudre4
    #b ,electricit ,statique1 ii41 #efa4
    #c ,deschanel's ,natural            
,philosophy1 ,sixth ,edition1 p4 #fda4  
#d ,fragments of ,science1 ,fifth       
,edition1 p4 #caa4    #e ,lecture on    
,thunderstorms1 ,nature1 vol4 xxii41 p4 
#cda4    #f ,third ,series1 vol4 v41 p4 
#afa4    #g ,phil4 ,trans4 ,royal       
,society1 #ahcd1 vol4 cxxv41 pp4        
#ehc-eia4    #h ,in experiments with a  
,leyden jar1 ,feddersen has shown that  
the  duration of the discharge is       
increased1 not only by increasing the   
striking distance1 but also by          
increasing the size of the jar4 ,now1 a 
flash of lightning may be regarded as   
the discharge of a ,leyden jar  of      
immense size1 with an enormous striking 
distance2 and therefore we  should      
expect that the duration of the         

discharge should be greatly  prolonged4 
,see ,american ,journal of ,science and 
,arts1 ,third ,series1  vol4 i41 p4 #ae4
    #i ,see original paper by ,swan1    
,trans4 ,royal ,society1 ,edinburgh1    
#ahdi1  vol4 xvi41 pp4 #eha-fjc2 also1 a
 second paper1 ib4 #ahfa1 vol4 xxii41   
pp4 #cc-ci4    #aj ,nature1 vol4        
xxviii41 p4 #ed4    #aa ,see1 however1  
an attempt to account for this          
phenomenon in ,de  ,larive's ,treatise  
on ,electricity1 ,london1 #ahec-h1 vol4 
iii41 pp4 #aii1  #bjj2 and another1     
quite recently1 by ,mr4 ,spottiswoode1  
in a ,lecture on  the ,electrical       
,discharge1 delivered before the        
,british ,association at  ,york1 in     
,september1 #ahha1 and published by     
,longmans1 ,london1 p4 #db4  ,see also1 
for recent evidence regarding the       
phenomenon itself1 ,scott's  ,elementary
 ,meteorology1 pp4 #age-h4    #ab ,see  
,jamin1 8,cours de ,physique10 i41      
#dhj-a2 ,tomlinson1 8,the               
,thunderstorm10 ,third ,edition1 pp4    

#ie-ajc2 8,thunderstorms10 a ,lecture by
  ,professor ,tait1 ,nature1 vol4 xxii41
 p4 #cef4    #ac ,professor ,tait1 ,on  
,thunderstorms1 ,nature1 vol4 xxii41 pp4
 #dcf-g4    #ad ,see note at the end of 
this ,lecture1 p4 #bf4    #ae ,see      
,tomlinson1 ,the ,thunderstorm1 pp4     
#hg-i4    #af ,see ,tait on             
,thunderstorms1 ,nature1 vol4 xxii41 p4 
#dcf4          ,,lecture ,,ii4          
,,lightning ,,conductors4      ,the     
effects of lightning1 on the bodies that
 it strikes1 are analogous  to those    
which may be produced by the discharge  
of our electric  machines and ,leyden   
jar batteries4 ,when the discharge of a 
battery  traverses a metal conductor of 
sufficient dimensions to allow it an    
easy passage1 it makes its way along    
silently and harmlessly4 ,but if  the   
conductor be so thin as to offer        
considerable resistance1 then the       
conductor itself is raised to intense   
heat1 and may be melted1 or even        
converted into vapor1 by the discharge4 

,on opposite page is shown a board on   
which a number of very thin wires  have 
been stretched1 over white paper1       
between brass balls4 ,the wires  are so 
thin that the full charge of the battery
 before you1 which  consists of nine    
large ,leyden jars1 is quite sufficient 
to convert them  in an instant into     
vapor4 ,i have already1 on former       
occasions1 sent the  charge through two 
of these wires1 and nothing remains of  
them now  but the traces of their vapor1
 which mark the path of the electric    
discharge from ball to ball4 ,at the    
present moment the battery stands  ready
 charged1 and ,i am going to discharge  
it through a third wire1 by  means of   
this insulated rod which ,i hold in my  
hand4 ,the discharge has  passed2 you   
saw a flash1 and a little smoke2 and    
now1 if you look at  the paper1 you will
 find that the wire is gone1 but that it
 has left  behind the track of its      
incandescent vapor1 marking the path of 
the  discharge4    ,illustration3       

,,discharge ,,of ,,leyden ,,jar         
,,battery ,,through ,,thin ,,wires4     
,destruction of ,buildings by           
,lightning4--,we learn from this        
experiment  that the electricity stored 
up in our battery passes1 without       
visible  effect1 through the stout wire 
of a discharging rod1 but that it       
instantly converts into vapor the thin  
wire stretched across the spark  board4 
,and so it is with a flash of lightning4
 ,it passes harmlessly1 as  every one   
knows1 through a stout metal rod1 but   
when it comes across  bell wires or     
telegraph wires1 it melts them1 or      
converts them into  vapor4 ,on the      
sixteenth of ,july1 #agei1 a flash of   
lightning struck  a house in ,southwark1
 on the south side of ,london1 and      
followed the  line of the bell wire4    
,after the lightning had passed1 the    
wire was no  longer to be found2 but the
 path of the lightning was clearly      
marked  by patches of vapor which were  
left1 here and there1 adhering to the   

surface of the wall4 ,in the year #aged1
 the lightning fell on a bell  tower at 
,newbury1 in the ,united ,states of     
,america1 and having dashed  the roof to
 pieces1 and scattered the fragments    
about1 it reached the  bell4 ,from this 
point it followed an iron wire1 about as
 thick as a  knitting needle1 melting it
 as it passed along1 leaving behind a   
black  streak of vapor on the surface of
 the walls4    ,again1 the electric     
discharge1 passing through a bad        
conductor1  produces mechanical         
disturbance1 and1 if the substance be   
combustible1  often sets it on fire4    
,so1 too1 as you know1 the lightning    
flash1  falling on a church spire1      
dashes it to pieces1 knocking the stones
  about in all directions1 while it sets
 fire to ships and wooden  buildings2   
and more than once it has caused great  
devastation by  exploding powder        
magazines4    ,let me give you one or   
two examples3 ,in ,january1 #agfb1 the  
lightning fell on a church tower in     

,cornwall1 and a stone--three           
hundred-weight--was torn from its place 
and hurled to a distance of #ahj  feet1 
while a smaller stone was projected as  
far as #a1bjj feet from the  building4  
,again1 in #ahji1 the lightning struck a
 house not far from  ,manchester1 and   
literally moved a massive wall twelve   
feet high and  three thick to a distance
 of several feet4 ,you may form some    
conception  of the enormous force here  
brought into action1 when ,i tell you   
that  the total weight of mason-work    
moved on this occasion was not less than
  twenty-three tons4    ,the church of  
,st4 ,george1 at ,leicester1 was        
severely damaged by  lightning on the   
#ast of ,august1 #ahdf4 ,about #h       
o'clock in the evening  the rector of   
the parish saw a vivid streak of light  
darting with  incredible velocity       
against the upper part of the spire4    
8,for the  distance of forty feet on the
 eastern side1 and nearly seventy on the
  west1 the massive stonework of the    

spire was instantly rent asunder and    
laid in ruins4 ,large blocks of stone   
were hurled in all directions1  broken  
into small fragments1 and in some cases1
 there is reason to  believe1 reduced to
 powder4 ,one fragment of considerable  
size was  hurled against the window of a
 house three hundred feet distant1      
shattering to pieces the woodwork1 and  
strewing the room within with  fine dust
 and fragments of glass4 ,it has been   
computed that a hundred  tons of stone  
were1 on this occasion1 blown to a      
distance of thirty  feet in three       
seconds4 ,in addition to the shivering  
of the spire1 the  pinnacles at the     
angles of the tower were all more or    
less damaged1 the  flying buttresses    
cracked through and violently shaken1   
many of the  open battlements at the    
base of the spire knocked away1 the roof
 of the  church completely riddled1 the 
roofs of the side entrances destroyed1  
and the stone staircases of the gallery 
shattered40#ag    ,lightning has been at

 all times the cause of great damage to 
property  by its power of setting fire  
to whatever is combustible4 ,fuller     
says1  in his ,church ,history1 that    
8scarcely a great abbey exists in       
,england  which once1 at least1 has not 
been burned by lightning from heaven40  
,he mentions1 as examples1 the ,abbey of
 ,croyland twice burned1 the  ,monastery
 of ,canterbury twice1 the ,abbey of    
,peterborough twice2 also  the ,abbey of
 ,st4 ,mary's1 in ,yorkshire1 the ,abbey
 of ,norwich1 and  several others4 ,sir 
,william ,snow ,harris1 writing about   
twenty years  ago1 tells us that 8the   
number of churches and church spires    
wholly or  partially destroyed by       
lightning is beyond all belief1 and     
would be too  tedious a detail to enter 
upon4 ,within a comparatively few years1
 in  #ahbb for instance1 we find the    
magnificent ,cathedral of ,rouen burned1
  and1 so lately as #ahej1 the beautiful
 ,cathedral of ,saragossa1 in ,spain1   
struck by lightning during divine       

service and set on fire4 ,in ,march of  
last year a dispatch from our ,minister 
at ,brussels1 ,lord ,howard de  ,walden1
 dated the #bdth of ,february1 was      
forwarded by ,lord ,russell to  the     
,royal ,society1 stating that1 on the   
preceding ,sunday1 a violent            
thunderstorm had spread over ,belgium2  
that twelve churches had been  struck by
 lightning2 and that three of these fine
 old buildings had  been totally        
destroyed40#ah    ,even in our own day  
the destruction caused by fires produced
 through  the agency of lightning is    
very great--far greater than is commonly
  supposed4 ,no general record of such  
fires is kept1 and consequently  our    
information on the subject is very      
incomplete and inexact4 ,i  may tell    
you1 however1 one small fact which1 so  
far as it goes1  is precise enough and  
very significant4 ,in the little        
province of  ,schleswig-,holstein1 which
 occupies an area less than one-fourth  
of the  area of ,ireland1 the           

,provincial ,fire ,assurance            
,association has paid in  sixteen years1
 for damage caused by lightning1        
somewhat over #ajj1jjj1  or at the rate 
of more than #f1jjj a year4 ,the total  
loss of property  every year in this    
province1 due to fires caused by        
lightning1 is  estimated at not less    
than #ab1ejj4ai      ,destruction of    
,ships at ,sea4--,the destructive       
effects of lightning  on ships at sea1  
before the general adoption of lightning
 conductors1  seems almost incredible at
 the present day4 ,from official records
  it appears that the damage done to the
 ,royal ,navy of ,england alone         
involved an expenditure of from #f1jjj  
to #aj1jjj a year4 ,we are  told by ,sir
 ,william ,snow ,harris1 who devoted    
himself for many years  to this subject 
with extraordinary zeal and complete    
success1 that  between the year #ahaj   
and the year #ahae--that is1 within a   
period of  five years--8no less than    
forty sail of the line1 twenty frigates1

 and  twelve sloops and corvettes were  
placed hors de combat by lightning4  ,in
 the merchant navy1 within a            
comparatively small number of years1  no
 less than thirty-four ships1 most of   
them large vessels with rich  cargoes1  
have been totally destroyed--been either
 burned or sunk--to  say nothing of a   
host of vessels partially destroyed or  
severely  damaged40#bj    ,and these    
statements1 be it observed1 take no     
account of ships that  were simply      
reported as missing1 some of which1 we  
can hardly doubt1  were struck by       
lightning in the open sea1 and went down
 with all hands  on board4 ,a famous    
ship of forty-four guns1 the            
,resistance1 was  struck by lightning in
 the ,straits of ,malacca1 and the      
powder magazine  exploding1 she went to 
the bottom4 ,of her whole crew only     
three were  saved1 who happened to be   
picked up by a passing boat4 ,it has    
been well  observed that1 were it not   
for these three chance survivors1       

nothing  would have been known          
concerning the fate of the vessel1 and  
she would  have been simply recorded as 
missing in the ,admiralty lists4        
,nothing is more fearful to contemplate 
than the scene on board a ship  when she
 is struck by lightning in the open sea1
 with the winds howling  around1 the    
waves rolling mountains high1 the rain  
coming down in  torrents1 and the vivid 
flashes lighting up the gloom at        
intervals1 and  carrying death and      
destruction in their track4 ,i will read
 you one or  two brief accounts of such 
a scene1 given in the pithy but         
expressive  language of the sailor4 ,in 
,january1 #aghf1 the ,thisbe1 of        
thirty-six  guns1 was struck by         
lightning off the coast of ,scilly1 and 
reduced to  the condition of a wreck4   
,here is an extract from the ship's log3
 8,four  ,a4 ,m41 strong gales2 handed  
mainsail and main top-sail2 hove to with
  storm staysails2 blowing very heavy1  
,s4 ,e4 #d4ae1 a flash of lightning1    

with tremendous thunder1 disabled some  
of our people4 ,a second flash  set the 
mainsail1 main-top1 and mizen staysails 
on fire4 ,obliged to cut  away the      
mainmast2 this carried away mizen       
top-mast and fore top-sail  yard4 ,found
 foremast also shivered by the          
lightning4 ,fore top-mast went  over the
 side about #i ,a4 ,m4 ,set the         
foresail40#ba    ,a few years later1 in 
,march1 #agif1 the ,lowestoffe was      
struck in the  ,mediterranean1 and we   
read as follows in the log of the ship3 
8,north  end of ,minorca2 heavy squalls2
 hail1 rain1 thunder1 and lightning4    
#ab4ae1 ship struck by lightning1 which 
knocked three men from the  masthead1   
one killed4 #ab4cj1 ship again struck2  
main top-mast shivered  in pieces2 many 
men struck senseless on the decks4 ,ship
 again struck1  and set on fire in the  
masts and rigging2 mainmast shivered in 
pieces2  fore top-mast shivered2 men    
benumbed on the decks1 and knocked out  
of the top2 one man killed on the spot4 

