Not only indeed is this the case in these changes of state, but it is also the case in the simple instance of mere changes in the temperature of bodies; different bodies require different degrees of heat to be communicated, or thrown into them, in order to produce the same increase of sensible temperature. This was the other great result to which we referred at first as the discovery of Dr. Black: he designated this peculiarity in bodies their _capacity for heat_; a term sufficiently expressive, but which is now more usually exchanged for the term _specific heat_. The establishment of the accurate values of this capacity or specific heat, in a number of different bodies, has afforded a wide field of research for subsequent experiments. It has been sometimes said that to Dr. Black’s discovery of latent heat we owe the steam-engine. This is, we think, a mistaken view of the matter. That heat will generate steam, and cold condense it, are facts that were well known, independently of the doctrine of latent heat; though that doctrine undoubtedly gives the explanation of them. The knowledge of these facts might therefore have been practically applied in the construction of the steam-engine, had Dr. Black’s discovery never been made. It is at the same time perfectly true, that this theory supplies us with accurate data dependent on the quantity of heat necessary to be communicated, on which calculation must proceed: and it is on the basis of such exact investigation, that the great improvements in the application of steam have been brought about. To return however to our narrative: though, as we have said, the leading ideas of these discoveries had occurred to the author probably about the year 1757, yet it was not till a few years afterwards that he had fully made out his theory. The discovery of specific heat was announced in 1760; and that of latent heat, with all the details of its experimental proof, was laid before a literary society in Glasgow, in a paper read April 23, 1762. After this period a full account of both subjects was regularly introduced by the author into his courses of lectures. He did not himself follow out the train of experimental research to which he had opened the way, but his friends and disciples entered largely upon the investigation of those valuable data, the numerical values expressing the quantities of latent heat and specific heat belonging to different substances. In 1766, Dr. Cullen having been promoted to the chair of medicine, Dr. Black, again treading in the steps of his revered friend and instructor, was called from Glasgow to the professorship of chemistry at Edinburgh. He was thus placed in a more conspicuous position, and the fame of the Edinburgh school was not a little raised by his accession to it. Students flocked from all quarters in increasing numbers, and Dr. Black now devoted himself entirely to perfecting his chemical lectures.