4O0 THE POPULAR SCIENCE MONTHLY. 



to set forth the problem correctly. We close by saying, with 

 Victor Hugo, "The future is with navigation of the air." — Trans- 

 lated for The Pojndar Science Monthly from Le Monde de la Sci- 

 ence et de V Industrie. 



THE POPULATION OF THE EARTH. 



AFTER an interval of nine years the publication of the Be- 

 volkerung 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 Mitteil- 

 ungen, the editors being the late Dr. Ernest Behm and Dr. Her- 

 mann Wagner, now Professor of Geograj)hy in the University of 

 Gottingen. Up to 1882 the Bevolkerung der Erde was issued on 

 an average every two years, always as a supplement to Peter- 

 mann'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 ap- 

 pears on the title-page as editor, associated with that ot Dr. Supaii, 

 who succeeded Dr. Behm as editor of the Mitteilungen, of which 

 the Bevolkerung 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 va- 

 rious 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 Bevolkerung der 

 Erde stands high above all other works of a similar kind. The 

 figures which it gives may be taken as the nearest apiiroximation 

 to the truth obtainable. It may be stated that Prof. Levasseur 

 in 1886-'87 published in the Bulletin of the International Statisti- 

 cal 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 Bevolkerung der Erde. 