#a4cj1 cut away the mainmast2  employed 
clearing wreck4 #d1 moderate2 set the   
foresail40#bb    ,again1 in #ahaj1 the  
,repulse1 a ship of seventy-four guns1  
was struck1  off the coast of ,spain4   
8,the wind had been variable in the     
morning--and  at #ab4ce there was a     
heavy squall1 with rain1 thunder1 and   
lightning4  ,the ship was struck by two 
vivid flashes of lightning1 which       
shivered  the maintop-gallant mast1 and 
severely damaged the mainmast4 ,seven   
men  were killed on the spot2 three     
others only survived a few days2 and ten
  others were maimed for life4 ,after   
the second discharge the rain fell  in  
torrents4 ,the ship was more completely 
crippled than if she had been  in       
action1 and the squadron1 then engaged  
on a critical service1 lost  for a time 
one of its fastest and best ships40#bc  
,destruction of ,powder                 
,magazines4--,not less appalling is the 
devastation caused by lightning when it 
falls on a powder magazine4  ,here is a 

striking example3 ,on the eighteenth of 
,august1 #agfi1 the  tower of ,st4      
,nazaire1 at ,brescia1 was struck by    
lightning4 ,underneath  the tower about 
#bjj1jjj pounds of gunpowder1 belonging 
to the ,republic  of ,venice1 were      
stored in vaults4 ,the powder exploded1 
leveling to  the ground a great part of 
the beautiful city of ,brescia1 and     
burying  thousands of its inhabitants in
 the ruins4 ,it is said that the tower  
itself was blown up bodily to a great   
height in the air1 and came down  in a  
shower of stones4 ,this is1 perhaps1 the
 most fearful disaster of  the kind on  
record4 ,but we are not without examples
 in our own times4  ,in the year #ahef  
the lightning fell on the ,church of    
,st4 ,john1 in the  ,island of ,rhodes4 
,a large quantity of gunpowder had been 
deposited in  the vaults of the church4 
,this was ignited by the flash2 the     
building  was reduced to a mass of      
ruins1 a large portion of the town was  
destroyed1 and a considerable number of 

the inhabitants were killed4  ,again1 in
 the following year1 the magazine of    
,joudpore1 in the ,bombay  ,presidency1 
was struck by lightning4 ,many thousand 
pounds of gunpowder  were blown up1 five
 hundred houses were destroyed1 and     
nearly a  thousand people are said to   
have been killed4#bd      ,experimental 
,illustrations4--,and now1 before       
proceeding further1  ,i will make one or
 two experiments1 with a view of showing
 that the  electricity of our machines  
is capable of producing effects similar 
to those produced by lightning1 though  
immeasurably inferior in point  of      
magnitude4 ,here is a common tumbler1   
about three-quarters full of  water4    
,into it ,i introduce two bent rods of  
brass1 which are carefully  insulated   
below the surface of the water by a     
covering of india-rubber4  ,the points1 
however1 are exposed1 and come to within
 an inch of one  another1 near the      
bottom of the tumbler4 ,outside the     
tumbler1 the  brass rods are mounted on 

a stand1 by means of which ,i can send  
the  full charge of this ,leyden jar    
battery through the water1 from point   
to point4 ,since water is a bad         
conductor of electricity1 as compared   
with metals1 the charge encounters great
 resistance in passing through  it1 and 
in overcoming this resistance produces  
considerable mechanical  commotion1     
which is usually sufficient to shiver   
the glass to pieces4    ,to charge the  
battery will take about twenty turns of 
this large ,holtz  machine4 ,observe how
 the pith ball of the electroscope rises
 as the  machine is worked1 showing that
 the charge is going in4 ,and now it    
remains stationary2 which is a sign that
 the battery is fully charged1  and can 
receive no more4 ,you will notice that  
the outside coating of  the battery has 
been already connected with one of the  
brass rods  dipping into the tumbler of 
water4 ,by means of this discharger ,i  
will  now bring the inside coating into 
connection with the other rod4 ,and     

see1 before contact is actually made1   
the spark has leaped across1 and  our   
tumbler is violently burst asunder from 
top to bottom4    ,illustration3 ,,glass
 ,,vessel ,,broken ,,by ,,discharge ,,of
 ,,leyden ,,jar ,,battery4    ,this will
 probably appear to you a very small    
affair1 when compared  with the tearing 
asunder of solid masonry1 and the       
hurling about of  stones by the ton     
weight4 ,no doubt it is2 and that is    
just one of  the lessons we have to     
learn from the experiment we have made4 
,for1  not only does it show us that    
effects of this kind may be caused by   
electricity artificially produced1 but  
it brings home forcibly to the  mind how
 incomparably more powerful is the      
lightning of the clouds than  the       
electricity of our machines4    ,the    
property which electricity has of       
setting fire to combustible  substances 
may be easily illustrated4 ,this        
india-rubber tube is  connected with the
 gas pipe under the floor1 and to the   

end of the  tube is fitted a brass      
stop-cock which ,i hold in my hand4 ,i  
open  the cock1 and allow the jet of gas
 to flow toward the conductor of        
,carr's machine1 while my assistant     
turns the handle2 a spark passes1  and  
the gas is lit4 ,again1 my assistant    
stands on this insulating  stool1       
placing his hand on the large conductor 
of the machine1 while  ,i turn the      
handle4 ,his body becomes electrified1  
and when he presents  his knuckle to    
this vessel of spirits of wine1 which is
 electrically  connected with the earth1
 a spark leaps across1 and the spirits  
of wine  are at once in a blaze4 ,once  
more2 ,i tie a little gun-cotton around 
one knob of the discharging rod1 and    
then use it to discharge a small        
,leyden jar2 at the moment of the       
discharge the gun-cotton is set on      
fire4    ,it would be easy to explode   
gunpowder with the electric spark1 but  
the  smoke of the explosion would make  
the lecture-hall very unpleasant for    

the remainder of the lecture4 ,i        
propose1 therefore1 to substitute for   
gunpowder an explosive mixture of oxygen
 and hydrogen1 with which ,i  have      
filled this little metal flask1 commonly
 known as ,volta's pistol4  ,by a very  
simple contrivance1 the electric spark  
is discharged through  the mixture1 when
 ,i hold the flask toward the conductor 
of the machine4  ,a cork is fitted      
tightly into the neck of the flask1 and 
at the moment  the spark passes you hear
 a loud explosion1 and you see the cork 
driven  violently up to the ceiling4    
,illustration3 ,,gun-,,cotton ,,set ,,on
 ,,fire ,,by ,,electric ,,spark4        
,destruction of ,life4--,the last effect
 of lightning to which ,i shall  refer1 
and which1 perhaps1 more than any other1
 strikes us with terror1  is the sudden 
and utter extinction of life1 when the  
lightning flash  descends on man or on  
beast4 ,so swift is this effect1 in most
 cases1  that death is1 in all          
probability1 absolutely painless1 and   

the victim  is dead before he can feel  
that he is struck4 ,i cannot give you1  
with  any degree of exactness1 the      
number of people killed every year by   
lightning1 because the record of such   
deaths has been hitherto very           
imperfectly kept1 in almost all         
countries1 and is1 beyond doubt1 very   
incomplete4 ,but perhaps you will be    
surprised to learn that the number  of  
deaths by lightning actually recorded   
is1 on an average1 in ,england  about   
#bb every year1 in ,france #hj1 in      
,prussia #aaj1 in ,austria #bab1 in     
,european ,russia #ddj4be    ,so far as 
can be gathered from the existing       
sources of information1  it would seem  
that the number of persons killed by    
lightning is1 on  the whole1 about one  
in three of those who are struck4 ,the  
rest are  sometimes only stunned1       
sometimes more or less burned1 sometimes
  made deaf for a time1 sometimes       
partially paralyzed4 ,on particular     
occasions1 however1 especially when the 

lightning falls on a large  assembly of 
people1 the number of persons struck    
down and slightly  injured1 in          
proportion to the number killed1 is very
 much increased4    ,an interesting case
 of this kind is reported by ,mr4       
,tomlinson4 8,on  the twenty-ninth of   
,august1 #ahdg1 at the parish church of 
,welton1  ,lincolnshire1 while the      
congregation were engaged in singing the
 hymn  before the sermon1 and the ,rev4 
,mr4 ,williamson had just ascended the  
pulpit1 the lightning was seen to enter 
the church from the belfry1  and        
instantly an explosion occurred in the  
centre of the edifice4 ,all  that could 
move made for the door1 and ,mr4        
,williamson descended from  the pulpit1 
endeavoring to allay the fears of the   
people4 ,but attention  was now called  
to the fact that several of the         
congregation were lying  in different   
parts of the church1 apparently dead1   
some of whom had  their clothing on     
fire4 ,five women were found injured1   

and having their  faces blackened and   
burned1 and a boy had his clothes almost
 entirely  consumed4 ,a respected old   
parishioner1 ,mr4 ,brownlow1 aged       
sixty-eight1  was discovered lying at   
the bottom of his pew1 immediately      
beneath one  of the chandeliers1 quite  
dead4 ,there were no marks on the body1 
but  the buttons of his waistcoat were  
melted1 the right leg of his trousers   
torn down1 and his coat literally burnt 
off4 ,his wife in the same pew  received
 no injury40#bf    ,illustration3       
,,volta',s ,,pistol2 ,,explosion        
,,caused ,,by ,,electric ,,spark4       
,not less striking is the story told by 
,dr4 ,plummer1 surgeon of the  ,illinois
 ,volunteers1 in the ,medical and       
,surgical ,reporter of ,june #ai1       
#ahfe3 8,our regiment was yesterday the 
scene of one of the most terrible       
calamities which it has been my lot to  
witness4 ,about two o'clock a  violent  
thunderstorm visited us4 ,while the old 
guard was being turned  out to receive  

the new1 a blinding flash of lightning  
was seen1  accompanied instantly by a   
terrific peal of thunder4 ,the whole of 
the  old guard1 together with part of   
the new1 were thrown violently to the   
earth4 ,the shock was so severe and     
sudden that1 in most cases1 the rear    
rank men were thrown across the front   
rank men4 ,one man was instantly        
killed1 and thirty-two men were more or 
less severely burned by the  electric   
fluid4 ,in some instances the men's     
boots and shoes were rent  from their   
feet and torn to pieces1 and1 strange as
 it may appear1 the  men were injured   
but little in the feet4 ,in all cases   
the burns appear  as if they had been   
caused by scalding-hot water1 in many   
instances the  skin being shriveled and 
torn off4 ,the men all seem to be doing 
well1  and a part of them will be able  
to resume their duties in a few days40  
,the ,return ,shock4--,it sometimes     
happens that people are struck down  and
 even killed at the moment a discharge  

of lightning takes place  between a     
cloud and the earth1 though they are    
very far from the  point where the flash
 is actually seen to pass2 while others1
 who are  situated between them and the 
lightning1 suffer very little1 or       
perhaps  not at all4 ,this curious      
phenomenon was first carefully          
investigated by  ,lord ,mahon in the    
year #aggi1 and was called by him the   
8return shock40  ,his theory1 which is  
now commonly accepted1 may be easily    
understood  with the aid of the sketch  
before you4    ,illustration3 ,,the     
,,return ,,shock ,,illustrated4    ,let 
us suppose ,,abc to represent the       
outline of a thundercloud which  dips   
down toward the earth at ,a and at ,c4  
,the electricity of the cloud  develops 
by inductive action a charge of the     
opposite kind in the earth  beneath it4 
,but the inductive action is most       
powerful at ,e and ,f1 where  the cloud 
comes nearest to the earth4 ,hence1     
bodies situated near these  points may  

