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MATHEMATICS.
27

they have their name as plane sections of a cone. This method is calcu­lated to produce a material simplification in these curves, and to make the proof of their properties more easily understood and remembered. It is also a powerful instrument in the solution of a large class of problems relating to these curves.

Jellet (John H.) — A TREATISE ON THE THEORY OF

FRICTION. By John H. Jellet, B.D., Senior Fellow of Trinity College, Dublin; President of the Royal Irish Academy.

8vo. 2s. 6d.

The theory of friction is as truly apart of Rational Mechanics as the theory of gravitation. This book is taken up with a special investigation of the laws of friction; and some of the principles contained in it are believed to be here enunciated for the first time. The work consists of eight Chapters as follows: — I. Definitions and Principles. II. Equilibrium with Friction. III. Extreme Positions of Equilibrium. IV. Movement of a Particle or System of Particles. V. Motion of a Solid Body. VI. Necessary and Possible Equilibrium. VII. Determination of the Actual Value of the Acting Force of Friction. VIII. Miscellaneous Problems — 1. Problem of the Top. 2. Friction Wheels and Locomotives. 3. Questions for Exercise. “The work is one of great research, and will add much to the already great reputation of its author.” — Scotsman.

Jones and Cheyne. — ALGEBRAICAL EXERCISES. Pro­gressively

arranged. By the Rev. C. A. Jones, M.A., and C. H. Cheyne, M.A., F.R.A.S., Mathematical Masters of Westminster

School. New Edition. 18mo. cloth. 2s. 6d.

This little book is intended to meet a difficulty which is probably felt more or less by all engaged in teaching Algebra to beginners. It is, that while new ideas are being acquired, old ones are forgotten. In the belief that constant practice is the only remedy for this, the present series of miscel­laneous exercises has been prepared. Their peculiarity consists in this, that though miscellaneous they are yet progressive, and may be used by the pupil almost from the commencement of his studies. The book being intended chiefly for Schools and Junior Students, the higher parts of Algebra have not been included.