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between varying numbers of atoms of definite weight, and then succeeded in confirming this view by the results of analyses made both by other chemists and by himself. This is precisely the inverse of the commonly accepted supposition.

This view of the genesis of Dalton's Atomic Theory has been published in a small volume with the title: 'A New View of the Dalton's Atomic Theory,' edited by Sir Henry E. Roscoe and Arthur Harden (London, 1896). The work contains also documents and letters by Dalton not previously published. No student of Dalton or of the atomic theory can afford to ignore this important contribution to history of chemistry.

Another volume in the Century Science Series deals with Sir Humphry Davy, poet and philosopher, and is by T. E. Thorpe (London, 1896). In preparing this Dr. Thorpe made use of the memoir on Davy by Dr. Paris (London, 1831), and that by Sir Humphry's brother, John Davy (London, 1858), as well as of contemporary periodicals, letters, and diaries of his friends and brother scientists. The first named of the earlier biographies has been found inaccurate as to matters of fact and extravagant in laudation; the second is written with candor and greater simplicity, and on the whole is more reliable. Dr. Thorpe's portrayal of the brilliant chemist is more correct and satisfactory; Davy's versatility is well brought out, his poetical writings, his philosophic studies, and his scientific labors, as well as his character as a man. Davy's discovery of the physiological effects of breathing 'laughing gas,' as it was called, made him conspicuous in the world of science when he was twenty-one years of age, and this prominence he maintained by his genius throughout life; at the age of thirty he isolated the metals of the alkalies, at the age of thirty-eight he invented the safety-lamp, at the early age of fifty-one he died.

One of Sir Humphry's most notable discoveries, certainly that which proved of the greatest benefit to mankind and to the progress of civilization (not excepting the safety-lamp), was Michael Faraday. The biography of this simple-minded and remarkable scientist, by Silvanus P. Thompson, forms another volume of the Century Science Series; two others deal with Justus von Liebig (by W. A. Shenstone) and with Pasteur (by Professor and Mrs. Percy Frankland), but the limited space at our command forbids further details.

Less brilliant, but no less patient an investigator was the Scotch chemist, Thomas Graham, whose career was very nearly conterminous with that of Liebig, and differed but little from that of Faraday. The Life and Works of Thomas Graham was prepared by Dr. Angus Smith, but owing to his feeble health (which terminated in death) the volume was edited by J. J. Coleman (Glasgow, 1884). Graham's life is rather inadequately depicted, but the book is enriched by more than sixty of his letters interspersed by brief notes of his contributions to science as well as by abstracts of all his published papers; among the latter may be mentioned those on the diffusion of gases and of liquids (1838-1863) and on the occlusion of hydrogen by metals (1868). In spite of his confining duties as Master of the Royal Mint, Graham found time for many other important investigations and for preparing a text-book which afterwards in connection with Friedrich Julius Otto became the celebrated and voluminous German 'Lehrbuch der Chemie' that passed through several editions.

The discovery of argon, and of other constituents of the atmosphere by Lord Rayleigh and William Ramsay in 1895 aroused renewed interest in the eccentric philosopher Cavendish, who narrowly escaped anticipating the recent discovery. The life of the Honorable Henry Cavendish, 'le plus riche de tous les savants et probablement aussi le plus savant de tous les riches'[1] was published by the Cavendish Society in

  1. The richest of all savants and the most eminent of all the rich.