be very highly electrified as compared  
with bodies at a  point between them1   
such as ,d4 ,now1 when a flash of       
lightning passes at  ,e1 the under part 
of the cloud is at once relieved of its 
electricity1  its inductive action      
ceases1 and1 therefore1 a person        
situated at ,f  suddenly ceases to be   
electrified4 ,this sudden change from a 
highly  electrified to a neutral state  
involves a shock to his system which    
may be severe enough to stun or even to 
kill him4 ,meanwhile1 people  at ,d1    
having been also electrified to some    
extent by the influence  of the         
thundercloud1 must in like manner       
undergo a change in their  electrical   
condition when the flash of lightning   
passes1 but this  change will be less   
violent because they were less highly   
electrified4    ,many experiments have  
been devised to illustrate this theory  
of ,lord  ,mahon4 ,but the best         
illustration ,i know is furnished by    
this electric  machine of ,carr's4 ,if  

you stand near one end of the large     
conductor  when the machine is in action
 and sparks are taken from the other    
end1  you will feel a distinct electric 
shock every time a spark passes4  ,the  
large conductor here takes the place of 
the cloud1 the spark that  passes at one
 end represents the flash of lightning1 
and the observer  at the other end gets 
the return shock1 though he is at a     
considerable  distance from the point   
where the flash is seen4    ,an         
experiment of this kind1 of course1     
cannot be made sensible to a  large     
audience like the present4 ,but ,i can  
give you a good idea of the  effect by  
means of this tuft of colored papers4   
,while the machine is in  action ,i hold
 the tuft of papers near that end of the
 conductor which  is farthest from the  
point where the discharge takes place4  
,you see the  paper ribbons are         
electrified by induction1 and1 in virtue
 of mutual  repulsion1 stand out from   
one another 8like quills upon the       

fretful  porcupine40 ,but1 when a spark 
passes1 the inductive action ceases1 the
  paper ribbons cease to be electrified1
 and the whole tuft suddenly  collapses 
into its normal state4    ,while fully  
accepting ,lord ,mahon's theory of the  
return shock as  perfectly good so far  
as it goes1 ,i would venture to point   
out another  influence which must often 
contribute largely to produce the effect
 in  question1 and which is not         
dependent on the form of the cloud4 ,it 
may  easily happen1 from the nature of  
the surface in the district affected  by
 a thundercloud1 that the point of most 
intense electrification--say  ,e in the 
figure--is in good electrical           
communication with a distant  point1    
such as ,f1 while it is very imperfectly
 connected with a much  nearer point1   
,d4 ,in such a case it is evident that  
bodies at ,f will  share largely in the 
highly-electrified condition of ,e1 and 
also share  largely in the sudden change
 of that condition the moment the flash 

of  lightning passes2 whereas bodies at 
,d will be less highly electrified      
before the discharge1 and less violently
 disturbed when the discharge  takes    
place4    ,this principle may be        
illustrated by a very simple experiment4
 ,here  is a brass chain about twenty   
feet long4 ,one end of it ,i hand to any
  one among the audience who will kindly
 take hold of it2 the other end  ,i hold
 in my hand4 ,i now stand near the      
conductor of the machine2 and  will ask 
some one to stand about ten feet away   
from me1 near the middle  of the chain1 
but without touching it4 ,now observe   
what happens when  the machine is worked
 and ,i take a spark from the conductor3
 ,my friend  at the far end of the      
chain1 twenty feet away1 gets a shock   
nearly  as severe as the one ,i get     
myself1 because he is in good electrical
  communication with the point where the
 discharge takes place4 ,but  my more   
fortunate friend1 who is ten feet nearer
 to the flash1 is  hardly sensible of   

any effect1 because he is connected with
 me only  through the floor of the hall1
 which is1 comparatively speaking1 a bad
  conductor of electricity4             
,summary4--,let me now briefly sum up   
the chief destructive effects  of       
lightning4 ,first1 with regard to good  
conductors3 though it passes  harmlessly
 through them if they be large enough to
 afford it an easy  passage1 it melts   
and converts them into vapor if they be 
of such  small dimensions as to offer   
considerable resistance4 ,secondly1     
lightning acts with great mechanical    
force on bad conductors2 it is  capable 
of tearing asunder large masses of      
masonry1 and of projecting  the         
fragments to a considerable distance4   
,thirdly1 it sets fire to  combustible  
materials4 ,and lastly1 it causes the   
instantaneous death of  men and animals4
      ,franklin's ,lightning            
,rods4--,the object of lightning        
conductors is to  protect life and      
property from these destructive effects4

 ,their use was  first suggested by     
,franklin1 in #agdi1 even before his    
famous experiment  with the kite2 and   
immediately after that experiment1 in   
#ageb1 he set  up1 on his own house1 in 
,philadelphia1 the first lightning      
conductor  ever made4 ,he even devised  
an ingenious contrivance1 by means of   
which  he received notice when a        
thundercloud was approaching4 ,the      
contrivance  consisted of a peal of     
bells1 which he hung on his lightning   
conductor1  and which were set ringing  
whenever the lightning conductor became 
charged with electricity4    ,franklin's
 lightning rods were soon adopted in    
,america2 and he himself  contributed   
very much to their popularity by the    
simple and lucid  instructions he issued
 every year1 for the benefit of his     
countrymen1  in the annual publication  
known as 8,poor ,richard's ,almanac40   
,it is  very interesting at this        
distance of time to read the homely     
practical  rules laid down by this great

 philosopher and statesman2 and1 though 
some modifications have been suggested  
by the experience of a hundred  and     
thirty years1 especially as regards the 
dimensions of the lightning  conductor1 
it is surprising to find how accurately 
the general  principles of its          
construction1 and of its action1 are    
here set forth4    8,it has pleased     
,god10 he says1 8in ,his goodness to    
mankind1 at length  to discover to them 
the means of securing their habitations 
and other  buildings from mischief by   
thunder and lightning4 ,the method is   
this3  ,provide a small iron rod1 which 
may be made of the rod-iron used by     
nailors1 but of such a length that one  
end being three or four feet in  the    
moist ground1 the other may be six or   
eight feet above the highest  part of   
the building4 ,to the upper end of the  
rod fasten about a foot  of brass wire1 
the size of a common knitting needle1   
sharpened to a  fine point2 the rod may 
be secured on the house by a few small  

staples4  ,if the house or barn be long1
 there may be a rod and point at each   
end1  and a middling wire along the     
ridge from one to the other4 ,a house   
thus  furnished will not be damaged by  
lightning1 it being attracted by the    
points and passing through the metal    
into the ground1 without hurting        
anything4 ,vessels also having a        
sharp-pointed rod fixed on the top of   
their masts1 with a wire from the foot  
of the rod reaching down round  one of  
the shrouds to the water1 will not be   
hurt by lightning40      ,introduction  
of ,lightning ,rods into ,england4--,the
 progress of  lightning conductors was  
more slow in ,england and on the        
,continent of  ,europe1 owing to a fear1
 not unnatural1 that they might1 in some
 cases1  draw down the lightning where  
it would not otherwise have fallen4     
,people preferred to take their chance  
of escaping as they had escaped  before1
 rather than invite1 as it were1 the    
lightning to descend on  their houses1  

in the hope that an iron rod would      
convey it harmless  to the earth4 ,but  
the immense amount of damage done every 
year by  lightning1 soon led practical  
men to entertain a proposal which       
offered  complete immunity from all     
danger on such easy terms2 and when it  
was  found that buildings protected by  
lightning conductors were1 over and     
over again1 struck by lightning without 
suffering any harm1 a general           
conviction of their utility was         
gradually established in the public     
mind4    ,the first public building     
protected by a lightning rod in ,england
 was  ,st4 ,paul's ,cathedral1 in       
,london4 ,on the eighteenth of ,june1   
#agfd1 the  beautiful steeple of ,saint 
,bride's ,church1 in the city1 was      
struck by  lightning and reduced to     
ruin4 ,this incident awakened the       
attention of  the dean and chapter of   
,st4 ,paul's to the danger of a similar 
calamity1  which seemed1 as it were1    
impending over their own church4 ,after 

long  deliberation1 they referred the   
matter to the ,royal ,society1 asking   
for  advice and instruction4 ,a         
committee of scientific men was         
appointed by  the ,royal ,society to    
consider the question4 ,benjamin        
,franklin himself1  who happened to be  
in ,london at the time1 as the          
representative of the  ,american ,states
 in their dispute with ,england1 was    
nominated a member  of the committee4   
,and the result of its deliberation was 
that1 in the  year #agfi1 a number of   
lightning conductors were erected on    
,st4 ,paul's  ,cathedral4    ,it was on 
this occasion that arose the celebrated 
controversy about  the respective merits
 of points and balls4 ,franklin had     
recommended a  pointed conductor2 but   
some members of the committee were of   
opinion  that the conductor should end  
in a ball and not in a point4 ,the      
decision of the committee was in favor  
of ,franklin's opinion1 and  pointed    
conductors were accordingly adopted for 

,st4 ,paul's ,cathedral4  ,but the      
controversy did not end here4 ,the time 
was one of great  political excitement1 
and party spirit infused itself even    
into the  peaceful discussions of       
science4 ,the weight of scientific      
opinion was  on the side of ,franklin2  
but it was hinted1 on the other side1   
that the  pointed conductors were       
tainted with republicanism1 and pregnant
 with  danger to the empire4 ,as a rule1
 the whigs were strongly in favor of    
points2 while the ,tories were          
enthusiastic in their support of balls4 
,for a time the ,tories seemed to       
prevail4 ,the king was on their side4   
,experiments on a grand scale were      
conducted in his presence1 at the       
,pantheon1 a large building in ,oxford  
street2 he was assured that these       
experiments proved the great superiority
 of balls over points2 and to  give     
practical effect to his convictions1 his
 majesty directed that a  large cannon  
ball should be fixed on the end of the  

lightning conductor  attached to the    
royal palace at ,kew4 ,but the committee
 of the ,royal  ,society remained       
unconvinced4 ,in course of time the heat
 of party  spirit abated2 experience as 
well as reason was found to be in favor 
of  ,franklin's views2 and the battle of
 the balls and points has long since    
passed into the domain of history4#bg   
,functions of a ,lightning              
,conductor4--,a lightning conductor     
fulfills  two functions4 ,first1 it     
favors a silent and gradual discharge of
  electricity between the cloud and the 
earth1 and thus tends to prevent  that  
accumulation which must of necessity    
take place before a flash  of lightning 
will pass4 ,secondly1 if a flash of     
lightning come1 the  lightning conductor
 offers it a safe channel through which 
it may pass  harmless to the earth4     
,these two functions of a lightning     
conductor may be easily illustrated  by 
experiment4 ,when our machine is in     
action1 if ,i present my closed  hand to

 the large brass conductor1 a spark     
passes between them1 and ,i  feel1 at   
the same moment1 a slight electric      
shock4 ,here the conductor  of the      
machine1 as usual1 holds the place of   
the electrified cloud2  my closed hand  
represents1 as it were1 a lofty building
 that stands  out prominently on the    
surface of the earth2 the spark is the  
flash of  lightning1 and the electric   
shock just suggests the destructive     
power  of the sudden disruptive         
discharge4    ,now let me protect this  
building by a lightning conductor4 ,for 
this  purpose1 ,i take in my hand a     
brass rod1 which ,i connect with the    
earth by a brass chain4 ,in the first   
instance1 ,i will have a metal  ball on 
the end of my lightning conductor4 ,you 
see the effect2 sparks  pass rapidly1   
but ,i feel no shock4 ,i can increase   
the strength of  the discharge by       
hanging this condensing jar on the      
conductor of the  machine4 ,sparks pass 
now1 much more brilliant and powerful   

than before1  but still ,i get no shock4
 ,it is evident1 therefore1 that my     
lightning  rod does not prevent the     
flash from passing1 but it conveys it   
harmless  to the ground4    ,i next take
 a rod which is sharply pointed1 and    
connecting it as before  with the earth 
by a brass chain1 ,i present the sharp  
point to the  conductor of the machine4 
,observe how different is the result2   
there is  no disruptive discharge2 no   
spark passes2 no shock is felt4         
,electricity  still continues to be     
generated in the machine1 and           
electricity is  generated1 by induction1
 in the brass rod1 and in my body4 ,but 
these  two opposite electricities       
discharge themselves silently1 by means 
of  this pointed rod1 and no sensible   
effect of any kind is exhibited4        
,these experiments are very simple1 but 
they really put before us1 in  the      
clearest possible way1 the whole theory 
of lightning conductors4  ,in           
particular1 they give us ocular         

demonstration that an efficient         
lightning rod not only makes the        
lightning harmless when it comes1  but  
tends very much to prevent its coming4  
,a remarkable example1 on a  large      
scale1 of this important property1 is   
furnished by the town of                
,pietermaritzburg1 the capital of the   
colony of ,natal1 in ,south ,africa4    
,this town is subject to the frequent   
visitation of thunderstorms1  at certain
 seasons of the year1 and much damage   
was formerly done  by lightning1 but    
since the erection of lightning         
conductors on the  principal buildings1 
the lightning has never fallen within   
the town4  ,thunderclouds come as       
before1 but they pass silently over the 
city1  and only begin to emit their     
lightning flashes when they reach the   
open country1 and have passed beyond the
 range of the lightning  conductors4#bh 
,but it will often happen1 even in the  
case of a pointed conductor1  that the  
accumulation of electricity goes on so  

fast that the silent  discharge is      
insufficient to keep it in check4 ,a    
disruptive discharge  will then take    
place1 from time to time1 and a flash of
 lightning will  pass4 ,under these     
circumstances1 the lightning conductor  
is called upon  to fulfill its second   
function1 and to convey the lightning   
harmless to  the earth4      ,conditions
 of a ,lightning ,conductor4--,from the 
consideration of  the functions which it
 has to fulfill1 we may now infer what  
are the  conditions necessary for an    
efficient lightning conductor4 ,the     
first  condition is that the end of the 
conductor1 projecting into the air1     
should have1 at least1 one sharp point4 
,our experiments have shown us  that a  
pointed conductor tends1 in a manner1 to
 suppress the flash  of lightning       
altogether2 whereas a blunt conductor1  
or one ending in  a ball1 tends only to 
make it harmless when it comes4 ,it is  
evident1  therefore1 that the pointed   
conductor offers the greater security4  

