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70 



THE AUKIFEKOUS GKAVELS OF THE SIERRA NEVADA. 



origin, and evidently entertained views quite similar to those of Mr. W. P. 

 Blake, supposing the erosion of the gravel deposit*, which he calls " shingle 

 terraces/' to have taken place during the upheaval of the continent* 



In I860, M. Laur, Ingenieur an Corps Imperial des Mines, was sent by the 

 French government to California and Nevada, for the purpose of examining 

 and reporting on the gold and silver mining interest of those States. In the 

 course of his investigations, he spent two months among the hydraulic and 

 quartz mines of the Sierra Nevada, and published his account of them in 1862 

 in the form of a Report to the Minister of Public Works. M. Laur describes 

 the high gravel deposits under the designation of " auriferous alluvia posterior 

 in age to the basalt." He considered them to have once extended over the 

 whole western slope of the Sierra, and maintained that they were thrown 

 into confusion (bouleverses) by the phenomena attendant on the eruption of 

 the basalts.f The views of this mining engineer were extremely crude; he 

 seems to have entirely misapprehended the nature of the phenomena and to 

 have failed to notice some of the most striking facts connected with the 

 occurrence of the gravel deposits, — facts which, even at that early period, 



i 



had made a strong impression on the miners themselves. 



During the years previous to 1860 there seem to have been many articles 

 published in the Californian newspapers in regard to the real nature of the 

 high gravels. Few of these can now be obtained, and most of them have 

 never met the eye of the writer. Some extracts, however, are preserved in 

 Mr. J. S. Hittell's Mining in the Pacific States of North America. In an 



have respecting the age of the terrace-accumulations is very imperfect. There can be no doubt that those 

 occupying the valleys of the Rocky Mountains, being farthest from the coast and at the greatest elevation, 

 are the most ancient, and that from the time of their deposit till now the rearrangement of the same ma- 

 terials lias been carried on during the gradual uprising of the continent." — James Hector, M. D., in 

 Quarterly Journal of the Geological Society of Lond.on, Vol. XVII. 1861. pp. 404, 405. 



* "It must have been during the period when tin's denudation of the eastern plains accompanied the 

 gradual emergence of the continent, but acting with very different results on the rocky sea-bottom and 

 successive ranges of iron-bound coast presented by the western slope, that these immense deposits of 

 shingle were formed and moulded into terraces," — Hector, 1. c. p. 405. 



t " Les alluvions auril'eres de formation antericure au basalte constituent par leur etendue et leur epais- 



seur les mines d'or les plus importantes de California Cette formation s'etendit primitivement 



sitr tout le versant occidental de la Nevada ; elle fut ensuite bouleversee par des phenomenes de Pepoque 

 des basaltes. En certains points, les depots furent reconverts par des coulees basalti<|ues ou des conches 

 de tufs sous lesquelles lis sont aujourd'hui exploiter. Allien rs ils furent attaque's par de violentes erosions 



qui les nrent disparaitre sur tout oil partie de lenr epaisseur." — P. Laur, in De la Production ties Mclaux 



Precieux en California. Rapport a s. Exc. M. le Ministre des Travaux Publics. Paris, 1862, 



