J~roct'cdl)zgs, etc. 319 in the cylinder, and a treatment of the subject of compound expansion. The well-known work of Dr. Emery is mentioned and quoted. The subject of valve gears and the theory of governing also receives considerable attention.
The discussion of what constitutes the best type of steam engines in different conditions, as evidenced by present-day practice, is rather slurred over, bttt few forms receiving any attention. In a practical work, while deprecating the tendency to profuse description too frequently indulged in by many writers, it would, nevertheless, seem as if some space, devoted to a detailed discussion of a number of characteristic types of engines, would have been wfluable. Thus, for example, a consideration of the relative merits of high-and low-speed engines ; the pros and cons regarding various types ot compound engines; the practical advantages gained by working with high steam pressures, etc., ere matters concerning which the average engineer requires fuller exposition.
The steam turbine has but a few pages given it, although many readers would have welcomed flfll information fiom so authoritative a writer, there being no question but that this form of motor is one of those things which, logically, should develop into a prilne mover of considerable practical value.
The closing chapter is on air, gas and off engines. Upon this subject, also, greater co,npleteness would have been desirable. Engines of this type are proving themselves of rapidly increasing value, in view of the downward tendency in the price of gas and the large development of natural gas supplies. The literature of tke subject, as is well known, is exceedingly incomplete and old-fashioned.
Ot~ the whole, the book is a valuable one and offers much that is suggestive, while the exposition, as previously mentioned, is clear and to the point. E. G, W.