472 Scientific Intelligence. 



Regarding the origin of the diamonds in these volcanic necks, 

 the author is not inclined to agree with those who place great 

 stress on the presence of enormous temperatures and pressures as 

 necessary conditions, basing their views on the artificial forma- 

 tion of the mineral in contracting cast iron by Moissan and others. 

 He adverts to Friedlander's experiments by which diamonds 

 were formed by stirring molten olivine with graphite rods, and 

 also to the fact that diamonds have been found in the mines in 

 olivine and in garnet, both of which are original minerals in the 

 kimberlite. From this he concludes that if the deep-seated ferro- 

 magnesian magma contained carbon or carbon-bearing gases, its 

 crystallization into the minerals mentioned above would natu- 

 rally give rise to the formation of diamonds. l. v. p. 



10. Pedogenesis ; by C. Doelter. Pp. 256, 8vo. Braun- 

 schweig, 1906 (Vieweg &Sohn). — The author, who is well known, 

 not only through his researches during the past in different fields 

 of petrographic study, but latterly, especially by his experiments 

 and those of his students in the artificial production of rocks and 

 minerals, gives in this volume a general introduction to the forma- 

 tion of rocks, not only igneous rocks but crystalline schists and 

 sediments as well. 



The subject is treated both from the point of view obtained by 

 geological observation and petrographic study, and also from the 

 results recently gained by researches along the lines of physical 

 chemistry. The work of different authorities and the views 

 expressed by them upon a great variety of subjects, such as the 

 differentiation of igneous rocks, are competently treated and 

 often subjected to a temperate criticism which the author's learn- 

 ing and experience render just and valuable. As an introduction 

 into the field of theoretic petrology the work will be of great 

 service to geologists, mineralogists and chemists. It includes 

 separate chapters upon the earth's interior and volcanic processes; 

 upon the mode of occurrence of the igneous rocks in which the 

 influences of pressure, of viscosity, of the role of mineralizing 

 vapors, etc., are treated ; upon the structure of igneous rocks ; 

 upon the differentiation of igneous magmas ; upon the order of 

 succession of magmas, etc., etc. 



It is clear that a work of this character which contains so many 

 theoretical views, often the personal ones of the author; invites 

 much discussion and criticism and in this way will be a benefit to 

 the science of petrology. Such discussion here would transcend 

 the proper limits of this notice, but we think, for example, that 

 the criticism of Professor Doelter of analytical methods used in 

 rock analysis (p. 65) is given a somewhat sharper form than it 

 justly deserves, and would tend, with those unfamiliar with such 

 processes, to give a wrong impression. The methods of analysis 

 to-day, which in the case of minerals such as tourmalines and 

 hornblendes yield ratios of exceeding sharpness, naturally will 

 give equal results in the case of rocks, which are only mixtures of 

 the same oxides in somewhat different proportions, provided the 



