A syllabus of a course of lectures on chemistry, delivered at the Royal Institution of Great Britain / [Sir Humphry Davy].

  • Humphry Davy
Date:
1802
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Licence: Public Domain Mark

Credit: A syllabus of a course of lectures on chemistry, delivered at the Royal Institution of Great Britain / [Sir Humphry Davy]. Source: Wellcome Collection.

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    I 7. Theories concerning the Mature of Heat. u Two theories concerning the nature of heat, have been most prevalent amongst philosophers. ]. It has been sup- posed to be a peculiar ethereal fluid. 2. It has been con- jectured to be a property of common matter; a specific motion of the particles of bodies. z* The arguments in favour of the first of these theories, have been chiefly deduced from the phenomena of latent heat, of radiant heat, and of change of capacity; whilst the last of them has been supported by experiments on the excitation of heat by friction, in cases in which there existed no perceptible source, from which, considered as a substance, it could possibly be derived. 3* The late experiments of Dr. Herschel have demon- strated, that radiant heat must be constituted by the mo- tions of a peculiar substance. And these motions may be conceived to beeither rectilinear projections, or undulations. 4* It has been lately supposed that they are undulations. And on this theory it has been assumed, 1. That an elastic ethereal medium exists in space. 2. That this medium is diffused through the pores of different ponderable sub- stances, in different states of density. 3. That radiant heat is constituted by particular undulations of it, when in a free state. 4. That sensible heat is occasioned by par- ticular undulations of it, in its states of diff usion through the pores of ponderable substances. 5.That certain peculiar vi- bratory motions of the particles of ponderable substances are capable of producing the undulations in the ethereal medium which constitute heat. 6. And reciprocally that those undulatory motions of the ethereal medium are capable of producing peculiar vibrations of the particles of ponderable substances. s* These propositions are evidently countenanced by the experiments of Count Rum ford, and Professor Pictet, on the heat produced by friction. They are rendered more conclusive by the analogy between the laws of the motions
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