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“This is, I imagine, the first time that any attempt has been made to adapt the subject of Geometrical Optics to the reading of the higher ''classes in our good schools. That this should be so is the more a matter'' for remark, since the subject would appear to be peculiarly fitted for such ''an adaptation. . . . . I have endeavoured, as much as possible, to avoid'' the example of those popular lecturers who explain difficulties by ignoring ''them. But as the nature of my design necessitated brevity, I have omitted'' entirely one or two portions of the subject which I considered unnecessary to a clear understanding of the rest, and which appear to me better learnt at a more advanced stage” —. “This book,” the says, “is carefully and lucidly written, and rendered as simple as possible by the use in all cases of the most elementary form of investigation.”

Of the Twelve Books into which the present treatise is divided, the first and second give the demonstration of the principles which bear directly on ''the constitution and the properties of matter. The next 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 mole&shy;cules'' is investigated and determined: and by it the general properties of ''bodies are explained. The eighth book treats of luminiferous œther. 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.

This treatise is specially intended for use in schools, The choice of matter has been chiefly guided by the requirements of the three days' examination