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60 ''three books contain a series of theorems and of problems on the laws of motion of elementary substances. In the sixth and seventh, the mechanical constitution of molecules is investigated and determined: and by it the general properties of bodies are explained. The eighth book treats of luminiferous ether. The ninth explains some special properties of bodies. The tenth and eleventh contain a radical and lengthy investigation of chemical principles and relations, which may lead to practical results of high importance. The twelfth and last book treats of molecular masses, distances, and powers.''

Boole.—Works by Author:George Boole, D.C.L, F.R.S., Professor of Mathematics in the Queen's University, Ireland:—

A TREATISE ON DIFFERENTIAL EQUATIONS. Third Edition. Edited by Author:I. Todhunter. Crown 8vo. cloth. 14s.

''Professor Boole has endeavoured in this treatise to convey as complete an account of the present state of knowledge on the subject of Differential Equations, as was consistent with the idea of a work intended, primarily, for elementary instruction. The earlier sections of each chapter contain that hind of matter which has usually been thought suitable for the beginner, "while the latter ones are devoted either to an account of recent discovery, or the discussion of suck deeper questions of principle as are likely to present themselves to the reflective student in connection with the methods and processes of his previous course. "A treatise incomparably superior to any other elementary book on the subject with which we are acquainted"''—Philosophical Magazine.

A TREATISE ON DIFFERENTIAL EQUATIONS. Supplementary Volume. Edited by I. Todhunter. Crown 8vo. cloth. 8s. 6d.

This volume contains all that Professor Boole wrote for the purpose of enlarging his treatise on Differential Equations.

THE CALCULUS OF FINITE DIFFERENCES. Crown 8vo. cloth, 10s. 6d. New Edition revised.

''In this exposition of the Calculus of Finite Differences, particular attention has been paid to the connection of its methods with those of the Differential Calculus —a connection which in some instances involves far more than a merely formal analogy. The work is in some measure designed as a sequel to Professor Boole's'' Treatise on Differential Equations.