Note 45 — Chapter VI
Reading edition
In the Philosophical Transactions, vol. xc., the following papers, by Sir William Herschel, may be consulted:—
Investigation of the powers of the prismatic colours to heat and illuminate objects; with remarks that prove the different refrangibility of radiant heat. To which is added, an inquiry into the method of viewing the sun advantageously, with telescopes of large apertures and high magnifying powers, p. 255. Experiments on the refrangibility of the invisible rays of the sun, p. 284. Experiments on the solar and on the terrestrial rays that occasion heat; with a comparative view of the laws to which light and heat, or rather the rays which occasion them, are subject; in order to determine whether they are the same or different, pp. 293, 437.
In connection with this inquiry, Sir William Herschel remarks, that since a red glass stops no less than 692 out of 1,000 such rays as are of the refrangibility of red light, we have a direct and simple proof, in the case of the red glass, that the rays of light are transmitted, while those of heat are stopped, and that thus they have nothing in common but a certain equal degree of refrangibility, which by the power of the glass must occasion them to be thrown together into the place which is pointed out to us by the visibility of the rays of light.
On the same subject, a Memoir, by Sir Henry Englefield, in the Journal of the Royal Institution for 1802, p. 202, may be consulted; and Researches on Light, by the Author.