,but a fine point is very liable to be  
melted when the lightning falls  upon   
it1 and thus to be rendered less        
efficient for future service4 ,to  meet 
this danger1 it has recently been       
suggested1 by the ,lightning ,rod       
,conference1 that the extreme end of the
 conductor should be a blunt  point1    
destined to receive the full force of   
the lightning flash1 when  it comes2 and
 that1 a little lower down1 a number of 
very fine points  should be provided1   
with a view to favor the silent         
discharge4 ,this  suggestion1 which     
appears admirably fitted to provide for 
the twofold  function of a lightning    
conductor1 deserves to be recorded in   
the exact  terms of the official report4
    8,it seems best to separate the     
double functions of the point1          
prolonging the upper terminal to the    
very summit1 and merely beveling  it    
off1 so that1 if a disruptive discharge 
does take place1 the full  conducting   
power of the rod may be ready to receive

 it4 ,at the same  time1 having regard  
to the importance of silent discharge   
from sharp  points1 we suggest that1 at 
one foot below the extreme top of the   
upper  terminal1 there be firmly        
attached1 by screws and solder1 a copper
  ring bearing three or four copper     
needles1 each six inches long1 and      
tapering from a quarter of an inch      
diameter to as fine a point as can  be  
made2 and with the object of rendering  
the sharpness as permanent  as possible1
 we advise that they be platinized1     
gilded1 or nickel  plated40#bi    ,the  
second condition of a lightning         
conductor is1 that it should be  made of
 such material1 and of such dimensions1 
as to offer an easy  passage to the     
greatest flash of lightning likely to   
fall on it2  otherwise it might be      
melted by the discharge1 and the        
lightning1  seeking for itself another  
path1 might force its way through bad   
conductors1 which it would partly rend  
asunder1 and partly consume  by fire4   

,copper is now generally regarded as the
 best material for  lightning           
conductors1 and it is almost universally
 employed in these  countries4 ,if it is
 used in the form of a rope1 it should  
not be less  than half an inch in       
diameter2 if a band of copper is        
preferred--and it  is often found more  
convenient by builders--it should be    
about an inch  and a half broad and an  
eighth of an inch thick4 ,in ,france it 
has been  hitherto more usual to employ 
iron rods for lightning conductors1 but 
since iron is much inferior to copper in
 its conducting power1 the iron  rod    
must be of much larger dimensions2 it   
should be at least one inch  in         
diameter4#cj    ,the third condition is 
that the lightning conductor should be  
continuous throughout its whole length1 
and should be placed in good  electrical
 contact with the earth4 ,this is a     
condition of the first  importance1 and 
experience has shown that it is the one 
most likely  of all to be neglected4 ,in

 a large town the best earth connection 
is  furnished by the system of          
water-mains and gas-mains1 each of which
  constitutes a great network of        
conductors everywhere in contact with   
the earth4 ,two points1 however1 must be
 carefully attended to--first1  that the
 electrical contact between the         
lightning conductor and the  metal pipe 
should be absolutely perfect2 and1      
secondly1 that the pipe  selected should
 be of such large dimensions as to allow
 the lightning  an easy passage through 
it to the principal main4    ,if no such
 system of water-pipes or gas-pipes is  
at hand1 then the  lightning rod should 
be connected with moist earth by means  
of a bed of  charcoal or a metal plate  
not less than three feet square4 ,this  
metal  plate should be always of the    
same material as the conductor1         
otherwise  a galvanic action would be   
set up between the two metals1 which in 
course of time might seriously damage   
the contact4 ,dry earth1 sand1  rock1   

and shingle are bad conductors2 and1 if 
such materials exist near  the surface  
of the earth1 the lightning rod must    
pass through them and  be carried down  
until it reaches water or permanently   
damp earth4      ,mischief ,done by ,bad
 ,conductors4--,if the earth contact is 
bad1 a  lightning conductor does more   
harm than good4 ,it invites the         
lightning  down upon the building       
without providing for it1 at the same   
time1 a  free passage to earth4 ,the    
consequence is that the lightning forces
  a way for itself1 violently bursting  
asunder whatever opposes its  progress1 
and setting fire to whatever is         
combustible4    ,i will give you some   
recent and striking examples4 ,in the   
month of ,may1  #ahgi1 the church of    
,laughton-en-le-,morthen1 in ,england1  
though provided  with a conductor1 was  
struck by lightning and sustained       
considerable  damage4 ,on examination it
 was found that the lightning followed  
the  conductor down along the spire as  

far as the roof2 then1 changing its     
course1 it forced its way through a     
buttress of massive masonwork1          
dislodging about two cartloads of       
stones1 and leaped over to the leads  of
 the roof1 about six feet distant4 ,it  
now followed the leads until it  came to
 the cast-iron down-pipes intended to   
discharge the rain-water1  and through  
these it descended to the earth4 ,when  
the earth contact  of the lightning     
conductor was examined1 it was found    
exceedingly  deficient4 ,the rod was    
simply bent underground1 and buried in  
dry  loose rubbish at a depth not       
exceeding eighteen inches4 ,this is a   
very  instructive example4 ,the         
lightning had a choice of two paths--one
 by  the conductor prepared for it1 the 
other by the leads of the roof  and the 
down-pipes--and1 by a kind of instinct  
which1 however we may  explain1 we must 
always contemplate with wonder1 it chose
 the path of  least resistance1 though  
in doing so it had to burst its way at  

the  outset through a massive wall of   
solid masonry4#ca    ,on the #eth of    
,june1 in the same year1 a flash of     
lightning struck the  house of ,mr4     
,osbaldiston1 near ,sheffield1 and1     
notwithstanding the  supposed protection
 of a lightning conductor1 it did damage
 to the  amount of about five hundred   
pounds4 ,the lightning here followed the
  conductor to a point about nine feet  
from the ground1 then passed  through a 
thick wall to a gas-pipe at the back of 
the drawing-room  mirror4 ,it melted the
 gas-pipe1 set fire to the gas1 smashed 
the  mirror to atoms1 broke the ,sevres 
vases on the chimney-piece1 and  dashed 
the furniture about4 ,in this case1 as  
in the former1 it was  found that the   
earth contact was bad2 and1 in addition1
 the conductor  itself was of too small 
dimensions4 ,hence1 the electric        
discharge  found an easier path to earth
 through the gas-pipes1 though to reach 
them it had to force for itself a       
passage through a resisting mass of     

non-conductors4#cb    ,again in the same
 year1 on the #bhth of ,may1 the house  
of ,mr4 ,tomes1 of  ,caterham1 was      
struck by lightning1 and some slight    
damage was done4  ,after a careful      
examination it was found that the       
greater part of  the discharge left the 
lightning conductor with which the house
 was  provided1 and passed over the     
slope of the roof to an attic room1 into
  which it forced its way through a     
brick wall1 and reached a small iron    
cistern4 ,this cistern was connected by 
an iron pipe of considerable  dimensions
 with two pumps in the basement story2  
and through them the  lightning found an
 easy passage to the earth1 and did but 
little harm  on its way4 ,when the earth
 contact of the lightning conductor was 
examined1 it was discovered that the end
 of the rod was simply stuck  into a dry
 chalky soil to a depth of about twelve 
inches4 ,thus in this  case1 as in the  
two former1 it was made quite clear that
 the lightning  conductor failed to     

fulfill its functions because the earth 
contact was  bad4#cc    ,cases are not  
uncommon in which builders provide      
underground a  carefully constructed    
reservoir of water1 into which the lower
 end  of the lightning rod is           
introduced4 ,the idea seems to prevail  
that a  reservoir of water constitutes a
 good earth contact2 and this is quite  
true of a natural reservoir1 such as a  
lake1 where the water is in  contact    
with moist earth over a considerable    
area4 ,but an artificial  reservoir may 
have quite an opposite character1 and   
practically  insulate the lightning     
conductor from the earth4 ,one which    
came under  my notice lately1 in the    
neighborhood of this city1 consists of a
 large  earthenware pipe set on end in a
 bed of cement1 and kept half full of   
water4 ,now1 the earthenware pipe is a  
good insulator1 and so is the bed  of   
cement in which it rests2 and the whole 
arrangement is identical1  in all       
essential features1 with the apparatus  

of ,professor ,richman1 in  which he    
introduced his lightning rod into a     
glass bottle1 and by which  he lost his 
life a hundred and thirty years ago4    
,a conductor mounted in this manner     
will1 probably enough1 draw down        
lightning from the clouds2 but it is    
more likely to discharge it1 with       
destructive effect1 into the building it
 is intended to guard1 than  to transmit
 it harmlessly to the earth4 ,an example
 is at hand in the  case of ,christ     
,church1 in the town of ,clevedon1 in   
,somersetshire4  ,this church was       
provided with a very efficient system of
 lightning  conductors1 five in number1 
corresponding to the four pinnacles and 
the  flagstaff1 on the summit of the    
principal tower4 ,the five conductors   
consisted of good copper-wire rope2 all 
were united together inside the  tower1 
through which they were carried down to 
earth1 and there ended  in an           
earthenware drain4 ,this kind of earth  
contact might be pretty  good as long as

 water was flowing in the drain2 but    
whenever the drain  was dry the         
conductor was practically insulated from
 the earth4 ,on the  fifteenth of       
,march1 #ahgf1 the church was struck by 
lightning1 which  for some distance     
followed the line of the conductor2 then
 finding its  passage barred by the     
earthenware drain1 which was dry at the 
time1 it  burst through the walls of the
 church1 displacing several             
hundredweight  of stone1 and making its 
way to earth through the gas-pipe4#cd   
,another very instructive example is    
furnished by the lightning  conductor   
attached to the lighthouse of           
,berehaven1 on the south-west  coast of 
,ireland4 ,it consists of a half-inch   
copper-wire rope1 which  is carried down
 the face of the tower 8until it reaches
 the rock  at its base1 where it        
terminates in a small hole1 three inches
 by  three inches1 jumped out of the    
rock1 about six inches under the        
surface40 ,here1 again1 we have a good  

imitation of ,professor ,richman's      
experiment1 with only this difference1  
that a small hole in the rock  is       
substituted for a glass bottle4 ,a      
lightning conductor of this kind        
fulfills two functions3 it increases the
 chance of the lightning coming  down on
 the building1 and it makes it          
positively certain that1 having  come1  
it cannot get to earth without doing    
mischief4    ,the lightning did come    
down on the ,berehaven ,lighthouse1     
about five  years ago4 ,as might have   
been expected1 it made no use of the    
lightning  conductor in finding a path  
to earth1 but forced its way through the
  building1 dealing destruction around  
as it descended from stage to  stage4   
,the ,board of ,irish ,lights furnished 
a detailed report of this  accident to  
the ,lightning ,rod ,conference1 in     
,march1 #ahhj1 from which  the above    
particulars have been derived4#ce       
,precaution ,against ,rival             
,conductors4--,but it is not enough to  

provide a good lightning conductor1     
which is itself able to convey  the     
electric discharge harmless to the      
earth2 we must take care that  there are
 no rival conductors near at hand in the
 building1 to draw  off the lightning   
from the path prepared for it1 and      
conduct it by  another route in which   
its course might be marked with         
destruction4  ,this precaution is of    
especial importance at the present day1 
owing to  the great extent to which     
metal1 of various kinds1 is employed in 
the  construction and fittings of modern
 buildings4 ,i will take a typical  case
 which will bring home this point       
clearly to your minds4    ,a great part 
of the roof of many large buildings is  
covered with lead4  ,the lead1 at one or
 more points may come near the gutters  
intended  to collect the rain water2 the
 gutters are in connection with the     
cast-iron down-pipes into which the     
water flows1 and these down-pipes  often
 pass into the earth1 which1 under the  

