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proved, as a consequence of his recluse and self-centred—life there are perhaps few investigators of the first rank of whose work and aims and procedure we have now more complete knowledge than of his.

The additions appended by Maxwell, in the form of thirty-five notes of elucidation and commentary, on modern lines, relating to Cavendish's results and methods, constitute an example of powerful and elegant relevant original investigation such as could hardly have been carried through by anyone else.

Advantage has been taken of the present reprint of the Electrical Researches, as constituting Volume I of a definitive edition of the Scientific Writings of Henry Cavendish, to add a few brief annotations and references such as were needed to bring Clerk Maxwell's commentary up to date. These notes, where appended to Cavendish's text, are enclosed in curved brackets to distinguish them from Maxwell's own. As examples, reference may be made to pp. 374, 413, 422. The printing of the original edition had probably proceeded at intervals, and the final consolidation must have gone on during Prof. Maxwell's last illness in the summer of 1879. Thus it has now been possible to improve the headings of the chapters and sections, and the headlines of the pages, so as to convey a clearer and more rapid view of the nature and content of the text. The index and table of contents have been improved.

Apart from his permanent contributions to experimental laws, it is possible to maintain that the theoretical views of Cavendish should now command on historical grounds even more interest than they could excite in 1878, when the Electrical Researches were made public in complete form by Clerk Maxwell. At that time attention was largely concentrated on the elucidation of the electric field, and the mode of transmission of electrical influence from one body to another. The formal settlement of that range of problems on the lines of the Faraday-Maxwell theory has now transferred investigation to the sources of electric influence; and problems of the distribution of electrons in conducting and insulating bodies, their relation to the electrically polarisable molecules of matter, their function in conduction and in radiation, even the exploration of crystals in atomic detail by radiations of molecular wave-length, are now opening out. These problems all involve interaction in a binary medium, electrons and molecules controlling activities in an aether; it is now an affair of relations of the field of transmission with electrically polar or polarisable molecules which are its sources; and though this is very different from Cavendish's idea of a uniform electric fluid pervading and interacting with material substances by mere attraction, yet the degree of success that had been attained by the earlier and simpler mode of representation can become again by contrast a subject of historical scientific interest. The title of one of Lord Kelvin's best-known memoirs, "Æpinus atomized," is evidence for this view.