uch that is of practical use in their respective callings. Those
in search of salable articles which can be manufactured on a small
scale, will find hundreds of most excellent suggestions. It should have
a place in every laboratory, factory and home.

An eight-page descriptive circular and complete table of contents will
be furnished on application.

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, $5.00. Half Morocco, $7.00

[Illustration: Books]

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

[Illustration: Book]

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._

Mechanical Movements,
Powers and Devices

By GARDNER D. HISCOX, M. E.

Octavo, 403 Pages, 1,788 Illustrations. Price, $2.50.

This is a collection of 1,788 specially made illustrations of different
mechanical movements, accompanied by appropriate descriptive text. It is
pra