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156 entertain some doubt whether it is sufficiently popular to initiate our fair countrywomen into a knowledge of the laws of the material universe. Excepting in the Appendix, on the explanation of terms, there is not a single diagram in the work; and when we consider how difficult it has always been found to convey to general readers a tolerable knowledge of physics, even with the aid of numerous and minute diagrams, and with the still better accompaniments of apparatus and experiments, we have some misgivings respecting the success of this part of Mrs Somerville's plan.

When a scientific expositor is not allowed to appeal to the eye in explaining phenomena which are susceptible of a figurate representation, he is forced to substitute a diffuse and circuitous illustration, and thus to make a severe and unnecessary demand both upon the memory and the judgment. But this is not the only objection to the want of ocular delineation. Even when the desired knowledge, whether it be a process of reasoning or the account of a phenomenon, has been actually communicated, the hold which it takes of the mind is much more permanent when it has been received through the intermedium of the eye. A diagram, indeed, and still more the exhibition of a phenomenon, not only associates with itself the ideas to which it relates, but forms the basis of a local memory, by which impressions, otherwise fleeting, may be rendered indelible. The mind is frequently unable either to apprehend or to fix ideas, of which the eye has not traced the symbols; and while there are many examples of the ear having parted with its acquisitions, there are few in which the eye has abandoned even its earliest phantasms. The memory of vision is certainly the trunk of the retentive faculty; and, when every branch has decayed, it remains the last and the firmest landmark of the mind.

Entertaining these views, we regret that, in imitation of La Place, in his celebrated 'Exposition of the System of the World,' Mrs Somerville should have declined the use of those auxiliaries which have been generally considered indispensable in the communication of scientific knowledge; and we would strongly urge her to reconsider this matter, before she publishes a second edition of her Treatise. A work on original science will not lose its value, even if it is conceived in mysticism, and written in hieroglyphics; but the ablest digest of physical knowledge, which is intended for the instruction of those who are not the best fitted for abstract study, will lose half its value, if it fails in accomplishing, or accomplishes imperfectly, its primary object.

From these general observations on Mrs Somerville's work, we shall now proceed to give our readers some idea of the