The Philosophical Magazine (Volume 39) (Paperback)

Book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1812. Excerpt: ... Acres. Brought forward 435,080 Rother (upper part6) 45,000 Schoo 10,000 Sence (in Ravenstone) 2,000 Sheaf (upper part) 5,000 Shelf 10,000 Trent (middle parts) 70,000 Wye 45,000 Total of Derbyshire 622,080 In my next I intend to follow up this subject, by extracting Mr. Farey's account of the more rocky and precipitous Pulleys, &c.--Editor.] XXIX. On the Radiation of Cold. Bxj a Correspondent. To Mr. Tilloch. Sir, Having lately seen repeated at the Royal Institution, the experiment of the supposed radiation of cold; and being dissatisfied with the explanations commonly offered of this phaenomenon, 1 am induced to trouble you with this communication, in order to learn whether an explanation which I have to offer, may appear to others more satisfactory than any of those usually given. The experiment is too familiar to men of science to need description; L will just .mention the explanation usually given, as I draw my conclusion frx, m precisely the same premises, without attempting any new experiments. Mr. Davy stated that heat constantly radiated from all bodies; and as the temperature of the thermometer placed in the focus of the one mirror is maintained by such radiation, if a piece of ice be placed in the focus of the other minor, it displaces a portion of air which before assisted by its rad.ation (for he said that air did radiate heat) in maintaining that, temperature: the thermometer therefore falls, but the ice being removed- it again risesi Were this explanation the true onerit would follow, that when the thermometer is placed in the focus of the one mirror, although there be nothing but air in the opposite one, it ought to rise; otherwise it could not-be depressed by the abstraction of that air, any more than by that of an equal quantity in anv other spot at an equa...