502 Scientific Intelligence. 



sents one of a large group of birds of prey which evidently came 

 to feast upon the unfortunate animals entrapped in the asphalt. 

 Teratornis, while showing a preponderance of characters which 

 would tend to link it with the vultures, is considered as represent- 

 ing a distinct family, the Teratornithidse. r. s. l. 



12. Igneous Mocks. Vol. I, Composition, Texture and Classi- 

 fication ; by Joseph P. Iddings. Pp. 464, 8vo, 22 cuts and 

 tigs, and 2 pis. New York, 1909 (Wiley & Sons). — It is promised 

 that a second volume will be devoted to the description and 

 occurrence of igneous rocks, tbis first one being confined to 

 what may be called the theoretical aspect of the subject. In 

 accordance with this the first chapter deals with the chemical 

 composition of igneous rocks, or magmas, and the various means 

 which have been used for diagrammatically representing chem- 

 ical relations among rock-groups, and of graphically picturing 

 rock analyses. This is followed by one in which the chemical 

 composition of the pyrogenetic minerals is treated. The third 

 chapter is especially timely and significant in that it presents in 

 clear, succinct form those principles of chemistry and physics 

 which are applicable to rock magmas and their solidification into 

 rocks. In this the latest views of physical chemistry which apply 

 to the subject are given, and many petrographers, students and 

 teachers alike, will find this one of the most useful and important 

 chapters in the volume. The more igneous rocks and the pyroge- 

 netic minerals are studied the more evident it becomes that rock 

 magmas are mixed solutions and that the general laws obtained 

 from recent studies in physical chemistry are applicable to them, 

 as well as to the solutions usually studied in the laboratory, 

 modified by the conditions of high temperature. The author 

 here gives full credit to the illuminating work now being carried 

 out in the Geophysical Laboratory of the Carnegie Institution. 

 This chapter is followed by one dealing with the chemical 

 reactions which take place in magmas; the chemical composition 

 of the important minerals and their formation and relation to 

 one another are considered. After this the separation of sub- 

 stances from solutions is discussed, and here the work of Vogt on 

 slags and of others in the field of physical chemistry are treated 

 in their relation to the problem in hand. Especially in its pre- 

 sentation of the r61e of eutectics will this chapter be found of 

 value. 



Following these matters of underlying and fundamental impor- 

 tance the actual crystallization and the texture of igneous rocks 

 are described. In respect to the latter feature the author uses and 

 amplifies the descriptive terms proposed not long since by himself 

 and several other American geologists in the Journal of Geology 

 (vol. xiv, p. 692, 1906). 



The seventh chapter deals with the differentiation of igneous 

 rocks and under this heading a variety of subjects, such as petro- 

 graphic provinces, pegmatites, facies of rocks, hybrid rocks, order 

 of eruption and complementary rocks, is treated. This is sue- 



