Experimental Science Elementary Practical and Experimental Physics By GEORGE M. HOPKINS Revised and Enlarged Edition. Two Octavo Volumes. 1,100 Pages. 900 Illustrations. Cloth Bound, USD5.00. Half Morocco, USD7.00 Elementary Practical and Experimental Physics

The object of the work is to afford to the student, the artisan, the mechanic, and in fact all who are interested in science, whether young or advanced in years, a ready means of acquiring a general knowledge of physics by the experimental method.

The leading principles of physics are illustrated by simple and inexpensive experiments and the endeavor has been made to make the explanations of both apparatus and experiment plain and easily understood. In the new edition, the scope of the work has been broadened and presents the more recent developments in modern science.

An illustrated circular and complete table of contents sent free on application.

MONOPLANES AND BIPLANES

Their Design, Construction and Operation

By GROVER CLEVELAND LOENING, B.Sc., A.M., C.E.

12mo, 340 Pages, 278 Illustrations. Price, $2.50 postpaid

A New and authoritative work, covering the whole subject of the aeroplane, its design, and the theory on which its design is based, and containing a detailed description and discussion of thirty-eight of the more highly successful types. It is a thoroughly practical work, and invaluable to any one interested in aviation. The scientific exactness of the valuable data and references, as well as the high character of the innumerable illustrations and diagrams, renders this work, easily, the most useful, practical and complete that has as yet been contributed to the literature on aeroplanes.

An illustrated descriptive circular sent free on application.