200 REVIEWS 



conglomerate, sandstone, shales, and "marls") and "Leroux formation" 

 (shales, with some sandstone and calcareous beds); and Quaternary 

 moraines and alluvium. The thickness of this generalized section is 

 about 2,500 feet. An unconformity occurs between the Kaibab and the 

 Moencopic, between the latter and the " Lithodendron formation," and 

 between the Triassic and later rocks. The Moencopic formation is a 

 fluviatile or shallow-water deposit; the Triassic beds are continental 

 deposits. The major structural feature of the region is a very flat anti- 

 cline which trends N. 30 W. 



Chap, iii gives detailed descriptions of the volcanoes and lava fields. 

 Three general periods of volcanic activity are recognized: (1) widespread 

 basaltic eruptions from small cones, (2) eruptions of lavas (andesites to 

 rhyolites) to form a few large cones, and laccolithic intrusions, (3) extru- 

 sion of basalt (less widespread but more cones built up than in the first 

 named) . San Francisco Mountain, which is the principal feature of the 

 area, is composed of "lavas and breccias belonging to five distinct stages 

 of eruption." 



"The Geologic History of the Volcanic Field and Adjacent Country" 

 is given in chap. iv. The volcanic activity of the first period occurred 

 in the late Pliocene after the peneplanation of the region, that of the 

 second period took place in the early Quaternary during or after the 

 mature dissection of the area, and that of the third period during the latter 

 part of the Quaternary subsequent to broad regional uplift. There 

 was folding and flexing during the latter half or at the close of the Eocene. 

 Faulting occurred at the close of the Miocene, at the close of the Pliocene, 

 and during the middle or latter part of the Quaternary. 



The last two chapters, v and vi, are devoted respectively to pe- 

 trography and petrology. 



V. O. T. 



Transactions of the American Institute of Mining Engineers. Vol. L. 

 New York, 1915. Pp.1008. 

 Material for this volume was presented at the Pittsburgh meeting 

 in October, 19 14. Three topics include the major portion of the volume: 

 (1) iron, geology, and metallurgy; (2) coal and coke with by-products; 

 and (3) petroleum. The volume contains less purely geological matter 

 than either of the preceding volumes for the year. Fifty-two papers 

 and discussions, many of which are illustrated, are included. 



A. D. B. 



