1901 - 2 .] Mr J. Fraser on Constitution of Matter and Ether. 41 
The Cause of Gravity. 
We may now consider the cause of gravity in bodies. I said at 
the end of the last paragraph that the pressure on any atom would 
he directly proportional to its mass, and not to its surface area, as 
would appear at a first view. I hope that any of my readers will 
not have the thousandth part of the trouble over the elucidation 
of this point as I had myself, before the explanation occurred to me. 
Preliminarily, then, it must be pointed out that each particle of 
every atom is, instant by instant, taking toll, as it were, of the 
store of pressure in the medium, and, instant by instant, restoring 
it again. This modicum of force, or pressure, is used up in curving 
the paths of the particles in their orbits, and it is restored again by 
their centrifugal tendencies. At any particular instant there is a 
certain quantity of force or pressure absent from the medium ; and 
to show that this quantity will be precisely proportional to the 
number of particles taking part in the process, I will use a homely 
illustration. Suppose two runners running round a circle, and one 
of the two to be running twice as fast as the other. Further, 
suppose the spectators to be stationed 10 yards apart all round the 
circle, and as each runner passed to bestow a kick on him, which 
was immediately returned by the runner, or rather both runner and 
spectator kicked almost simultaneously, it is perfectly clear that 
the fastest runner would receive most kicks, but also they would be 
quicker returned ; and supposing the first kick was not returned by 
him till he received the second, nor the second until he received 
the third, and so on, it is clear that he would never be the recipi- 
ent of but one unpaid kick at any moment. The fastest runner, 
then, would receive twice as many kicks in the same time as the 
slow one, but at any instant he would be the recipient of only one 
unpaid kick, just like the slow one. 
Or take another case : Suppose two traders to be dealing at the 
same bank, and one to borrow money at the rate of £100 per 
week, to be repaid at the end of the week, without interest, when 
another £100 would be withdrawn; and the other to borrow at 
the rate of £100 per month, to be repaid at the end of each month, 
also without interest — a proceeding which no bank out of Utopia 