circumstances1 is generally  moist1 and1
 therefore1 in good electrical contact  
with the metal pipes4  ,here1 then1 is  
an irregular line of conductors1 which1 
though it has  gaps here and there1 may1
 under certain conditions1 offer to the 
lightning discharge a path not less free
 than the lightning conductor  itself4  
,what is the consequence8 ,the flash of 
lightning1 or a part of  it1 will quit  
the lightning rod1 and make its way to  
earth through the  broken series of     
conductors1 doing1 perhaps1 serious     
mischief1 as it  leaps across1 or bursts
 asunder1 the non-conducting links in   
the chain4    ,another illustration may 
be taken from the gas and water-pipes1  
with  which almost all buildings in     
great cities are now provided1 and which
  constitute a network of conductors1   
spreading out over the walls and        
ceilings1 and stretching down into the  
earth1 with which they have  the best   
possible electrical contact4 ,now1 it   
often happens that a  lightning         

conductor1 at some point in its course1 
comes within a short  distance of this  
network of pipes4 ,in such a case1 a    
portion of the  electrical discharge is 
apt to leave the lightning conductor1   
force  its way destructively through    
masses of masonry1 enter the network of 
pipes1 melt the leaden gas-pipe1 ignite 
the gas1 and set the building  on fire4 
,these are not merely the speculations  
of philosophers4 ,all the various       
incidents ,i have just described have   
occurred1 over and over again1  during  
the last few years4 ,you will remember1 
in some of the examples  ,i have already
 set before you1 when the electric      
discharge failed to  find a sufficient  
path to earth through the lightning rod1
 it followed  some such broken series of
 chance conductors as we are now        
considering4  ,but this broken series of
 conductors seems to bring with it a    
special  danger of its own1 even when   
the lightning conductor is otherwise in 
efficient working order4 ,i will give   

you just one case in point4    ,on the  
fifth of ,june1 #ahgi1 the ,church of   
,saint ,marie1 ,rugby1 was  struck by   
lightning and set on fire1 and narrowly 
escaped being  burned to the ground4 ,a 
number of workmen were engaged on that  
day in  repairing the spire of the      
church4 ,about three o'clock they saw a 
dense  black cloud approaching1 and they
 came down to take shelter within the   
building4 ,in a few minutes they heard a
 terrific crash just overhead2  at the  
same moment the gas was lighted under   
the organ loft and the  woodwork was set
 in a blaze4 ,the men soon succeeded in 
putting out the  fire1 and the church   
escaped with very little damage4        
,now1 in this case there was no reason  
to suppose that the lightning  conductor
 was in any way defective4 ,but about   
half-way up the spire  there was a peal 
of eight bells4 ,attached to these bells
 were iron  wires1 about the eighth of  
an inch in diameter1 leading from the   
clappers down to the organ-loft1 where  

they came within a short  distance of a 
gas-pipe fixed in the wall4 ,it would   
seem that a great  part of the discharge
 was carried safely to earth by the     
lightning  conductor4 ,but a part       
branched off at the bells in the spire1 
descended  by the iron wires1 and forced
 its way into the organ loft1 to reach  
the network of gas-pipes1 through which 
it passed down to the earth1  melting   
the soft leaden gas-pipe in its course  
and lighting the gas4    ,the remedy for
 this danger is obvious4 ,all large     
masses of metal used  in the structure  
of a building--the leads and gutters of 
the roof1  the cast-iron down-pipes1 the
 iron gas and water mains--should be put
  in good metallic connection with the  
lightning conductor1 and1 as  far as may
 be1 with one another4 ,connected in    
this way they furnish  a continuous and 
effective line of conductors leading    
safely down to  earth2 and1 instead of  
being a dangerous rival1 they become a  
useful  auxiliary to the lightning rod4 

,i would observe1 however1 that the     
lightning conductor ought not to  be    
connected directly with the soft leaden 
pipes which are commonly  employed to   
convey gas and water to the several     
parts of a building4  ,such pipes1 as we
 have seen1 are liable to be melted when
 any  considerable part of the lightning
 discharge passes through them2 and     
thus much harm might be done1 and the   
building might even be set on  fire by  
the lighting of the gas4 ,every good end
 will be attained if the  conductor is  
put in metallic connection with the iron
 gas and water  mains either inside or  
outside the building4      ,insulation  
of ,lightning ,conductors4--,it is a    
question often asked  whether a         
lightning rod should be insulated from  
the building it  is intended to protect4
 ,i believe that this practice was      
formerly  recommended by some writers1  
and ,i have observed that glass         
insulators  are still employed not      
infrequently by builders in the erection

 of  lightning conductors2 but1 from the
 principles ,i have set before  you     
to-day1 it seems clear that any         
insulation of this kind is1 to  say the 
least1 altogether useless4 ,the building
 to be protected is  itself in          
electrical communication with the earth1
 and the lightning  conductor1 if       
efficient1 is also in electrical        
communication with the                  
earth--therefore1 the lightning         
conductor and the building are in       
electrical communication with each other
 through the earth1 and any  attempt at 
insulating them from one another above  
the earth is only  labor thrown away4   
,further1 ,i have just shown you that   
the masses of metal employed in  the    
structure or decoration of a building   
ought to be electrically  connected with
 each other and with the lightning      
conductor4 ,now1 if  this be done1 the  
lightning conductor is1 by the fact1 in 
direct  communication with the building1
 and the glass insulators are utterly   

futile4 ,again1 the building itself1    
during a thunderstorm1 becomes  highly  
electrified by the inductive action of  
the cloud1 and needs to  be discharged  
through the conductor just as the       
surrounding earth needs  to be          
discharged2 therefore1 the more         
thoroughly it is connected with  the    
conductor1 the more effectively will the
 conductor fulfill its  functions4      
,personal ,safety in a                  
,thunderstorm4--,i suppose there is     
hardly any one  to whom the question has
 not occurred1 at some time or another1 
what  he had best do to secure his      
personal safety during a thunderstorm4  
,this question is of so much practical  
interest that ,i think ,i shall  be     
excused if ,i say a few words about it1 
though perhaps1 strictly  speaking1 it  
is somewhat beside the subject of       
lightning conductors4    ,at the outset1
 perhaps1 ,i shall surprise you when ,i 
say that you would  enjoy the most      
perfect security if you were in a       

chamber entirely  composed of metal     
plates1 or in a cage constructed of     
metal bars1 or  if you were incased1    
like the knights of old1 in a complete  
suit of  metal armor4 ,this kind of     
defense is looked upon as so perfect1   
among  scientific men1 that ,professor  
,tait does not hesitate to recommend    
his adventurous young friends devoted to
 the cause of science to  provide       
themselves with a light suit of copper1 
and1 thus protected1  take the first    
opportunity of plunging into a          
thundercloud1 there  to investigate1 at 
its source1 the process by which        
lightning is  manufactured4#cf    ,the  
reason why a metal covering affords     
complete protection is that1  when a    
conductor is electrified1 the whole     
charge of electricity  exists on the    
outside surface of the conductor2 and   
therefore1 when a  discharge takes      
place1 it is only the outside surface   
that is affected4  ,thus1 if you were   
completely incased in a metal covering1 

and then  charged with electricity by   
the inductive action of a thundercloud1 
it  is only the metal covering that     
would undergo any change of electrical  
condition2 and when the lightning flash 
would pass1 it is only the  metal       
covering that would be discharged4      
,let me show you a very pretty and      
interesting experiment to illustrate    
this principle3 ,here is a hollow brass 
cylinder1 open at the ends1  mounted on 
an insulating stand4 ,on the outside is 
erected a light brass  rod with two pith
 balls suspended from it by linen       
threads4 ,two pith  balls are also      
suspended by linen threads from the     
inner surface of  the cylinder4 ,you    
know that these pith balls will indicate
 to us the  electrical condition of the 
surfaces to which they are attached4 ,if
 the  surface be electrified1 the pith  
balls attached to it will share in  its 
electrical condition1 and will repel    
each other2 if the surface be  neutral1 
the pith balls attached to it will be   

neutral1 and will remain  at rest4    ,i
 now put this apparatus under the       
influence of our thundercloud1 that  is1
 the large brass conductor of our       
machine4 ,the moment my assistant  turns
 the handle1 the electricity begins to  
be developed on the  conductor1 and you 
see1 at once1 the effect on the brass   
cylinder4 ,the  pith balls attached to  
the outer surface fly asunder2 those    
attached  to the inner surface remain at
 rest4 ,and now a spark passes2 our     
thundercloud is discharged2 the         
inductive action ceases2 the pith balls 
on the outside suddenly collapse1 while 
those on the inside are in no  way      
affected4    ,illustration3 ,,protection
 ,,from ,,lightning ,,furnished ,,by ,a 
,,closed  ,,conductor4    ,it is not    
necessary that the brass cylinder should
 be insulated4 ,to  vary the experiment1
 ,i will now connect it with the earth  
by a chain2  you will observe that the  
effect is precisely the same as before4 
,flash after flash passes while the     

machine continues in action2 the        
outside pith balls fly about violently1 
being charged and discharged            
alternately2 the inside pith balls      
remain all the time at rest4 ,thus  you 
see clearly that1 if you were sitting   
inside such a metal chamber  as this1 or
 covered with a complete suit of metal  
armor1 you would  be perfectly secure   
during a thunderstorm1 whether the      
chamber were  electrically connected    
with the earth or insulated from it4    
,practical ,rules4--,but it rarely      
happens1 when a thunderstorm comes1     
that an iron hut or a complete suit of  
armor is at hand1 and you will          
naturally ask me what you ought to do   
under ordinary circumstances4  ,first1  
let me tell you what you ought not to   
do4 ,you ought not to take  shelter     
under a tree1 or under a haystack1 or   
under the lee of a house2  you ought not
 to stand on the bank of a river1 or    
close to a large  sheet of water4 ,if   
indoors1 you ought not to stay near the 

fireplace1  or near any of the flues or 
chimneys2 you ought not to stand under a
  gasalier hanging from the ceiling2 you
 ought not to remain close to the  gas  
pipes or water-pipes1 or any large      
masses of metal1 whether used in  the   
construction of the building1 or lying  
loosely about4    ,the necessity for    
these precautions is sufficiently       
evident from the  principles ,i have    
already put before you4 ,you want to    
prevent your body  from becoming a link 
in that broken chain of conductors      
which1 as we  have seen1 the electric   
discharge between earth and cloud is    
likely to  follow4 ,now a tree is a     
better conductor than the air2 and your 
body is  a better conductor than a tree4
 ,hence1 the lightning1 in choosing the 
path of least resistance1 would leave   
the air to pass through the tree1  and  
would leave the tree to pass through    
you4 ,a like danger would await  you if 
you stood under the lee of a haystack or
 of a house4    ,the number of people   

who lose their lives by taking refuge   
under trees  in thunderstorms is very   
remarkable4 ,as one instance out of     
many1 ,i  may cite the following case   
which was reported in the ,times1 ,july 
#ad1 #ahhg3 8,yesterday the funeral of a
 negress was being conducted in a       
graveyard at ,mount ,pleasant1 sixty    
miles north of ,nashville1 ,tennessee1  
when a storm came on1 and the crowd ran 
for shelter under the trees4  ,nine     
persons stood under a large oak1 which  
the lightning struck1  killing everyone1
 including three clergymen1 and the     
mother and two  sisters of the girl who 
had been buried40    ,again1 every large
 sheet of water constitutes practically 
a great  conductor1 which offers a very 
perfect medium of discharge between the 
earth round about and the cloud4        
,therefore1 when a thundercloud is      
overhead1 the sheet of water is likely  
to become one end of the line of  the   
lightning discharge2 and if you be      
standing near it1 the line of  discharge

 may pass through your body4    ,when   
lightning strikes a building1 it is very
 apt to use the stack  of chimneys in   
making its way to earth1 partly because 
the stack of  chimneys is generally the 
most prominent part of the building1 and
  partly because1 on account of the     
heated air and the soot within the      
chimney1 it is usually a moderately good
 conductor4 ,therefore1 if  you be      
indoors1 you must keep well away from   
the chimneys2 and for a  similar reason1
 you must keep as far as you can from   
large masses of  metal of every kind4   
,having pointed out the sources of      
danger which you must try to avoid  in a
 thunderstorm1 ,i have nearly exhausted 
all the practical advice  that ,i have  
at my command4 ,but there are some      
occasions on which it may  be possible1 
not only to avoid evident sources of    
danger1 but to make  special provision  
for your own security4 ,thus1 for       
example1 in the open  country1 if you   
stand a short distance from a wood1 you 

