Reviews — De Lapparent^ s Qeology. 123 



in the introduction, the work will be divided into two sections, the 

 first of which will be devoted to the study of present phenomena, 

 under the heads of teri'estrial morphology, physiography, and to 

 the external and internal dynamical agencies. 



The second section will treat of geology proper or the study of 

 the phenomena of past time, such as the general composition of the 

 earth's crust, the sedimentary strata or those of external origin, the 

 eruptive rocks or those of internal origin, the changes and disloca- 

 tions which the crust of the globe has undergone, and the various 

 geological theories. 



The first three Livraisons comprise some of the phenomena 

 belonging to the first section, and show considerable attention to 

 the selection and arrangement of the facts bearing on the principles 

 of geology and the causes at present in operation. 



The fourth Livraison concludes the account of the most important 

 geysers, as those of Iceland, New Zealand, Yellowstone Park, and 

 the Azores, treating of their chemical phenomena, and the origin of 

 the siliceous and calcareous substances deposited by them. 



The other evidences of declining volcanic activity, as Suffioni, 

 thermal springs, gaseous exhalations of carbonic acid (mofi'etes) 

 and of hydrocarbons, are succinctly treated, M. de Lapparent con- 

 sidering that the '* ensemble " of volcanic phenomena from the most 

 violent paroxysms to the simple mofettes form one continuous and 

 admirable ordinate series. 



The fourth section, which concludes the first part of the work, 

 describes the various facts and phenomena connected with earth- 

 quakes (in which the views of Mr. Mallet and other authors are 

 fully considered), and of the oscillations of the earth's crust, in 

 relation to the elevation of shore-lines, and of land-surfaces, the 

 author observing, that the great movements of the crust of the 

 globe and the various volcanic manifestations are chiefly due to the 

 progressive cooling of the inner igneous nucleus. 



The second part, or geology proper, commences with a description 

 of the mineral constituents of rocks, either as essential or accessory 

 minerals, followed by an account of the chemical and mechanical 

 processes for the examination of rocks, and of their classification, 

 ■under which the author proposes three main divisions, — acid, basic, 

 and neutral rocks : these are again divided into an ancient and a 

 modern series, with a further subdivision based upon their texture, 

 as the granitoid, trachytoid and vitreous types. Three tables are 

 given, pp. 579, 691, and 606, showing the kinds of rocks belonging 

 to each division, and an appendix on meteorites. 



The work will consist of seven parts, forming a volume of about 

 1100 pages, with 500 illusti'ations, so that, when completed, in 

 the same methodical and instructive manner as the portion already 

 published, it will form a valuable manual of physiography and 

 geology both for the general reader and the advanced student of 

 the science. J. M. 



