The curious thermodynamics of rubber was first reported by John Gough (b. 1757), of Middleshaw, near Kendal in the English Lake District. Gough was a Quaker. It is said that he was descended from William Goffe, one of the three regicide judges (together with Whalley and Dixwell) for whom principal New Haven avenues were named, but his genealogy doesn't show it.
Though Gough was blind from the age of two, and epileptic, his knowledge of classics, languages, mathematics, physics, botany and zoology was legendary. In lines 498-514 of Book Seven of"The Excursion" (1813) William Wordsworth wrote of Gough:
--No floweret blooms
Throughout the lofty range of these rough hills,
Nor in the woods, that could from him conceal
Its birth-place; none whose figure did not live
Upon his touch. The bowels of the earth
Enriched with knowledge his industrious mind;
The ocean paid him tribute from the stores
Lodged in her bosom; and, by science led,
His genius mounted to the plains of heaven.
--Methinks I see him--how his eye-balls rolled,
Beneath his ample brow, in darkness paired,--
But each instinct with spirit; and the frame
Of the whole countenance alive with thought,
Fancy, and understanding; while the voice
With eloquence, and such authentic power,
That, in his presence, humbler knowledge stood
Abashed, and tender pity overawed.
Mathematics students from Cambridge would journey nearly 200 miles to Kendal for his tutoring. A number of them became "wrangler" (first class in the mathematical tripos examination at Cambridge University), and two became masters of Cambridge colleges, including the physicist William Whewell.
Among chemists Gough's most famous student was John Dalton. Dalton's most famous student was James Prescott Joule, the experimental physicist who would confirm Gough's observations on rubber thermodynamics 57 years later. From age 16 Joule was tutored by Dalton twice a week for two years, but at the end of this time he had only completed arithmetic and the first book of Euclid, and they never got to chemistry.
The following is Gough's 1802 paper on Rubber (called Caoutchouc) from "Memoirs of the Literary and Philosophical Society of Manchester" Second Series, Volume I, 1805, pp. 288-295. This paper immediately follows the paper in which Dalton presents the first, quite inaccurate, table of atomic weights, and it preceeds the paper in which Gough vigorously criticizes Dalton's theory.
Experiment 1 (p. 290) describes the evolution of heat on stretching rubber (an apology is made for measuring with the lips rather than with a thermometer).Experiment 2 (p. 292) describes the counterintuitive contraction of stretched rubber upon heating (although it becomes less dense).
Gough's interpretation involves absorption and expulsion of caloric by pores of the rubber.
Information on Gough from E. C. Patterson, John Dalton and the Atomic Theory, Doubleday, New York, 1970.
Wordsworth "The Excursion" from http://www.columbia.edu/acis/bartleby/wordsworth/ww397.html