SPECIFIC 
GRAVITY 
OF NITROGEN, ETC. 
345 
particles according to some given law, and each attracting the 
other also according to some given law. Now, this is but a 
particular case of the following general proposition. Let 
there be any number of sorts of matter, each repelling its 
own particles and attracting each or any of the others, the 
forces being in each case governed by a given law; and pro- 
ceeding from the centre outward, indefinitely, without change 
of direction in any of them; then, after the equilibrium is 
attained, there can be neither attraction nor repulsion on dis- 
tant atoms. Admitting the new theory, it becomes a problem 
to ascertain the relative dimensions of the spheres of re- 
pulsion of the elements, as well as their atomic weights. The 
atoms of permanently gaseous bodies have large spheres of 
repulsion, especially if the atomic weights are small: thus 
hydrogen and nitrogen have large spheres of repulsion; and 
many reasons may be adduced to show that nitrogen has the 
greatest radius of repulsion of all the elements. The metals 
have very small spheres of repulsion, to which, probably, we 
may approximate from the atomic weights and specific 
gravities of the metals. Carbon seems to have the least sphere 
of repulsion of any known element: this follows from, — 1st, 
its fixed nature, not being volatilized by the greatest heat; 
2d, its retaining the form it had in the vegetable; 3d, its 
giving out a very great quantity of caloric when two pieces 
of fresh charcoal are suitably placed in the electric current; 
4th, its great hardness and reflective power, after having 
given out the caloric; 5th, its giving out caloric while absorb- 
ing light, from which arises its blackness; 6th, its different 
bulk in the form of lamp-black, being twenty or thirty times 
greater than in common cases, when it is prepared after the 
best manner; with other reasons, particularly the great 
variety of compounds of carbon and hydrogen which occur, 
with the frequency of their being isomeric. Mr. Exley con- 
cluded by suggesting an opinion, that there is another ele- 
mentary body, not yet discovered, which has both an exceed- 
ingly small sphere of repulsion, and an exceedingly small 
atomic weight, or absolute force. This probably enters 
largely into the composition of animalcules, and especially 