may consider  yourself as practically   
protected by a lightning conductor4 ,for
 a  wood1 by its numerous branches and  
leaves1 favors very much a quiet        
discharge of electricity1 thus tending  
to suppress altogether the flash  of    
lightning2 and if the flash of lightning
 does come1 it is much more  likely to  
strike the wood than to strike you1     
because the wood is a far  more         
prominent body1 and offers1 on the      
whole1 an easier path to earth4  ,in    
like manner1 if you place yourself near 
a tall solitary tree1 some  twenty or   
thirty yards outside its longest        
branches1 you will be in a  position of 
comparative safety4 ,if the storm       
overtake you in the open  plain1 far    
away from trees and buildings1 you will 
be safer lying flat  on the ground than 
standing erect4    ,in an ordinary      
dwelling house1 the best situation is   
probably the  middle story1 and the best
 position in the room is in the middle  
of  the floor2 provided1 of course1 that

 there is no gasalier hanging from  the 
ceiling above or below you4 ,strictly   
speaking1 the middle of the  room would 
be a still safer position than the      
middle of the floor2  and nothing could 
be more perfect than the plan suggested 
by ,franklin1  to get into 8a hammock1  
or swinging bed1 suspended by silk      
cords1 and  equally distant from the    
walls on every side1 as well as from the
  ceiling and floor1 above and below40  
,an interesting case has been  recently 
recorded1 by a resident of ,venezuela1  
which illustrates in a  remarkable way  
the excellence of this advice4 8,the    
lightning10 he says1  8struck a         
rancho--a small country house1 built of 
wood and mud1 and  thatched with straw  
or large leaves--where one man slept in 
a hammock1  another lay under the       
hammock on the ground1 and three women  
were busy  about the floor2 there were  
also several hens and a pig4 ,the man in
  the hammock did not receive any injury
 whatever1 while the other four  persons

 and the animals were killed40#cg       
,but1 as ,i can hardly hope that many of
 you when the thunderstorm  actually    
comes will find yourselves provided with
 a hammock1 ,i would  recommend1 as more
 generally useful1 another plan of      
,franklin's1 which  is simply to sit on 
one chair in the middle of the floor and
 put your  feet up on another4 ,this    
arrangement will approach very nearly to
  absolute security if you take the     
further precaution1 also mentioned by   
,franklin1 of putting a feather bed or a
 couple of hair mattresses under  the   
chairs4#ch      ,security ,afforded by  
,lightning ,rods4--,you might1 perhaps1 
be inclined  to infer hastily1 from the 
examples ,i have set before you1 in the 
course of this lecture1 of buildings    
which were struck and severely  injured 
by lightning though provided with       
lightning conductors1 that a  lightning 
rod affords a very imperfect protection 
to life and property4  ,but such an idea
 would be entirely at variance with the 

evidence at  hand on the subject4 ,in   
all the cases to which ,i have referred1
 and in  many others which might easily 
have been cited1 the damage was done    
simply because the lightning rods were  
deficient in one or more of the         
conditions on which ,i have so much     
insisted4 ,where these conditions are   
fulfilled1 the lightning flash will     
either not come down at all upon  the   
building1 or1 if it do come1 it will be 
carried harmless to the  earth4         
,perhaps there is no one fact that so   
forcibly brings home to the  mind the   
complete protection afforded by         
lightning conductors as the  change     
which followed their introduction into  
the ,royal ,navy4 ,i have  already told 
you that in former times the damage done
 by lightning to  ships of the ,royal   
,navy was a regular source of           
expenditure1 amounting  every year to   
several thousand pounds sterling4 ,but1 
after the general  adoption of lightning
 conductors about forty years ago1      

through the  indefatigable exertions of 
,sir ,william ,snow ,harris1 this source
 of  expenditure absolutely disappeared1
 and injury to life and property has    
long been practically unknown in ,her   
,majesty's ,fleet4    ,i should say1    
however1 that the trial of lightning    
conductors in the  ,navy1 though it     
lasted long enough to prove their       
perfect efficiency1  has almost come to 
an end in our own days4 ,the great iron 
monsters  which in recent times have    
taken the place of the wooden ships of  
,old ,england are quite independent of  
lightning rods in the common  sense of  
the word4 ,their ponderous masts are    
virtually lightning rods  of colossal   
dimensions1 and their unsightly hulls   
are1 so to speak1  earth-plates of      
enormous size in perfect electrical     
contact with the  ocean4 ,to add to such
 structures lightning conductors of the 
common  kind would be nothing better    
than 8wasteful and ridiculous excess40  
,as regards buildings on land1 ,i may   

refer to the little province  of        
,schleswig-,holstein1 of which ,i have  
already spoken to you4 ,from  some cause
 or other this small peninsula is       
singularly exposed to  thunderstorms1   
and of late years it has been more      
abundantly provided  with lightning     
conductors than1 perhaps1 any other     
district of equal  extent in ,europe4   
,now1 as a simple illustration of the   
protection  afforded by these lightning 
conductors1 ,i may mention that1 on the 
#bfth of ,may1 #ahgh1 a violent         
thunderstorm burst over the little town 
of ,utersen4 ,five several flashes of   
lightning fell in different parts  of   
the town1 but not the slightest harm was
 done1 each flash being  safely carried 
to earth by a lightning conductor4      
,further1 it appears  from the records  
of the fire insurance company that1 out 
of #eeb  buildings injured by lightning 
during a period of eight years--from    
#ahgj to #ahgh--only four had lightning 
conductors2 and in these four  cases it 

was found1 on examination1 that the     
lightning conductors were  defective4#ci
    ,it would be easy to multiply       
evidence on this subject4 ,but as ,i    
have  already trespassed1 ,i fear1 too  
far on your patience1 ,i will content   
myself with saying1 in conclusion1 that 
according to all the highest            
authorities1 both practical and         
theoretical1 any structure provided     
with a lightning conductor properly     
fitted up in conformity with the        
principles ,i have set before you to-day
 is perfectly secure against  lightning4
 ,the lightning1 indeed1 may fall upon  
it1 but it will pass  harmless to the   
earth2 and the experience of more than a
 hundred years  has fully justified the 
simple and modest words of the great    
inventor  of lightning conductors3 8,it 
has pleased ,god1 in ,his goodness to   
mankind1 at length to discover to them  
the means of securing their  habitations
 and other buildings from mischief by   
thunder and lightning40      ,,note ,i4 

,,on ,,the ,,lightning ,,conductor ,,at 
,,berehaven4#dj     ,it is satisfactory 
to know that the lightning conductor    
referred to   in my lecture as attached 
to the lighthouse at ,berehaven has been
   put in good order under the best     
scientific guidance4 ,the following     
interesting letter from ,professor      
,tyndall1 which appeared in the         
,times1 ,august #ca1 #ahhg1 gives the   
history of the matter very   clearly1   
and fully bears out the views put       
forward in my lecture3     8,your recent
 remarks on thunderstorms and their     
effects induce me to   submit to you the
 following facts and considerations4    
,some years ago   a rock lighthouse on  
the coast of ,ireland was struck and    
damaged by   lightning4 ,an engineer was
 sent down to report on the occurrence2 
and1 as ,i then held the honorable and  
responsible post of scientific   adviser
 to the ,trinity ,house and ,board of   
,trade1 the report was   submitted to   
me4 ,the lightning conductor had been   

carried down the   lighthouse tower1 its
 lower extremity being carefully        
embedded in a   stone perforated to     
receive it4 ,if the object had been to  
invite the   lightning to strike the    
tower1 a better arrangement could hardly
 have   been adopted4     8,i gave      
directions to have the conductor        
immediately prolonged1 and   to have    
added to it a large terminal plate of   
copper1 which was to be   completely    
submerged in the sea4 ,the obvious      
convenience of a chain as   a           
prolongation of the conductor caused the
 authorities in ,ireland to   propose   
it2 but ,i was obliged to veto the      
adoption of the chain4 ,the   contact of
 link with link is never perfect4 ,i    
had1 moreover1 beside   me a portion of 
a chain cable through which a lightning 
discharge had   passed1 the electricity 
in passing from link to link            
encountering   a resistance sufficient  
to enable it to partially fuse the      
chain4   ,the abolition of resistance is

 absolutely necessary in connecting   a 
lightning conductor with the earth1 and 
this is done by closely   embedding in  
the earth a plate of good conducting    
material and of   large area4 ,the      
largeness of area makes atonement for   
the imperfect   conductivity of earth4  
,the plate1 in fact1 constitutes a wide 
door   through which the electricity    
passes freely into the earth1 its       
disruptive and damaging effects being   
thereby avoided4     8,these truths are 
elementary1 but they are often          
neglected4 ,i watched   with interest   
some time ago the operation of setting  
up a lightning   conductor on the house 
of a neighbor of mine in the country4   
,the   wire rope which formed part of   
the conductor was carried down the      
wall and comfortably laid in the earth  
below without any terminal   plate      
whatever4 ,i expostulated with the man  
who did the work1 but   he obviously    
thought he knew more about the matter   
than ,i did4 ,i am   credibly informed  

that this is a common way of dealing    
with lightning   conductors by ignorant 
practitioners1 and the ,bishop of       
,winchester's   palace at ,farnham has  
been mentioned to me as an edifice      
#8protected'   in this fashion4 ,if my  
informant be correct1 the #8protection' 
is a   mockery1 a delusion1 and a       
snare40      ,,note ,,ii4    ,,books    
,,of ,,reference4     ,as some of my    
readers may wish to pursue the study of 
lightning and   lightning conductors    
beyond the limits to which a popular    
lecture   must1 of necessity1 be        
confined1 ,i subjoin a list of the books
 which   ,i think they would be likely  
to find most useful for the purpose4    
,among ordinary text-books on           
physics--,jamin1 ,cours de ,physique1   
vol4 i41 pp4 #dgj-did2 ,mascart1 ,trait 
d',electricit ,statique1 vol4   ii41 pp4
 #eee-egi2 ,de ,larive1 ,a ,treatise on 
,electricity1 in three   volumes1       
,london1 #ahec-h1 vol4 iii41 pp4        
#ij-bja2 ,daguin1 ,trait   de ,physique1

 vol4 iii41 pp4 #bji-bhj2 ,riess1 ,die  
,lehre von der   ,reibungs-,elektricitt1
 vol4 ii41 pp4 #did-efd2                
,mller-,pouillet1   ,lehrbuch der       
,physik1 ,braunschweig1 #ahha1 vol4     
iii41 pp4 #baj-bbe2   ,scott1           
,elementary ,meteorology1 chap4 x4 ,of  
the numerous special   treatises and    
detached papers on the subject1 ,i would
 recommend   ,instruction sur les       
,paratonnerres adopt par l',acadmie des 
,sciences1   ,part i41 #ahbc1 ,part ii41
 #ahed1 ,part iii41 #ahfg1 ,paris1      
#ahgd2 ,arago1   ,sur le ,tonnerre1     
,paris1 #ahcg2 also his ,meteorological 
,essays1   translated by ,sabine1       
,london1 #ahee2 ,sir ,william ,snow     
,harris1 ,on the   ,nature of           
,thunderstorms1 ,london1 #ahdc2 also by 
the same writer1   ,a ,treatise on      
,frictional ,electricity1 ,london1      
#ahfg2 and various   papers on lightning
 conductors1 from #ahbb to #ahei2       
,tomlinson1 ,the   ,thunderstorm1       
,london1 #ahgg2 ,anderson1 ,lightning   

