700 Proceedings of Royal Society of Edinburgh. [sess. 
be subjected to a greater battering of radiations of electricity than 
if it were absent, so that the end of the conductor nearest the 
electrified body becomes more negative, the motion escaping to 
where the pressure is least. 
If the electrified body were negative all the foregoing would be 
reversed, the atoms would expand, and the speed of their particles 
slow down by the conversion of their actual into potential energy. 
There would be less pressure on the body under induction than if 
the dielectric were absent, with the result that motion would flow 
to the place of least pressure. The thinner the dielectric the 
greater is its efficiency, because a limited supply of electricity, 
whether positive or negative, cannot have the same effect on an 
unlimited amount of matter as on a small quantity. If the 
electricity is positive and the quantity of matter small, there will 
be a greater concentration of the effect, as absolutely none of the 
motion can escape to more distant parts ; it is not subdivided 
between so many atoms of matter. And if the electricity is 
negative, the less number of atoms the less support, in the shape of 
electricity, will they get from their neighbours. 
I had intended touching on the Leyden jar and other condensers, 
but really there does not seem to be anything to say that has not 
been said already, or that cannot readily be deduced from what 
has been said. We will therefore pass on to consider the current. 
27. Current Electricity. 
Without entering into the details of batteries, with which I 
have only a very slight acquaintance, I proceed to give my idea 
of the origin of current electricity, as deduced from the 
hypothetical bubble atom. Well, then, if two of these atoms, of 
the same hind , be united together to form a molecule, it appears 
evident, since the constituent particles of both atoms move with 
the same speed, that as much of the motion of the particles of 
the one atom as may happen to be transferred to those of the 
other must be exactly returned, neither more nor less. But it 
is also as evident that if atoms of different kinds, whose particles 
move with different velocities, be united in a molecule, that the 
transfer of speed from atom to atom will not be equal, but that 
