Note 759 — Chapter V · (continued 2)

Black's Lectures on Chemistry, vol. i. pp. 116, 117; and in various places. Dr. Robison, the editor of these Lectures, says, p. 513, ‘Nothing could be more simple than his doctrines of latent heat. The experience of more than a century had made us consider the thermometer as a sure and accurate indicator of heat, and of all its variations. We had learned to distrust all others. Yet, in the liquefaction and vaporization of bodies, we had proofs uncontrovertible of the entrance of heat into the bodies. And we could, by suitable processes, get it out of them again. Dr. Black said that it was concealed in them,—latent,—it was as much concealed as carbonic acid is in marble, or water in zeolite,—it was concealed till Dr. Black detected it. He called it Latent Heat. He did not mean by this term that it was a different kind of heat from the heat which expanded bodies, but merely that it was concealed from our sense of heat, and from the thermometer.’ See also p. xxxvii.: ‘Philosophers had long been accustomed to consider the thermometer as the surest means for detecting the presence of heat or fire in bodies, and they distrusted all others.’