620 PROCEEDINGS OF WASHINGTON MEETING. 



51. Old quarry north of the Penrhyn slate company's quarries, Middle Granville, 



Washington county, New York. Illustration of the dip of the slate. Size, 

 6x8 inches. Photographed by C. D. Walcott, 1890. 



52. Same as 50; the light-colored stratum is a brecciated limestone conglomerate in 



a massive layer coincident with the cleavage of the roofing slate. Northern and 

 eastern sides of quarry. 



53. Same as 52. 



54. Spherical sundering in cliff of basalt, northern Table mountain, Golden, Colorado. 



The most distinct spheres are from one to two feet in diameter, with several 

 concentric shells. Size, 8 x 10 inches. Photographed by C. Whitman Cross, 

 1883. 



55. Decomposed trap rock in Newark system at Wadesborough, North Carolina. 



Size, 8 X 10 inches. Photographed by I. C. Russell. 



56. Typical field of gabbro bowlders in northern Delaware and southeastern Pennsyl- 



vania, 3 miles west of Claymont, Delaware. Size, 6x8 inches. By W J 

 McGee, 1888. 



57. Cherty layers interbedded in Sillery shales, 8 miles below Quebec, Canada, on the 



southern side of St. Lawrence river. Size, 6x8 inches. Photographed bv C. 

 D. Walcott, 1889. 



EROSION and deposition. 

 Caflons of the Colorado, Yellowstone, etc. 



58. Grand cafion of the Colorado at the foot of the Toroweap, in Arizona. The outer 



canon, of which only the northern wall in seen, is here 5 miles wide and 2,000 feet 

 deep. The inner gorge cut in the floor of the outer one is 3,000 feet deep and 

 from 3,500 to 4,000 feet wide from crest to crest. Size, 10 x 13 inches. Photo- 

 graphed by J. K. Hillers, 1882. Published in Tertiary History of the Grand 

 Caiion District by Captain C. E. Dutton, p. 86. 



59. Shinimo altar from the brink of Marble canon of the Colorado river, Arizona. 



Size, 10 X 13 inches. Photographed by J. K. Hillers, 1882. 



60. Upper falls and Upper canon of the Yellowstone, Yellowstone National Park. 

 ^ Size, 10 X 13 inches. Photographed by W. H. Jackson. 



61. Grand caiion of the Yellowstone, Yellowstone National Park. Size, 10 x 13 



inches. Photographed by W. H. Jackson. 



62. Canon de Chelly, Arizona. Size, 10x13 inches. Photographed by J. K. Hil- 



lers, 1885. 



63. Oak caiion, Arizona. Bedding and cross-bedding. Ruins of cliff dwellings on 



the left.' Size, 10 x 13 inches. Photographed by J. K. Hillers, 1885. 



64. Lava-capped river bed of the ancient Sacramento, near Delta, California. The 



embankment midway between the river below and its ancient bed beneath the 

 lava above is occupied by a railroad. The lava stream is from Mount Shasta 

 and it follows the caiion of the Sacramento for nearly 50 miles. Size, 8 x 10 

 inches. Photographed by J. S. Diller, 1888. 



65. Navajo church, near Fort Wingate, New Mexico. Prominent columns of erosion, 



cross-bedding. Size, 10 x 13 inches. Photographed by J. K. Hillers, 1885. 



Gorges of the Potoynac and Susquehanna. (Photographed under the direction of W J 

 McGee, 1889. Size, 6x8 inches.) 



66. Junction of the Shenandoah and Potomac. Photographed by E. P. Hough. 



67. The Shenandoah near Harper's ferry. Photographed by E, P. Hough. 



68. The Potomac near Harper's ferry. Photographed by E. P. Hough. 



69. The Great falls of the Potomac. Photographed by E. P. Hough, 1888. 



70. The gorge of the lower Susquehanna. Published in Seventh Ann. Rept. U. S. 



Geol. Survey, pi. LVI, 1888. Size, 10x13 inches. Photographed bv C. C. 

 Jones, 1886. 



