,,soap-,,bubbles  ,,and ,,the  ,,forces 
,,which ,,mould ,,them4  ,illustration3 
,experiment for showing by intermittent 
light the apparently stationary drops   
into which a fountain is broken up by   
the action of a musical sound4 7,see    
page #aji47     ,,soap-,,bubbles  ,,and 
,,the  ,,forces ,,which ,,mould ,,them4 
,,being ,a ,,course ,,of ,,three        
,,lectures  ,,delivered ,,in ,,the      
,,theatre ,,of ,,the ,,london           
,,institution ,,on ,,the ,,afternoons   
,,of ,,dec4 #cj1 #ahhi1 ,,jan4 #a ,,and 
#c1 #ahij1 ,,before ,a ,,juvenile       
,,audience4  ,,by  ,c4 ,v4 ,,boys1      
,a4,r4,s4,m41 ,f4,r4,s41  ,,assistant   
,,professor ,,of ,,physics ,,at ,,the   
,,royal ,,college ,,of ,,science1       
,,south ,,kensington4  ,,published      
,,under ,,the ,,direction ,,of ,,the    
,,general ,,literature ,,committee4     
,,society ,,for ,,promoting ,,christian 
,,knowledge1 ,,london3 ,,northumberland 
,,avenue1 ,w4,c42 #dc1 ,,queen          
,,victoria ,,street1 ,e4,c4 ,,brighton3 

#abi1 ,,north ,,street4 ,new ,york3 ,e4 
,j4 ,b4 ,,young  ,,co4 #ahif4   ,,to    
,g4 ,f4 ,,rodwell1  ,,the ,,first       
,,science-,,master ,,appointed ,,at     
,,marlborough ,,college1  ,this ,book is
 ,dedicated  ,,by ,,the ,,author  ,,as  
,a ,,token ,,of ,,esteem ,,and          
,,gratitude1  ,,and ,,in ,,the ,,hope   
,,that  ,,it ,,may ,,excite ,,in ,a     
,,few ,,young ,,people ,,some ,,small   
,,fraction ,,of ,,the ,,interest ,,and  
,,enthusiasm ,,which  ,,his ,,advent    
,,and ,,his ,,lectures ,,awakened  ,,in 
,,the ,,author1 ,,upon ,,whom ,,the     
,,light  ,,of ,,science ,,then ,,shone  
,,for  ,,the ,,first ,,time4            
,,preface4   ,i would ask those readers 
who have grown up1 and who may be       
disposed to find fault with this book1  
on the ground that in so many points it 
is incomplete1 or that much is so       
elementary or well known1 to remember   
that the lectures were meant for        
juveniles1 and for juveniles only4      
,these latter ,i would urge to do their 

best to repeat the experiments          
described4 ,they will find that in many 
cases no apparatus beyond a few pieces  
of glass or india-rubber pipe1 or other 
simple things easily obtained are       
required4 ,if they will take this       
trouble they will find themselves well  
repaid1 and if instead of being         
discouraged by a few failures they will 
persevere with the best means at their  
disposal1 they will soon find more to   
interest them in experiments in which   
they only succeed after a little trouble
 than in those which go all right at    
once4 ,some are so simple that no help  
can be wanted1 while some will probably 
be too difficult1 even with assistance2 
but to encourage those who wish to see  
for themselves the experiments that ,i  
have described1 ,i have given such hints
 at the end of the book as ,i thought   
would be most useful4  ,i have freely   
made use of the published work of many  
distinguished men1 among whom ,i may    
mention ,savart1 ,plateau1 ,clerk       

,maxwell1 ,sir ,william ,thomson1 ,lord 
,rayleigh1 ,mr4 ,chichester ,bell1 and  
,prof4 ,rucker4 ,the experiments have   
mostly been described by them1 some have
 been taken from journals1 and ,i have  
devised or arranged a few4 ,i am also   
indebted to ,prof4 ,rucker for the use  
of various pieces of apparatus which had
 been prepared for his lectures4        
,,soap-,,bubbles1 ,,and ,,the ,,forces  
,,which ,,mould ,,them4   ,i do not     
suppose that there is any one in this   
room who has not occasionally blown a   
common soap-bubble1 and while admiring  
the perfection of its form1 and the     
marvellous brilliancy of its colours1   
wondered how it is that such a          
magnificent object can be so easily     
produced4  ,i hope that none of you are 
yet tired of playing with bubbles1      
because1 as ,i hope we shall see during 
the week1 there is more in a common     
bubble than those who have only played  
with them generally imagine4  ,the      
wonder and admiration so beautifully    

portrayed by ,millais in a picture1     
copies of which1 thanks to modern       
advertising enterprise1 some of you may 
possibly have seen1 will1 ,i hope1 in no
 way fall away in consequence of these  
lectures2 ,i think you will find that it
 will grow as your knowledge of the     
subject increases4 ,you may be          
interested to hear that we are not the  
only juveniles who have played with     
bubbles4 ,ages ago children did the     
same1 and though no mention of this is  
made by any of the classical authors1 we
 know that they did1 because there is an
 ,etruscan vase in the ,louvre in ,paris
 of the greatest antiquity1 on which    
children are represented blowing bubbles
 with a pipe4 ,there is however1 no     
means of telling now whose soap they    
used4  ,it is possible that some of you 
may like to know why ,i have chosen     
soap-bubbles as my subject2 if so1 ,i am
 glad to tell you4 ,though there are    
many subjects which might seem to a     
beginner to be more wonderful1 more     

brilliant1 or more exciting1 there are  
few which so directly bear upon the     
things which we see every day4 ,you     
cannot pour water from a jug or tea from
 a tea-pot2 you cannot even do anything 
with a liquid of any kind1 without      
setting in action the forces to which ,i
 am about to direct your attention4 ,you
 cannot then fail to be frequently      
reminded of what you will hear and see  
in this room1 and1 what is perhaps most 
important of all1 many of the things ,i 
am going to show you are so simple that 
you will be able without any apparatus  
to repeat for yourselves the experiments
 which ,i have prepared1 and this you   
will find more interesting and          
instructive than merely listening to me 
and watching what ,i do4  ,there is one 
more thing ,i should like to explain1   
and that is why ,i am going to show     
experiments at all4 ,you will at once   
answer because it would be so dreadfully
 dull if ,i didn't4 ,perhaps it would4  
,but that is not the only reason4 ,i    

would remind you then that when we want 
to find out anything that we do not     
know1 there are two ways of proceeding4 
,we may either ask somebody else who    
does know1 or read what the most learned
 men have written about it1 which is a  
very good plan if anybody happens to be 
able to answer our question2 or else we 
may adopt the other plan1 and by        
arranging an experiment1 try for        
ourselves4 ,an experiment is a question 
which we ask of ,nature1 who is always  
ready to give a correct answer1 provided
 we ask properly1 that is1 provided we  
arrange a proper experiment4 ,an        
experiment is not a conjuring trick1    
something simply to make you wonder1 nor
 is it simply shown because it is       
beautiful1 or because it serves to      
relieve the monotony of a lecture2 if   
any of the experiments ,i show are      
beautiful1 or do serve to make these    
lectures a little less dull1 so much the
 better2 but their chief object is to   
enable you to see for yourselves what   

the true answers are to questions that  
,i shall ask4  ,illustration3 ,fig4 #a4 
,now ,i shall begin by performing an    
experiment which you have all probably  
tried dozens of times4 ,i have in my    
hand a common camel's-hair brush4 ,if   
you want to make the hairs cling        
together and come to a point1 you wet   
it1 and then you say the hairs cling    
together because the brush is wet4 ,now 
let us try the experiment2 but as you   
cannot see this brush across the room1  
,i hold it in front of the lantern1 and 
you can see it enlarged upon the screen 
7,fig4 #a1 left hand74 ,now it is dry1  
and the hairs are separately visible4 ,i
 am now dipping it in the water1 as you 
can see1 and on taking it out1 the      
hairs1 as we expected1 cling together   
7,fig4 #a1 right hand71 because they are
 wet1 as we are in the habit of saying4 
,i shall now hold the brush in the      
water1 but there it is evident that the 
hairs do not cling at all 7,fig4 #a1    
middle71 and yet they surely are wet    

now1 being actually in the water4 ,it   
would appear then that the reason which 
we always give is not exactly correct4  
,this experiment1 which requires nothing
 more than a brush and a glass of water1
 then shows that the hairs of a brush   
cling together not only because they are
 wet1 but for some other reason as well 
which we do not yet know4 ,it also shows
 that a very common belief as to opening
 our eyes under water is not founded on 
fact4 ,it is very commonly said that if 
you dive into the water with your eyes  
shut you cannot see properly when you   
open them under water1 because the water
 gums the eyelashes down over the eyes2 
and therefore you must dive in with your
 eyes open if you wish to see under     
water4 ,now as a matter of fact this is 
not the case at all2 it makes no        
difference whether your eyes are open or
 not when you dive in1 you can open them
 and see just as well either way4 ,in   
the case of the brush we have seen that 
water does not cause the hairs to cling 

together or to anything else when under 
the water1 it is only when taken out    
that this is the case4 ,this experiment1
 though it has not explained why the    
hairs cling together1 has at any rate   
told us that the reason always given is 
not sufficient4  ,i shall now try       
another experiment as simple as the     
last4 ,i have a pipe from which water is
 very slowly issuing1 but it does not   
fall away continuously2 a drop forms    
which slowly grows until it has attained
 a certain definite size1 and then it   
suddenly falls away4 ,i want you to     
notice that every time this happens the 
drop is always exactly the same size and
 shape4 ,now this cannot be mere chance2
 there must be some reason for the      
definite size1 and shape4 ,why does the 
water remain at all8 ,it is heavy and is
 ready to fall1 but it does not fall2 it
 remains clinging until it is a certain 
size1 and then it suddenly breaks away1 
as if whatever held it was not strong   
enough to carry a greater weight4 ,mr4  

,worthington has carefully drawn on a   
magnified scale the exact shape of a    
drop of water of different sizes1 and   
these you now see upon the diagram on   
the wall 7,fig4 #b74 ,these diagrams    
will probably suggest the idea that the 
water is hanging suspended in an elastic
 bag1 and that the bag breaks or is torn
 away when there is too great a weight  
for it to carry4 ,it is true there is no
 bag at all really1 but yet the drops   
take a shape which suggests an elastic  
bag4 ,to show you that this is no fancy1
 ,i have supported by a tripod a large  
ring of wood over which a thin sheet of 
india-rubber has been stretched1 and now
 on allowing water to pour in from this 
pipe you will see the rubber slowly     
stretching under the increasing weight1 
and1 what ,i especially want you to     
notice1 it always assumes a form like   
those on the diagram4 ,as the weight of 
water increases the bag stretches1 and  
now that there is about a pailful of    
water in it1 it is getting to a state   

which indicates that it cannot last much
 longer2 it is like the water-drop just 
before it falls away1 and now suddenly  
it changes its shape 7,fig4 #c71 and it 
would immediately tear itself away if it
 were not for the fact that india-rubber
 does not stretch indefinitely2 after a 
time it gets tight and will withstand a 
greater pull without giving way4 ,you   
therefore see the great drop now        
permanently hanging which is almost     
exactly the same in shape as the        
water-drop at the point of rupture4 ,i  
shall now let the water run out by means
 of a syphon1 and then the drop slowly  
contracts again4 ,now in this case we   
clearly have a heavy liquid in an       
elastic bag1 whereas in the drop of     
water we have the same liquid but no bag
 that is visible4 ,as the two drops     
behave in almost exactly the same way1  
we should naturally be led to expect    
that their form and movements are due to
 the same cause1 and that the small     
water-drop has something holding it     

together like the india-rubber you now  
see4  ,illustration3 ,fig4 #b4          
,illustration3 ,fig4 #c4  ,let us see   
how this fits the first experiment with 
the brush4 ,that showed that the hairs  
do not cling together simply because    
they are wet2 it is necessary also that 
the brush should be taken out of the    
water1 or in other words it is necessary
 that the surface or the skin of the    
water should be present to bind the     
hairs together4 ,if then we suppose that
 the surface of water is like an elastic
 skin1 then both the experiments with   
the wet brush and with the water-drop   
will be explained4  ,let us therefore   
try another experiment to see whether in
 other ways water behaves as if it had  
an elastic skin4  ,i have here a plain  
wire frame fixed to a stem with a weight
 at the bottom1 and a hollow glass globe
 fastened to it with sealing-wax4 ,the  
globe is large enough to make the whole 
thing float in water with the frame up  
in the air4 ,i can of course press it   

down so that the frame touches the      
water4 ,to make the movement of the     
frame more evident there is fixed to it 
a paper flag4  ,now if water behaves as 
if the surface were an elastic skin1    
then it should resist the upward passage
 of the frame which ,i am now holding   
below the surface4 ,i let go1 and       
instead of bobbing up as it would do if 
there were no such action1 it remains   
tethered down by this skin of the water4
 ,if ,i disturb the water so as to let  
the frame out at one corner1 then1 as   
you see1 it dances up immediately 7,fig4
 #d74 ,you can see that the skin of the 
water must have been fairly strong1     
because a weight of about one quarter of
 an ounce placed upon the frame is only 
just sufficient to make the whole thing 
sink4  ,this apparatus which was        
originally described by ,van der        
,mensbrugghe ,i shall make use of again 
in a few minutes4  ,illustration3 ,fig4 
#d4  ,i can show you in a more striking 
way that there is this elastic layer or 

skin on pure clean water4 ,i have a     
small sieve made of wire gauze          
sufficiently coarse to allow a common   
pin to be put through any of the holes4 
,there are moreover about eleven        
thousand of these holes in the bottom of
 the sieve4 ,now1 as you know1 clean    
wire is wetted by water1 that is1 if it 
is dipped in water it comes out wet2 on 
the other hand1 some materials1 such as 
paraffin wax1 of which paraffin candles 
are made1 are not wetted or really      
touched by water1 as you may see for    
yourselves if you will only dip a       
paraffin candle into water4 ,i have     
melted a quantity of paraffin in a dish 
and dipped this gauze into the melted   
paraffin so as to coat the wire all over
 with it1 but ,i have shaken it well    
while hot to knock the paraffin out of  
the holes4 ,you can now see on the      
screen that the holes1 all except one or
 two1 are open1 and that a common pin   
can be passed through readily enough4   
,this then is the apparatus4 ,now if    

water has an elastic skin which it      
requires force to stretch1 it ought not 
to run through these holes very readily2
 it ought not to be able to get through 
at all unless forced1 because at each   
hole the skin would have to be stretched
 to allow the water to get to the other 
side4 ,this you understand is only true 
if the water does not wet or really     
touch the wire4 ,now to prevent the     
water that ,i am going to pour in from  
striking the bottom with so much force  
as to drive it through1 ,i have laid a  
small piece of paper in the sieve1 and  
am pouring the water on to the paper1   
which breaks the fall 7,fig4 #e74 ,i    
have now poured in about half a tumbler 
of water1 and ,i might put in more4 ,i  
take away the paper but not a drop runs 
through4 ,if ,i give the sieve a jolt   
then the water is driven to the other   
side1 and in a moment it has all        
escaped4 ,perhaps this will remind you  
of one of the exploits of our old friend
 ,simple ,simon1      ,who went for     

water in a sieve1     ,but soon it all  
ran through4  ,but you see if you only  
manage the sieve properly1 this is not  
quite so absurd as people generally     
suppose4  ,illustration3 ,fig4 #e4  ,if 
now ,i shake the water off the sieve1 ,i
 can1 for the same reason1 set it to    
float on water1 because its weight is   
not sufficient to stretch the skin of   
the water through all the holes4 ,the   
water1 therefore1 remains on the other  
side1 and it floats even though1 as ,i  
have already said1 there are eleven     
thousand holes in the bottom1 any one of
 which is large enough to allow an      
ordinary pin to pass through4 ,this     
experiment also illustrates how         
difficult it is to write real and       
perfect nonsense4  ,you may remember one
 of the stories in ,lear's book of      
,nonsense ,songs4      ,they went to sea
 in a sieve1 they did1       ,in a sieve
 they went to sea3     ,in spite of all 
their friends could say1     ,on a      
winter's morn1 on a stormy day1         

,in a sieve they went to sea4           
99    99    99      ,they sailed away in
 a sieve1 they did1       ,in a sieve   
they sailed so fast1     ,with only a   
beautiful pea-green veil1     ,tied with
 a riband by way of a sail1       ,to a 
small tobacco-pipe mast2  ,and so on4   
,you see that it is quite possible to go
 to sea in a sieve--that is1 if the     
sieve is large enough and the water is  
not too rough--and that the above lines 
are now realized in every particular    
7,fig4 #f74  ,illustration3 ,fig4 #f4   
,i may give one more example of the     
power of this elastic skin of water4 ,if
 you wish to pour water from a tumbler  
into a narrow-necked bottle1 you know   
how if you pour slowly it nearly all    
runs down the side of the glass and gets
 spilled about1 whereas if you pour     
quickly there is no room for the great  
quantity of water to pass into the      
bottle all at once1 and so it gets      
spilled again4 ,but if you take a piece 
of stick or a glass rod1 and hold it    

against the edge of the tumbler1 then   
the water runs down the rod and into the
 bottle1 and none is lost 7,fig4 #g72   
you may even hold the rod inclined to   
one side1 as ,i am now doing1 but the   
water runs down the wet rod because this
 elastic skin forms a kind of tube which
 prevents the water from escaping4 ,this
 action is often made use of in the     
country to carry the water from the     
gutters under the roof into a water-butt
 below4 ,a piece of stick does nearly as
 well as an iron pipe1 and it does not  
cost anything like so much4             
,illustration3 ,fig4 #g4  ,i think then 
,i have now done enough to show that on 
the surface of water there is a kind of 
elastic skin4 ,i do not mean that there 
is anything that is not water on the    
surface1 but that the water while there 
acts in a different way to what it does 
inside1 and that it acts as if it were  
an elastic skin made of something like  
very thin india-rubber1 only that it is 
perfectly and absolutely elastic1 which 

india-rubber is not4  ,you will now be  
in a position to understand how it is   
that in narrow tubes water does not find
 its own level1 but behaves in an       
unexpected manner4 ,i have placed in    
front of the lantern a dish of water    
coloured blue so that you may the more  
easily see it4 ,i shall now dip into the
 water a very narrow glass pipe1 and    
immediately the water rushes up and     
stands about half an inch above the     
general level4 ,the tube inside is wet4 
,the elastic skin of the water is       
therefore attached to the tube1 and goes
 on pulling up the water until the      
weight of the water raised above the    
general level is equal to the force     
exerted by the skin4 ,if ,i take a tube 
about twice as big1 then this pulling   
action which is going on all round the  
tube will cause it to lift twice the    
weight of water1 but this will not make 
the water rise twice as high1 because   
the larger tube holds so much more water
 for a given length than the smaller    

