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literature of chemistry has recently been enriched by several biographies of chemists and by carefully edited works reproducing the letters that passed between certain chemists; the importance and value of these volumes is enhanced by the reflection that the history of the lives of the leading men in a growing science constitutes the most complete history of the science in that period during which they labored, and their lives and labors are reflected in their letters. These notions are appreciated by most of the editors of the correspondence we have in mind, and they make their tasks of double value by introducing numerous bibliographic and explanatory notes.

No student of the progress of chemistry in France during the second quarter of the century just closed can acquire a full and correct knowledge of the subject without a perusal of the life of Charles Gerhardt, edited by his son (bearing the same name), and by Edouard Grimaux (Paris, 1900). In his short life of only forty years, Gerhardt introduced ideas into chemistry that were at first thought to be revolutionary, but were eventually adopted even by his adversaries; his services to organic chemistry were of the highest importance; he first doubled the atomic weights of carbon, oxygen and sulfur, divided acids according to their basicity, and completely established the individuality of the equivalent, the atom and the molecule.

Of a very different type was his contemporary living across the Rhine, Schönbein, whose life has been sympathetically written by his successor in the University chair. Dr. Geo. W. A. Kahlbaum (Leipzig, 1899-1901,2 vols.). The painstaking, indefatigable discoverer of ozone, of gun-cotton, of collodion, and of the passive state of iron, forms a strong contrast to the brilliant, keen-sighted investigator in organic chemistry, Gerhardt. Schönbein's busy yet uneventful life reaped but a paltry reward for a discovery that subsequently brought the Swedish manufacturer a colossal fortune; but none knew better than Schönbein that the reward sought by the investigator in the chemical laboratory is success in wresting from nature her hidden truths.

Schönbein was a voluminous writer of letters; Dr. Kahlbaum made a collection of over 1,600, besides 350 printed papers, and analyzed them carefully in compiling the volumes named. One of his most regular and valued correspondents was Faraday, and the letters interchanged with him have been published in another volume edited by Dr. Kahlbaum and Francis V. Darbishire (Basle and London, 1899). These letters number 155 and cover the period from 1836 to 1862, beginning with a letter from Schönbein announcing the peculiar behavior of iron in nitric acid of a certain strength, and ending with a brief note from Faraday that painfully discloses his mental distress. The first mention of a 'phosphorus smell developed by electricity' occurs in a letter to Faraday dated April 4, 1840, and the exciting cause of this odor occupies some part of nearly every letter to Faraday during the succeeding twenty-two years.

Dr. Kahlbaum, with others, has published 'Twenty Letters,' exchanged by Schönbein and Berzelius in the years 1836 to 1847 (Basle, 1898), and the