952 Dr. Wollaston on the [Ocr. 
the tendency to accumulate may be counteracted by the inter- 
ference of other kinds of matter, or of other powers of which we 
have no experience, and concerning which we cannot expect to 
reason correctly. ‘ 
Now, though we have not the means of ascertaining the 
extent of our own atmosphere, those of other planetary bodies 
are nevertheless objects for astronomical investigation ; and it 
may be deserving of consideration, whether, in any instance, a 
deficiency of such matter can be proved, and whether, from this 
source, any conclusive argument can be drawn in favour of ulti- 
mate 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 elastic, if it can be ascertained 
that any one body consists of particles no longer divisible, we 
then can scarcely doubt that all other bodies are similarly con- 
stituted ; 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-exist- 
ence 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 surface, 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 which has 
the greatest power, and see whether even there the non-appear- 
ance of those phenomena which might be expected from such 
an atmosphere, will warrant the inference that our own is con- 
fined to this one planet by the limit set to its divisibility. 
By converse of the same rule which gives an estimate of 
extreme rarity at the moon’s surface, we may form a conception 
at what distance round the sun refraction from such a cause 
‘should be perceived. Ifwe calculate at what apparent distance 
from the body of the sun his force is equal to that of gravity at 
the surface of the earth, it is there that his power would be suffi- 
cient to accumulate (from an infinitely diyisible medium filling 
