4AS 
Arricue XXIII. 
On the Forces which regulate the Internal Constitution of 
Bodies. By O. F. Mossor71. 
From a Memoir addressed to M. Plana, published separately, and communicated 
by M. Farapay, Esq., D.C.L., F.R.S., &e. 
PRELIMINARY REMARKS. 
i Tue study of the phenomena of nature has led philosophers to 
consider bodies as being composed of molecules held in a state of fixed 
equilibrium at a certain distance from each other. Such a state re- 
quires that they should be endued with a certain action. Some pe- 
culiarities of this action we are already able to assign, but its.complete 
characteristics are not yet well defined. 
As the resistance opposed by bodies to compression increases indefi- 
nitely with the reduction of their volume, though their molecules have 
not come into contact with each other, it shows that the force which they 
exercise is repulsive at the least distances. At a distance greater than 
these, but still imperceptible, it must vary with great rapidity, and be- 
come attractive, in order that a steady equilibrium of the molecules 
may be possible; and finally, when it has become perceptible, it must 
decrease in the inverse ratio of the square of the distance, in order to 
represent the universal attraction. The limits of the distance at which 
the negative action becomes positive vary according to the temperature 
and nature of the molecules, and determine whether the body which 
they form be solid, liquid, or aériform. 
There is a class of phenomena, rather singular at first sight, in 
which however it appears that nature designed, by separating the 
forces which she employs, to present herself in all her simplicity. 
Such are the phenomena which constitute what we denominate 
statical electricity. It is well known with what admirable facility 
Franklin explained these phenomena, by supposing that the mole- 
cules of bodies are surrounded by a quantity of fluid or ether, the 
atoms of which, while they repel each other, are attracted by the 
molecules. It is known also how Coulomb subsequently proved that 
the force with which the repulsion of atoms and the attraction of 
the molecules are produced, is, like universal attraction, regulated by 
the law of the inverse ratio of the square of the distance. Indeed, the 
latter philosopher has substituted for the hypothesis of Franklin, which 
is that generally followed in England, Germany, and Italy, another 
hypothesis, in which a second fluid is supposed to perform the part as- 
signed to matter in that of Franklin ; and this mode of explaining the 