tube4 ,it will not even pull it up as   
high as it did in the case of the       
smaller tube1 because if it were pulled 
up as high the weight of the water      
raised would in that case be four times 
as great1 and not only twice as great1  
as you might at first think4 ,it will   
therefore only raise the water in the   
larger tube to half the height1 and now 
that the two tubes are side by side you 
see the water in the smaller tube       
standing twice as high as it does in the
 larger tube4 ,in the same way1 if ,i   
were to take a tube as fine as a hair   
the water would go up ever so much      
higher4 ,it is for this reason that this
 is called ,capillarity1 from the ,latin
 word capillus1 a hair1 because the     
action is so marked in a tube the size  
of a hair4  ,illustration3 ,fig4 #h4    
,supposing now you had a great number of
 tubes of all sizes1 and placed them in 
a row with the smallest on one side and 
all the others in the order of their    
sizes1 then it is evident that the water

 would rise highest in the smallest tube
 and less and less high in each tube in 
the row 7,fig4 #h71 until when you came 
to a very large tube you would not be   
able to see that the water was raised at
 all4 ,you can very easily obtain the   
same kind of effect by simply taking two
 square pieces of window glass and      
placing them face to face with a common 
match or small fragment of anything to  
keep them a small distance apart along  
one edge while they meet together along 
the opposite edge4 ,an india-rubber ring
 stretched over them will hold them in  
this position4 ,i now take this pair of 
plates and stand it in a dish of        
coloured water1 and you at once see that
 the water creeps up to the top of the  
plates on the edge where they meet1 and 
as the distance between the plates      
gradually increases1 so the height to   
which the water rises gradually gets    
less1 and the result is that the surface
 of the liquid forms a beautifully      
regular curve which is called by        

mathematicians a rectangular hyperbola  
7,fig4 #i74 ,i shall have presently to  
say more about this and some other      
curves1 and so ,i shall not do more now 
than state that the hyperbola is formed 
because as the width between the plates 
gets greater the height gets less1 or1  
what comes to the same thing1 because   
the weight of liquid pulled up at any   
small part of the curve is always the   
same4  ,illustration3 ,fig4 #i4  ,if the
 plates or the tubes had been made of   
material not wetted by water1 then the  
effect of the tension of the surface    
would be to drag the liquid away from   
the narrow spaces1 and the more so as   
the spaces were narrower4 ,as it is not 
easy to show this well with paraffined  
glass plates or tubes and water1 ,i     
shall use another liquid which does not 
wet or touch clean glass1 namely1       
quicksilver4 ,as it is not possible to  
see through quicksilver1 it will not do 
to put a narrow tube into this liquid to
 show that the level is lower in the    

tube than in the surrounding vessel1 but
 the same result may be obtained by     
having a wide and a narrow tube joined  
together4 ,then1 as you see upon the    
screen1 the quicksilver is lower in the 
narrow than in the wide tube1 whereas in
 a similar apparatus the reverse is the 
case with water 7,fig4 #aj74            
,illustration3 ,fig4 #aj4  ,i want you  
now to consider what is happening when  
two flat plates partly immersed in water
 are held close together4 ,we have seen 
that the water rises between them4      
,those parts of these two plates1 which 
have air between them and also air      
outside them 7indicated by the letter a 
in ,fig4 #aa71 are each of them pressed 
equally in opposite directions by the   
pressure of the air1 and so these parts 
do not tend to approach or to recede    
from one another4 ,these parts again    
which have water on each side of each of
 them 7as indicated by the letter c7 are
 equally pressed in opposite directions 
by the pressure of the water1 and so    

these parts do not tend to approach or  
to recede from one another4 ,but those  
parts of the plates 7b7 which have water
 between them and air outside would1 you
 might think1 be pushed apart by the    
water between them with a greater force 
than that which could be exerted by the 
air outside1 and so you might be led to 
expect that on this account a pair of   
plates if free to move would separate at
 once4 ,but such an idea though very    
natural is wrong1 and for this reason4  
,the water that is raised between the   
plates being above the general level    
must be under a less pressure1 because1 
as every one knows1 as you go down in   
water the pressure increases1 and so as 
you go up the pressure must get less4   
,the water then that is raised between  
the plates is under a less pressure than
 the air outside1 and so on the whole   
the plates are pushed together4 ,you can
 easily see that this is the case4 ,i   
have two very light hollow glass beads  
such as are used to decorate a          

,christmas tree4 ,these will float in   
water if one end is stopped with        
sealing-wax4 ,these are both wetted by  
water1 and so the water between them is 
slightly raised1 for they act in the    
same way as the two plates1 but not so  
powerfully4 ,however1 you will have no  
difficulty in seeing that the moment ,i 
leave them alone they rush together with
 considerable force4 ,now if you refer  
to the second figure in the diagram1    
which represents two plates which are   
neither of them wetted1 ,i think you    
will see1 without any explanation from  
me1 that they should be pressed         
together1 and this is made evident by   
experiment4 ,two other beads which have 
been dipped in paraffin wax so that they
 are neither of them wetted by water    
float up to one another again when      
separated as though they attracted each 
other just as the clean glass beads did4
  ,illustration3 ,fig4 #aa4  ,if you    
again consider these two cases1 you will
 see that a plate that is wetted tends  

to move towards the higher level of the 
liquid1 whereas one that is not wetted  
tends to move towards the lower level1  
that is if the level of the liquid on   
the two sides is made different by      
capillary action4 ,now suppose one plate
 wetted and the other not wetted1 then1 
as the diagram imperfectly shows1 the   
level of the liquid between the plates  
where it meets the non-wetted plate is  
higher than that outside1 while where it
 meets the wetted plate it is lower than
 that outside2 so each plate tends to go
 away from the other1 as you can see now
 that ,i have one paraffined and one    
clean ball floating in the same water4  
,they appear to repel one another4  ,you
 may also notice that the surface of the
 liquid near a wetted plate is curved1  
with the hollow of the curve upwards1   
while near a non-wetted plate the       
reverse is the case4 ,that this         
curvature of the surface is of the first
 importance ,i can show you by a very   
simple experiment1 which you can repeat 

at home as easily as the last that ,i   
have shown4 ,i have a clean glass bead  
floating in water in a clean glass      
vessel1 which is not quite full4 ,the   
bead always goes to the side of the     
vessel4 ,it is impossible to make it    
remain in the middle1 it always gets to 
one side or the other directly4 ,i shall
 now gradually add water until the level
 of the water is rather higher than that
 of the edge of the vessel4 ,the surface
 is then rounded near the vessel1 while 
it is hollow near the bead1 and now the 
bead sails away towards the centre1 and 
can by no possibility be made to stop   
near either side4 ,with a paraffined    
bead the reverse is the case1 as you    
would expect4 ,instead of a paraffined  
bead you may use a common needle1 which 
you will find will float on water in a  
tumbler1 if placed upon it very gently4 
,if the tumbler is not quite full the   
needle will always go away from the     
edge1 but if rather over-filled it will 
work up to one side1 and then possibly  

roll over the edge2 any bubbles1 on the 
other hand1 which were adhering to the  
glass before will1 the instant that the 
water is above the edge of the glass1   
shoot away from the edge in the most    
sudden and surprising manner4 ,this     
sudden change can be most easily seen by
 nearly filling the glass with water1   
and then gradually dipping in and taking
 out a cork1 which will cause the level 
to slowly change4  ,so far ,i have given
 you no idea what force is exerted by   
this elastic skin of water4             
,measurements made with narrow tubes1   
with drops1 and in other ways1 all show 
that it is almost exactly equal to the  
weight of three and a quarter grains to 
the inch4 ,we have1 moreover1 not yet   
seen whether other liquids act in the   
same way1 and if so whether in other    
cases the strength of the elastic skin  
is the same4  ,you now see a second tube
 identical with that from which drops of
 water were formed1 but in this case the
 liquid is alcohol4 ,now that drops are 

forming1 you see at once that while     
alcohol makes drops which have a        
definite size and shape when they fall  
away1 the alcohol drops are not by any  
means so large as the drops of water    
which are falling by their side4 ,two   
possible reasons might be given to      
explain this4 ,either alcohol is a      
heavier liquid than water1 which would  
account for the smaller drop if the skin
 in each liquid had the same strength1  
or else if alcohol is not heavier than  
water its skin must be weaker than the  
skin of water4 ,as a matter of fact     
alcohol is a lighter liquid than water1 
and so still more must the skin of      
alcohol be weaker than that of water4   
,illustration3 ,fig4 #ab4  ,we can      
easily put this to the test of          
experiment4 ,in the game that is called 
the tug-of-war you know well enough     
which side is the strongest2 it is the  
side which pulls the other over the     
line4 ,let us then make alcohol and     
water play the same game4 ,in order that

 you may see the water1 it is coloured  
blue4 ,it is lying as a shallow layer on
 the bottom of this white dish4 ,at the 
present time the skin of the water is   
pulling equally in all directions1 and  
so nothing happens2 but if ,i pour a few
 drops of alcohol into the middle1 then 
at the line which separates the alcohol 
from the water we have alcohol on one   
side pulling in1 while we have water on 
the other side pulling out1 and you see 
the result4 ,the water is victorious2 it
 rushes away in all directions1 carrying
 a quantity of the alcohol away with it1
 and leaves the bottom of the dish dry  
7,fig4 #ac74  ,illustration3 ,fig4 #ac4 
,this difference in the strength of the 
skin of alcohol and of water1 or of     
water containing much or little alcohol1
 gives rise to a curious motion which   
you may see on the side of a wine-glass 
in which there is some fairly strong    
wine1 such as port4 ,the liquid is      
observed to climb up the sides of the   
glass1 then to gather into drops1 and to

 run down again1 and this goes on for a 
long time4 ,this is explained as        
follows3--,the thin layer of wine on the
 side of the glass being exposed to the 
air1 loses its alcohol by evaporation   
more quickly than the wine in the glass4
 ,it therefore becomes weaker in alcohol
 or stronger in water than that below1  
and for this reason it has a stronger   
skin4 ,it therefore pulls up more wine  
from below1 and this goes on until there
 is so much that drops form1 and it runs
 back again into the glass1 as you now  
see upon the screen 7,fig4 #ad74 ,there 
can be no doubt that this movement is   
referred to in ,proverbs xxiii4 #ca3    
,look not thou upon the wine when it is 
red1 when it giveth his colour in the   
cup1 when it moveth itself aright4  ,if 
you remember that this movement only    
occurs with strong wine1 and that it    
must have been known to every one at the
 time that these words were written1 and
 used as a test of the strength of wine1
 because in those days every one drank  

wine1 then you will agree that this     
explanation of the meaning of that verse
 is the right one4 ,i would ask you also
 to consider whether it is not probable 
that other passages which do not now    
seem to convey to us any meaning        
whatever1 may not in the same way have  
referred to the common knowledge and    
customs of the day1 of which at the     
present time we happen to be ignorant4  
,illustration3 ,fig4 #ad4  ,ether1 in   
the same way1 has a skin which is weaker
 than the skin of water4 ,the very      
smallest quantity of ether on the       
surface of water will produce a         
perceptible effect4 ,for instance1 the  
wire frame which ,i left some time ago  
is still resting against the water-skin4
 ,the buoyancy of the glass bulb is     
trying to push it through1 but the      
upward force is just not sufficient4 ,i 
will however pour a few drops of ether  
into a glass1 and simply pour the vapour
 upon the surface of the water 7not a   
drop of liquid is passing over71 and    

almost immediately sufficient ether has 
condensed upon the water to reduce the  
strength of the skin to such an extent  
that the frame jumps up out of the      
water4  ,there is a well-known case in  
which the difference between the        
strength of the skins of two liquids may
 be either a source of vexation or1 if  
we know how to make use of it1 an       
advantage4 ,if you spill grease on your 
coat you can take it out very well with 
benzine4 ,now if you apply benzine to   
the grease1 and then apply fresh benzine
 to that already there1 you have this   
result--there is then greasy benzine on 
the coat to which you apply fresh       
benzine4 ,it so happens that greasy     
benzine has a stronger skin than pure   
benzine4 ,the greasy benzine therefore  
plays at tug-of-war with pure benzine1  
and being stronger wins and runs away in
 all directions1 and the more you apply 
benzine the more the greasy benzine runs
 away carrying the grease with it4 ,but 
if you follow the directions on the     

bottle1 and first make a ring of clean  
benzine round the grease-spot1 and then 
apply benzine to the grease1 you then   
have the greasy benzine running away    
from the pure benzine ring and heaping  
itself together in the middle1 and      
escaping into the fresh rag that you    
apply1 so that the grease is all of it  
removed4  ,there is a difference again  
between hot and cold grease1 as you may 
see1 when you get home1 if you watch a  
common candle burning4 ,close to the    
flame the grease is hotter than it is   
near the outside4 ,it has therefore a   
weaker skin1 and so a perpetual         
circulation is kept up1 and the grease  
runs out on the surface and back again  
below1 carrying little specks of dust   
which make this movement visible1 and   
making the candle burn regularly4  ,you 
probably know how to take out           
grease-stains with a hot poker and      
blotting-paper4 ,here again the same    
kind of action is going on4  ,a piece of
 lighted camphor floating in water is   

another example of movement set up by   
differences in the strength of the skin 
of water owing to the action of the     
camphor4  ,i will give only one more    
example4  ,if you are painting in       
water-colours on greasy paper or certain
 shiny surfaces the paint will not lie  
smoothly on the paper1 but runs together
 in the well-known way2 a very little   
ox-gall1 however1 makes it lie          
perfectly1 because ox-gall so reduces   
the strength of the skin of water that  
it will wet surfaces that pure water    
will not wet4 ,this reduction of the    
surface tension you can see if ,i use   
the same wire frame a third time4 ,the  
ether has now evaporated1 and ,i can    
again make it rest against the surface  
of the water1 but very soon after ,i    
touch the water with a brush containing 
ox-gall the frame jumps up as suddenly  
as before4  ,it is quite unnecessary    
that ,i should any further insist upon  
the fact that the outside of a liquid   
acts as if it were a perfectly elastic  

skin stretched with a certain definite  
force4  ,suppose now that you take a    
small quantity of water1 say as much as 
would go into a nut-shell1 and suddenly 
let it go1 what will happen8 ,of course 
it will fall down and be dashed against 
the ground4 ,or again1 suppose you take 
the same quantity of water and lay it   
carefully upon a cake of paraffin wax   
dusted over with lycopodium which it    
does not wet1 what will happen8 ,here   
again the weight of the drop--that which
 makes it fall if not held--will squeeze
 it against the paraffin and make it    
spread out into a flat cake4 ,what would
 happen if the weight of the drop or the
 force pulling it downwards could be    
prevented from acting8 ,in such a case  
the drop would only feel the effect of  
the elastic skin1 which would try to    
pull it into such a form as to make the 
surface as small as possible4 ,it would 
in fact rapidly become a perfectly round
 ball1 because in no other way can so   
small a surface be obtained4 ,if1       

instead of taking so much water1 we were
 to take a drop about as large as a     
pin's head1 then the weight which tends 
to squeeze it out or make it fall would 
be far less1 while the skin would be    
just as strong1 and would in reality    
have a greater moulding power1 though   
why ,i cannot now explain4 ,we should   
therefore expect that by taking a       
sufficiently small quantity of water the
 moulding power of the skin would       
ultimately be able almost entirely to   
counteract the weight of the drop1 so   
that very small drops should appear like
 perfect little balls4 ,if you have     
found any difficulty in following this  
argument1 a very simple illustration    
will make it clear4 ,many of you        
probably know how by folding paper to   
make this little thing which ,i hold in 
my hand 7,fig4 #ae74 ,it is called a    
cat-box1 because of its power of        
dispelling cats when it is filled with  
water and well thrown4 ,this one1 large 
enough to hold about half a pint1 is    

made out of a small piece of the ,times 
newspaper4 ,you may fill it with water  
and carry it about and throw it with    
your full power1 and the strength of the
 paper skin is sufficient to hold it    
together until it hits anything1 when of
 course it bursts and the water comes   
out4 ,on the other hand1 the large one  
made out of a whole sheet of the ,times 
is barely able to withstand the weight  
of the water that it will hold4 ,it is  
only just strong enough to allow of its 
being filled and carried1 and then it   
may be dropped from a height1 but you   
cannot throw it4 ,in the same way the   
weaker skin of a liquid will not make a 
large quantity take the shape of a ball1
 but it will mould a minute drop so     
perfectly that you cannot tell by       
looking at it that it is not perfectly  
round every way4 ,this is most easily   
seen with quicksilver4 ,a large quantity
 rolls about like a flat cake1 but the  
very small drops obtained by throwing   
some violently on the table and so      

breaking it up appear perfectly round4  
,you can see the same difference in the 
beads of gold now upon the screen 7,fig4
 #af74 ,they are now solid1 but they    
were melted and then allowed to cool    
without being disturbed4 ,though the    
large bead is flattened by its weight1  
the small one appears perfectly round4  
,finally1 you may see the same thing    
with water if you dust a little         
lycopodium on the table4 ,then water    
falling will roll itself up into perfect
 little balls4 ,you may even see the    
same thing on a dusty day if you water  
the road with a water-pot4              
,illustration3 ,fig4 #ae4               
,illustration3 ,fig4 #af4  ,if it were  
not for the weight of liquids1 that is  
the force with which they are pulled    
down towards the earth1 large drops     
would be as perfectly round as small    
ones4 ,this was first beautifully shown 
by ,plateau1 the blind experimentalist1 
who placed one liquid inside another    
which is equally heavy1 and with which  

it does not mix4 ,alcohol is lighter    
than oil1 while water is heavier1 but a 
suitable mixture of alcohol and water is
 just as heavy as oil1 and so oil does  
not either tend to rise or to fall when 
immersed in such a mixture4 ,i have in  
front of the lantern a glass box        
containing alcohol and water1 and by    
means of a tube ,i shall slowly allow   
oil to flow in4 ,you see that as ,i     
remove the tube it becomes a perfect    
ball as large as a walnut4 ,there are   
now two or three of these balls of oil  
all perfectly round4 ,i want you to     
notice that when ,i hit them on one side
 the large balls recover their shape    
slowly1 while the small ones become     
round again much more quickly4 ,there is
 a very beautiful effect which can be   
produced with this apparatus1 and though
 it is not necessary to refer to it1 it 
is well worth while now that the        
apparatus is set up to show it to you4  
,in the middle of the box there is an   
axle with a disc upon it to which ,i can

 make the oil adhere4 ,now if ,i slowly 
turn the wire and disc the oil will turn
 also4 ,as ,i gradually increase the    
speed the oil tends to fly away in all  
directions1 but the elastic skin retains
 it4 ,the result is that the ball       
becomes flattened at its poles like the 
earth itself4 ,on increasing the speed1 
the tendency of the oil to get away is  
at last too much for the elastic skin1  
and a ring breaks away 7,fig4 #ag71     
which almost immediately contracts again
 on to the rest of the ball as the speed
 falls4 ,if ,i turn it sufficiently fast
 the ring breaks up into a series of    
balls which you now see4 ,one cannot    
help being reminded of the heavenly     
bodies by this beautiful experiment of  
,plateau's1 for you see a central body  
and a series of balls of different sizes
 all travelling round in the same       
direction 7,fig4 #ah72 but the forces   
which are acting in the two cases are   
totally distinct1 and what you see has  
nothing whatever to do with the sun and 