,conductors1 ,london1   #ahhj2 ,holtz1  
,ueber die ,theorie1 die ,anlage1 und   
die ,prfung der   ,blitzableiter1       
,greifswald1 #ahgh2 ,weber1 ,berichte   
ber ,blitzschlge   in der ,provinz      
,schleswig-,holstein1 ,kiel1 #ahhj-a2   
,tait1 ,a ,lecture   on ,thunderstorms1 
delivered in the ,city ,hall1 ,glasgow1 
in #ahhj1   ,nature1 vol4 xxii42 ,report
 of the ,lightning ,rod ,conference1    
,london1   #ahhb4 ,this last-mentioned  
volume comes to us with very high       
authority1 representing1 as it does1 the
 joint labors of several   eminent      
scientific men selected from the        
following societies3 ,the               
,meteorological ,society1 the ,royal    
,institute of ,british ,architects1 the 
,society of ,telegraph ,engineers and   
,electricians1 the ,physical ,society4  
,since the above was in print1 two      
lectures given before the ,society   of 
,arts by ,professor ,oliver ,lodge1 ,f4 
,r4 ,s41 have appeared in the           
,electrician1 ,june and ,july1 #ahhh1 in

 which some new views are put   forward 
respecting lightning conductors1 that   
seem deserving of   careful             
consideration4      ,,footnotes3    #ag 
,the ,thunderstorm1 by ,charles         
,tomlinson1 ,f4 ,r4 ,s41 ,third         
,edition1  pp4 #aec-d4    #ah ,two      
,lectures on ,atmospheric ,electricity  
and ,protection from  ,lightning1       
published at the end of his ,treatise on
 ,frictional  ,electricity1 p4 #bgc4    
#ai ,see ,report of ,lightning ,rod     
,conference1 p4 #aai4    #bj ,loco      
citato4    #ba ,sir ,william ,snow      
,harris1 loco citato1 p4 #bgd4    #bb   
,id41 p4 #bge4    #bc ,the              
,thunderstorm1 by ,charles ,tomlinson1  
,f4,r4,s41 ,third ,edition1 p4  #agb4   
#bd ,see for these facts1 ,anderson1    
,lightning ,conductors1 p4 #aig2        
,tomlinson1 ,the ,thunderstorm1 pp4     
#afg-i2 ,harris1 loco citato1 pp4       
#bgc-d4    #be ,see ,anderson1          
,lightning ,conductors1 pp4 #agj-e4     
#bf ,the ,thunderstorm1 pp4 #aeh-i4 ,see

 also an account of four persons  who   
were struck on the ,matterhorn1 in      
,july1 #ahfi1 all of whom were  hurt1   
and none killed3 ,whymper's ,scrambles  
,among the ,alps1 pp4 #dad1 #dae4    #bg
 ,see ,philosophical ,transactions of   
the ,royal ,society1 #aggc1 p4 #db1  and
 #aggh1 part i41 p4 #bcb2 ,anderson's   
,lightning ,conductors1 pp4 #dj-b2      
,lighting ,rod ,conference1 pp4 #gf-i4  
#bh ,see ,a ,lecture on ,thunderstorms1 
by ,professor ,tait of ,edinburgh1      
published in ,nature1 vol4 xxii41 p4    
#cfe4    #bi ,report of the ,lightning  
,rod ,conference1 p4 #d4    #cj ,the    
dimensions here set forth are greater in
 some respects than  those 8recommended 
as a minimum0 in the report of the      
,lightning ,rod  ,conference1 page #f4  
,but it will be observed by those who   
consult the  report that the minimum    
recommended is just the size which1 in  
the  preceding paragraph of the report1 
is said to have been actually melted  by
 a flash of lightning2 and1 therefore1  

it seems not to be a very  safe minimum4
 ,it will be also seen that there is    
some confusion in the  figures given1   
and that they contradict one another4   
,for the dimensions  of iron rods1 see  
the instructions adopted by the ,academy
 of ,science1  ,paris1 ,may #bj1 #ahge2 
,lightning ,rod ,conference1 pp4 #fg-h4 
#ca ,see letter of ,mr4 ,r4 ,s4 ,newall1
 ,f4 ,r4 ,s41 in the ,times1 ,may #cj1  
#ahgi4    #cb ,see ,nature1 ,june #ab1  
#ahgi1 vol4 xx41 p4 #adf4    #cc ,see   
letter of ,mr4 ,tomes in ,nature1 vol4  
xx41 p4 #ade2 also  ,lightning ,rod     
,conference1 pp4 #baj-ae4    #cd ,see   
,anderson1 ,lightning ,conductors1 pp4  
#bjh-aj4    #ce ,see ,lightning ,rod    
,conference1 pp4 #bjh-aj2 see also the  
note at the  end of this ,lecture1 p4   
#eb4    #cf ,lecture on ,thunderstorms1 
,nature1 vol4 xxii41 pp4 #cfe1 #dcg4    
,see1  also1 a very interesting paper by
 the late ,professor ,j4 ,clerk         
,maxwell1  read before the ,british     
,association at ,glasgow in #ahgf1 and  

reprinted  in the report of the         
,lightning ,rod ,conference1 pp4 #aji1  
#aaj4    #cg ,nature1 vol4 xxxi41 p4    
#dei4    #ch ,see further information on
 this interesting subject in the ,report
  of the ,lightning ,rod ,conference1   
pp4 #bcc-e4    #ci ,see 8,die ,theorie1 
die ,anlage1 und die ,prfung der        
,blitzableiter10  von ,doctor ,w4       
,holtz1 ,griefswald1 #ahgh4    #dj ,see 
page #dd4          ,,appendix4          
,,recent ,,controversy ,,on ,,lightning 
,,conductors4      ,the lecture on      
lightning conductors contained in this  
volume fairly  represents1 ,i think1 the
 theory hitherto received on the        
subject4 ,it  is1 moreover1 entirely in 
accord with the report of the ,lightning
 ,rod  ,conference1 brought out in      
#ahhc1 by a committee of most eminent   
men1  representing several branches of  
science1 who were specially chosen to   
consider this question some ten years   
ago4      ,lectures of ,professor       
,lodge4--,but1 in the month of ,march1  

#ahhh1  two lectures were given before  
the ,society of ,arts1 in ,london1 by   
,professor ,oliver ,lodge1 in which this
 theory was directly challenged1  and   
attacked with cogent arguments1         
supported by striking and original      
experiments4 ,these lectures gave rise  
to an animated controversy1 which       
culminated in a formal discussion at the
 recent meeting of the ,british         
,association in ,bath4 ,the discussion  
was carried on with great spirit1  and  
most of the leading representatives of  
physical and mechanical  science took an
 active part in it4 ,the greater portion
 of this volume  was printed off before 
the meeting of the ,british ,association
 took  place4 ,but the discussion on the
 theory of lightning conductors seemed  
to me so interesting and important that 
,i thought it right1 in the form  of an 
,appendix1 to give some account of the  
questions at issue1 and of  the opinions
 expressed upon them4    ,professor     
,lodge maintains#da that the received   

theory of lightning  rods is open to two
 objections4 ,first1 it takes account   
only of the  conducting power of the    
lightning rod1 and takes no account of  
the  phenomenon known as self-induction1
 or electrical inertia4 ,secondly1  it  
assumes that the whole substance of a   
lightning rod acts as a  conductor1 in  
all cases of lightning discharge2       
whereas there is reason  to believe     
that1 in many cases1 it is only a thin  
outer shell that  really comes into     
action4 ,i will deal with these two     
points separately4      ,the ,effect of 
,self-,induction4--,when an electric    
discharge begins  to pass through a     
conductor1 a momentary back             
electro-motive force  is developed in   
the conductor1 which obstructs its      
passage4 ,this  phenomenon is called by 
some self-induction1 by others          
electrical  inertia2 but its existence  
is admitted by all4 ,now1 when a flash  
of lightning1 so to say1 falls on a     
lightning rod1 the back  electro-motive 

force developed is very considerable2   
and it may  offer so great an           
obstruction that the discharge will find
 an easier  passage by some other route1
 such as the stone walls and woodwork1  
and  furniture of the building4         
,according to this view1 the obstruction
 which a flash of lightning  encounters 
in a conductor consists partly of the   
resistance of the  conductor1 in the    
ordinary sense of the word resistance1  
and partly of  the back electro-motive  
force due to self-induction4 ,the sum of
 these  two ,professor ,lodge calls the 
impedance of the lightning rod2 and he  
considers that the impedance may be     
enormously great1 even when the         
resistance1 in the ordinary sense1 is   
comparatively small4    ,in support of  
this view he has devised the following  
extremely  ingenious and remarkable     
experiment4 ,a large ,leyden jar1 ,l1   
was  arranged in such a manner that1    
while it received a steady charge from  
an electrical machine1 it discharged    

itself1 at intervals1 across the  air   
space at ,a1 between two brass balls4   
,the discharge had then two  alternative
 paths before it2 one through a         
conducting wire1 ,c1 the  other across a
 second air space1 between two brass    
balls at ,b4 ,during  the experiment1   
the two balls at ,a were kept at a fixed
 distance of one  inch apart2 but the   
distance between the two balls at ,b was
 varied4  ,the conductor1 ,c1 used in   
the first instance1 was a stout copper  
wire1  about forty feet long1 and having
 a resistance of only one-fortieth of   
an ohm4    ,illustration3 ,,induction   
,,effect ,,of ,,leyden ,,jar            
,,discharge4      ,m ,electrical        
,machine4    ,l ,leyden ,jar4    ,a ,b  
,air ,spaces between ,brass ,knobs4     
,c ,conducting ,wire4    ,it was found  
that1 so long as the distance between   
the ,b knobs was less  than #a4dc       
inches1 all the discharges passed across
 between the knobs1  in the form of a   
spark4 ,when the distance exceeded #a4dc

 inches1 all  the discharges passed     
through the conductor1 ,c1 and no spark 
appeared  between the balls at ,b4 ,and 
when the distance was exactly #a4dc     
inches1  the discharge sometimes took   
place between the knobs1 and sometimes  
followed the conductor1 ,c4 ,the        
interpretation given to these facts  is 
that the obstruction offered by the     
conductor ,c was about equal  to the    
resistance of #a4dc inches of air2 and  
it is proposed to call  this distance1  
under the conditions of the experiment1 
the critical  distance4    ,coming now  
to the application of these results1    
,professor ,lodge argues  that the      
conductor ,c1 in his experiment1        
represents a lightning rod  of          
unimpeachable excellence2 and yet1 in   
certain cases1 the discharge  refuses to
 follow the conductor1 and prefers to   
leap across a  considerable space of    
air1 notwithstanding the enormous       
resistance it  there encounters4 ,in    
like manner1 he says1 a flash of        

lightning may1  in certain cases1 leave 
a lightning rod fitted up in the most   
orthodox  manner1 and force its way to  
earth through resisting masses of mason 
work and such chance conductors as may  
come across its path4    ,this          
conclusion1 he admits1 is altogether at 
variance with the received  views on the
 subject2 but he contends that it is    
perfectly in accord  with the scientific
 theory of an electrical discharge4 ,the
 moment  the discharge begins to pass in
 the conductor1 it encounters the       
obstruction due to self-induction2 and  
this obstruction is so great  that the  
bad conductors offer1 on the whole1 an  
easier path to earth4      ,variation of
 the ,experiment4--,when the experiment 
was varied by  substituting a thin iron 
wire for the stout copper wire at first 
employed1 a very curious result was     
obtained4 ,the wire chosen was of  the  
same length as the copper1 but had a    
resistance about #a1cjj times  as great2
 its resistance being1 in fact1 #cc4c   

ohms4 ,nevertheless1 in  this           
experiment1 when the ,b knobs were at a 
distance of #a4dc inches1  no spark     
passed1 which showed that the discharge 
always followed the  line of the        
conductor1 and therefore that the       
conductor offered less  obstruction than
 #a4dc inches of air4 ,the knobs were   
then brought  gradually nearer and      
nearer2 and it was not until the        
distance was  considerably reduced that 
the sparks began to pass between them4  
,when  the distance was exactly #a4jc   
inches1 the discharge sometimes passed  
between the knobs1 and sometimes through
 the conductor2 this was1  therefore1   
the critical distance1 in the case of   
the iron wire4 ,thus  it appeared that  
the obstruction offered to the discharge
 by the iron  wire was much less than   
that offered by the copper1 the one     
being equal  to a resistance of only    
#a4jc inches of air1 the other to a     
resistance  of #a4dc inches4    ,it does
 not appear that ,professor ,lodge      

undertakes to offer any  satisfactory   
explanation of this result4 ,he has come
 to the conclusion1  from his various   
experiments1 that1 in the case of a     
sudden discharge1  difference of        
conducting power between fairly good    
conductors is a  matter of practically  
no account2 and that difference of      
sectional area  is a matter of only     
trifling account4 ,but he does not see  
why a thin  iron wire should have a     
smaller impedance than a much thicker   
wire of  copper4 ,he proposes to repeat 
the experiments so as to confirm or to  
modify the result1 which for the present
 seems to him anomalous4#db      ,the   
,outer ,shell only of a ,lightning ,rod 
,acts as a ,conductor4--,as a           
consequence of self-induction or        
electrical inertia1 ,professor ,lodge   
contends that a lightning discharge in a
 conductor consists of a  series of     
oscillations4 ,these oscillations follow
 one another with  extraordinary        
rapidity--there may be a hundred        

thousand in a second1  there may be a   
million4 ,now it has been shown that1   
when a current  starts in a conductor1  
it does not start at once all through   
its  section2 it begins on the outside1 
and then gradually1 but rapidly1        
penetrates to the interior4 ,from this  
he infers that the extremely  rapid     
oscillations of a lightning discharge   
have not time to penetrate  to the      
interior of a conductor4 ,the           
electricity keeps surging to  and fro in
 the superficial layer or outer shell1  
while the interior  substance of the rod
 remains inert and takes no part in the 
action4 ,a  conductor1 therefore1 will  
be most efficient for carrying off a    
flash  of lightning if it present the   
greatest possible amount of surface2 a  
thin1 flat tape will be more efficient  
than a rod of the same mass2 and  a     
number of detached wires more efficient 
than a solid cylinder4 ,as for  existing
 lightning conductors1 the greater part 
of their mass would1  in many cases1    

