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XXX. Notices respecting New Rooks. 



The Structure of a Portion of the Sierra Nevada of California. By 

 George F. Becker. Bullet. Greol. Soc. of America, vol. ii. 1891. 

 X^ROM the South Fork of the Stauilaus Eiver to the True-knee, a 

 -*- distance of about eighty miles, and for some thirty miles to the 

 west of the eastern scarp of the range, Dr. Becker found the rocks 

 to be chiefly granite and diorite overlain in part by andesite and 

 basalt ; and the area to have been glaciated up to the summits of 

 the passes. The rocks are intersected by extremely numerous 

 fissures, — vertical, diagonal, and horizontal; the last giving a 

 terraced aspect to the granite, and the two former rendering it 

 columnar. The fissures are more or less susceptible of being 

 grouped as systems ; and are found to be true fault-planes, with 

 dislocations, slickensides, and slaty shearing. These multitudinous 

 faultings are referred to a late Tertiary period, in part contem- 

 porary with the andesitic eruptions. 



An inductive examination of dislocating forces treats of the 

 physical characters of these faults and fissures in detail, both as to 

 horizontal and vertical movements. The author shows " that the 

 existence of the vertical fissure systems attended by evidences 

 of compression leads inevitably to the theory of a horizontal 

 thrust, which is further confirmed by the occurrence of relatively 

 rare fissures dipping at angles of 45°." So also as to " the fissure 

 systems formed by the vertical thrust, . . . the horizontal partings 

 could be produced without raising the sheets of granite, while the 

 vertical Assuring and faulting by the vertical thrust component 

 involved either the raising of a sheet against gravity, or a downward 

 movement into the underlying mass. When the vertical fissures 

 and the horizontal fissures were once formed, the stress still present 

 would be relieved rather by relative motion on these fissures than 

 by the establishment of new ones." 



The hypothesis of the tilting of the range, to account for the 

 deep erosion of the river-beds, is not supported by Dr. Becker's 

 observations. He considers that the fissure-systems broke up the 

 area in such a manner that glaciers, which are really unequal to 

 the excavation of valleys themselves, cleared away the movable 

 debris from the surface, giving the country its peculiar physical 

 features of canons, out of shattered zones, and domes from isolated 

 prismatic masses of rock. 



Antiquities from under Tuolumne Table Mountain in California. 



By George P. Becker. Bullet. G-eol. Soc. of America, vol. ii. 



1891. 

 The occurrence of human bones and of grinding implements in the 

 auriferous gravel under the lava at the foot of Table Mountain in 

 California has been doubted, but Dr. Becker supports Prof. Whit- 

 ney's announcement of these discoveries by further and independent 

 evidence of the facts. Plant-remains, like those of Tertiary age, 