the planets4  ,illustration3 ,fig4 #ag4 
,illustration3 ,fig4 #ah4  ,we have thus
 seen that a large ball of liquid can be
 moulded by the elasticity of its skin  
if the disturbing effect of its weight  
is neutralized1 as in the last          
experiment4 ,this disturbing effect is  
practically of no account in the case of
 a soap-bubble1 because it is so thin   
that it hardly weighs anything4 ,you all
 know1 of course1 that a soap-bubble is 
perfectly round1 and now you know why2  
it is because the elastic film1 trying  
to become as small as it can1 must take 
the form which has the smallest surface 
for its content1 and that form is the   
sphere4 ,i want you to notice here1 as  
with the oil1 that a large bubble       
oscillates much more slowly than a small
 one when knocked out of shape with a   
bat covered with baize or wool4  ,the   
chief result that ,i have endeavoured to
 make clear to-day is this4 ,the outside
 of a liquid acts as if it were an      
elastic skin1 which will1 as far as it  

is able1 so mould the liquid within it  
that it shall be as small as possible4  
,generally the weight of liquids1       
especially when there is a large        
quantity1 is too much for the feebly    
elastic skin1 and its power may not be  
noticed4 ,the disturbing effect of      
weight is got rid of by immersing one   
liquid in another which is equally heavy
 with which it does not mix1 and it is  
hardly noticed when very small drops are
 examined1 or when a bubble is blown1   
for in these cases the weight is almost 
nothing1 while the elastic power of the 
skin is just as great as ever4          
,,lecture ,,ii4   ,i did not in the last
 lecture by any direct experiment show  
that a soap-film or bubble is really    
elastic1 like a piece of stretched      
india-rubber4  ,a soap-bubble           
consisting1 as it does1 of a thin layer 
of liquid1 which must have of course    
both an inside and an outside surface or
 skin1 must be elastic1 and this is     
easily shown in many ways4 ,perhaps the 

easiest way is to tie a thread across a 
ring rather loosely1 and then to dip the
 ring into soap water4 ,on taking it out
 there is a film stretched over the     
ring1 in which the thread moves about   
quite freely1 as you can see upon the   
screen4 ,but if ,i break the film on one
 side1 then immediately the thread is   
pulled by the film on the other side as 
far as it can go1 and it is now tight   
7,fig4 #ai74 ,you will also notice that 
it is part of a perfect circle1 because 
that form makes the space on one side as
 great1 and therefore on the other side1
 where the film is1 as small1 as        
possible4 ,or again1 in this second ring
 the thread is double for a short       
distance in the middle4 ,if ,i break the
 film between the threads they are at   
once pulled apart1 and are pulled into a
 perfect circle 7,fig4 #bj71 because    
that is the form which makes the space  
within it as great as possible1 and     
therefore leaves the space outside it as
 small as possible4 ,you will also      

notice1 that though the circle will not 
allow itself to be pulled out of shape1 
yet it can move about in the ring quite 
freely1 because such a movement does not
 make any difference to the space       
outside it4  ,illustration3 ,fig4 #ai4  
,illustration3 ,fig4 #bj4               
,illustration3 ,fig4 #ba4               
,illustration3 ,fig4 #bb4  ,i have now  
blown a bubble upon a ring of wire4 ,i  
shall hang a small ring upon it1 and to 
show more clearly what is happening1 ,i 
shall blow a little smoke into the      
bubble4 ,now that ,i have broken the    
film inside the lower ring1 you will see
 the smoke being driven out and the ring
 lifted up1 both of which show the      
elastic nature of the film4 ,or again1  
,i have blown a bubble on the end of a  
wide pipe2 on holding the open end of   
the pipe to a candle flame1 the         
outrushing air blows out the flame at   
once1 which shows that the soap-bubble  
is acting like an elastic bag 7,fig4    
#ba74 ,you now see that1 owing to the   

elastic skin of a soap-bubble1 the air  
inside is under pressure and will get   
out if it can4 ,which would you think   
would squeeze the air inside it most1 a 
large or a small bubble8 ,we will find  
out by trying1 and then see if we can   
tell why4 ,you now see two pipes each   
with a tap4 ,these are joined together  
by a third pipe in which there is a     
third tap4 ,i will first blow one bubble
 and shut it off with the tap #a 7,fig4 
#bb71 and then the other1 and shut it   
off with the tap #b4 ,they are now      
nearly equal in size1 but the air cannot
 yet pass from one to the other because 
the tap #c is turned off4 ,now if the   
pressure in the largest one is greatest 
it will blow air into the other when ,i 
open this tap1 until they are equal in  
size2 if1 on the other hand1 the        
pressure in the small one is greatest1  
it will blow air into the large one1 and
 will itself get smaller until it has   
quite disappeared4 ,we will now try the 
experiment4 ,you see immediately that ,i

 open the tap #c the small bubble shuts 
up and blows out the large one1 thus    
showing that there is a greater pressure
 in a small than in a large bubble4 ,the
 directions in which the air and the    
bubble move is indicated in the figure  
by arrows4 ,i want you particularly to  
notice and remember this1 because this  
is an experiment on which a great deal  
depends4 ,to impress this upon your     
memory ,i shall show the same thing in  
another way4 ,there is in front of the  
lantern a little tube shaped like a ,u  
half filled with water4 ,one end of the 
,u is joined to a pipe on which a bubble
 can be blown 7,fig4 #bc74 ,you will now
 be able to see how the pressure changes
 as the bubble increases in size1       
because the water will be displaced more
 when the pressure is more1 and less    
when it is less4 ,now that there is a   
very small bubble1 the pressure as      
measured by the water is about one      
quarter of an inch on the scale4 ,the   
bubble is growing and the pressure      

indicated by the water in the gauge is  
falling1 until1 when the bubble is      
double its former size1 the pressure is 
only half what it was2 and this is      
always true1 the smaller the bubble the 
greater the pressure4 ,as the film is   
always stretched with the same force1   
whatever size the bubble is1 it is clear
 that the pressure inside can only      
depend upon the curvature of a bubble4  
,in the case of lines1 our ordinary     
language tells us1 that the larger a    
circle is the less is its curvature2 a  
piece of a small circle is said to be a 
quick or a sharp curve1 while a piece of
 a great circle is only slightly curved2
 and if you take a piece of a very large
 circle indeed1 then you cannot tell it 
from a straight line1 and you say it is 
not curved at all4 ,with a part of the  
surface of a ball it is just the        
same--the larger the ball the less it is
 curved2 and if the ball is very large  
indeed1 say #hjjj miles across1 you     
cannot tell a small piece of it from a  

true plane4 ,level water is part of such
 a surface1 and you know that still     
water in a basin appears perfectly flat1
 though in a very large lake or the sea 
you can see that it is curved4 ,we have 
seen that in large bubbles the pressure 
is little and the curvature is little1  
while in small bubbles the pressure is  
great and the curvature is great4 ,the  
pressure and the curvature rise and fall
 together4 ,we have now learnt the      
lesson which the experiment of the two  
bubbles1 one blown out by the other1    
teaches us4  ,illustration3 ,fig4 #bc4  
,illustration3 ,fig4 #bd4  ,a ball or   
sphere is not the only form which you   
can give to a soap-bubble4 ,if you take 
a bubble between two rings1 you can pull
 it out until at last it has the shape  
of a round straight tube or cylinder as 
it is called4 ,we have spoken of the    
curvature of a ball or sphere2 now what 
is the curvature of a cylinder8 ,looked 
at sideways1 the edge of the wooden     
cylinder upon the table appears         

straight1 i4 e4 not curved at all2 but  
looked at from above it appears round1  
and is seen to have a definite curvature
 7,fig4 #bd74 ,what then is the         
curvature of the surface of a cylinder8 
,we have seen that the pressure in a    
bubble depends upon the curvature when  
they are spheres1 and this is true      
whatever shape they have4 ,if1 then1 we 
find what sized sphere will produce the 
same pressure upon the air inside that a
 cylinder does1 then we shall know that 
the curvature of the cylinder is the    
same as that of the sphere which        
balances it4 ,now at each end of a short
 tube ,i shall blow an ordinary bubble1 
but ,i shall pull the lower bubble by   
means of another tube into the          
cylindrical form1 and finally blow in   
more or less air until the sides of the 
cylinder are perfectly straight4 ,that  
is now done 7,fig4 #be71 and the        
pressure in the two bubbles must be     
exactly the same1 as there is a free    
passage of air between the two4 ,on     

measuring them you see that the sphere  
is exactly double the cylinder in       
diameter4 ,but this sphere has only half
 the curvature that a sphere half its   
diameter would have4 ,therefore the     
cylinder1 which we know has the same    
curvature that the large sphere has1    
because the two balance1 has only half  
the curvature of a sphere of its own    
diameter1 and the pressure in it is only
 half that in a sphere of its own       
diameter4  ,illustration3 ,fig4 #be4  ,i
 must now make one more step in         
explaining this question of curvature4  
,now that the cylinder and sphere are   
balanced ,i shall blow in more air1     
making the sphere larger2 what will     
happen to the cylinder8 ,the cylinder   
is1 as you see1 very short2 will it     
become blown out too1 or what will      
happen8 ,now that ,i am blowing in air  
you see the sphere enlarging1 thus      
relieving the pressure2 the cylinder    
develops a waist1 it is no longer a     
cylinder1 the sides are curved inwards4 

,as ,i go on blowing and enlarging the  
sphere1 they go on falling inwards1 but 
not indefinitely4 ,if ,i were to blow   
the upper bubble till it was of an      
enormous size the pressure would become 
extremely small4 ,let us make the       
pressure nothing at all at once by      
simply breaking the upper bubble1 thus  
allowing the air a free passage from the
 inside to the outside of what was the  
cylinder4 ,let me repeat this experiment
 on a larger scale4 ,i have two large   
glass rings1 between which ,i can draw  
out a film of the same kind4 ,not only  
is the outline of the soap-film curved  
inwards1 but it is exactly the same as  
the smaller one in shape 7,fig4 #bf74   
,as there is now no pressure there ought
 to be no curvature1 if what ,i have    
said is correct4 ,but look at the       
soap-film4 ,who would venture to say    
that that was not curved8 and yet we had
 satisfied ourselves that the pressure  
and the curvature rose and fell         
together4 ,we now seem to have come to  

an absurd conclusion4 ,because the      
pressure is reduced to nothing we say   
the surface must have no curvature1 and 
yet a glance is sufficient to show that 
the film is so far curved as to have a  
most elegant waist4 ,now look at the    
plaster model on the table1 which is a  
model of a mathematical figure which    
also has a waist4  ,illustration3 ,fig4 
#bf4  ,let us therefore examine this    
cast more in detail4 ,i have a disc of  
card which has exactly the same diameter
 as the waist of the cast4 ,i now hold  
this edgeways against the waist 7,fig4  
#bg71 and though you can see that it    
does not fit the whole curve1 it fits   
the part close to the waist perfectly4  
,this then shows that this part of the  
cast would appear curved inwards if you 
looked at it sideways1 to the same      
extent that it would appear curved      
outwards if you could see it from above4
 ,so considering the waist only1 it is  
curved both towards the inside and also 
away from the inside according to the   

way you look at it1 and to the same     
extent4 ,the curvature inwards would    
make the pressure inside less1 and the  
curvature outwards would make it more1  
and as they are equal they just balance1
 and there is no pressure at all4 ,if we
 could in the same way examine the      
bubble with the waist1 we should find   
that this was true not only at the waist
 but at every part of it4 ,any curved   
surface like this which at every point  
is equally curved opposite ways1 is     
called a surface of no curvature1 and so
 what seemed an absurdity is now        
explained4 ,now this surface1 which is  
the only one of the kind symmetrical    
about an axis1 except a flat surface1 is
 called a catenoid1 because it is like a
 chain1 as you will see directly1 and1  
as you know1 catena is the ,latin for a 
chain4 ,i shall now hang a chain in a   
loop from a level stick1 and throw a    
strong light upon it1 so that you can   
see it well 7,fig4 #bh74 ,this is       
exactly the same shape as the side of a 

bubble drawn out between two rings1 and 
open at the end to the air4#a           
,illustration3 ,fig4 #bg4               
,illustration3 ,fig4 #bh4  ,footnote #a3
 ,if the reader finds these geometrical 
relations too difficult to follow1 he or
 she should skip the next pages1 and go 
on again at ,we have found4444 p4 #gg4  
,let us now take two rings1 and having  
placed a bubble between them1 gradually 
alter the pressure4 ,you can tell what  
the pressure is by looking at the part  
of the film which covers either ring1   
which ,i shall call the cap4 ,this must 
be part of a sphere1 and we know that   
the curvature of this and the pressure  
inside rise and fall together4 ,i have  
now adjusted the bubble so that it is a 
nearly perfect sphere4 ,if ,i blow in   
more air the caps become more curved1   
showing an increased pressure1 and the  
sides bulge out even more than those of 
a sphere 7,fig4 #bi74 ,i have now       
brought the whole bubble back to the    
spherical form4 ,a little increased     

pressure1 as shown by the increased     
curvature of the cap1 makes the sides   
bulge more2 a little less pressure1 as  
shown by the flattening of the caps1    
makes the sides bulge less4 ,now the    
sides are straight1 and the cap1 as we  
have already seen1 forms part of a      
sphere of twice the diameter of the     
cylinder4 ,i am still further reducing  
the pressure until the caps are plane1  
that is1 not curved at all4 ,there is   
now no pressure inside1 and therefore   
the sides have1 as we have already seen1
 taken the form of a hanging chain2 and 
now1 finally1 the pressure inside is    
less than that outside1 as you can see  
by the caps being drawn inwards1 and the
 sides have even a smaller waist than   
the catenoid4 ,we have now seen seven   
curves as we gradually reduced the      
pressure1 namely--       #a4 ,outside   
the sphere4       #b4 ,the sphere4      
#c4 ,between the sphere and the         
cylinder4       #d4 ,the cylinder4      
#e4 ,between the cylinder and the       

catenoid4       #f4 ,the catenoid4      
#g4 ,inside the catenoid4               
,illustration3 ,fig4 #bi4  ,now ,i am   
not going to say much more about all    
these curves1 but ,i must refer to the  
very curious properties that they       
possess4 ,in the first place1 they must 
all of them have the same curvature in  
every part as the portion of the sphere 
which forms the cap2 in the second      
place1 they must all be the curves of   
the least possible surface which can    
enclose the air and join the rings as   
well4 ,and finally1 since they pass     
insensibly from one to the other as the 
pressure gradually changes1 though they 
are distinct curves there must be some  
curious and intimate relation between   
them4 ,this though it is a little       
difficult1 ,i shall explain4 ,if ,i were
 to say that these curves are the       
roulettes of the conic sections ,i      
suppose ,i should alarm you1 and at the 
same time explain nothing1 so ,i shall  
not put it in that way2 but instead1 ,i 

shall show you a simple experiment which
 will throw some light upon the subject1
 which you can try for yourselves at    
home4  ,illustration3 ,fig4 #cj4  ,i    
have here a common bedroom candlestick  
with a flat round base4 ,hold the       
candlestick exactly upright near to a   
white wall1 then you will see the shadow
 of the base on the wall below1 and the 
outline of the shadow is a symmetrical  
curve1 called a hyperbola4 ,gradually   
tilt the candle away from the wall1 you 
will then notice the sides of the shadow
 gradually branch away less and less1   
and when you have so far tilted the     
candle away from the wall that the flame
 is exactly above the edge of the       
base1--and you will know when this is   
the case1 because then the falling      
grease will just fall on the edge of the
 candlestick and splash on to the       
carpet1--,i have it so now1--the sides  
of the shadow near the floor will be    
almost parallel 7,fig4 #cj71 and the    
shape of the shadow will have become a  

curve1 known as a parabola2 and now when
 the candlestick is still more tilted1  
so that the grease misses the base      
altogether and falls in a gentle stream 
upon the carpet1 you will see that the  
sides of the shadow have curled round   
and met on the wall1 and you now have a 
curve like an oval1 except that the two 
ends are alike1 and this is called an   
ellipse4 ,if you go on tilting the      
candlestick1 then when the candle is    
just level1 and the grease pouring away1
 the shadow will be almost a circle2 it 
would be an exact circle if the flame   
did not flare up4 ,now if you go on     
tilting the candle1 until at last the   
candlestick is upside down1 the curves  
already obtained will be reproduced in  
the reverse order1 but above instead of 
below you4  ,you may well ask what all  
this has to do with a soap-bubble4 ,you 
will see in a moment4 ,when you light a 
candle1 the base of the candlestick     
throws the space behind it into         
darkness1 and the form of this dark     

space1 which is everywhere round like   
the base1 and gets larger as you get    
further from the flame1 is a cone1 like 
the wooden model on the table4 ,the     
shadow cast on the wall is of course the
 part of the wall which is within this  
cone4 ,it is the same shape that you    
would find if you were to cut a cone    
through with a saw1 and so these curves 
which ,i have shown you are called conic
 sections4 ,you can see some of them    
already made in the wooden model on the 
table4 ,if you look at the diagram on   
the wall 7,fig4 #ca71 you will see a    
complete cone at first upright 7,a71    
then being gradually tilted over into   
the positions that ,i have specified4   
,the black line in the upper part of the
 diagram shows where the cone is cut    
through1 and the shaded area below shows
 the true shape of these shadows1 or    
pieces cut off1 which are called        
sections4 ,now in each of these sections
 there are either one or two points1    
each of which is called a focus1 and    

these are indicated by conspicuous dots4
 ,in the case of the circle 7,d ,fig4   
#ca71 this point is also the centre4    
,now if this circle is made to roll like
 a wheel along the straight line drawn  
just below it1 a pencil at the centre   
will rule the straight line which is    
dotted in the lower part of the figure2 
but if we were to make wheels of the    
shapes of any of the other sections1 a  
pencil at the focus would certainly not 
draw a straight line4 ,what shape it    
would draw is not at once evident4      
,first consider any of the elliptic     
sections 7,c1 ,e1 or ,f7 which you see  
on either side of the circle4 ,if these 
were wheels1 and were made to roll1 the 
pencil as it moved along would also move
 up and down1 and the line it would draw
 is shown dotted as before in the lower 
part of the figure4 ,in the same way the
 other curves1 if made to roll along a  
straight line1 would cause pencils at   
their focal points to draw the other    
dotted lines4  ,illustration3 ,fig4 #ca4

