14 THOUGHTS ON NATURAL PHILOSOPHY. 
One of the most difficult problems in connection with this 
subject is the following:—Why is it that in combustion, 
although the particles must move at varying rates of speed, 
only the products (and the same products each time) with 
which we are acquainted are produced? The explanation 
appears to be as follows: Imagine a box of billiard balls 
revolving rapidly, and the balls suddenly thrown therefrom 
at high rates of speed on to a very large billiard table ; some 
during their movements would eventuate into groups. 
Repeat this as often as you like, and if the forces are exactly 
alike in all particulars, on each occasion you will get like 
results. You must have definite temperatures to produce 
definite chemical results, and with like forces you of course 
get like results. It is possible that in some cases other 
substances are in the act of formation, in a fraction of time, 
amidst the war of the atoms; but the battling of the atoms 
breaks up those nascent combinations before they can escape, 
and only those combinations remain stable and escape to 
which it is possible so to do under the given circumstances. 
The atoms having definite weights (the granules of matter 
must have some weight, and according to their number, or 
weight, in the atom so must be its weight), the resulting 
combination must have definite weights; and as you get like 
results under like circumstances, you get a like rule of 
combination weights. ? 
Returning to the strip of wood, it is evident that it is the 
speed, weight, and movement of the atoms or molecules, etc., 
that give to the substance its character that we term wood. 
If the atoms, etc., moved at sufficient speed to unite with 
oxygen in combustion, it would result in and be something 
that certainly is not wood. They must move more slowly 
than the oxygen to be wood. Their rate of speed and arrange- 
ment makes them wood. 
