This little work embodies the more generally interesting portions of lectures first written for delivery at the Stevens Institute of Technology, in the winter of 1871-’72, to a mixed audience, composed, however, principally of engineers by profession, and of mechanics; it comprises, also, some material prepared for other occasions.

            These lectures have been rewritten and considerably extended, and have been given a form which is more appropriate to this method of presentation of the subject. The account of the gradual development of the philosophy of the steam-engine has been extended and considerably changed, both in arrangement and in method. That part in which the direction of improvement during the past history of the steam-engine, the course which it is to-day taking, and the direction and limitation of that improvement in the future, are traced, has been somewhat modified to accord with the character of the revised work.