792 



SCIENCE. 



[N. S. Vol. II. No. 50. 



and a length of several miles, is of economic 

 importance for polishing, packing, making 

 explosives and other purposes. 



FOLIO 17, MARYSVILLE, CALIFORNIA, 1895. 



This folio consists of 2 pages of text de- 

 scriptive of the Marysville tract, signed by 

 Waldemar Lindgren and H. W. Turner, 

 geologists, and G. F. Becker, geologist in 

 charge; a topographic map (scale 1:125,000) 

 of the tract, a sheet showing the areal geol- 

 ogy, another showing the economic ge- 

 ology and a third exhibiting structure sec- 

 tions. 



The Marysville tract includes the ter- 

 ritory between the meridians 121° 30' and 

 122° and the parallels 39° and 39°30', 

 and contains 925 square miles. The tract 

 is located near the center of the Sacra- 

 mento Valley. The lai-ger part of it is oc- 

 cupied by the alluvial plains of the Sacra- 

 mento and Feather rivers. The extreme 

 northeastern corner includes the first rolling 

 foot hills of the Sierra Nevada. In the 

 center of the tract rises the isolated moun- 

 tain group of the Marysville Buttes. 



The alluvial lands consist of sands, 

 clays and gravels, deposited by the shift- 

 ing currents of the streams. The foot-hill 

 region of the northeastern corner is prin- 

 cipally occupied by the gravels of Pleis- 

 tocene and Neocene age. The area com- 

 posed of the bed-rock series of the Sierra 

 Nevada is small and consists of diabase and 

 porphyrite. The mountain group of the 

 Marysville Buttes is an extinct volcano of 

 probably late Neocene age, the internal 

 structure of which is to a certain extent laid 

 bare by erosion. The eruptive rocks of 

 the buttes are andesites and rhyolites. In 

 describing the structure of the group three 

 parts may be distinguished : First, the 

 central core of massive andesite and rhy- 

 olite ; second, the upturned sedimentary 

 rocks surrounding the massive core, evi- 

 dently brought into their present position 



by the force of the ascending lavas ; the 

 sediments are of Eocene and Neocene age ; 

 third, the external ring of tuffs and brec- 

 cias. The feature of greatest interest in 

 connection with the Marysville Buttes is 

 doubtless the presence of upturned sedi- 

 ments around the central core. 



The shore gravels in the northeastern 

 corner contain some gold and have been 

 washed superficially. Somewhat auriferous 

 gravels are also found in the upturned 

 sediments of the Marysville Buttes. Coal 

 and natural gas have been found in small 

 amounts in the Marysville Buttes. 



A GLACIER IN THE MONTANA ROCKIES. 



The section of the Rocky Mountains 

 lying between the Great Northern Railway 

 and the international boundary has thus 

 far been but little explored. Until the ad- 

 vent of the railway there was such diffi- 

 culty in reaching these mountains that only 

 an occasional prospector or trapper pene- 

 trated their fastness. As access has become 

 easier it has been gromnglj^ evident that it 

 is a region of remarkable scenic and geol- 

 ogical interest. Thus far it has been reached 

 largely from the eastern side, but this has 

 been troublesome from the fact that skirt- 

 ing the eastern slope of the mountains is 

 the great Blackfoot Indian reservation, over 

 which it is impossible to travel without 

 much annoyance. 



Several glaciers have been known to exist 

 in these mountains and two are located 

 upon the military maps of the department 

 of Dakota. The largest of these is known 

 as the Grinnell glacier from Mr. George 

 Bird Grinnell, who has made a number of 

 expeditions into the region and has done 

 more than anyone else to attract attention 

 to it. The Grinnell glacier is not easily 

 accessible and for some time efforts have 

 been made to discover others which could 

 be more easily reached by the ordinary 

 tourist. About a j^ear and a half ago Dr. 



