REPORT OF COMMITTEP: ON PHOTOGKAPHS. 627 



212. Lateral view of sandstone dike, Dry creek, Tehama county, California, p. 414. 



213. Sandstone dike penetrating Cretaceous sandstones and shales, Dry creek, Tehama 



county, California, The dike is 10 inches thick below. 



214. Four small sandstone dikes penetrating Cretaceous shales on Dry creek, Tehama 



county, California. The dikes are each about 4 inches thick. Some are regular 

 and others very irregular. 



VOLCANIC PHENOMENA. 



Scene of a late Volcanic Eruption in Northern Calif 07mia. (Photographed by J. S. 

 Diller, 1888 and 1890. Size, 8*x 10 inches.) 



Nos. 215-22G, published in Bulletin 79, U. S. Geol. Survey, with the designations 

 given below. 



215. Model of cinder cone, lava field and ash-covered slopes. The cinder cone is 040 



feet high, the crater is 240 feet deep, and the lava field is about 3 miles long. 

 Snag lake, at the left end of the lava field, was formed by the lava dam. Fig. 1. 



216. Lava field and cinder cone looking southwest across Lake Bidwell, Lassen peak 



in the distance. PI. II. 



217. The cinder cone from the south , earlier lava partly covered by volcanic sand. 



The dead trees extend down 7 feet through the volcanic sand to the original 

 soil beneath. PI. III. 



218. The cinder from the east. Earlier lava near the cone is covered by volcanic 



sand; later lava in the foreground uncovered. PL IX. 



219. Volcanic bombs at the base of cinder cone ; the largest is 8 feet in diameter. PI. 



IV. 



220. The lava field looking southeast from the base of the cinder cone towards Snag 



lake. PI. VIII. 



221. Surface of lava field; breaking of the lava crust. Photographed by W. B. 



Smith. PI. VII. 



222. The tree projecting from beneath the lava was pushed over by the advancing 



lava. The dead tree on the left extends 10 feet down through the coating of 

 volcanic sand to the original soil beneath. The living trees, some of which are 

 about 200 years old, have grown up entirely since the eruption. PL XIV. 



223. Lava dam which formed Snag lake at the time of the eruption and drowned the 



trees whose stumps are seen in the lake. PL XIII. 



224. Snag lake, with lava dam in the distance and the stumps of drowned trees in the 



foreground. PL XII. 



225. Lava front at the corner of Snag lake. PL VI. 



226. Near view of lava blocks on edge of lava field. The lava is basalt, which is re- 



markable in containing numerous phenocrysts of quartz, which are uniformly 

 distributed throughout the mass. The white spots seen in the lava are quartz. 

 PL XVI. 

 227.. Hand specimen of quartz basalt from lava field near Snag lake. The white spots 

 are quartz. 



Laccolitic Domes and Plugs of the Black Hills. (Photographed by I. C. Kussell, 1888. 



Size, 6x8 inches.) 



228. Little Sun Dance hill, South Dakota. A dome of Carboniferous limestone, with 



Jurassic and Triassic rocks on the outer bench. The upheaval is due to vol- 

 canic rocks injected far beneath. 



229. Little Sun Dance hill, from the top of Sun Dance hill, South Dakota. 



230. Little Sun Dance hill. South Dakota. Near view. 



231. Sun Dance hill. South Dakota. The volcanic rock injected from beneath ex- 



posed by erosion. 



