440 abstracts: geology and botany 



the granodiorite and in fissures. The contact metamorphic deposits 

 contain axinite indicating deposition under pneumatolitic conditions. 

 The fissure deposits are associated with the dikes and with contempo- 

 raneous or later quartz veins. They occur principally in the granodi- 

 orite. 



The post-Miocene deposits are argentiferous gold ores. They occur 

 in quartz-adularia veins in the older rhyolite of the Jarbidge district. 

 The fissures are comprised mostly in two main systems which converge 

 downward. The present gangue minerals were deposited by ascending 

 thermal solutions that dissolved and replaced an older calcite gangue. 



F. C. S. 



GEOLOGY. — Geology and mineral resources of the Peoria quadrangle. 

 J. A. Udden. Bulletin, U. S. Geological Survey No. 506. Pp. 103, 

 with maps, sections and views. 



The Peoria 30 minute quadrangle, in north-central Illinois, is located 

 along the Illinois River and on the northwestward rise of the eastern 

 interior coalfield, tho it is far within the border of the latter. The 

 stratigraphy and economic geology are accordingly largely concerned 

 with the Pennsylvanian coal measures and coals, the latter of Allegheny 

 age being easy of access. Special attention is given to the overthrusts 

 and faults exposed in the mines of the region and to the origin of the 

 "white top" while some places overlies coal No. 6. The thrusts of the 

 softer beds of the "coal measures" which are not very deeply buried, 

 are attributed by Udden to the pressure and motion of a continental ice 

 sheet in Pleistocene time. Considerable very interesting evidence is 

 adduced in support of this view. The "white top," a mixture of shale, 

 sand and limestone in a chalk-like groundmass, is conclusively explained 

 as residual and inwashed material occupying solution channels cut in 

 the base of the limestone which overlies the coal. 



Other notable features of the bulletin are the discussion of the pre- 

 Quaternary topography and the interpretation of the deep well records. 



David White. 



BOTANY. — The grasses and grass-like plants of New Mexico. E. 0. 

 Wooton and Paul C. Standley. New Mexico Agricultural Exper- 

 iment Station Bulletin, 81: 1-175, with numerous illustrations. 

 1912. 

 The introduction contains a discussion of life zones and grass societies 



in New Mexico, with maps illustrating each. Five grass societies are 



