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400 to set forth the problem correctly. We close by saying, with Victor Hugo, "The future is with navigation of the air."—Translated for The Popular Science Monthly from Le Monde de la Science et de l'Industrie.



FTER an interval of nine years the publication of the Bevölkerung der Erde has been resumed by the well-known geographical establishment of Perthes of Gotha. This is the eighth issue of this invaluable and authoritative publication. It first appeared in 1872 as a supplement to Petermann's Mitteilungen, the editors being the late Dr. Ernest Behm and Dr. Hermann Wagner, now Professor of Geography in the University of Göttingen. Up to 1882 the Bevölkerung der Erde was issued on an average every two years, always as a supplement to Petermann's Mitteilungen. While the eighth issue was being prepared Dr. Behm died, and Prof. Wagner was not able to undertake by himself the preparation of the vast mass of statistics involved. Owing to various causes, a period of nine years has elapsed before the publication has been resumed. Dr. Wagner's name still appears on the title-page as editor, associated with that of Dr. Supan, who succeeded Dr. Behm as editor of the Mitteilungen, of which the Bevölkerung continues to be a supplement. The form has, however, been changed from a quarto to a large octavo, which makes the work much handier for consultation. It covers two hundred and seventy pages, and is the one work that exhibits in detail the area and population of the earth in all its divisions and subdivisions. It is no mere indiscriminate collection of statistics. The whole is systematically arranged under the great divisions of the globe. Every figure has been critically examined; in all cases the sources of the statistics are given; where there are various figures, the value of each is discussed; where there is no authoritative census, the greatest pains have been taken to obtain trustworthy estimates. Equal care has been bestowed on the calculation of areas, new measurements of a large extent of the earth's surface having been specially undertaken for the work. Thus, it will be seen that Wagner and Supan's Bevölkerung der Erde stands high above all other works of a similar kind. The figures which it gives may be taken as the nearest approximation to the truth obtainable. It may be stated that Prof. Levasseur in 1886-'87 published in the Bulletin of the International Statistical Institute a collection of statistics on the area and population of the countries of the world, which were good and trustworthy so far as they went, though they are not nearly so detailed as those contained in the new issue of the Bevölkerung der Erde. 