Geology and Mineralogy. 515 



by D. B. Dowling, covered the Survey's publications from .1863 

 to the end of the Old Series in 1884. 



7. Mission scientifique ait Dahomey; par H. Hubert; -8°, 

 568 pp., 86 pis. and tigs, and geol. map. Paris, 1908 (E. Larose). 

 — This volume contains the results of two years of exploration 

 in the Dahomey region of Africa, during which the principal 

 subjects of study were the geological formations and the mineral 

 resources of the colony. It is in fact, however, a detailed inves- 

 tigation of all the factors which determine the surface relief and 

 climate of the area. The work was carried on under the auspices 

 of the colonial government, aided by the French Association for 

 the Advancement of Science. 



After a general description of the topography and history of 

 the country, the author presents the result of a study of its 

 meteorology and then considers the action of exterior geological 

 agencies in modifying its relief and the eifects produced, notably 

 the action of the atmosphere, of the surface waters, both from the 

 chemical and mechanical sides, and of the sea. These detailed 

 studies of an equatorial region contain many observations of 

 interest and of value and the main geographical features of the 

 country are now well determined. 



The larger part of the volume is devoted to the areal geology. 

 As a general result of his work the author finds that the rocks 

 may be divided into three main series of undetermined age and 

 these series cover each a remarkable extent of surface. The 

 oldest consists of folded crystalline schists which form two great 

 peneplains. The second are bedded rocks of unchanged altitude, 

 which may be of early Paleozoic age, and the third are surficial 

 deposits of recent formation. Unfortunately the lack of fossils 

 prevents exact determination and correlation. A large area of 

 deposits not far from the coast is thought to be of Eocene age. 

 The folding of the first series is parallel and this has profoundly 

 affected the evolution of the geography; the folds have deter- 

 mined the courses of the rivers, such as the windings, rapids, etc<, 

 of the Niger. 



These rocks are cut by, or mingled with, eruptive masses in 

 places, such as granites of various types, diorites, diabases and 

 gabbros. Some of the gneisses are also recognized as of eruptive 

 origin. The results of detailed microscopic study of these 

 various rock types are also given, the most interesting being of 

 certain alkalic granites containing riebeckite. 



The last part of the work contains the results of the study of 

 the distribution of certain plants and animals, that is of the 

 biologic zones, and concludes with an ethnographic sketch of the 

 region in which it is shown that the human grouping stands in 

 close relation to certain features of geography. 



The whole work is an important contribution to our knowledge 

 of a very interesting country. l. v. p. 



