On new properties of heat, as exhibited in its propagation along plates of glass. By David Brewster, LL. D. F. R. S. Lond. and Edinb. In a letter addressed to the Right Hon. Sir Joseph Banks, Bart. G. C. B. P. R. S
In a paper communicated to the Society in May 1814, Dr. Brewster observed that glass, when raised to a high temperature, had the property of depolarizing light, and in this respect resembled crystallized substances; but he did not at that time succeed in tracing a resemblance in other points, which he left for future investigation. On resuming this inquiry in the present paper, the subject is divided into two parts; in the former of which he describes the transient effects exhibited during the propagation of heat along plates of glass, whether received from adjacent bodies or communicated to them; and in the latter he describes the permanent optical properties produced in glass by being suddenly and partially cooled when red hot.