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POPULAR SCIENCE MONTHLY.

same in an English dress (London, 1900), also the 'Letters of Schönbein and Liebig, 1853-1869' (Leipzig, 1898), so that the correspondence of Schönbein is largely accessible to students seeking details.

These several volumes of correspondence suggest others that are analogous. The 'Letters of Berzelius and Liebig, 1831 to 1845,' edited by Justus Carrière with the cooperation of the Bavarian Academy of Sciences (Munich, 1893), and the correspondence between Berzelius and Wöhler, published by the Royal Academy of Göttingen, and edited by O. Wallach (Leipzig, 1901, 2 vols.).

And to complete this series of letters that passed between eminent chemists there remains the 'Correspondence of Liebig and Wöhler,' edited by A. W. von Hofmann, and Emilie Wöhler (Braunschweig, 1888, 2 vols). These cover the long period from 1829 to 1883. The inter-relations of these six works with the dates of the correspondence and of the death of each chemist, may be graphically shown by a diagram.

PSM V60 D574 Paths of correspondence between scientists.png

The perusal of letters between intimate friends having mutual interests in kindred studies is much like listening to conversation carried on between them; they reveal their daily life, domestic happiness and difficulties, their likes and dislikes, their humor and their satire, their successes and failures in research, and their ambitions and discouragements. They also disclose their weaknesses and perhaps their foibles, and they unconsciously divulge the greatness of their intellects, all in simple language, not written to produce startling effects nor to exaggerate their own importance in the minds of readers.

All these volumes are illustrated by one or more portraits, and some of them contain facsimiles of manuscripts.

MOSQUITOES.

A Monograph of the 'Culicidæ or Mosquitoes of the World' has just been prepared by Mr. Fred. V. Theobald, and is published by the British Museum as one of its regular series. There are two volumes of text aggregating 835 pages and one volume of plates, numbering 37 and containing 148 colored figures of adults. Then there are 5 plates, each containing six solar prints of microphotographs illustrating wing scales. In the text are 318 woodcuts, half-tones or similar figures. In these books 258 species of mosquitoes, divided among 22 genera, are described, and 37 species in 10 genera are credited to North America. Although the work is just off the press it is already out of date, and in the introductory remarks by the director of the museum, dated November, 1901, a supplementary volume is promised. All these facts indicate the remarkable interest that has been of late universally aroused in the subject, and the enormous collections that have been and are now being made in all parts of the world. In the United States several new species were recognized and described in 1901, two of them from New Jersey. The life history of several species has been made out, and good structural characters for their separation appear as the result of American study. Mr. Theobald describes 136 new species; almost as many as were described in all previous