abstracts: geology 449 



flicker photometer, shows that their mean characteristic is very approxi- 

 mately the same as that of the average of the 114. 



Furthermore, the flicker values found in this intercomparison and 

 also by Crittenden and Richtmyer for the tungsten lamps at 1.5 wpc 

 are in agreement with the Bureau's values. Hence it is concluded 

 that the values which were originally assigned to the new 1.5 wpc 

 tungsten standards as a result of the intercomparison with the National 

 Physical Laboratory can be considered as average eye values. 



G. W. M. 



GEOLOGY. — Economic geology of the North Laramie Mountains, 



Converse and Albany Counties, Wyoming. Arthur C. Spencer. 



U. S. Geological Survey Bulletin No. 626, pp. 46-81, with 2 



plates and 4 figures. 



This report includes a description of the broader geological features 



of the North Laramie Mountains and detailed notes on localities where 



prospecting work has been done in the search for copper ores. A colored 



geologic map of the general region, contributed by N. H. Darton, shows 



a central belt of pre-Cambrian rocks, flanked by areas of stratified 



rocks ranging in age from Carboniferous to late Cretaceous. With 



one exception the metalliferous deposits examined occur in the old 



crystalline rocks, which comprise granite, serpentine, and schists of 



various kinds. 



In general the copper deposits of the region are not promising, though 

 it is possible that in a few places small deposits will be profitably worked. 

 Deposits of chromite and of asbestos occmring in the western part of 

 the region appear not to be of economic impc rtance. 



A. C. S. 



GEOLOGY. — Geology and underground water of Luna County, New 

 Mexico. N. H. Darton. U. S. Geological Survey Bulletin No. 618. 

 Pp. 188, colored map, 12 other plates, 15 text figures. 1916. 

 A large part of Luna County consists of a desert plain underlain by 

 sand, gravel, and clay of Quaternary age. Rising from this plain are 

 narrow rocky ridges which contain a thick succession of sedimentary and 

 igneous formations resting on pre-Cambrian granite, the whole consider- 

 ably flexed and faulted. The sedimentary rocks include formations of 

 Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Triassic (?), 

 Cretaceous, and Tertiary age but only a portion of each period is repre- 

 sented. Most of the formations present features similar to those in 



