On stresses in rarified gasses arising from inequalities of temperature.

London, The Royal Society, 1879 [1880]. 4to (29.7 x 23.1 cm). 26 pp. [numbered 231-256]. Disbound. = The Scottish physicist and mathematician James Clerk Maxwell (1831-1879) is world-famous for demonstrating that light, electricity and magnetism are manifestations of the same phenomenon, all based on the underlying electromagnetic field. This was the first major step in uniting these forces of nature into one theory. Later, he turned his attention to thermodynamics, and the present work is his last (but not least) contribution to this subject, published in the year he died, at the early age of 48. "Maxwell's paper created the science of rarefied gas dynamics" (DSB). Here, he introduced the notion of "thermal transpiration" which causes the movement in Crookes radiometer, or "light mill", a near vacuum bulb with a set of vanes mounted on a spindle, and still a popular novelty item today because of its "perpetuum mobile"-like behaviour: the vanes rotate when exposed to light, with faster rotation for more intense light, providing a quantitative measurement of electromagnetic radiation intensity. The reason for the rotation has historically been a cause of much scientific debate (Wikipedia), but with this paper Maxwell actually "won" the debate, showing that a molecular phenomenon lies at its base, and that a supposed "light force" could not be responsible. Part of the Philosophical Transactions for the year MDCCCLXXIX (volume 170, part I). Small gap in the left margin of the first leaf; a few small, light, marginal spots, otherwise a very good, clean copy. DSB 9, pp. 224-225.