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MATHEMATICS.
23

Drewcontinued.

may find it an easy and interesting continuation of his geometrical studies. With a view, also, of rendering the work a complete manual of what is required at the Universities, there have either been embodied into the text or inserted among the examples, every book-work question, problem, and rider, which has been proposed in the Cambridge examinations up to the present time.

SOLUTIONS TO THE PROBLEMS IN DREW'S CONIC SECTIONS. Crown 8vo. cloth. 4s. 6d.
Earnshaw (S.) — PARTIAL DIFFERENTIAL EQUA­TIONS.

An Essay towards an entirely New Method of Inte­grating them. By S. Earnshaw, M.A., St. John's College,

Cambridge. Crown 8vo. 5s.

The peculiarity of the system expounded in this work is, that in every equation, whatever be the number of original independent variables, the work of integration is at once reduced to the use of one independent variable only. The author's object is merely to render his method thoroughly intel­ligible. The various steps of the investigation are all obedient to one general principle, and though in some degree novel, are not really difficult, but on the contrary easy when the eye has become accustomed to the novelties of the notation. Many of the results of the integrations are far more general than they were in the shape in which they have appeared in former treatises, and many Equations will be found in this Essay integrated with ease in finite terms which were never so integrated before.

Edgar (J. H.) and Pritchard (G. S.) — NOTE-BOOK ON

PRACTICAL SOLID OR DESCRIPTIVE GEOMETRY. Containing Problems with help for Solutions. By J. H. Edgar, M.A., Lecturer on Mechanical Drawing at the Royal School of Mines, and G. S. Pritchard, late Master for Descriptive Geometry, Royal Military Academy, Woolwich, Second Edition,

revised and enlarged. Globe 8vo. 3s.

In teaching a large class, if the method of lecturing and demonstrating from the black board only is pursued, the more intelligent students have generally to be kept back, from the necessity of frequent repetition, for the sake of the less promising; if the plan of setting problems to each pupil is adopted, the teacher finds a difficulty in giving to each sufficient attention.