which fall to engineers, feel to be of the very highest importance. Each of these works is a text book on the subject to which it relates, and an authority established in the estimation of those engaged in these pursuits. The labour and mental power required for the production of these works place the author on an eminence rarely attainable. But great as is the distinction which the authorship of these works proclaim, there is yet another and grander achievement for which science is indebted to you. The new science of modern times which embraces the relation of all physical energy is largely your own. It is to you that we chiefly owe the development of that branch of the science called Thermo-dynamics, which has revolutionised the theory of heat and the principles of all the machines dependent on that theory. The steam engine, the most important instrument, I believe, in existence, is now placed on two principles. Its operation before the development of this science was to a considerable extent obscure, and although there are some features that still require consideration, you have done more than was ever done before to instruct us in its true principle and operation. Your development of thermo-dynamics, coupled with the great discovery of Joule of the numerical relation of heat and dynamic effect, or the quantity of the one that is equal to a quantity of the other, places within our reach the numerical result to be obtained from assumed elements of heat--prime movers. Your name, and that of Clausers, and Joule, and our distinguished friend Thomson, will ever be associated with this science, which has done much towards explaining important laws of nature." We may add that Mr. Rankine is a painstaking and conscientious teacher, and takes great care to impart to his students a correct and intelligible knowledge of their studies. He is no sciolist himself, and he does not believe in merely superficial attainments in his pupils. As to his social qualities, it is well known to his more intimate friends that Professor Rankine is a _bon vivant_ of the first water. He is in his element at the "Red Lion" dinners of the British Association, where he has frequently displayed vocal powers of a high order of merit; and it is worth while mentioning that he is the composer of the words and music alike of some of his best songs. One of his most familiar productions as a song writer appeared originally in _Blackwood's Magazine_, and is entitled "The Engine Driver's Address to his Engine." PROFESSOR ALLEN THOMSON.