The author states, that in a former paper on this subject, having confined himself to the establishment of a number of new facts in the science of heat, embracing its polarization by reflection, refraction, and double refraction, and the depolarizing action of doubly refracting crystals, he proceeded, on resuming the subject, to ascertain more accurately the laws of these phenomena.

The first section of the paper relates to the methods of observation employed, and the examination of the values of the degrees of the galvanometer, which, for the most part, do not indicate equal increments of force. Two tables are given. By the first, the statical deviations of the needle are reduced, so as to be measures of the force producing them; and, by the second, the dynamical effect, or arc moved over by the initial disturbing action, is reduced to the final or statical effect, and thence to the true measure of heat. Several peculiarities attendant on the use of the galvanometer are kewise discussed.