I.-CAAIATAS 
Geology of the Yellowstone National Park. Part II]. Descriptive 
Geology, Petrography, and Paleontology. By ARNOLD HaGugE, 
(cee lip pinesy Welty WV BED. C.D. Warcorn Gal Girny, 
T. W. Stanton, and F. H. Know.ton. Washington: Gov- 
ernment) Printing Office, 1899. Pp. xvili-=- 893, 121 plates 
and 4 figures. Monograph XXXII of the United States 
Geological Survey. 
This compendious monograph is about equally divided between pet- 
rography and paleontology, having about 440 pages of text in each 
division, and of the 121 plates 62 are given to fossils, and 59 and the 
four figures to petrography and geology. Of the fourteen chapters 
Iddings furnished seven* on the petrography, Iddings and Weed 
two on the geology, Weed and Hague each one on the geology. 
Walcott’s work on the Cambrian fossils and Girty’s on the Devonian and 
Carboniferous go into onechapter. Stanton furnishes one on the Meso- 
zoic fossils and Knowlton one on paleobotany. 
The first chapter, by Iddings and Weed, is on the descriptive geol- 
ogy of the Gallatin Mountains, which mountains extend eighteen miles 
within the boundary of the park. The diversity of the geological fea- 
tures in this area is remarkable. The sedimentary rocks begin with the 
Cambrian and range through the Silurian, Devonian, Carboniferous, 
and Juratrias into the Laramie division of the Upper Cretaceous. Cut- 
ting through the sedimentary series are intrusions of igneous masses in 
the form of laccoliths, sheets, and dikes. The sedimentary rocks are 
slightly folded and strongly faulted. Extensive erosion has exposed 
large areas of the rocks in their structural relations. To still add to 
the diversity, the surface has been glaciated. 
The second chapter describes the intrusive rocks of the Gallatin 
Mountains. These consist mainly of fine-grained, aphanitic masses, 
mostly porphyritic and andesitic in character. The Indian Creek lac- 
colith is hornblende-mica-andesite-porphyry. The Bighorn Pass sheet 
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