  ,we are now almost able to see what   
the conic section has to do with a      
soap-bubble4 ,when a soap-bubble was    
blown between two rings1 and the        
pressure inside was varied1 its outline 
went through a series of forms1 some of 
which are represented by the dotted     
lines in the lower part of the figure1  
but in every case they could have been  
accurately drawn by a pencil at the     
focus of a suitable conic section made  
to roll on a straight line4 ,i called   
one of the bubble forms1 if you         
remember1 by its name1 catenoid2 this is
 produced when there is no pressure4    
,the dotted curve in the second figure  
,b is this one2 and to show that this   
catenary can be so drawn1 ,i shall roll 
upon a straight edge a board made into  
the form of the corresponding section1  
which is called a parabola1 and let the 
chalk at its focus draw its curve upon  
the black board4 ,there is the curve1   
and it is as ,i said1 exactly the curve 
that a chain makes when hung by its two 

ends4 ,now that a chain is so hung you  
see that it exactly lies over the chalk 
line4  ,all this is rather difficult to 
understand1 but as these forms which a  
soap-bubble takes afford a beautiful    
example of the most important principle 
of continuity1 ,i thought it would be a 
pity to pass it by4 ,it may be put in   
this way4 ,a series of bubbles may be   
blown between a pair of rings4 ,if the  
pressures are different the curves must 
be different4 ,in blowing them the      
pressures slowly and continuously       
change1 and so the curves cannot be     
altogether different in kind4 ,though   
they may be different curves1 they also 
must pass slowly and continuously one   
into the other4 ,we find the bubble     
curves can be drawn by rolling wheels   
made in the shape of the conic sections 
on a straight line1 and so the conic    
sections1 though distinct curves1 must  
pass slowly and continuously one into   
the other4 ,this we saw was the case1   
because as the candle was slowly tilted 

the curves did as a fact slowly and     
insensibly change from one to the other4
 ,there was only one parabola1 and that 
was formed when the side of the cone was
 parallel to the plane of section1 that 
is when the falling grease just touched 
the edge of the candlestick2 there is   
only one bubble with no pressure1 the   
catenoid1 and this is drawn by rolling  
the parabola4 ,as the cone is gradually 
inclined more1 so the sections become at
 first long ellipses1 which gradually   
become more and more round until a      
circle is reached1 after which they     
become more and more narrow until a line
 is reached4 ,the corresponding bubble  
curves are produced by a gradually      
increasing pressure1 and1 as the diagram
 shows1 these bubble curves are at first
 wavy 7,c71 then they become straight   
when a cylinder is formed 7,d71 then    
they become wavy again 7,e and ,f71 and 
at last1 when the cutting plane1 i4 e4  
the black line in the upper figure1     
passes through the vertex of the cone   

the waves become a series of            
semicircles1 indicating the ordinary    
spherical soap-bubble4 ,now if the cone 
is inclined ever so little more a new   
shape of section is seen 7,g71 and this 
being rolled1 draws a curious curve with
 a loop in it2 but how this is so it    
would take too long to explain4 ,it     
would also take too long to trace the   
further positions of the cone1 and to   
trace the corresponding sections and    
bubble curves got by rolling them4      
,careful inspection of the diagram may  
be sufficient to enable you to work out 
for yourselves what will happen in all  
cases4 ,i should explain that the bubble
 surfaces are obtained by spinning the  
dotted lines about the straight line in 
the lower part of ,fig4 #ca as an axis4 
,as you will soon find out if you try1  
you cannot make with a soap-bubble a    
great length of any of these curves at  
one time1 but you may get pieces of any 
of them with no more apparatus than a   
few wire rings1 a pipe1 and a little    

soap and water4 ,you can even see the   
whole of one of the loops of the dotted 
curve of the first figure 7,a71 which is
 called a nodoid1 not a complete ring1  
for that is unstable1 but a part of such
 a ring4 ,take a piece of wire or a     
match1 and fasten one end to a piece of 
lead1 so that it will stand upright in a
 dish of soap water1 and project half an
 inch or so4 ,hold with one hand a sheet
 of glass resting on the match in       
middle1 and blow a bubble in the water  
against the match4 ,as soon as it       
touches the glass plate1 which should be
 wetted with the soap solution1 it will 
become a cylinder1 which will meet the  
glass plate in a true circle4 ,now very 
slowly incline the plate4 ,the bubble   
will at once work round to the lowest   
side1 and try to pull itself away from  
the match stick1 and in doing so it will
 develop a loop of the nodoid1 which    
would be exactly true in form if the    
match or wire were slightly bent1 so as 
to meet both the glass and the surface  

of the soap water at a right angle4 ,i  
have described this in detail1 because  
it is not generally known that a        
complete loop of the nodoid can be made 
with a soap-bubble4  ,illustration3     
,fig4 #cb4  ,illustration3 ,fig4 #cc4   
,we have found that the pressure in a   
short cylinder gets less if it begins to
 develop a waist1 and greater if it     
begins to bulge4 ,let us therefore try  
and balance one with a bulge against    
another with a waist4 ,immediately that 
,i open the tap and let the air pass1   
the one with a bulge blows air round to 
the one with a waist and they both      
become straight4 ,in ,fig4 #cb the      
direction of the movement of the air and
 of the sides of the bubble is indicated
 by arrows4 ,let us next try the same   
experiment with a pair of rather longer 
cylinders1 say about twice as long as   
they are wide4 ,they are now ready1 one 
with a bulge and one with a waist4      
,directly ,i open the tap1 and let the  
air pass from one to the other1 the one 

with a waist blows out the other still  
more 7,fig4 #cc71 until at last it has  
shut itself up4 ,it therefore behaves   
exactly in the opposite way that the    
short cylinder did4 ,if you try pairs of
 cylinders of different lengths you will
 find that the change occurs when they  
are just over one and a half times as   
long as they are wide4 ,now if you      
imagine one of these tubes joined on to 
the end of the other1 you will see that 
a cylinder more than about three times  
as long as it is wide cannot last more  
than a moment2 because if one end were  
to contract ever so little the pressure 
there would increase1 and the narrow end
 would blow air into the wider end      
7,fig4 #cd71 until the sides of the     
narrow end met one another4 ,the exact  
length of the longest cylinder that is  
stable1 is a little more than three     
diameters4 ,the cylinder just becomes   
unstable when its length is equal to its
 circumference1 and this is #c-a_/g     
diameters almost exactly4               

,illustration3 ,fig4 #cd4  ,i will      
gradually separate these rings1 keeping 
up a supply of air1 and you will see    
that when the tube gets nearly three    
times as long as it is wide it is       
getting very difficult to manage1 and   
then suddenly it grows a waist nearer   
one end than the other1 and breaks off  
forming a pair of separate and unequal  
bubbles4  ,if now you have a cylinder of
 liquid of great length suddenly formed 
and left to itself1 it clearly cannot   
retain that form4 ,it must break up into
 a series of drops4 ,unfortunately the  
changes go on so quickly in a falling   
stream of water that no one by merely   
looking at it could follow the movements
 of the separate drops1 but ,i hope to  
be able to show to you in two or three  
ways exactly what is happening4 ,you may
 remember that we were able to make a   
large drop of one liquid in another1    
because in this way the effect of the   
weight was neutralized1 and as large    
drops oscillate or change their shape   

much more slowly than small1 it is more 
easy to see what is happening4 ,i have  
in this glass box water coloured blue on
 which is floating paraffin1 made       
heavier by mixing with it a bad-smelling
 and dangerous liquid called bisulphide 
of carbon4  ,sidenote3 ,see ,diagram at 
the end of the ,book4  ,fig4 #ce4  ,the 
water is only a very little heavier than
 the mixture4 ,if ,i now dip a pipe into
 the water and let it fill1 ,i can then 
raise it and allow drops to slowly form4
 ,drops as large as a shilling are now  
forming1 and when each one has reached  
its full size1 a neck forms above it1   
which is drawn out by the falling drop  
into a little cylinder4 ,you will notice
 that the liquid of the neck has        
gathered itself into a little drop which
 falls away just after the large drop4  
,the action is now going on so slowly   
that you can follow it4 ,fig4 #ce       
contains forty-three consecutive views  
of the growth and fall of the drop taken
 photographically at intervals of       

one-twentieth of a second4 ,for the use 
to which this figure is to be put1 see  
page #adi4 ,if ,i again fill the pipe   
with water1 and this time draw it       
rapidly out of the liquid1 ,i shall     
leave behind a cylinder which will break
 up into balls1 as you can easily see   
7,fig4 #cf74 ,i should like now to show 
you1 as ,i have this apparatus in its   
place1 that you can blow bubbles of     
water containing paraffin in the        
paraffin mixture1 and you will see some 
which have other bubbles and drops of   
one or other liquid inside again4 ,one  
of these compound bubble drops is now   
resting stationary on a heavier layer of
 liquid1 so that you can see it all the 
better 7,fig4 #cg74 ,if ,i rapidly draw 
the pipe out of the box ,i shall leave a
 long cylindrical bubble of water       
containing paraffin1 and this1 as was   
the case with the water-cylinder1 slowly
 breaks up into spherical bubbles4      
,illustration3 ,fig4 #cf4               
,illustration3 ,fig4 #cg4               

,illustration3 ,fig4 #ch4  ,having now  
shown that a very large liquid cylinder 
breaks up regularly into drops1 ,i shall
 next go the other extreme1 and take as 
an example an excessively fine cylinder4
 ,you see a photograph of a spider on   
her geometrical web 7,fig4 #ch74 ,if ,i 
had time ,i should like to tell you how 
the spider goes to work to make this    
beautiful structure1 and a great deal   
about these wonderful creatures1 but ,i 
must do no more than show you that there
 are two kinds of web--those that point 
outwards1 which are hard and smooth1 and
 those that go round and round1 which   
are very elastic1 and which are covered 
with beads of a sticky liquid4 ,now     
there are in a good web over a quarter  
of a million of these beads which catch 
the flies for the spider's dinner4 ,a   
spider makes a whole web in an hour1 and
 generally has to make a new one every  
day4 ,she would not be able to go round 
and stick all these in place1 even if   
she knew how1 because she would not have

 time4 ,instead of this she makes use of
 the way that a liquid cylinder breaks  
up into beads as follows4 ,she spins a  
thread1 and at the same time wets it    
with a sticky liquid1 which of course is
 at first a cylinder4 ,this cannot      
remain a cylinder1 but breaks up into   
beads1 as the photograph taken with a   
microscope from a real web beautifully  
shows 7,fig4 #ci74 ,you see the         
alternate large and small drops1 and    
sometimes you even see extra small drops
 between these again4 ,in order that you
 may see exactly how large these beads  
really are1 ,i have placed alongside a  
scale of thousandths of an inch1 which  
was photographed at the same time4 ,to  
prove to you that this is what happens1 
,i shall now show you a web that ,i have
 made myself by stroking a quartz fibre 
with a straw dipped in castor-oil4 ,the 
same alternate large and small beads are
 again visible just as perfect as they  
were in the spider's web4 ,in fact it is
 impossible to distinguish between one  

of my beaded webs and a spider's by     
looking at them4 ,and there is this     
additional similarity--my webs are just 
as good as a spider's for catching      
flies4 ,you might say that a large      
cylinder of water in oil1 or a          
microscopic cylinder on a thread1 is not
 the same as an ordinary jet of water1  
and that you would like to see if it    
behaves as ,i have described4 ,the next 
photograph 7,fig4 #dj71 taken by the    
light of an instantaneous electric      
spark1 and magnified three and a quarter
 times1 shows a fine column of water    
falling from a jet4 ,you will now see   
that it is at first a cylinder1 that as 
it goes down necks and bulges begin to  
form1 and at last beads separate1 and   
you can see the little drops as well4   
,the beads also vibrate1 becoming       
alternately long and wide1 and there can
 be no doubt that the sparkling portion 
of a jet1 though it appears continuous1 
is really made up of beads which pass so
 rapidly before the eye that it is      

impossible to follow them4 7,i should   
explain that for a reason which will    
appear later1 ,i made a loud note by    
whistling into a key at the time that   
this photograph was taken47             
,illustration3 ,fig4 #ci4               
,illustration3 ,fig4 #dj4  ,lord        
,rayleigh has shown that in a stream of 
water one twenty-fifth of an inch in    
diameter1 necks impressed upon the      
stream1 even though imperceptible1      
develop a thousandfold in depth every   
fortieth of a second1 and thus it is not
 difficult to understand that in such a 
stream the water is already broken      
through before it has fallen many       
inches4 ,he has also shown that free    
water drops vibrate at a rate which may 
be found as follows4 ,a drop two inches 
in diameter makes one complete vibration
 in one second4 ,if the diameter is     
reduced to one quarter of its amount1   
the time of vibration will be reduced to
 one-eighth1 or if the diameter is      
reduced to one-hundredth1 the time will 

be reduced to one-thousandth1 and so on4
 ,the same relation between the diameter
 and the time of breaking up applies    
also to cylinders4 ,we can at once see  
how fast a bead of water the size of one
 of those in the spider's web would     
vibrate if pulled out of shape1 and let 
go suddenly4 ,if we take the diameter as
 being one eight-hundredth of an inch1  
and it is really even finer1 then the   
bead would have a diameter of one       
sixteen-hundredth of a two-inch bead1   
which makes one vibration in one second4
 ,it will therefore vibrate sixty-four  
thousand times as fast1 or sixty-four   
thousand times a second4 ,water-drops   
the size of the little beads1 with a    
diameter of rather less than one        
three-thousandth of an inch1 would      
vibrate half a million times a second1  
under the sole influence of the feebly  
elastic skin of water6 ,we thus see how 
powerful is the influence of the feebly 
elastic water-skin on drops of water    
that are sufficiently small4  ,i shall  

now cause a small fountain to play1 and 
shall allow the water as it falls to    
patter upon a sheet of paper4 ,you can  
see both the fountain itself and its    
shadow upon the screen4 ,you will notice
 that the water comes out of the nozzle 
as a smooth cylinder1 that it presently 
begins to glitter1 and that the separate
 drops scatter over a great space 7,fig4
 #da74 ,now why should the drops        
scatter8 ,all the water comes out of the
 jet at the same rate and starts in the 
same direction1 and yet after a short   
way the separate drops by no means      
follow the same paths4 ,now instead of  
explaining this1 and then showing       
experiments to test the truth of the    
explanation1 ,i shall reverse the usual 
order1 and show one or two experiments  
first1 which ,i think you will all agree
 are so like magic1 so wonderful are    
they and yet so simple1 that if they had
 been performed a few hundred years ago1
 the rash person who showed them might  
have run a serious risk of being burnt  

alive4  ,illustration3 ,fig4 #da4       
,illustration3 ,fig4 #db4  ,you now see 
the water of the jet scattering in all  
directions1 and you hear it making a    
pattering sound on the paper on which it
 falls4 ,i take out of my pocket a stick
 of sealing-wax and instantly all is    
changed1 even though ,i am some way off 
and can touch nothing4 ,the water ceases
 to scatter2 it travels in one          
continuous line 7,fig4 #db71 and falls  
upon the paper making a loud rattling   
noise which must remind you of the rain 
of a thunder-storm4 ,i come a little    
nearer to the fountain and the water    
scatters again1 but this time in quite a
 different way4 ,the falling drops are  
much larger than they were before4      
,directly ,i hide the sealing-wax the   
jet of water recovers its old           
appearance1 and as soon as the          
sealing-wax is taken out it travels in a
 single line again4  ,now instead of the
 sealing-wax ,i shall take a smoky flame
 easily made by dipping some cotton-wool

 on the end of a stick into benzine1 and
 lighting it4 ,as long as the flame is  
held away from the fountain it produces 
no effect1 but the instant that ,i bring
 it near so that the water passes       
through the flame1 the fountain ceases  
to scatter2 it all runs in one line and 
falls in a dirty black stream upon the  
paper4 ,ever so little oil fed into the 
jet from a tube as fine as a hair does  
exactly the same thing4  ,illustration3 
,fig4 #dc4  ,i shall now set a          
tuning-fork sounding at the other side  
of the table4 ,the fountain has not     
altered in appearance4 ,i now touch the 
stand of the tuning-fork with a long    
stick which rests against the nozzle4   
,again the water gathers itself together
 even more perfectly than before1 and   
the paper upon which it falls is humming
 out a note which is the same as that   
produced by the tuning-fork4 ,if ,i     
alter the rate at which the water flows 
you will see that the appearance is     
changed again1 but it is never like a   

jet which is not acted upon by a musical
 sound4 ,sometimes the fountain breaks  
up into two or three and sometimes many 
more distinct lines1 as though it came  
out of as many tubes of different sizes 
and pointing in slightly different      
directions 7,fig4 #dc74 ,the effect of  
different notes could be very easily    
shown if any one were to sing to the    
piece of wood by which the jet is held4 
,i can make noises of different pitches1
 which for this purpose are perhaps     
better than musical notes1 and you can  
see that with every new noise the       
fountain puts on a different appearance4
 ,you may well wonder how these trifling
 influences--sealing-wax1 the smoky     
flame1 or the more or less musical      
noise--should produce this mysterious   
result1 but the explanation is not so   
difficult as you might expect4  ,i hope 
to make this clear when we meet again4  
,,lecture ,,iii4   ,at the conclusion of
 the last lecture ,i showed you some    
curious experiments with a fountain of  

water1 which ,i have now to explain4    
,consider what ,i have said about a     
liquid cylinder4 ,if it is a little more
 than three times as long as it is wide1
 it cannot retain its form2 if it is    
made very much more than three times as 
long1 it will break up into a series of 
beads4 ,now1 if in any way a series of  
necks could be developed upon a cylinder
 which were less than three diameters   
apart1 some of them would tend to heal  
up1 because a piece of a cylinder less  
than three diameters long is stable4 ,if
 they were about three diameters apart1 
the form being then unstable1 the necks 
would get more pronounced in time1 and  
would at last break through1 so that    
beads would be formed4 ,if necks were   
made at distances more than three       
diameters apart1 then the cylinder would
 go on breaking up by the narrowing of  
these necks1 and it would most easily   
break up into drops when the necks were 
just four and a half diameters apart4   
,in other words1 if a fountain were to  

issue from a nozzle held perfectly      
still1 the water would most easily break
 into beads at the distance of four and 
a half diameters apart1 but it would    
break up into a greater number closer   
together1 or a smaller number further   
apart1 if by slight disturbances of the 
jet very slight waists were impressed   
upon the issuing cylinder of water4     
,when you make a fountain play from a   
jet which you hold as still as possible1
 there are still accidental tremors of  
all kinds1 which impress upon the       
issuing cylinder slightly narrow and    
wide places at irregular distances1 and 
so the cylinder breaks up irregularly   
into drops of different sizes and at    
different distances apart4 ,now these   
drops1 as they are in the act of        
separating from one another1 and are    
drawing out the waist1 as you have seen1
 are being pulled for the moment towards
 one another by the elasticity of the   
skin of the waist2 and1 as they are free
 in the air to move as they will1 this  

will cause the hinder one to hurry on1  
and the more forward one to lag behind1 
so that unless they are all exactly     
alike both in size and distance apart   
they will many of them bounce together  
before long4 ,you would expect when they
 hit one another afterwards that they   
would join1 but ,i shall be able to show
 you in a moment that they do not2 they 
act like two india-rubber balls1 and    
bounce away again4 ,now it is not       
difficult to see that if you have a     
series of drops of different sizes and  
at irregular distances bouncing against 
one another frequently1 they will tend  
to separate and to fall1 as we have     
seen1 on all parts of the paper down    
below4 ,what did the sealing-wax or the 
smoky flame do8 and what can the musical
 sound do to stop this from happening8  
,let me first take the sealing-wax4 ,a  
piece of sealing-wax rubbed on your coat
 is electrified1 and will attract light 
bits of paper up to it4 ,the sealing-wax
 acts electrically on the different     

