504c Scientific Intelligence. 



normal cycle is complete, these follow in the order given. The 

 second chapter is devoted to vulcanicity; if earth movements 

 are of two kinds, vertical movements, giving rise to plateau build- 

 ing, and horizontal ones, giving rise to folded mountain regions, 

 then there are two contrasted forms of volcanic eruptions, fissure 

 and central eruptions, the first connected with plateau-building, 

 the latter with mountain formation. Fissure eruptions are 

 normally quiet and non-explosive , while the central type gives 

 rise to active volcanoes. 



The author then takes up the subject of intrusions and these 

 again he divides into two groups, as previously described for 

 extrusions. Laccoliths and sills are normal intrusions in plateau 

 districts, while stocks, batholiths, sheets and dikes are char- 

 acteristic for folded mountain regions. Curved lenticles of 

 igneous rock occurring in folded beds are termed phacolites. 

 After this the subject of petrographical provinces is discussed 

 followed by the mutual relations of associated igneous rocks. 

 Under this Barker states that in volcanic extrusions the law 

 holds that succeeding eruptions are successively more diverse, 

 more acid or more basic, than the initial type, while in the major 

 intrusions the rule is that the most basic type is intruded first 

 and successive ones are more and more acid ; in the phase of 

 minor intrusions the reverse is true, the most acid types are the 

 older, the basic ones, such a*s the lamprophyres, the younger. 

 Here also the question of increasing divergence arises to pro- 

 duce complexity and serial relationships. In following chapters 

 the writer discusses the chemical composition of magmas, the 

 physical properties of the rock-forming minerals, and the various 

 problems of crystallization which arise from considering the 

 solidification of magmas. These subjects, which are of the 

 greatest interest to penologists, occupy a considerable portion of 

 the volume and are treated in accordance with the most recent 

 views in physical chemistry. In this phase of the general sub- 

 ject the author mainly follows the ideas of Vogt. Successive 

 chapters on the structure of igneous rocks, on mineralizers and 

 pneumatolysis, and on magmatic differentiation, indicate also the 

 scope of the volume, which closes with an essay on classification. 

 The American quantitative classification the author views with 

 disfavor as being too artificial. He believes that the classifica- 

 tion should be a natural one based on the relationships of rocks; 

 he does not show how this is to be given practical form, but 

 leaves this for'the future to determine and states certain princi- 

 ples which should govern attempts to formulate a classification. 



The work as a whole is an interesting and important contri- 

 bution in the field of petrology; it contains new ideas and is 

 stimulating and should find a place in the working library of 

 every teacher and worker in this field of science. l. v. p. 



14. Journeys through Korea ; by B. Koto. Journal Coll. Sci. 

 Imp. Univ. Tokyo, Japan, Vol. XXVI, Art. 2, 1909, pp. 1-207, 

 36 pis. — This work is the author's second contribution to the 



