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POPULAR SCIENCE MONTHLY. 



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 sup- 

 position. 



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 pub- 

 lished. 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 Sci- 

 ence Series deals with Sir Humphry 

 Davy, poet and philosopher, and is by 

 T. E. Thorpe (London, 1896). In pre- 

 paring 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 sim- 

 plicity, and on the whole is more reli- 

 able. 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 phys- 

 iological effects of breathing 'laughing 

 gas,' as it was called, made him con- 

 spicuous 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 ex- 

 cepting the safety-lamp), was Michael 

 Faraday. The biography of this sim- 

 ple-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 Frank- 

 land ) , but the limited space at our com- 

 mand 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 men- 

 tioned 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 im- 

 portant investigations and for prepar- 

 ing 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 dis- 

 covery. The life of the Honorable 

 Henry Cavendish, 'le plus riche de tous 

 les savants et probablement aussi le 

 plus savant de tous les riches/ was 

 published by the Cavendish Society in 