water-drops1 causing them to attract one
 another1 feebly1 it is true1 but with  
sufficient power where they meet to make
 them break through the air-film between
 them and join4 ,to show that this is no
 fancy1 ,i have now in front of the     
lantern two fountains of clean water    
coming from separate bottles1 and you   
can see that they bounce apart perfectly
 7,fig4 #dd74 ,to show that they do     
really bounce1 ,i have coloured the     
water in the two bottles differently4   
,the sealing-wax is now in my pocket2 ,i
 shall retire to the other side of the  
room1 and the instant it appears the    
jets of water coalesce 7,fig4 #de74     
,this may be repeated as often as you   
like1 and it never fails4 ,these two    
bouncing jets are in fact one of the    
most delicate tests for the presence of 
electricity that exist4 ,you are now    
able to understand the first experiment4
 ,the separate drops which bounced away 
from one another1 and scattered in all  
directions1 are unable to bounce when   

the sealing-wax is held up1 because of  
its electrical action4 ,they therefore  
unite1 and the result is1 that instead  
of a great number of little drops       
falling all over the paper1 the stream  
pours in a single line1 and great drops1
 such as you see in a thunder-storm1    
fall on the top of one another4 ,there  
can be no doubt that it is for this     
reason that the drops of rain in a      
thunder-storm are so large4 ,this       
experiment and its explanation are due  
to ,lord ,rayleigh4  ,illustration3     
,fig4 #dd4  ,illustration3 ,fig4 #de4   
,the smoky flame1 as lately shown by    
,mr4 ,bidwell1 does the same thing4 ,the
 reason probably is that the dirt breaks
 through the air-film1 just as dust in  
the air will make the two fountains join
 as they did when they were electrified4
 ,however1 it is possible that oily     
matter condensed on the water may have  
something to do with the effect         
observed1 because oil alone acts quite  
as well as a flame1 but the action of   

oil in this case1 as when it smooths a  
stormy sea1 is not by any means so      
easily understood4  ,when ,i held the   
sealing-wax closer1 the drops coalesced 
in the same way2 but they were then so  
much more electrified that they repelled
 one another as similarly electrified   
bodies are known to do1 and so the      
electrical scattering was produced4     
,you possibly already see why the       
tuning-fork made the drops follow in one
 line1 but ,i shall explain4 ,a musical 
note is1 as is well known1 caused by a  
rapid vibration2 the more rapid the     
vibration the higher is the pitch of the
 note4 ,for instance1 ,i have a         
tooth-wheel which ,i can turn round very
 rapidly if ,i wish4 ,now that it is    
turning slowly you can hear the separate
 teeth knocking against a card that ,i  
am holding in the other hand4 ,i am now 
turning faster1 and the card is giving  
out a note of a low pitch4 ,as ,i make  
the wheel turn faster and faster1 the   
pitch of the note gradually rises1 and  

it would1 if ,i could only turn fast    
enough1 give so high a note that we     
should not be able to hear it4 ,a       
tuning-fork vibrates at a certain       
definite rate1 and therefore gives a    
definite note4 ,the fork now sounding   
vibrates #abh times in every second4    
,the nozzle1 therefore1 is made to      
vibrate1 but almost imperceptibly1 #abh 
times a second1 and to impress upon the 
issuing cylinder of water #abh          
imperceptible waists every second4 ,now 
it just depends what size the jet is1   
and how fast the water is issuing1      
whether these waists are about four and 
a half diameters apart in the cylinder4 
,if the jet is larger1 the water must   
pass more quickly1 or under a greater   
pressure1 for this to be the case2 if   
the jet is finer1 a smaller speed will  
be sufficient4 ,if it should happen that
 the waists so made are anywhere about  
four diameters apart1 then even though  
they are so slightly developed that if  
you had an exact drawing of them1 you   

would not be able to detect the         
slightest change of diameter1 they will 
grow at a great speed1 and therefore the
 water column will break up regularly1  
every drop will be like the one behind  
it1 and like the one in front of it1 and
 not all different1 as is the case when 
the breaking of the water merely depends
 upon accidental tremors4 ,if the drops 
then are all alike in every respect1 of 
course they all follow the same path1   
and so appear to fall in a continuous   
stream4 ,if the waists are about four   
and a half diameters apart1 then the jet
 will break up most easily2 but it will1
 as ,i have said1 break up under the    
influence of a considerable range of    
notes1 which cause the waists to be     
formed at other distances1 provided they
 are more than three diameters apart4   
,if two notes are sounded at the same   
time1 then very often each will produce 
its own effect1 and the result is the   
alternate formation of drops of         
different sizes1 which then make the jet

 divide into two separate streams4 ,in  
this way1 three1 four1 or even many more
 distinct streams may be produced4      
,illustration3 ,fig4 #df4  ,i can now   
show you photographs of some of these   
musical fountains1 taken by the         
instantaneous flash of an electric      
spark1 and you can see the separate     
paths described by the drops of         
different sizes 7,fig4 #df74 ,in one    
photograph there are eight distinct     
fountains all breaking from the same    
jet1 but following quite distinct paths1
 each of which is clearly marked out by 
a perfectly regular series of drops4    
,you can also in these photographs see  
drops actually in the act of bouncing   
against one another1 and flattened when 
they meet1 as if they were india-rubber 
balls4 ,in the photograph now upon the  
screen the effect of this rebound1 which
 occurs at the place marked with a      
cross1 is to hurry on the upper and more
 forward drop1 and to retard the other  
one1 and so to make them travel with    

slightly different velocities and       
directions4 ,it is for this reason that 
they afterwards follow distinct paths4  
,the smaller drops had no doubt been    
acted on in a similar way1 but the part 
of the fountain where this happened was 
just outside the photographic plate1 and
 so there is no record of what occurred4
 ,the very little drops of which ,i have
 so often spoken are generally thrown   
out from the side of a fountain of water
 under the influence of a musical sound1
 after which they describe regular      
little curves of their own1 quite       
distinct from the main stream4 ,they1 of
 course1 can only get out sideways after
 one or two bouncings from the regular  
drops in front and behind4 ,you can     
easily show that they are really formed 
below the place where they first appear1
 by taking a piece of electrified       
sealing-wax and holding it near the     
stream close to the nozzle and gradually
 raising it4 ,when it comes opposite to 
the place where the little drops are    

really formed1 it will act on them more 
powerfully than on the large drops1 and 
immediately pull them out from a place  
where the moment before none seemed to  
exist4 ,they will then circulate in     
perfect little orbits round the         
sealing-wax1 just as the planets do     
round the sun2 but in this case1 being  
met by the resistance of the air1 the   
orbits are spirals1 and the little drops
 after many revolutions ultimately fall 
upon the wax1 just as the planets would 
fall into the sun after many            
revolutions1 if their motion through    
space were interfered with by friction  
of any kind4  ,there is only one thing  
needed to make the demonstration of the 
behaviour of a musical jet complete1 and
 that is1 that you should yourselves see
 these drops in their different         
positions in an actual fountain of      
water4 ,now if ,i were to produce a     
powerful electric spark1 then it is true
 that some of you might for an instant  
catch sight of the drops1 but ,i do not 

think that most would see anything at   
all4 ,but if1 instead of making merely  
one flash1 ,i were to make another when 
each drop had just travelled to the     
position which the one in front of it   
occupied before1 and then another when  
each drop had moved on one place again1 
and so on1 then all the drops1 at the   
moments that the flashes of light fell  
upon them1 would occupy the same        
positions1 and thus all these drops     
would appear fixed in the air1 though of
 course they really are travelling fast 
enough4 ,if1 however1 ,i do not quite   
succeed in keeping exact time with my   
flashes of light1 then a curious        
appearance will be produced4 ,suppose1  
for instance1 that the flashes of light 
follow one another rather too quickly1  
then each drop will not have had quite  
time enough to get to its proper place  
at each flash1 and thus at the second   
flash all the drops will be seen in     
positions which are just behind those   
which they occupied at the first flash1 

and in the same way at the third flash  
they will be seen still further behind  
their former places1 and so on1 and     
therefore they will appear to be moving 
slowly backwards2 whereas if my flashes 
do not follow quite quickly enough1 then
 the drops will1 every time that there  
is a flash1 have travelled just a little
 too far1 and so they will all appear to
 be moving slowly forwards4 ,now let us 
try the experiment4 ,there is the       
electric lantern sending a powerful beam
 of light on to the screen4 ,this ,i    
bring to a focus with a lens1 and then  
let it pass through a small hole in a   
piece of card4 ,the light then spreads  
out and falls upon the screen4 ,the     
fountain of water is between the card   
and the screen1 and so a shadow is cast 
which is conspicuous enough4 ,now ,i    
place just behind the card a little     
electric motor1 which will make a disc  
of card which has six holes near the    
edge spin round very fast4 ,the holes   
come one after the other opposite the   

hole in the fixed card1 and so at every 
turn six flashes of light are produced4 
,when the card is turning about #ba-a_/b
 times a second1 then the flashes will  
follow one another at the right rate4 ,i
 have now started the motor1 and after a
 moment or two ,i shall have obtained   
the right speed1 and this ,i know by    
blowing through the holes1 when a       
musical note will be produced1 higher   
than the fork if the speed is too high1 
and lower than the fork if the speed is 
too low1 and exactly the same as the    
fork if it is right4  ,to make it still 
more evident when the speed is exactly  
right1 ,i have placed the tuning-fork   
also between the light and the screen1  
so that you may see it illuminated1 and 
its shadow upon the screen4 ,i have not 
yet allowed the water to flow1 but ,i   
want you to look at the fork4 ,for a    
moment ,i have stopped the motor1 so    
that the light may be steady1 and you   
can see that the fork is in motion      
because its legs appear blurred at the  

ends1 where of course the motion is most
 rapid4 ,now the motor is started1 and  
almost at once the fork appears quite   
different4 ,it now looks like a piece of
 india-rubber1 slowly opening and       
shutting1 and now it appears quite      
still1 but the noise it is making shows 
that it is not still by any means4 ,the 
legs of the fork are vibrating1 but the 
light only falls upon them at regular   
intervals1 which correspond with their  
movement1 and so1 as ,i explained in the
 case of the water-drops1 the fork      
appears perfectly still4 ,now the speed 
is slightly altered1 and1 as ,i have    
explained1 each new flash of light1     
coming just too soon or just too late1  
shows the fork in a position which is   
just before or just behind that made    
visible by the previous flash4 ,you thus
 see the fork slowly going through its  
evolutions1 though of course in reality 
the legs are moving backwards and       
forwards #abh times a second4 ,by       
looking at the fork or its shadow1 you  

will therefore be able to tell whether  
the light is keeping exact time with the
 vibrations1 and therefore with the     
water-drops4  ,now the water is running1
 and you see all the separate drops     
apparently stationary1 strung like      
pearls or beads of silver upon an       
invisible wire 7see ,frontispiece74 ,if 
,i make the card turn ever so little    
more slowly1 then all the drops will    
appear to slowly march onwards1 and what
 is so beautiful1--but ,i am afraid few 
will see this1--each little drop may be 
seen to gradually break off1 pulling out
 a waist which becomes a little drop1   
and then when the main drop is free it  
slowly oscillates1 becoming wide and    
long1 or turning over and over1 as it   
goes on its way4 ,if it so happens that 
a double or multiple jet is being       
produced1 then you can see the little   
drops moving up to one another1         
squeezing each other where they meet and
 bouncing away again4 ,now the card is  
turning a little too fast and the drops 

appear to be moving backwards1 so that  
it seems as if the water is coming up   
out of the tank on the floor1 quietly   
going over my head1 down into the       
nozzle1 and so back to the water-supply 
of the place4 ,of course this is not    
happening at all1 as you know very well1
 and as you will see if ,i simply try   
and place my finger between two of these
 drops4 ,the splashing of the water in  
all directions shows that it is not     
moving quite so quietly as it appears4  
,there is one more thing that ,i would  
mention about this experiment4 ,every   
time that the flashing light gains or   
loses one complete flash1 upon the      
motion of the tuning-fork1 it will      
appear to make one complete oscillation1
 and the water-drops will appear to move
 back or on one place4  ,i must now come
 to one of the most beautiful           
applications of these musical jets to   
practical purposes which it is possible 
to imagine1 and what ,i shall now show  
are a few out of a great number of the  

experiments of ,mr4 ,chichester ,bell1  
cousin of ,mr4 ,graham ,bell1 the       
inventor of the telephone4  ,to begin   
with ,i have a very small jet of water  
forced through the nozzle at a great    
pressure1 as you can see if ,i point it 
towards the ceiling1 as the water rises 
eight or ten feet4 ,if ,i allow this    
stream of water to fall upon an         
india-rubber sheet1 stretched over the  
end of a tube as big as my little       
finger1 then the little sheet will be   
depressed by the water1 and the more so 
if the stream is strong4 ,now if ,i hold
 the jet close to the sheet the smooth  
column of liquid will press the sheet   
steadily1 and it will remain quiet2 but 
if ,i gradually take the jet further    
away from the sheet1 then any waists    
that may have been formed in the liquid 
column1 which grow as they travel1 will 
make their existence perfectly evident4 
,when a wide part of the column strikes 
the sheet it will be depressed rather   
more than usual1 and when a narrow part 

follows1 the depression will be less4   
,in other words1 any very slight        
vibration imparted to the jet will be   
magnified by the growth of waists1 and  
the sheet of india-rubber will reproduce
 the vibration1 but on a magnified      
scale4 ,now if you remember that sound  
consists of vibrations1 then you will   
understand that a jet is a machine for  
magnifying sound4 ,to show that this is 
the case ,i am now directing the jet on 
to the sheet1 and you can hear nothing2 
but ,i shall hold a piece of wood       
against the nozzle1 and now1 if on the  
whole the jet tends to break up at any  
one rate rather than at any other1 or if
 the wood or the sheet of rubber will   
vibrate at any rate most easily1 then   
the first few vibrations which          
correspond to this rate will be imparted
 to the wood1 which will impress them   
upon the nozzle and so upon the cylinder
 of liquid1 where they will become      
magnified2 the result is that the jet   
immediately begins to sing of its own   

accord1 giving out a loud note 7,fig4   
#dg74  ,i will now remove the piece of  
wood4 ,on placing against the nozzle an 
ordinary lever watch1 the jolt which is 
imparted to the case at every tick1     
though it is so small that you cannot   
detect it1 jolts the nozzle also1 and   
thus causes a neck to form in the jet of
 water which will grow as it travels1   
and so produce a loud tick1 audible in  
every part of this large room 7,fig4    
#dh74 ,now ,i want you to notice how the
 vibration is magnified by the action ,i
 have described4 ,i now hold the nozzle 
close to the rubber sheet1 and you can  
hear nothing4 ,as ,i gradually raise it 
a faint echo is produced1 which         
gradually gets louder and louder1 until 
at last it is more like a hammer        
striking an anvil than the tick of a    
watch4  ,illustration3 ,fig4 #dg4       
,illustration3 ,fig4 #dh4  ,i shall now 
change this watch for another which1    
thanks to a friend1 ,i am able to use4  
,this watch is a repeater1 that is1 if  

you press upon a nob it will strike1    
first the hour1 then the quarters1 and  
then the minutes4 ,i think the water-jet
 will enable you all to hear what time  
it is4 ,listen6 one1 two1 three1        
four2444 ting-tang1 ting-tang2444 one1  
two1 three1 four1 five1 six4 ,six       
minutes after half-past four4 ,you      
notice that not only did you hear the   
number of strokes1 but the jet          
faithfully reproduced the musical notes1
 so that you could distinguish one note 
from the others4  ,i can in the same way
 make the jet play a tune by simply     
making the nozzle rest against a long   
stick1 which is pressed upon a          
musical-box4 ,the musical-box is        
carefully shut up in a double box of    
thick felt1 and you can hardly hear     
anything2 but the moment that the nozzle
 is made to rest against the stick and  
the water is directed upon the          
india-rubber sheet1 the sound of the box
 is loudly heard1 ,i hope1 in every part
 of the room4 ,it is usual to describe a

 fountain as playing1 but it is now     
evident that a fountain can even play a 
tune4 ,there is1 however1 one           
peculiarity which is perfectly evident4 
,the jet breaks up at certain rates more
 easily than at others1 or1 in other    
words1 it will respond to certain sounds
 in preference to others4 ,you can hear 
that as the musical-box plays1 certain  
notes are emphasized in a curious way1  
producing much the same effect that     
follows if you lay a penny upon the     
upper strings of a horizontal piano4    
,illustration3 ,fig4 #di4  ,now1 on     
returning to our soap-bubbles1 you may  
remember that ,i stated that the        
catenoid and the plane were the only    
figures of revolution which had no      
curvature1 and which therefore produced 
no pressure4 ,there are plenty of other 
surfaces which are apparently curved in 
all directions and yet have no          
curvature1 and which therefore produce  
no pressure2 but these are not figures  
of revolution1 that is1 they cannot be  

obtained by simply spinning a curved    
line about an axis4 ,these may be       
produced in any quantity by making wire 
frames of various shapes and dipping    
them in soap and water4 ,on taking them 
out a wonderful variety of surfaces of  
no curvature will be seen4 ,one such    
surface is that known as the            
screw-surface4 ,to produce this it is   
only necessary to take a piece of wire  
wound a few times in an open helix      
7commonly called spiral71 and to bend   
the two ends so as to meet a second wire
 passing down the centre4 ,the          
screw-surface developed by dipping this 
frame in soap-water is well worth seeing
 7,fig4 #di74 ,it is impossible to give 
any idea of the perfection of the form  
in a figure1 but fortunately this is an 
experiment which any one can easily     
perform4  ,illustration3 ,fig4 #ej4     
,then again1 if a wire frame is made in 
the shape of the edges of any of the    
regular geometrical solids1 very        
beautiful figures will be found upon    

them after they have been dipped in     
soap-water4 ,in the case of the         
triangular prism these surfaces are all 
flat1 and at the edges where these      
planes meet one another there are always
 three meeting each other at equal      
angles 7,fig4 #ej74 ,this1 owing to the 
fact that the frame is three-sided1 is  
not surprising4 ,after looking at this  
three-sided frame with three films      
meeting down the central line1 you might
 expect that with a four-sided or square
 frame there would be four films meeting
 each other in a line down the middle4  
,but it is a curious thing that it does 
not matter how irregular the frame may  
be1 or how complicated a mass of froth  
may be1 there can never be more than    
three films meeting in an edge1 or more 
than four edges1 or six films1 meeting  
in a point4 ,moreover the films and     
edges can only meet one another at equal
 angles4 ,if for a moment by any        
accident four films do meet in the same 
edge1 or if the angles are not exactly  

equal1 then the form1 whatever it may   
be1 is unstable2 it cannot last1 but the
 films slide over one another and never 
rest until they have settled down into a
 position in which the conditions of    
stability are fulfilled4 ,this may be   
illustrated by a very simple experiment 
which you can easily try at home1 and   
which you can now see projected upon the
 screen4 ,there are two pieces of       
window-glass about half an inch apart1  
which form the sides of a sort of box   
into which some soap and water have been
 poured4 ,on blowing through a pipe     
which is immersed in the water1 a great 
number of bubbles are formed between the
 plates4 ,if the bubbles are all large  
enough to reach across from one plate to
 the other1 you will at once see that   
there are nowhere more than three films 
meeting one another1 and where they meet
 the angles are all equal4 ,the         
curvature of the bubbles makes it       
difficult to see at first that the      
angles really are all alike1 but if you 

