Page:Scientific Memoirs, Vol. 1 (1837).djvu/481

the third gives, for the determination of $r$,

$gv^{2}({\bar {\omega }}+\mathrm {q} )^{2}{\frac {(1+\alpha r)e^{-\alpha r}}{r^{2}}}-(g-\gamma )v^{2}{\bar {\omega }}^{2}{\frac {1}{r^{2}}}=0.$

If the density of the æther into which the molecules are plunged, or the quantity $q_{o}$, becomes greater, the density q given by the equation (6) will increase also; that value of $r$ which will satisfy the foregoing equation will consequently become greater, and the molecules will fix themselves in equilibrium at a greater distance. We see in this result that the æther performs the functions of caloric, and that it is to its greater or less density we are to ascribe the temperature and volume of the body. For what else, in fact, is an increase or diminution of temperature in respect to a body, than a new state in which its molecules, placed in equilibrium, form, in consequence of their being more or less widely separated, a greater or less volume. It has been known to philosophers since the time of Galileo, who was the first that clearly pointed out this difference, that we are not to confound the sensation which we experience while this new arrangement of the molecules of our body is taking place, with the motion by which it is produced.

---

NOTE.

[The readers of this Memoir will doubtless be interested in referring to Dr. Roget's "Treatise on Electricity" in the Library of Useful Knowledge, published March 15th, 1828; the following passage from which was noticed with reference to M. Mossotti's views, by Prof. Faraday in his lecture at the Royal Institution, Jan. 20th of the present year.—Edit.]

"(239.) It is a great though a common error to imagine, that the condition assumed by Æpinus, namely that the particles of matter when devoid of electricity repel one another, is in opposition to the law of universal gravitation established by the researches of Newton; for this law applies, in every instance to which inquiry has extended, to matter in its ordinary state; that is, combined with a certain proportion of electric fluid. By supposing, indeed, that the mutual repulsive action between the particles of matter is, by a very small quantity, less than that between the particles of the electric fluid, a small balance would be left in favour of the attraction of neutral bodies for one another, which might constitute the very force which operates under the name of gravitation; and thus both classes of phænomena may be included in the same law."