Geology and Mineralogy. 427 



The above classification will serve to show the point of view 

 adopted by the author, which he has systematically followed 

 throughout the development of the different parts of the subject. 

 There is thus a unity of general treatment which adds much to 

 the value of the work. The book is also consistent in minor 

 points, as in the use of the units adopted, in employing diagram- 

 matic illustrations instead of pictorial representations of elaborate 

 apparatus and in other respects. It is compactly printed, so that 

 the large amount of matter included is embraced in 900 pages ; 

 the reader could wish, however, that a little less compression had 

 been used by the printer at some points, for the printing of analyt- 

 ical expressions in the body of the text detracts much from their 

 clearness, especially as first presented to the mind of the student. 



The ultimate test of the adaptability of a text book to the pur- 

 poses of general instruction must always.be its actual use in the 

 class-room, and it is to be hoped that this new Physics may here 

 meet with the success which the author's careful labor makes it 

 merit. 



II. Geology and Mineralogy. 



1. Geological Survey of Texas, 3d Annual Report for 1891, 

 E. T. Dumble State Geologist. 410 pp. 8vo, with maps and 

 plates. — This volume, after the general Report of the State Geol- 

 ogist, contains papers on Houston Co., and on a section from 

 Terrell to Sabine Pass, by W. Kennedy ; on the Llano Estacado 

 with a geological map and notes on the geology of the country 

 west of the Plain, by W. F. Cttmmings ; on the Triassic in north- 

 western Texas, by N. L. Drake ; on shells of a northern chai*- 

 acter in a dry salt lake near Eddy, New Mexico, by V. Steeki ; 

 on the Cretaceous of Texas, north of the Colorado River, by J. 

 A. Taff ; on Trans-Pecos Texas, by W. H. Von Steeruwitz. 

 On the map of the Llano Estacado the general surface is made 

 Tertiary, on the basis of the fossil Vertebrates found in surface 

 deposits. In the southern part of the Plain there are Cretaceous 

 beds, and beneath these and along a large part of its border, 

 Triassic beds, as described by Mr. Drake. The Vertebrate 

 fossils of the Llano Estacado, here described by Prof. Cope (and 

 also in the Proceedings of the Amer. Phil. Soc. 1892, p. 128), 

 occur in Crosby County, in a White diatomaceous deposit, the 

 so-called Blanco beds. They are species of Equus, Mastodon, 

 Creccoides (a new genus of birds), and Testudo : Equus simpli- 

 cidens Cope, Mastodon angustidens (or a related species), Crec- 

 coides Osborni Cope, and Testudo turgida Cope. The Blanco 

 beds are regarded as older than the Equus beds and newer than 

 the Loup Fork, the latter containing Mastodon angustidens but 

 no species of Equus. The specimens described for the Survey by 

 Professor Cope were collected by Mr. Cummins. 



2. Geological Survey of Alabama, by E. A. Smith, State 

 Geologist. Bulletin No. 3, On the lower gold belt of Alabama 



