9i 
finite extent of the atmosphere. 
ther, from this source, any conclusive argument can be drawn 
in favour of ultimate atoms of matter in general. For, since 
the law of definite proportions discovered by chemists is the 
same for all kinds of matter, whether solid, or fluid, or elas- 
tic, if it can be ascertained that any one body consists of par- 
ticles no longer divisible, we then can scarcely doubt that all 
other bodies are similarly constituted ; and we may without 
hesitation conclude that those equivalent quantities, which 
we have learned to appreciate by proportionate numbers, do 
really express the relative weights of elementary atoms, the 
ultimate objects of chemical research. 
These reflections were originally suggested by hearing an 
opinion hazarded without due consideration, that the non- 
existence of perceptible atmosphere around the moon, might 
be regarded as conclusive against the indefinite divisibility of 
matter. There was, however, an oversight in this inference, 
as the quantity of such matter, which the moon would retain 
around her, could not possibly be perceived by the utmost 
power of any instruments hitherto invented for astronomical 
purposes. For, since the density of an atmosphere of infinite 
divisibility at her surface would depend on the force of her 
gravitation at that point, it would not be greater than that of 
our atmosphere is where the earth's attraction is equal to 
that of the moon at her surface. At this height, which by a 
simple computation is about 5000 miles from the earth's sur- 
face, we obviously can have no perceptible atmosphere, and 
consequently, should not expect to discern an atmosphere of 
similar rarity around the moon. 
It is manifestly in the opposite direction that we are to 
look for information. We should examine first that body 