only look at a very short piece close to
 where they meet1 and so avoid being    
bewildered by the curvature1 you will   
see that what ,i have said is true4 ,you
 will also see1 if you are quick1 that  
when the bubbles are blown1 sometimes   
four for a moment do meet1 but that then
 the films at once slide over one       
another and settle down into their only 
possible position of rest 7,fig4 #ea74  
,the air inside a bubble is generally   
under pressure1 which is produced by its
 elasticity and curvature4 ,if the      
bubble would let the air pass through it
 from one side to the other of course it
 would soon shut up1 as it did when a   
ring was hung upon one1 and the film    
within the ring was broken4 ,but there  
are no holes in a bubble1 and so you    
would expect that a gas like air could  
not pass through to the other side4     
,nevertheless it is a fact that gases   
can slowly get through to the other     
side1 and in the case of certain vapours
 the process is far more rapid than any 

one would think possible4               
,illustration3 ,fig4 #ea4               
,illustration3 ,fig4 #eb4  ,ether       
produces a vapour which is very heavy1  
and which also burns very easily4 ,this 
vapour can get to the other side of a   
bubble almost at once4 ,i shall pour a  
little ether upon blotting-paper in this
 bell jar1 and fill the jar with its    
heavy vapour4 ,you can see that the jar 
is filled with something1 not by looking
 at it1 for it appears empty1 but by    
looking at its shadow on the screen4    
,now ,i tilt it gently to one side1 and 
you see something pouring out of it1    
which is the vapour of ether4 ,it is    
easy to show that this is heavy2 it is  
only necessary to drop into the jar a   
bubble1 and so soon as the bubble meets 
the heavy vapour it stops falling and   
remains floating upon the surface as a  
cork does upon water 7,fig4 #eb74 ,now  
let me test the bubble and see whether  
any of the vapour has passed to the     
inside4 ,i pick it up out of the jar    

with a wire ring and carry it to a      
light1 and at once there is a burst of  
flame4 ,but this is not sufficient to   
show that the ether vapour has passed to
 the inside1 because it might have      
condensed in sufficient quantity upon   
the bubble to make it inflammable4 ,you 
remember that when ,i poured some of    
this vapour upon water in the first     
lecture1 sufficient condensed to so     
weaken the water-skin that the frame of 
wire could get through to the other     
side4 ,however1 ,i can see whether this 
is the true explanation or not by       
blowing a bubble on a wide pipe1 and    
holding it in the vapour for a moment4  
,now on removing it you notice that the 
bubble hangs like a heavy drop2 it has  
lost the perfect roundness that it had  
at first1 and this looks as if the      
vapour had found its way in1 but this is
 made certain by bringing a light to the
 mouth of the tube1 when the vapour1    
forced out by the elasticity of the     
bubble1 catches fire and burns with a   

flame five or six inches long 7,fig4    
#ec74 ,you might also have noticed that 
when the bubble was removed1 the vapour 
inside it began to pass out again and   
fell away in a heavy stream1 but this   
you could only see by looking at the    
shadow upon the screen4  ,illustration3 
,fig4 #ec  ,you may have noticed when ,i
 made the drops of oil in the mixture of
 alcohol and water1 that when they were 
brought together they did not at once   
unite2 they pressed against one another 
and pushed each other away if allowed1  
just as the water-drops did in the      
fountain of which ,i showed you a       
photograph4 ,you also may have noticed  
that the drops of water in the paraffin 
mixture bounced against one another1 or 
if filled with the paraffin1 formed     
bubbles in which often other small      
drops1 both of water and paraffin1      
remained floating4  ,in all these cases 
there was a thin film of something      
between the drops which they were unable
 to squeeze out1 namely1 water1         

paraffin1 or air1 as the case might be4 
,will two soap-bubbles also when knocked
 together be unable to squeeze out the  
air between them8 ,this you can try at  
home just as well as ,i can here1 but ,i
 will perform the experiment at once4 ,i
 have blown a pair of bubbles1 and now  
when ,i hit them together they remain   
distinct and separate 7,fig4 #ed74      
,illustration3 ,fig4 #ed4  ,i shall next
 place a bubble on a ring1 which it is  
just too large to get through4 ,in my   
hand ,i hold a ring1 on which ,i have a 
flat film1 made by placing a bubble upon
 it and breaking it on one side4 ,if ,i 
gently press the bubble with the flat   
film1 ,i can push it through the ring to
 the other side 7,fig4 #ee71 and yet the
 two have not really touched one another
 at all4 ,the bubble can be pushed      
backwards and forwards in this way many 
times4  ,illustration3 ,fig4 #ee4  ,i   
have now blown a bubble and hung it     
below a ring4 ,to this bubble ,i can    
hang another ring of thin wire1 which   

pulls it a little out of shape4 ,since  
the pressure inside is less than that   
corresponding to a complete sphere1 and 
since it is greater than that outside1  
and this we can tell by looking at the  
caps1 the curve is part of one of those 
represented by the dotted lines in ,c or
 ,e1 ,fig4 #ca4 ,however1 without       
considering the curve any more1 ,i shall
 push the end of the pipe inside1 and   
blow another bubble there1 and let it   
go4 ,it falls gently until it rests upon
 the outer bubble2 not at the bottom1   
because the heavy ring keeps that part  
out of reach1 but along a circular line 
higher up 7,fig4 #ef74 ,i can now drain 
away the heavy drops of liquid from     
below the bubbles with a pipe1 and leave
 them clean and smooth all over4 ,i can 
now pull the lower ring down1 squeezing 
the inner bubble into a shape like an   
egg 7,fig4 #eg71 or swing it round and  
round1 and then with a little care peel 
away the ring from off the bubble1 and  
leave them both perfectly round every   

way 7,fig4 #eh74 ,i can draw out the air
 from the outer bubble till you can     
hardly see between them1 and then blow  
in1 and the harder ,i blow1 the more is 
it evident that the two bubbles are not 
touching at all2 the inner one is now   
spinning round and round in the very    
centre of the large bubble1 and finally1
 on breaking the outer one the inner    
floats away1 none the worse for its very
 unusual treatment4  ,illustration3     
,fig4 #ef4  ,illustration3 ,fig4 #eg4   
,illustration3 ,fig4 #eh4  ,there is a  
pretty variation of the last experiment1
 which1 however1 requires that a little 
green dye called fluorescine1 or better1
 uranine1 should be dissolved in a      
separate dish of the soap-water4 ,then  
you can blow the outer bubble with clean
 soap-water1 and the inner one with the 
coloured water4 ,then if you look at the
 two bubbles by ordinary light1 you will
 hardly notice any difference2 but if   
you allow sunlight1 or electric light   
from an arc lamp1 to shine upon them1   

the inner one will appear a brilliant   
green1 while the outer one will remain  
clear as before4 ,they will not mix at  
all1 showing that though the inner one  
is apparently resting against the outer 
one1 there is in reality a thin cushion 
of air between4  ,now you know that     
coal-gas is lighter than air1 and so a  
soap-bubble blown with gas1 when let go1
 floats up to the ceiling at once4 ,i   
shall blow a bubble on a ring with      
coal-gas4 ,it is soon evident that it is
 pulling upwards4 ,i shall go on feeding
 it with gas1 and ,i want you to notice 
the very beautiful shapes that it takes 
7,fig4 #ei1 but imagine the globe inside
 removed74 ,these are all exactly the   
curves that a water-drop assumes when   
hanging from a pipe1 except that they   
are the other way up4 ,the strength of  
the skin is now barely able to withstand
 the pull1 and now the bubble breaks    
away just as the drop of water did4     
,illustration3 ,fig4 #ei4  ,i shall next
 place a bubble blown with air upon a   

ring1 and blow inside it a bubble blown 
with a mixture of air and gas4 ,it of   
course floats up and rests against the  
top of the outer bubble 7,fig4 #fj74    
,now ,i shall let a little gas into the 
outer one1 until the surrounding gas is 
about as heavy as the inner bubble4 ,it 
now no longer rests against the top1 but
 floats about in the centre of the large
 bubble 7,fig4 #fa71 just as the drop of
 oil did in the mixture of alcohol and  
water4 ,you can see that the inner      
bubble is really lighter than air1      
because if ,i break the outer one1 the  
inner one rises rapidly to the ceiling4 
,illustration3 ,fig4 #fj4  ,instead of  
blowing the first bubble on a heavy     
fixed ring1 ,i shall now blow one on a  
light ring1 made of very thin wire4     
,this bubble contains only air4 ,if ,i  
blow inside this a bubble with coal-gas1
 then the gas-bubble will try and rise1 
and will press against the top of the   
outer one with such force as to make it 
carry up the wire ring and a yard of    

cotton1 and some paper to which the     
cotton is tied 7,fig4 #fb72 and all this
 time1 though it is the inner one only  
which tends to rise1 the two bubbles are
 not really touching one another at all4
  ,illustration3 ,fig4 #fa4             
,illustration3 ,fig4 #fb4  ,i have now  
blown an air-bubble on the fixed ring1  
and pushed up inside it a wire with a   
ring on the end4 ,i shall now blow      
another air-bubble on this inner ring4  
,the next bubble that ,i shall blow is  
one containing gas1 and this is inside  
the other two1 and when let go it rests 
against the top of the second bubble4 ,i
 next make the second bubble a little   
lighter by blowing a little gas into it1
 and then make the outer one larger with
 air4 ,i can now peel off the inner ring
 and take it away1 leaving the two inner
 bubbles free1 inside the outer one     
7,fig4 #fc74 ,and now the multiple      
reflections of the brilliant colours of 
the different bubbles from one to the   
other1 set off by the beautiful forms   

which the bubbles themselves assume1    
give to the whole a degree of symmetry  
and splendour which you may go far to   
see equalled in any other way4 ,i have  
only to blow a fourth bubble in real    
contact with the outer bubble and the   
ring1 to enable it to peel off and float
 away with the other two inside4        
,illustration3 ,fig4 #fc4  ,we have seen
 that bubbles and drops behave in very  
much the same way4 ,let us see if       
electricity will produce the same effect
 that it did on drops4 ,you remember    
that a piece of electrified sealing-wax 
prevented a fountain of water from      
scattering1 because where two drops met1
 instead of bouncing1 they joined       
together4 ,now there are on these two   
rings bubbles which are just resting    
against one another1 but not really     
touching 7,fig4 #fd74 ,the instant that 
,i take out the sealing-wax you see they
 join together and become one 7,fig4    
#fe74 ,two soap-bubbles1 therefore1     
enable us to detect electricity1 even   

when present in minute quantity1 just as
 two water fountains did4               
,illustration3 ,fig4 #fd4               
,illustration3 ,fig4 #fe4  ,we can use a
 pair of bubbles to prove the truth of  
one of the well-known actions of        
electricity4 ,inside an electrical      
conductor it is impossible to feel any  
influence of electricity outside1       
however much there may be1 or however   
near you go to the surface4 ,let us1    
therefore1 take the two bubbles shown in
 ,fig4 #ef1 and bring an electrified    
stick of sealing-wax near4 ,the outer   
bubble is a conductor2 there is1        
therefore1 no electrical action inside1 
and this you can see because1 though the
 sealing-wax is so near the bubble that 
it pulls it all to one side1 and though 
the inner one is so close to the outer  
one that you cannot see between them1   
yet the two bubbles remain separate4    
,had there been the slightest electrical
 influence inside1 even to a depth of a 
hundred-thousandth of an inch1 the two  

bubbles would have instantly come       
together4  ,illustration3 ,fig4 #ff4    
,there is one more experiment which ,i  
must show1 and this will be the last2 it
 is a combination of the last two1 and  
it beautifully shows the difference     
between an inside and an outside bubble4
 ,i have now a plain bubble resting     
against the side of the pair that ,i    
have just been using4 ,the instant that 
,i take out the sealing-wax the two     
outer bubbles join1 while the inner one 
unharmed and the heavy ring slide down  
to the bottom of the now single outer   
bubble 7,fig4 #ff74  ,and now that our  
time has drawn to a close ,i must ask   
you whether that admiration and wonder  
which we all feel when we play with     
soap-bubbles has been destroyed by these
 lectures2 or whether now that you know 
more about them it is not increased4 ,i 
hope you will all agree with me that the
 actions upon which such common and     
every-day phenomena as drops and bubbles
 depend1 actions which have occupied the

 attention of the greatest philosophers 
from the time of ,newton to the present 
day1 are not so trivial as to be        
unworthy of the attention of ordinary   
people like ourselves4     ,,practical  
,,hints4   ,i hope that the following   
practical hints may be found useful by  
those who wish themselves to            
successfully perform the experiments    
already described4   ,drop with         
,india-rubber ,surface4  ,a sheet of    
thin india-rubber1 about the thickness  
of that used in air-balls1 as it appears
 before they have been blown out1 must  
be stretched over a ring of wood or     
metal eighteen inches in diameter1 and  
securely wired round the edge4 ,the wire
 will hold the india-rubber better if   
the edge is grooved4 ,this does not     
succeed if tried on a smaller scale4    
,this experiment was shown by ,sir ,w4  
,thomson at the ,royal ,institution4    
,jumping ,frame4  ,this is easily made  
by taking a light glass globe about two 
inches in diameter1 such1 for instance1 

as a silvered ball used to ornament a   
,christmas-tree or the bulb of a        
pipette1 which is what ,i used4 ,pass   
through the open necks of the bulb a    
piece of wire about one-twentieth of an 
inch in diameter1 and fix it permanently
 and water-tight upon the wire by       
working into the necks melted           
sealing-wax4 ,an inch or two above the  
globe1 fasten a flat frame of thin wire 
by soldering1 or if this is too         
difficult1 by tying and sealing-wax4 ,a 
lump of lead must then be fastened or   
hung on to the lower end1 and gradually 
scraped away until the wire frame will  
just be unable to force its way through 
the surface of the water4 ,none of the  
dimensions or materials mentioned are of
 importance4   ,paraffined ,sieve4      
,obtain a piece of copper wire gauze    
with about twenty wires to the inch1 and
 cut out from it a round piece about    
eight inches in diameter4 ,lay it on a  
round block1 of such a size that it     
projects about one inch all round4 ,then

 gently go round and round with the     
hands pressing the edge down and keeping
 it flat above1 until the sides are     
evenly turned down all round4 ,this is  
quite easy1 because the wires can allow 
of the kind of distortion necessary4    
,then wind round the turned-up edge a   
few turns of thick wire to make the     
sides stiff4 ,this ought to be soldered 
in position1 but probably careful wiring
 will be good enough4  ,melt some       
paraffin wax or one or two paraffin     
candles of the best quality in a clean  
flat dish1 not over the fire1 which     
would be dangerous1 but on a hot plate4 
,when melted and clear like water1 dip  
the sieve in1 and when all is hot       
quickly take it out and knock it once or
 twice on the table to shake the        
paraffin out of the holes4 ,leave upside
 down until cold1 and then be careful   
not to scratch or rub off the paraffin4 
,this had best be done in a place where 
a mess is of no consequence4  ,there is 
no difficulty in filling it or in       

setting it to float upon water4         
,narrow ,tubes and ,capillarity4  ,get  
some quill-glass tube from a chemist1   
that is1 tube about the size of a pen4  
,if it is more than1 say1 a foot long1  
cut off a piece by first making a firm  
scratch in one place with a             
three-cornered file1 when it will break 
at the place easily4 ,to make very      
narrow tube from this1 hold it near the 
ends in the two hands very lightly1 so  
that the middle part is high up in the  
brightest part of an ordinary bright and
 flat gas flame4 ,keep it turning until 
at last it becomes so soft that it is   
difficult to hold it straight4 ,it can  
then be bent into any shape1 but if it  
is wanted to be drawn out it must be    
held still longer until the black smoke 
upon it begins to crack and peel up4    
,then quickly take it out of the flame1 
and pull the two ends apart1 when a long
 narrow tube will be formed between4    
,this can be made finer or coarser by   
regulating the heat and the manner in   

which it is pulled out4 ,no directions  
will tell any one so much as a very     
little practice4 ,for drawing out tubes 
the flame of a ,bunsen burner or of a   
blow-pipe is more convenient2 but for   
bending tubes nothing is so good as the 
flat gas flame4 ,do not clean off smoke 
till the tubes are cold1 and do not     
hurry their cooling by wetting or       
blowing upon them4 ,in the country where
 gas is not to be had1 the flame of a   
large spirit-lamp can be made to do1 but
 it is not so good as a gas-flame4 ,the 
narrower these tubes are1 the higher    
will clean water be observed to rise in 
them4 ,to colour the water1 paints from 
a colour-box must not be used4 ,they are
 not liquid1 and will clog the very fine
 tubes4 ,some dye that will quite       
dissolve 7as sugar does7 must be used4  
,an aniline dye1 called soluble blue1   
does very well4 ,a little vinegar added 
may make the colour last better4        
,capillarity between ,plates4  ,two     
plates of flat glass1 say three to five 

inches square1 are required4 ,provided  
they are quite clean and well wetted    
there is no difficulty4 ,a little soap  
and hot water will probably be          
sufficient to clean them4   ,tears of   
,wine4  ,these are best seen at dessert 
in a glass about half filled with port4 
,a mixture of from two to three parts of
 water1 and one part of spirits of wine 
containing a very little rosaniline 7a  
red aniline dye71 to give it a nice     
colour1 may be used1 if port is not     
available4 ,a piece of the dye about as 
large as a mustard-seed will be enough  
for a large wine-glass4 ,the sides of   
the glass should be wetted with the     
wine4   ,cat-,boxes4  ,every school-boy 
knows how to make these4 ,they are not  
the boxes made by cutting slits in      
paper4 ,they are simply made by folding1
 and are then blown out like the frog1  
which is also made of folded paper4     
,liquid ,beads4  ,instead of melting    
gold1 water rolled on to a table thickly
 dusted with lycopodium1 or other fine  

dust1 or quicksilver rolled or thrown   
upon a smooth table1 will show the      
difference in the shape of large and    
small beads perfectly4 ,a               
magnifying-glass will make the          
difference more evident4 ,in using      
quicksilver1 be careful that none of it 
falls on gold or silver coins1 or       
jewellery1 or plate1 or on the          
ornamental gilding on book-covers4 ,it  
will do serious damage4   ,plateau's    
,experiment4  ,to perform this with very
 great perfection requires much care and
 trouble4 ,it is easy to succeed up to a
 certain point4 ,pour into a clean      
bottle about a table-spoonful of        
salad-oil1 and pour upon it a mixture of
 nine parts by volume spirits of wine   
7not methylated spirits71 and seven     
parts of water4 ,shake up and leave for 
a day if necessary1 when it will be     
found that the oil has settled together 
by itself4 ,fill a tumbler with the same
 mixture of spirit and water1 and then  
with a fine glass pipe1 dipping about   

half-way down1 slowly introduce a very  
little water4 ,this will make the liquid
 below a little heavier4 ,dip into the  
oil a pipe and take out a little by     
closing the upper end with the finger1  
and carefully drop this into the        
tumbler4 ,if it goes to the bottom1 a   
little more water is required in the    
lower half of the tumbler4 ,if by chance
 it will not sink at all1 a little more 
spirit is wanted in the upper half4 ,at 
last the oil will just float in the     
middle of the mixture4 ,more can then be
 added1 taking care to prevent it from  
touching the sides4 ,if the liquid below
 is ever so little heavier1 and the     
liquid above ever so little lighter than
 oil1 the drop of oil perhaps as large  
as a halfpenny will be almost perfectly 
round4 ,it will not appear round if seen
 through the glass1 because the glass   
magnifies it sideways1 but not up and   
down1 as may be seen by holding a coin  
in the liquid just above it4 ,to see the
 drop in its true shape the vessel must 

either be a globe1 or one side must be  
made of flat glass4  ,spinning the oil  
so as to throw off a ring is not        
material1 but if the reader can contrive
 to fix a disc about the size of a      
threepenny-piece upon a straight wire1  
and spin it round without shaking it1   
then he will see the ring break off1 and
 either return if the rotation is       
quickly stopped1 or else break up into  
three or four perfect little balls4 ,the
 disc should be wetted with oil before  
being dipped into the mixture of spirit 
and water4   ,a ,good ,mixture for      
,soap-,bubbles4  ,common yellow soap is 
far better than most of the fancy soaps1
 which generally contain a little soap  
and a lot of rubbish4 ,castille soap is 
very good1 and this may be obtained from
 any chemist4  ,bubbles blown with soap 
and water alone do not last long enough 
for many of the experiments described1  
though they may sometimes be made to    
succeed4 ,plateau added glycerine1 which
 greatly improves the lasting quality4  

