10 
acts as if it were an elastic skin, and, therefore, when a brush is 
immersed in water, and left in the liquid, the hairs do not cling 
to one another, because there is no surface of water acting on 
them, but as soon as the brush is taken out of the water, the 
liquid remaining on it has a free surface, and immediately 
surface tension, or surface force, is developed, and the brush acts 
as if the wet surface were an elastic membrane which brought 
the hairs together. So too, in the case of the formation of the 
drop. As the drop forms at the hole in the glass tube, on the 
surface of the water where it is not touching the glass, surface 
tension, or force, comes into play, and the advancing drop 
behaves as if the outside of it were an elastic membrane, holding 
up the water; when the weight of the drop becomes too great to 
be supported by this force, it breaks away and falls. 
The force at the surface moulds the water so that it occupies 
the least possible space, and so a sphere is produced. 
By means of a lantern, shadows were thrown on a screen, and 
it was shown that when alcohol was allowed to fall in drops from 
the glass tube, the drop was less in size than was a drop of 
water: the reason of this being that the surface force of alcohol 
is less than the surface force of water, and in consequence a less 
quantity of alcohol is supported by the surface force before the 
drop breaks away. 
A soap bubble or a soap film consists of a very thin layer of 
liquid, and has therefore an outside and an inside surface or skin, 
and each surface being the surface of a liquid, is elastic, giving 
rise to the existence of surface force. This was demonstrated by 
means of a soap bubble blown on a wide-mouthed funnel, on the 
open end of the pipe being placed near a candle flame, the air 
rushing out blew out the flame. 
The pressure of air inside a soap bubble is greater in a small, 
than in a large bubble, as was shown by connecting the air 
inside a bubble with a manometer. 
An explanation of the colouration of a soap bubble was given. 
Other properties of soap films were demonstrated—the floating 
of a bubble in a heavy atmosphere of aether—the diffusion of 
aether from the outside to within a bubble. 
A soap film was made to assume other forms than th 
spherical. 
It was also shown that a number of bubbles in contact with 
one another arrange themselves so that three bubbles always 
meet at a line of contact, and the angles between the films are 
all equal. 
By means of two rings between which a bubble was blown, 
the possibility of drawing out the spherical bubble with a 
cylindrical bubble was shown. 
