Mr. _J. E. Marr_ has prepared his exposition of _The Principles of Stratigraphical Geology_ (Cambridge University Press; The Macmillan Company, New York, $1.60), under the belief that an idea of the subject can be obtained most satisfactorily if a large number of the details connected with the study of the stratified rocks are omitted. He has accordingly given very brief accounts of the strata of the different systems, paying more attention to the bearings of the facts than to their enumeration. The history of the earth is presented as a connected one, in which one period is linked on to the next, every event that occurs introducing a new complication into the conditions, which are consequently never quite the same--the changes showing an advance from the simple to the more complex. The study proves that an enormous period elapsed subsequent to the formation of the earth and previous to the deposition of the stratified rocks, of which we have only the slightest, if any, knowledge. The stratigraphical geologist has to establish the order of succession of the strata for the chronology, and to ascertain as far as he can the conditions existing during the deposition of the several strata or groups of strata. After an account of the growth and progress of stratigraphical geology, the nature of the stratified rocks and the law of superposition are discussed; the test of included organisms and the methods of classification are explained, the evidences of conditions under which strata were formed, and other theoretical points are considered, and the several geological systems or periods are enumerated under the English nomenclature. Finally, the various estimates of geological time and the bases on which they are made are reviewed. The American Book Company publishes as a part of the Eclectic System of Industrial Drawing an excellent manual of the _Elements of Perspective_, by _Christine Gordon Sullivan_, of the Cincinnati public schools. It consists of explicit directions and rules on the general principles of the art, with applications in Isometric Projection and Oblique Perspective, given in concise form and simple, clear language, amply illustrated, and supplemented by problems, in solving which the rules are made practical. A convenient manual on _Gas and Petroleum Engines_ has been prepared by _A. G. Elliott_ from the French of _Henry de Graffigny_ for Whittaker's Electro-Mechanical Series, in recognition of the interest that has been awakened in the application of such engines to supply the place now occupied by horses in drawing vehicles. One chapter deals exclusively with the theory of the gas engines. Other topics treated of are the history of the gas engine, the description of existing gas engines, carbureted air engines, petroleum engines, gas-generating plants, engines for use with poor gases, and the maintenance of gas and oil engines. (The Macmillan Company, 75 cents.)