,the glycerine should be pure2 common   
glycerine is not good1 but ,price's     
answers perfectly4 ,the water should be 
pure distilled water1 but if this is not
 available1 clean rain-water will do4   
,do not choose the first that runs from 
a roof after a spell of dry weather1 but
 wait till it has rained for some time1 
the water that then runs off is very    
good1 especially if the roof is blue    
slate or glass4 ,if fresh rain-water is 
not to be had1 the softest water should 
be employed that can be obtained4       
,instead of ,castille soap1 ,plateau    
found that a pure soap prepared from    
olive-oil is still better4 ,this is     
called oleate of soda4 ,it should be    
obtained freshly prepared from a        
manufacturing chemist4 ,old1 dry stuff  
that has been kept a long time is not so
 good4 ,i have always used a            
modification of ,plateau's formula1     
which ,professors ,reinold and ,rucker  
found to answer so well4 ,they used less
 glycerine than ,plateau4 ,it is best   

made as follows4 ,fill a clean stoppered
 bottle three-quarters full of water4   
,add one-fortieth part of its weight of 
oleate of soda1 which will probably     
float on the water4 ,leave it for a day1
 when the oleate of soda will be        
dissolved4 ,nearly fill up the bottle   
with ,price's glycerine and shake well1 
or pour it into another clean bottle and
 back again several times4 ,leave the   
bottle1 stoppered of course1 for about a
 week in a dark place4 ,then with a     
syphon1 that is1 a bent glass tube which
 will reach to the bottom inside and    
still further outside1 draw off the     
clear liquid from the scum which will   
have collected at the top4 ,add one or  
two drops of strong liquid ammonia to   
every pint of the liquid4 ,then         
carefully keep it in a stoppered bottle 
in a dark place4 ,do not get out this   
stock bottle every time a bubble is to  
be blown1 but have a small working      
bottle4 ,never put any back into the    
stock4 ,in making the liquid do not warm

 or filter it4 ,either will spoil it4   
,never leave the stoppers out of the    
bottles or allow the liquid to be       
exposed to the air more than is         
necessary4 ,this liquid is still        
perfectly good after two years' keeping4
 ,i have given these directions very    
fully1 not because ,i feel sure that all
 the details are essential1 but because 
it exactly describes the way ,i happen  
to make it1 and because ,i have never   
found any other solution so good4       
,castille soap1 ,price's glycerine1 and 
rain-water will almost certainly answer 
every purpose1 and the same proportions 
will probably be found to work well4    
,rings for ,bubbles4  ,these may be made
 of any kind of wire4 ,i have used      
tinned iron about one-twentieth of an   
inch in diameter4 ,the joint should be  
smoothly soldered without lumps4 ,if    
soldering is a difficulty1 then use the 
thinnest wire that is stiff enough to   
support the bubbles steadily1 and make  
the joint by twisting the end of the    

wire round two or three times4 ,rings   
two inches in diameter are convenient4  
,i have seen that dipping the rings in  
melted paraffin is recommended1 but ,i  
have not found any advantage from this4 
,the nicest material for the light rings
 is thin aluminium wire1 about as thick 
as a fine pin 7,no4 #bf to #cj1 ,b4 ,w4 
,g471 and as this cannot be soldered1   
the ends must be twisted4 ,if this is   
not to be had1 very fine wire1 nearly as
 fine as a hair 7,no4 #cf1 ,b4 ,w4 ,g471
 of copper or of any other metal1 will  
answer4 ,the rings should be wetted with
 the soap mixture before a bubble is    
placed upon them1 and must always be    
well washed and dried when done with4   
,threads in ,ring4  ,there is no        
difficulty in showing these experiments4
 ,the ring with the thread may be dipped
 in the soap solution1 or stroked across
 with the edge of a piece of paper or   
india-rubber sheet that has been dipped 
in the liquid1 so as to form a film on  
both sides of the thread4 ,a needle that

 has also been wetted with the soap may 
be used to show that the threads are    
loose4 ,the same needle held for a      
moment in a candle-flame supplies a     
convenient means of breaking the film4  
,blow out ,candle with ,soap-,bubble4   
,for this1 the bubble should be blown on
 the end of a short wide pipe1 spread   
out at one end to give a better hold for
 the bubble4 ,the tin funnel supplied   
with an ordinary gazogene answers       
perfectly4 ,this should be washed before
 it is used again for filling the       
gazogene4   ,bubbles balanced against   
one another4  ,these experiments are    
most conveniently made on a small scale4
 ,pieces of thin brass tube1            
three-eighths or half an inch in        
diameter1 are suitable4 ,it is best to  
have pieces of apparatus1 specially     
prepared with taps1 for easily and      
quickly stopping the air from leaving   
either bubble1 and for putting the two  
bubbles into communication when         
required4 ,it should not be difficult to

 contrive to perform the experiments1   
using india-rubber connecting tubes1    
pinched with spring clips to take the   
place of taps4 ,there is one little     
detail which just makes the difference  
between success and failure4 ,this is to
 supply a mouth-piece for blowing the   
bubble1 made of glass tube1 which has   
been drawn out so fine that these little
 bubbles cannot be blown out suddenly by
 accident4 ,it is very difficult1       
otherwise1 to adjust the quantity of air
 in such small bubbles with any         
accuracy4 ,in balancing a spherical     
against a cylindrical bubble1 the short 
piece of tube1 into which the air is    
supplied1 must be made so that it can be
 easily moved to or from a fixed piece  
of the same size closed at the other    
end4 ,then the two ends of the short    
tube must have a film spread over them  
with a piece of paper1 or india-rubber1 
but there must be no film stretched     
across the end of the fixed tube4 ,the  
two tubes must at first be near         

together1 until the spherical bubble has
 been formed4 ,they may then be         
separated gradually more and more1 and  
air blown in so as to keep the sides of 
the cylinder straight1 until the        
cylinder is sufficiently long to be     
nearly unstable4 ,it will then far more 
evidently show1 by its change of form1  
than it would if it were short1 when the
 pressure due to the spherical bubble   
exactly balances that due to a          
cylindrical one4 ,if the shadow of the  
bubbles1 or an image formed by a lens on
 a screen1 is then measured1 it will be 
found that the sphere has a diameter    
which is very accurately double that of 
the cylinder4   ,thaumatrope for showing
 the ,formation and ,oscillations of    
,drops4  ,the experiment showing the    
formation of water-drops can be very    
perfectly imitated1 and the movements   
actually made visible1 without any      
necessity for using liquids at all1 by  
simply converting ,fig4 #ce 7at end of  
book7 into the old-fashioned instrument 

called a thaumatrope4 ,what will then be
 seen is a true representation1 because 
the forms in the figure are copies of a 
series of photographs taken from the    
moving drops at the rate of forty-three 
photographs in two seconds4#b  ,footnote
 #b3 ,for particulars see ,philosophical
 ,magazine1 ,september #ahij4  ,obtain a
 piece of good card-board as large as   
the figure1 and having brushed it all   
over on one side with thin paste1 lay   
the figure upon it1 and press it down   
evenly4 ,place it upon a table1 and     
cover it with a few thicknesses of      
blotting-paper1 and lay over all a flat 
piece of board large enough to cover it4
 ,weights sufficient to keep it all flat
 may be added4 ,this must be left all   
night at least1 until the card is quite 
dry1 or else it will curl up and be     
useless4 ,now with a sharp chisel or    
knife1 but a chisel if possible1 cut out
 the forty-three slits near the edge1   
accurately following the outline        
indicated in black and white1 and       

keeping the slits as narrow as possible4
 ,then cut a hole in the middle1 so as  
to fit the projecting part of a         
sewing-machine cotton-reel1 and fasten  
the cotton-reel on the side away from   
the figure with glue or small nails4 ,it
 must be fixed exactly in the middle4   
,the edge should of course be cut down  
to the outside of the black rim4  ,now  
having found a pencil or other rod on   
which the cotton-reel will freely turn1 
use this as an axle1 and holding the    
disc up in front of a looking-glass1 and
 in a good light1 slowly and steadily   
make it turn round4 ,the image of the   
disc seen through the slit in the       
looking-glass will then perfectly       
represent every feature of the growing  
and falling drop4 ,as the drop grows it 
will gradually become too heavy to be   
supported1 a waist will then begin to   
form which will rapidly get narrower1   
until the drop at last breaks away4 ,it 
will be seen to continue its fall until 
it has disappeared in the liquid below1 

but it has not mixed with this1 and so  
it will presently appear again1 having  
bounced out of the liquid4 ,as it falls 
it will be seen to vibrate as the result
 of the sudden release from the         
one-sided pull4 ,the neck which was     
drawn out will meanwhile have gathered  
itself in the form of a little drop1    
which will then be violently hit by the 
oscillations of the remaining pendant   
drop above1 and driven down4 ,the       
pendant drop will be seen to vibrate and
 grow at the same time1 until it again  
breaks away as before1 and so the       
phenomena are repeated4  ,in order to   
perfectly reproduce the experiment1 the 
axle should be firmly held upon a stand1
 and the speed should not exceed one    
turn in two seconds4  ,the effect is    
still more real if a screen is placed   
between the disc and the mirror1 which  
will only allow one of the drops to be  
seen4   ,water-drops in ,paraffin and   
,bisulphide of ,carbon4  ,all that was  
said in describing the ,plateau         

experiment applies here4 ,perfectly     
spherical and large drops of water can  
be formed in a mixture so made that the 
lower parts are very little heavier1 and
 the upper parts very little lighter1   
than water4 ,the addition of bisulphide 
of carbon makes the mixture heavier4    
,this liquid--bisulphide of carbon--is  
very dangerous1 and has a most dreadful 
smell1 so that it had better not be     
brought into the house4 ,the form of a  
hanging drop1 and the way in which it   
breaks off1 can be seen if water is used
 in paraffin alone1 but it is much more 
evident if a little bisulphide of carbon
 is mixed with the paraffin1 so that    
water will sink slowly in the mixture4  
,pieces of glass tube1 open at both ends
 from half an inch to one inch in       
diameter1 show the action best4 ,having 
poured some water coloured blue into a  
glass vessel1 and covered it to a depth 
of several inches with paraffin1 or the 
paraffin mixture1 dip the pipe down into
 the water1 having first closed the     

upper end with the thumb or the palm of 
the hand4 ,on then removing the hand1   
the water will rush up inside the tube4 
,again close the upper end as before1   
and raise the tube until the lower end  
is well above the water1 though still   
immersed in the paraffin4 ,then allow   
air to enter the pipe very slowly by    
just rolling the thumb the least bit to 
one side4 ,the water will escape slowly 
and form a large growing drop1 the size 
of which1 before it breaks away1 will   
depend on the density of the mixture and
 the size of the tube4  ,to form a water
 cylinder in the paraffin the tube must 
be filled with water as before1 but the 
upper end must now be left open4 ,then  
when all is quiet the tube is to be     
rather rapidly withdrawn in the         
direction of its own length1 when the   
water which was within it will be left  
behind in form of a cylinder1 surrounded
 by the paraffin4 ,it will then break up
 into spheres so slowly1 in the case of 
a large tube1 that the operation can be 

watched4 ,the depth of paraffin should  
be quite ten times the diameter of the  
tube4  ,to make bubbles of water in the 
paraffin1 the tube must be dipped down  
into the water with the upper end open  
all the time1 so that the tube is mostly
 filled with paraffin4 ,it must then be 
closed for a moment above and raised    
till the end is completely out of the   
water4 ,then if air is allowed to enter 
slowly1 and the tube is gently raised1  
bubbles of water filled with paraffin   
will be formed which can be made to     
separate from the pipe1 like            
soap-bubbles from a churchwarden1 by a  
suitable sudden movement4 ,if a number  
of water-drops are floating in the      
paraffin in the pipe1 and this can be   
easily arranged1 then the bubbles made  
will contain possibly a number of other 
drops1 or even other bubbles4 ,a very   
little bisulphide of carbon poured      
carefully down a pipe will form a heavy 
layer above the water1 on which these   
compound bubbles will remain floating4  

,cylindrical bubbles of water in        
paraffin may be made by dipping the pipe
 down into the water and withdrawing it 
quickly without ever closing the top at 
all4 ,these break up into spherical     
bubbles in the same way that the        
cylinder of liquid broke up into spheres
 of liquid4   ,beaded ,spider-webs4     
,these are found in the spiral part of  
the webs of all the geometrical spiders4
 ,the beautiful geometrical webs may be 
found out of doors in abundance in the  
autumn1 or in green-houses at almost any
 time of the year4 ,to mount these webs 
so that the beads may be seen1 take a   
small flat ring of any material1 or a   
piece of card-board with a hole cut out 
with a gun-wad cutter1 or otherwise4    
,smear the face of the ring1 or the     
card1 with a very little strong gum4    
,choose a freshly-made web1 and then    
pass the ring1 or the card1 across the  
web so that some of the spiral web 7not 
the central part of the web7 remains    
stretched across the hole4 ,this must be

 done without touching or damaging the  
pieces that are stretched across1 except
 at their ends4 ,the beads are too small
 to be seen with the naked eye4 ,a      
strong magnifying-glass1 or a low power 
microscope1 will show the beads and     
their marvellous regularity4 ,the beads 
on the webs of very young spiders are   
not so regular as those on spiders that 
are fully grown4 ,those beautiful beads1
 easily visible to the naked eye1 on    
spider lines in the early morning of an 
autumn day1 are not made by the spider1 
but are simply dew4 ,they very perfectly
 show the spherical form of small       
water-drops4   ,photographs of          
,water-jets4  ,these are easily taken by
 the method described by ,mr4           
,chichester ,bell4 ,the flash of light  
is produced by a short spark from a few 
,leyden-jars4 ,the fountain1 or jet1    
should be five or six feet away from the
 spark1 and the photographic plate      
should be held as close to the stream of
 water as is possible without touching4 

,the shadow is then so definite that the
 photograph1 when taken1 may be examined
 with a powerful lens1 and will still   
appear sharp4 ,any rapid dry plate will 
do4 ,the room1 of course1 must be quite 
dark when the plate is placed in        
position1 and the spark then made4 ,the 
regular breaking up of the jet may be   
effected by sound produced in almost any
 way4 ,the straight jet1 of which ,fig4 
#da is a representation1 magnified about
 three and a quarter times1 was         
regularly broken up by simply whistling 
to it with a key4 ,the fountains were   
broken up regularly by fastening the    
nozzle to one end of a long piece of    
wood clamped at the end to the stand of 
a tuning-fork1 which was kept sounding  
by electrical means4 ,an ordinary       
tuning-fork1 made to rest when sounding 
against the wooden support of the       
nozzle1 will answer quite as well1 but  
is not quite so convenient4 ,the jet    
will break up best to certain notes1 but
 it may be tuned to a great extent by   

altering the size of the orifice or the 
pressure of the water1 or both4         
,fountain and ,sealing-wax4  ,it is     
almost impossible to fail over this very
 striking yet simple experiment4 ,a     
fountain of almost any size1 at any rate
 between one-fiftieth and a quarter of  
an inch in the smooth part1 and up to   
eight feet high1 will cease to scatter  
when the sealing-wax is rubbed with     
flannel and held a few feet away4 ,a    
suitable size of fountain is one about  
four feet high1 coming from an orifice  
anywhere near one-sixteenth of an inch  
in diameter4 ,the nozzle should be      
inclined so that the water falls        
slightly on one side4 ,the sealing-wax  
may be electrified by being rubbed on   
the coat-sleeve1 or on a piece of fur or
 flannel which is dry4 ,it will then    
make little pieces of paper or cork     
dance1 but it will still act on the     
fountain when it has ceased to produce  
any visible effect on pieces of paper1  
or even on a delicate gold-leaf         

electroscope4   ,bouncing ,water-jets4  
,this beautiful experiment of ,lord     
,rayleigh's requires a little management
 to make it work in a satisfactory      
manner4 ,take a piece of quill-glass    
tube and draw it out to a very slight   
extent 7see a former note71 so as to    
make a neck about one-eighth of an inch 
in diameter at the narrowest part4      
,break the tube just at this place1     
after first nicking it there with a     
file4 ,connect each of these tubes by   
means of an india-rubber pipe1 or       
otherwise1 with a supply of water in a  
bottle1 and pinch the tubes with a      
screw-clip until two equal jets of water
 are formed4 ,so hold the nozzles that  
these meet in their smooth portions at  
every small angle4 ,they will then for a
 short time bounce away from one another
 without mixing4 ,if the air is very    
dusty1 if the water is not clean1 or if 
air-bubbles are carried along in the    
pipes1 the two jets will at once join   
together4 ,in the arrangement that ,i   

used in the lantern1 the two nozzles    
were nearly horizontal1 one was about   
half an inch above the other1 and they  
were very slightly converging4 ,they    
were fastened in their position by      
melting upon them a little sealing-wax4 
,india-rubber pipes connected them with 
two bottles about six inches above them1
 and screw-clips were used to regulate  
the supply4 ,one of the bottles was made
 to stand on three pieces of sealing-wax
 to electrically insulate it1 and the   
corresponding nozzle was only held by   
its sealing-wax fastening4 ,the water in
 the bottles had been filtered1 and one 
was coloured blue4 ,if these precautions
 are taken1 the jets will remain        
distinct quite long enough1 but are     
instantly caused to recombine by a piece
 of electrified sealing-wax six or eight
 feet away4 ,they may be separated again
 by touching the water issuing near one 
nozzle with the finger1 which deflects  
it2 on quietly removing the finger the  
jet takes up its old position and       