have no efficacy whatever in carrying   
off a flash of  lightning4      ,the    
,discussion4--,the discussion at the    
meeting of the ,british  ,association   
was opened by ,mr4 ,william ,h4 ,preece1
 ,f4,r4,s41 ,electrician  to the ,post  
,office1 who claimed to have #ejj1jjj   
lightning conductors  under his control4
 ,he expressed his conviction that a    
lightning rod1  properly erected and    
duly maintained1 was a perfect          
protection against  injury from         
lightning2 and in support of this       
conviction he urged  very strongly the  
report of the ,lightning ,rod           
,conference4 ,this report  represented  
the mature judgment of the most eminent 
scientific men1  who had devoted years  
to the study of the question2 and he    
wished  particularly to bring before the
 meeting their clear and decisive       
assertion--an assertion he was there to 
defend--that 8there is no  authentic    
case on record where a properly         
constructed conductor failed  to do its 

duty40    ,the new views put forward by 
,professor ,lodge were based1 in great  
measure1 on his theory that a lightning 
discharge consisted of a series  of     
rapid oscillations4 ,but this theory    
should be received with great  caution4 
,it seemed to be nothing more than a    
deduction from certain  mathematical    
formulas1 and was not supported by any  
solid basis of  observation or          
experiment4 ,besides1 there were many   
facts against  it4 ,they all knew that a
 flash of lightning magnetized steel    
bars1  deranged the compasses of ships  
at sea1 and transmitted signals on      
telegraph wires4 ,but such effects could
 not be produced by a series of         
oscillations1 which1 being equal and    
opposite1 would neutralize each  other4 
,it was alleged that these rapid        
oscillations occurred in the  discharge 
of a ,leyden jar4 ,that might be true1  
and probably was true2  but they were   
not dealing with ,leyden jars1 they were
 dealing with  flashes of lightning4 ,if

 there was any analogy between the      
discharge of  a ,leyden jar and a flash 
of lightning1 it was to be found1 not in
 the  external discharge employed by    
,professor ,lodge in his experiments1   
but  in the bursting of the glass       
cylinder between the two coatings of the
  jar4    ,lord ,rayleigh thought the   
experiments of ,professor ,lodge were   
likely  to have important practical     
applications to lightning conductors4   
,but  though these experiments were     
valuable as suggestions1 they did not   
furnish a sufficient ground for adopting
 any new system of protection4  ,it was 
only by experience with lightning       
conductors themselves that the  question
 could be finally settled4    ,sir      
,william ,thomson hoped for great fruit 
from the further  investigation of      
self-induction in the case of sudden    
electrical  discharges4 ,he warmly      
encouraged ,professor ,lodge to continue
 his  researches2 but he expressed no   
decided opinion on the question at      

issue4 ,incidentally he observed that   
the best security for a gun-powder      
magazine was an iron house2 no lightning
 conductor at all1 but an iron  roof1   
iron walls1 and an iron floor4 ,wooden  
boards should1 of course1  be placed    
over the floor to prevent the danger of 
sparks from people  walking on          
sheet-iron4 ,this iron magazine might be
 placed on a dry  granite rock1 or on   
wet ground2 it might even be placed on a
 foundation  under water2 it might be   
placed anywhere they pleased2 no matter 
what  the surroundings were1 the        
interior would be safe4 ,he thought that
 was  an important practical conclusion 
which might safely be drawn from the    
consideration of these electrical       
oscillations and the experiments        
regarding them4    ,professor ,rowland1 
of the ,johns ,hopkins ,university1     
,america1 said that  the question seemed
 to be whether the experiment of        
,professor ,lodge  actually represented 
the case of lightning4 ,he was very much

 disposed  to think it did not4 ,in the 
experiment almost the whole circuit     
consisted of good conductors2 whereas1  
in the case of lightning1 the  path of  
the discharge was1 for the most part1   
through the air1 and  therefore it might
 be an entirely different phenomenon4   
,the air being a  very bad conductor1 a 
flash of lightning might1 perhaps1 not  
consist of  oscillations1 but rather of 
a single swing4 ,moreover1 it was not at
 all  clear that the length of the      
spark1 in the experiment1 could be taken
  as a measure of the obstruction       
offered by the conductor4 ,professor    
,george ,forbes was greatly impressed   
with the beauty and significance of     
,professor ,lodge's experiments1 but he 
did not think the result so clear  that 
they should be warranted in abandoning  
the principles laid down by  the        
,lightning ,rod ,conference4    ,m4 de  
,fonvielle1 of ,paris1 supported the    
views of ,mr4 ,preece4 ,he cited  the   
example of ,paris1 where they had       

erected a sufficient number  of         
lightning conductors1 according to the  
received principles1 and  calamities    
from lightning were practically unknown4
 ,he suggested that  the ,eiffel ,tower1
 which they were now building1 and which
 would be  raised to the height of a    
thousand feet1 would furnish an         
unrivalled  opportunity for experiments 
on lightning conductors4    ,sir ,james 
,douglass1 ,chief ,engineer to the      
,corporation of ,trinity ,house1  had a 
large experience with lighthouse towers4
 ,the lightning rods on  these towers   
had been erected and maintained during  
the last fifty  years entirely according
 to the advice of ,faraday4 ,they never 
had a  serious accident2 and such minor 
accidents as did occur from time to     
time were always traced to some defect  
in the conductor4 ,they had now         
established a more rigid system of      
inspection1 and he1 for one1 should     
feel perfectly safe in any tower where  
this system was carried out4    ,mr4    

,symons1 ,f4,r4,s41 ,secretary to the   
,meteorological ,society1 had taken     
part in a discussion on lightning       
conductors as long ago as #ahei4 ,it    
had been a hobby with him all his life  
to investigate the circumstances  of    
every case he came across in which      
damage was done by lightning1  and the  
general impression left by his          
investigations entirely  coincided with 
the views just expressed by ,sir ,james 
,douglass4 ,he had  been a member of the
 ,lightning ,rod ,conference1 and was   
the editor of  their report2 and he     
wished to enter his protest against the 
idea of  rejecting all that had hitherto
 been done in connection with lightning 
conductors on the strength of mere      
laboratory experiments4    ,professor   
,lodge1 in reply1 said he could         
perfectly understand the  position of   
those who held that a lightning rod     
properly fitted up  never failed to do  
its duty1 because1 whenever it failed1  
they said  it was not properly fitted   

up4 ,the great resource in such cases   
was  to ascribe the failure to bad earth
 contact4 ,he thought a good earth      
contact was a very good thing1 but he   
could not understand why such           
extraordinary importance should be      
attached to it4 ,a lightning rod  had   
two ends--an earth end and a sky        
end--and he did not see why good        
contact was more necessary at one end   
than at the other4 ,if a few sharp      
points sticking out from the conductor  
were sufficient for a good sky  contact1
 why were they not sufficient also for a
 good earth contact8    ,besides1 though
 a bad earth contact might explain why a
 certain amount  of disruption should   
take place at the earth where the bad   
contact  existed1 he did not see how it 
accounted for the flash shooting off    
sideways half-way down the conductor4   
,again1 what does a bad earth  contact  
mean8 ,if an electrical engineer finds a
 resistance of a  hundred ohms1 he will 
rightly pronounce the earth contact to  

be very  bad indeed4 ,but why should the
 lightning flash leave a conductor  with
 a resistance of a hundred ohms in order
 to follow a line of  non-conductors    
where it encounters a resistance of many
 thousand ohms8    ,he accepted the     
statement of ,mr4 ,preece that his whole
 theory depended  on the existence of   
oscillations in the lightning discharge2
 but there  was good reason to believe  
they existed1 because they were proved  
to  exist in the discharge of a ,leyden 
jar4 ,mr4 ,preece objected that an      
oscillating discharge could not produce 
magnetic effects1 as a flash of         
lightning was known to do4 ,he confessed
 he was unable to explain how  an       
oscillating discharge produced such     
effects2#dc but that it could  produce  
them there was no doubt whatever1 for   
the discharge of a ,leyden  jar produces
 magnetic effects1 and we have ocular   
demonstration that  the discharge of a  
,leyden jar is an oscillating discharge4
    ,as to the assurances we had        

received from electrical engineers that 
a properly fitted lightning conductor   
never fails1 he should like to  ask them
 how the ,hotel de ,ville1 in ,brussels1
 had been set on fire by  lightning on  
the #ast of last ,june4 ,the system of  
lightning conductors  on this building  
had been erected in accordance with the 
received  theory1 and had been held up  
by writers on the subject as the most   
perfect in ,europe4 ,unless some        
explanation were forthcoming to account 
for its failure1 we could no longer     
regard lightning conductors as a        
perfect security against danger4    ,the
 ,president of ,section ,a1 ,professor  
,fitzgerald1 in bringing the  discussion
 to a close1 observed that one result of
 this meeting would  be to give a new   
interest to the phenomena of static     
electricity and  its practical          
applications4 ,he was inclined himself  
to think that the  experiments of       
,professor ,lodge were not quite        
analogous to the case of  a flash of    

lightning4 ,in comparing the discharge  
of a ,leyden jar with  a flash of       
lightning they should look for the      
analogy1 not so much in  the external   
discharge through a series of           
conductors1 but rather1  as ,mr4 ,preece
 had observed1 in the bursting of the   
glass between the  two coatings of the  
jar4 ,as regarded the oscillations in a 
,leyden jar  discharge1 he did not think
 such oscillations were at all necessary
  to account for the phenomena observed 
in the experiments4 ,many of  the       
results which ,professor ,lodge seemed  
to think would require some  millions of
 oscillations per second would be       
produced by a single  discharge lasting 
for a millionth of a second4            
,improvements1 perhaps1  were possible  
in our present system of lightning      
conductors1 but  practical experience   
had shown1 however we might reason on   
the matter1  that1 on the whole1        
lightning conductors had been a great   
protection to  mankind from the dangers 

of lightning4      ,summary4--,i will   
now try to sum up the results of this   
interesting  discussion1 and state      
briefly the conclusions which1 as it    
seems to  me1 may be deduced from it4   
,first1 ,i would remind my readers that 
a  lightning rod has two functions to   
fulfill4 ,its first function is to      
promote a gradual1 but rapid1 discharge 
of electricity according as it  is      
developed1 and thus to prevent such an  
accumulation as would lead  to a flash  
of lightning4 ,its second function is to
 convey the flash  of lightning1 when it
 does come1 harmless to the earth4 ,now1
 the new  views advanced by ,professor  
,lodge in no way impugn the efficiency  
of  lightning rods as regards their     
first function2 and it is evident that  
the greater the number of lightning rods
 distributed over a given area1  the    
more perfectly will this function be    
fulfilled4 ,this is a point of  great   
practical importance which seemed to me1
 in some degree1 lost  sight of during  

the progress of the discussion4         
,secondly1 it was practically admitted  
by the highest authorities that  the    
experiments and reasoning of ,professor 
,lodge afford good grounds  for         
reconsidering the received theory of    
lightning conductors as  regards their  
second function--that of carrying the   
lightning flash  harmless to the earth4 
,but there was undoubtedly a general    
feeling  that it would be rash to set   
aside1 all at once1 the received theory 
on the strength of laboratory           
experiments made under conditions widely
  different from those which actually   
exist in a lightning discharge4         
,experiments are wanted on a larger     
scale2 and1 if possible1 experiments    
with lightning rods themselves4         
,thirdly1 the testimony of electrical   
engineers who have had large  experience
 with lightning conductors seems almost 
unanimous that a  lightning conductor   
erected and maintained in accordance    
with the  conditions prescribed by the  

,lightning ,rod ,conference gives       
perfect  protection4 ,it was certainly  
unfortunate that the ,hotel de ,ville1  
in  ,brussels1 which was reputed the    
best protected building in ,europe1     
should have been damaged by lightning   
just two months before the  discussion  
took place2 but no certain conclusion   
can be drawn from  this catastrophe     
until we know exactly the conditions    
under which it  occurred4    ,so the    
matter stands1 awaiting further         
investigation4      ,,footnotes3    #da 
,see his ,lectures1 published in the    
,electrician1 ,june #bb1 ,june  #bi1    
,july #f1 and ,july #ac1 #ahhh4    #db  
,see paper read at the meeting of the   
,british ,association1 in ,bath1  #ahhh1
 published in the ,electrician1 page    
#fjg4 ,september #ad4    #dc ,see a very
 ingenious hypothesis1 to account for   
this phenomenon1  suggested by          
,professor ,ewing in the ,electrician1  
p4 #gab4 ,october #e1  #ahhh4           
,transcriber's ,notes    ,errors and    

omissions in punctuation have been      
corrected4    ,page #aa3 8continuous    
inpression0 changed to 8continuous      
impression0    ,page #da3 8full         
conconducting power0 changed to 8full   
conducting power0    ,page #dd3 8it     
base0 changed to 8its base0    ,page    
#eh3 8follow one an-another0 changed to 
8follow one another0