This doctrine of _capacities_ did not give general satisfaction. Dr. Black himself said of it, that it was neither _probable_ nor _ingenious_;[75] notwithstanding which, it continued to be received, and even very generally adopted. Dr. Crawford, so well known for his writings on this subject, has adopted the idea, and Dr. Girtanner, in the passage above quoted from him, appears to be of the same opinion. The doctrine, however, had several opponents, among whom were the Monthly Reviewers. In their account of Nicholson’s First Principles of Chemistry, they express themselves in the following manner: “We only wish, that, in the doctrine of heat, he had avoided, which he might easily have done, Dr. Crawford’s idea of bodies having different _capacities_ for heat. In the melting of ice, for instance, a quantity of heat is absorbed, without any increase of the temperature, that is, without making the water sensibly warmer than the ice before its liquefaction; which is said to be owing to the water having a greater _capacity_ for heat, or being able to _hold more_ of it, than the ice; and, in like manner, when converted into vapour, its capacity is further increased, or it can hold more still. This appears to us a very unchemical, and a very inadequate idea of the matter: for, admitting water to have a greater capacity than ice, how is the change from one state to the other to be effected? Can the properties which a body is found to possess, after a change has taken place, be assigned as a cause of the change itself? Or will it be said, that the heat first enlarges the capacity, and then hides itself in that capacity so enlarged? We should think it much better to say, consonantly with the phenomena of other combinations in chemistry, that a certain quantity of heat, uniting with the ice, first _liquefies_ it, as a certain quantity of acid only neutralizes an alkali; that if any surplus quantity must be introduced, that surplus, remaining free and uncombined, must act and be sensible as heat in the one case, and acid other; and that different bodies require different quantities of heat or acid to be combined with them, for producing the changes in question.”[76] [75] These words are to be found in the M. S. Copies of his lectures circulated at Edinburgh. Dr. Black himself never published any thing to the world upon the subject. [76] Monthly Review, for 1790, p. 165.