bounces off the other as before4 ,they  
can thus be separated and made to       
combine ten or a dozen times in a       
minute4   ,fountain and ,intermittent   
,light4  ,this can be successfully shown
 to a large number of people at once    
only by using an electric arc1 but there
 is no occasion to produce this light if
 not more than one person at a time     
wishes to see the evolution of the      
drops4 ,it is then merely necessary to  
make the fountain play in front of a    
bright background such as the sky1 to   
break it up with a tuning-fork or other 
musical sound as described1 and then to 
look at it through a card disc equally  
divided near the edge into spaces about 
two or three inches wide1 with a hole   
about one-eighth of an inch in diameter 
between each pair of spaces4 ,a disc of 
card five inches in diameter1 with six  
equidistant holes half an inch from the 
edge1 answers well4 ,the disc must be   
made to spin by any means very regularly
 at such a speed that the tuning-fork1  

or stretched string if this be used1    
when looked at through the holes1       
appears quiet1 or nearly quiet1 when    
made to vibrate4 ,the separate drops    
will then be seen1 and everything       
described in the preceding pages1 and a 
great deal more1 will be evident4 ,this 
is one of the most fascinating          
experiments1 and it is well worth while 
to make an effort to succeed4 ,the      
little motor that ,i used is one of     
,cuttriss and ,co4's ,p4 #a4 motors1    
which are very convenient for           
experiments of this kind4 ,it was driven
 by four ,grove's cells4 ,these make it 
rotate too fast1 but the speed can be   
reduced by moving the brushes slightly  
towards the position used for reversing 
the motor1 until the speed is almost    
exactly right4 ,it is best to arrange   
that it goes only just too fast1 then   
the speed can be perfectly regulated by 
a very light pressure of the finger on  
the end of the axle4   ,mr4 ,chichester 
,bell's ,singing ,water-jet4  ,for these

 experiments a very fine hole about one 
seventy-fifth of an inch in diameter is 
most suitable4 ,to obtain this1 ,mr4    
,bell holds the end of a quill-glass    
tube in a blow-pipe flame1 and          
constantly turns it round and round     
until the end is almost entirely closed 
up4 ,he then suddenly and forcibly blows
 into the pipe4 ,out of several nozzles 
made in this way1 some are sure to do   
well4 ,lord ,rayleigh makes nozzles     
generally by cementing to the end of a  
glass 7or metal7 pipe a piece of thin   
sheet metal in which a hole of the      
required size has been made4 ,the water 
pressure should be produced by a head of
 about fifteen feet4 ,the water must be 
quite free from dust and from           
air-bubbles4 ,this may be effected by   
making it pass through a piece of tube  
stuffed full of flannel1 or cotton-wool1
 or something of the kind to act as a   
filter4 ,there should be a yard or so of
 good black india-rubber tube1 about    
one-eighth of an inch in diameter       

inside1 between the filter and the      
nozzle4 ,it is best not to take the     
water direct from the water-main1 but   
from a cistern about fifteen feet above 
the nozzle4 ,if no cistern is available1
 a pail of water taken up-stairs1 with a
 pipe coming down1 is an excellent      
substitute1 and this has the further    
advantage that the head of water can be 
easily changed so as to arrive at the   
best result4  ,the rest of the apparatus
 is very simple4 ,it is merely necessary
 to stretch and tie over the end of a   
tube about half an inch in diameter a   
piece of thin india-rubber sheet1 cut   
from an air-ball that has not been blown
 out4 ,the tube1 which may be of metal  
or of glass1 may either be fastened to a
 heavy foot1 in which case a side tube  
must be joined to it1 as in ,fig4 #dg1  
or it may be open at both ends and be   
held in a clamp4 ,it is well to put a   
cone of card-board on the open end      
7,fig4 #dh71 if the sound is to be heard
 by many at a time4 ,if the experimenter

 alone wishes to hear as well as        
possible when faint sounds are produced1
 he should carry a piece of smooth      
india-rubber tube about half an inch in 
diameter from the open end to his ear4  
,this1 however1 would nearly deafen him 
with such loud noises as the tick of a  
watch4   ,bubbles and ,ether4           
,experiments with ether must be         
performed with great care1 because1 like
 the bisulphide of carbon1 it is        
dangerously inflammable4 ,the bottle of 
ether must never be brought near a      
light4 ,if a large quantity is spilled1 
the heavy vapour is apt to run along the
 floor and ignite at a fire1 even on the
 other side of a room4 ,any vessel may  
be filled with the vapour of ether by   
merely pouring the liquid upon a piece  
of blotting-paper reaching up to the    
level of the edge4 ,very little is      
required1 say half a wine-glassful1 for 
a basin that would hold a gallon or     
more4 ,in a draughty place the vapour   
will be lost in a short time4 ,bubbles  

can be set to float upon the vapour     
without any difficulty4 ,they may be    
removed in five or ten seconds by means 
of one of the small light rings with a  
handle1 provided that the ring is wetted
 with the soap solution and has no film 
stretched across it4 ,if taken to a     
light at a safe distance the bubble will
 immediately burst into a blaze4 ,if a  
neighbouring light is not close down to 
the table1 but well up above the jar on 
a stand1 it may be near with but little 
risk4 ,to show the burning vapour1 the  
same wide tube that was used to blow out
 the candle will answer well4 ,the pear 
shape of the bubble1 owing to its       
increased weight after being held in the
 vapour for ten or fifteen seconds1 is  
evident enough on its removal1 but the  
falling stream of heavy vapour1 which   
comes out again afterwards1 can only be 
shown if its shadow is cast upon a      
screen by means of a bright light4      
,experiment with ,internal ,bubbles4    
,for these experiments1 next to a good  

solution1 the pipe is of the greatest   
importance4 ,a churchwarden is no use4  
,a glass pipe #e_/af inch in diameter at
 the mouth is best4 ,if this is merely a
 tube bent near the end through a right 
angle1 moisture condensed in the tube   
will in time run down and destroy the   
bubble occasionally1 which is very      
annoying in a difficult experiment4 ,i  
have made for myself the pipe of which  
,fig4 #fg is a full size representation1
 and ,i do not think that it is possible
 to improve upon this4 ,those who are   
not glass-blowers will be able1 with the
 help of cork1 to make a pipe with a    
trap as shown in ,fig4 #fh1 which is as 
good1 except in appearance and          
handiness4  ,in knocking bubbles        
together to show that they do not touch1
 care must be taken to avoid letting    
either bubble meet any projection in the
 other1 such as the wire ring1 or a     
heavy drop of liquid4 ,either will      
instantly destroy the two bubbles4      
,there is also a limit to the violence  

which may be used1 which experience will
 soon indicate4  ,in pushing a bubble   
through a ring smaller than itself1 by  
means of a flat film on another ring1 it
 is important that the bubble should not
 be too large2 but a larger bubble can  
be pushed through than would be         
expected4 ,it is not so easy to push it 
up as down because of the heavy drop of 
liquid1 which it is difficult to        
completely drain away4  ,illustration3  
,fig4 #fg4 ,length of ,stem #i ,inches  
,illustration3 ,fig4 #fh4 ,length of    
,stem #i ,inches  ,to blow one bubble   
inside another1 the first1 as large as  
an average orange1 should be blown on   
the lower side of a horizontal ring4 ,a 
light wire ring should then be hung on  
to this bubble to slightly pull it out  
of shape4 ,for this purpose thin        
aluminium rings are hardly heavy enough1
 and so either a heavier metal should be
 used1 or a small weight should be      
fastened to the handle of the ring4 ,the
 ring should be so heavy that the sides 

of the bubble make an angle of thirty or
 forty degrees with the vertical1 where 
they meet the ring as indicated in ,fig4
 #ef4 ,the wetted end of the pipe is now
 to be inserted through the top of the  
bubble1 until it has penetrated a clear 
half inch or so4 ,a new bubble can now  
be blown any size almost that may be    
desired4 ,to remove the pipe a slow     
motion will be fatal1 because it will   
raise the inner bubble until it and the 
outer one both meet the pipe at the same
 place4 ,this will bring them into true 
contact4 ,on the other hand1 a violent  
jerk will almost certainly produce too  
great a disturbance4 ,a rather rapid    
motion1 or a slight jerk1 is all that is
 required4 ,it is advisable before      
passing the pipe up through the lower   
ring1 so as to touch the inner bubble1  
and so drain away the heavy drop1 to    
steady this with the other hand4 ,the   
superfluous liquid can then be drained  
from both bubbles simultaneously4 ,care 
must be taken after this that the inner 

bubble is not allowed to come against   
either wire ring1 nor must the pipe be  
passed through the side where the two   
bubbles are very close together4 ,to    
peel off the lower ring it should be    
pulled down a very little way and then  
inclined to one side4 ,the peeling will 
then start more readily1 but as soon as 
it has begun the ring should be raised  
so as not to make the peeling too rapid1
 otherwise the final jerk1 when it      
leaves the lower ring1 will be too much 
for the bubbles to withstand4  ,bubbles 
coloured with fluorescine1 or uranine1  
do not show their brilliant fluorescence
 unless sunlight or electric light is   
concentrated upon them with a lens or   
mirror4 ,the quantity of dye required is
 so small that it may be difficult to   
take little enough4 ,as much as can be  
picked up on the last eighth of an inch 
of a pointed pen-knife will be1 roughly 
speaking1 enough for a wine-glassful of 
the soap solution4 ,if the quantity is  
increased beyond something like the     

proportion stated1 the fluorescence     
becomes less and very soon disappears4  
,the best quantity can be found in a few
 minutes by trial4  ,to blow bubbles    
containing either coal-gas or air1 or a 
mixture of the two1 the most convenient 
plan is to have a small ,t-shaped glass 
tube which can be joined by one arm of  
the ,t to the blow-pipe by means of a   
short piece of india-rubber tube1 and be
 connected by its vertical limb with a  
sufficient length of india-rubber pipe1 
one-eighth of an inch in diameter       
inside1 to reach to the floor1 after    
which it may be connected by any kind of
 pipe with the gas supply4 ,the gas can 
be stopped either by pinching the       
india-rubber tube with the left hand1 if
 that is at liberty1 or by treading on  
it if both hands are occupied4          
,meanwhile air can be blown in by the   
other arm of the ,t1 and the end closed 
by the tongue when gas alone is         
required4 ,this end of the tube should  
be slightly spread out when hot by      

rapidly pushing into it the cold tang of
 a file1 and twisting it at the same    
time1 so that it may be lightly held by 
the teeth without fear of slipping4  ,if
 a light ,t-piece or so great a length  
of small india-rubber tube cannot be    
obtained1 then the mouth must be removed
 from the pipe and the india-rubber tube
 slipped in when air is to be changed   
for gas4 ,this makes the manipulation   
more difficult1 but all the experiments1
 except the one with three bubbles1 can 
be so carried out4  ,the pipe must in   
every case be made to enter the highest 
point of a bubble in order to start an  
internal one4 ,if it is pushed          
horizontally through the side1 the inner
 bubble is sure to break4 ,if the inner 
bubble is being blown with gas1 it will 
soon tend to rise4 ,the pipe must then  
be turned over in such a manner that the
 inner bubble does not creep along it1  
and so meet the outer one where         
penetrated by the pipe4 ,a few trials   
will show what is meant4 ,the inner     

bubble may then be allowed to rest      
against the top of the outer one while  
being enlarged4 ,when it is desired     
after withdrawing the pipe to blow more 
air or gas into either the inner or the 
outer bubble1 it is not safe after      
inserting the pipe again to begin to    
blow at once2 the film which is now     
stretched across the mouth of the pipe  
will probably become a third bubble1 and
 this1 under the circumstances1 is      
almost certain to cause a failure4 ,an  
instantaneous withdrawal of the air     
destroys this film by drawing it into   
the pipe4 ,air or gas may then be blown 
without danger4  ,if the same experiment
 is performed upon a light ring with    
cotton and paper attached1 the left hand
 will be occupied in holding this ring1 
and then the gas must be controlled by  
the foot1 or by a friend4 ,the light    
ring should be quite two inches in      
diameter4 ,if1 when the inner bubble has
 begun to carry away the ring1 c41 the  
paper is caught hold of1 it is possible1

 by a judicious pull1 to cause the two  
bubbles to leave the ring and so escape 
into the air one inside the other4 ,for 
this purpose the smallest ring that will
 carry the paper should be used4 ,with  
larger rings the same effect may be     
produced by inclining the ring1 and so  
allowing the outer bubble to peel off1  
or by placing the mouth of the pipe     
against the ring and blowing a third    
bubble in real contact with the ring and
 the outer bubble4 ,this will assist the
 peeling process4  ,to blow three       
bubbles1 one inside the other two1 is   
more difficult4 ,the following plan ,i  
have found to be fairly certain4 ,first 
blow above the ring a bubble the size of
 a large orange4 ,then take a small ring
 about an inch in diameter1 with a      
straight wire coming down from one side 
to act as a handle1 and after wetting it
 with the solution1 pass it carefully up
 through the fixed ring so that the     
small ring is held well inside the      
bubble4 ,now pass the pipe1 freshly     

dipped in the solution1 into the outer  
or ,no4 #a bubble until it is quite     
close to the small ring1 and begin to   
blow the ,no4 #b bubble4 ,this must be  
started with the pipe almost in contact 
with the inner ring1 as the film on this
 ring would destroy a bubble that had   
attained any size4 ,withdraw the pipe1  
dip it into the liquid1 and insert it   
into the inner bubble1 taking care to   
keep these two bubbles from meeting     
anywhere4 ,now blow a large gas-bubble1 
which may rest against the top of ,no4  
#b while it is growing4 ,no4 #b may now 
rest against the top of ,no4 #a without 
danger4 ,remove pipe from ,no4 #c by    
gently lowering it1 and let some gas    
into ,no4 #b to make it lighter1 and at 
the same time diminish the pressure     
between ,nos4 #b and #c4 ,presently the 
small ring can be peeled off ,no4 #b and
 removed altogether4 ,but if there is a 
difficulty in accomplishing this1       
withdraw the pipe from ,no4 #b and blow 
air into ,no4 #a to enlarge it1 which   

will make the process easier4 ,then     
remove the pipe from ,no4 #a4 ,the three
 bubbles are now resting one inside the 
other4 ,by blowing a fourth bubble1 as  
described above1 against the fixed ring1
 ,no4 #a bubble will peel off1 and the  
three will float away4 ,no4 #a can1     
while peeling1 be transferred to a light
 wire ring from which paper1 c4 are     
suspended4 ,this description sounds     
complicated1 but after a little practice
 the process can be carried out almost  
with certainty in far less time than it 
takes to describe it2 in fact1 so       
quickly can it be done1 and so simple   
does it appear1 that no one would       
suppose that so many details had to be  
attended to4   ,bubbles and             
,electricity4  ,these experiments are on
 the whole the most difficult to perform
 successfully4 ,the following details   
should be sufficient to prevent failure4
 ,two rings are formed at the end of a  
pair of wires about six inches long in  
the straight part4 ,about one inch at   

the opposite end from the ring is turned
 down at a right angle4 ,these          
turned-down ends rest in two holes      
drilled vertically in a non-conductor   
such as ebonite1 about two or three     
inches apart4 ,then if all is right the 
two rings are horizontal and at the same
 level1 and they may be moved towards or
 away from one another4 ,separate them a
 few inches1 and blow a bubble above or 
below each1 making them nearly the same 
size4 ,then bring the two rings nearer  
together until the bubbles just1 and    
only just1 rest against one another4    
,though they may be hammered together   
without joining1 they will not remain   
long resting in this position1 as the   
convex surfaces can readily squeeze out 
the air4 ,the ebonite should not be     
perfectly warm and dry1 for it is then  
sure to be electrified1 and this will   
give trouble4 ,it must not be wet1      
because then it will conduct1 and the   
sealing-wax will produce no result4 ,if 
it has been used as the support for the 

rings for some of the previous          
experiments1 it will have been          
sufficiently splashed by the bursting of
 bubbles to be in the best condition4   
,it must1 however1 be well wiped        
occasionally4  ,a stick of sealing-wax  
should be held in readiness under the   
arm1 in a fold or two of dry flannel or 
fur4 ,if the wax is very strongly       
electrified1 it is apt to be far too    
powerful1 and to cause the bubbles1 when
 it is presented to them1 to destroy    
each other4 ,a feeble electrification is
 sufficient2 then the instant it is     
exposed the bubbles coalesce4 ,the wax  
may be brought so near one bubble in    
which another one is resting1 that it   
pulls them to one side1 but the inner   
one is screened from electrical action  
by the outer one4 ,it is important not  
to bring the wax very near1 as in that  
case the bubble will be pulled so far as
 to touch it1 and so be broken4 ,the    
wetting of the wax will make further    
electrification very uncertain4 ,in     

showing the difference between an inner 
and an outer bubble1 the same remarks   
with regard to undue pressure1          
electrification1 or loss of time apply4 
,i have generally found that it is      
advisable in this experiment not to     
drain the drops from both the bubbles1  
as their weight seems to steady them2   
the external bubble may be drained1 and 
if it is not too large1 the process of  
electrically joining the outer bubbles1 
without injury to the inner one1 may be 
repeated many times4 ,i once caused     
eight or nine single bubbles to unite   
with the outer one of a pair in         
succession before it became too unwieldy
 for more accessions to be possible4    
99       99       99       99       99  
,it would be going outside my subject to
 say anything about the management of   
lanterns4 ,i may1 however1 state that   
while the experiments with the small    
bubbles are best projected with a lens  
upon the screen1 the larger bubbles     
described in the last lecture can only  

be projected by their shadows4 ,for this
 purpose the condensing lens is removed1
 and the bare light alone made use of4  
,an electric arc is far preferable to a 
lime-light1 both because the shadows are
 sharper1 and because the colours are so
 much more brilliant4 ,no oil lamp would
 answer1 even if the light were         
sufficient in quantity1 because the     
flame would be far too large to cast a  
sharp shadow4  ,in these hints1 which   
have in themselves required a rather    
formidable chapter1 ,i have given all   
the details1 so far as ,i am able1 which
 a considerable experience has shown to 
be necessary for the successful         
performance or the experiments in       
public4 ,the hints will ,i hope         
materially assist those who are not in  
the habit of carrying out experiments1  
but who may wish to perform them for    
their own satisfaction4 ,though people  
who are not experimentalists may        
consider that the hints are overburdened
 with detail1 it is probable that in    

repeating the experiments they will find
 here and there1 in spite of all my care
 to provide against unforeseen          
difficulties1 that more detail would    
have been desirable4  ,though it is     
unusual to conclude such a book as this 
with the fullest directions for carrying
 out the experiments described1 ,i      
believe that the innovation in the      
present instance is good1 more          
especially because many of the          
experiments require none of the         
elaborate apparatus which so often is   
necessary4   ,,the ,,end4  ,richard     
,clay  ,sons1 ,limited1 ,london         
,bungay4  ,illustration3 ,fig4 #ce      
,,thaumatrope for showing the formation 
and oscillation of drops4