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120, were, as they ought to be, aids to the proper end of the teacher. The best proof of this was the number of individual minds that were stimulated to a scientific or intellectual career by the study of the work. The hearty testimony borne by Herschel and Whewell to the merits of the 'Physics,' scientific as well as expository, was incompatible with any infusion of claptrap.

"It would be easy to set forth the art, or rather the genius, of Arnott, in the composition of his book. He had great literary power, in the mere command of expression, and in the composition of his sentences, which are both lucid and flowing. Many scientific writers have had this much. But he had also a thorough and unfaltering perception of the intellectual capabilities of an average reader, and never for a moment presumed too much upon these. He labored, with no small success, to bring the doctrines of natural philosophy down to a level of mind that had never before been permeated by them; and, if any part of the subject was hopelessly intractable, he passed it by.

"Besides his amassed store of popular illustrations, stated in easy language, the work had the further charm of a species of sentiment or eloquence, often enough attempted in connection with science, but not often so well kept up. The author fully complied with Plato's condition of philosophical teaching—to exhibit the goodness of the divine plan of the Cosmos. His eloquent passages on this subject, together with his choicest illustrations of physical laws, were largely adopted into the common-school reading-books.

"The new editors have shown themselves aware of the backward state of the exposition in many parts, and have freely employed the power of excision and substitution. We should say, from a rough estimate, that a full half of the work is new. In the branches of Acoustics, Heat, Light, and Electricity, many additions were obviously necessary. In Mechanics, there has been more permanence, and Arnott's exposition is less interfered with; but it was essential to supplement his chapter on Motion and Force with a view of the doctrine of conservation of energy, which the author would have been delighted to handle in his own peculiar way, but scarcely touched upon even in his latest edition. However the work of revision may have been distributed among the three editors, they have been successful in bringing up the subjects to the most recent views, and in illustrating them by well-chosen examples and diagrams. The work is one likely to keep its place among treatises on a similar scale. Extending to nearly 900 pages, it comprises a tolerably full body of information in all the branches, while the reader has still the benefit of the expository genius and eloquence that charmed and astonished the world forty years ago, and has not yet been superseded."