TEREAOES A^'D SEA-CLIFFS. 101 



The highest of these numerous shore lines we have named tlie "Lahon- 

 tan Beach," as it records the highest water stage of the former lake. Its 

 elevation above the sea, as shown by lines of level connecting with the Cen- 

 tral Pacific Railroad survej^s, is 4,343 feet at Mill City, and from 4,418 to 

 4,427 feet at the lower end of Humboldt Lake.*" Barometric measurements 

 of the altitude of Pyramid Lake, for which I am indebted to Messrs. J. S. 

 Diller and M. B. Kerr," determine its 1882 level to have been 3,783 feet above 

 the sea. The Lahontan beach in the vicinity of the lake, as measured by 

 several lines of leveling, is 630 feet above its 1882 level, and therefore 4,313 

 feet above the sea. The altitude of the surface of the former lake, as deter- 

 mined by Clarence Kuig, was 4,388 feet.^^ These results, together with 

 many measurements with the aneroid barometer and by angulation, show 

 that the old shore lines are not now horizontal, owing to the orographic 

 movement that has taken place since their formation, as will be described in 

 Chapter X. What their original horizon may have been is not now suscept- 

 ible of accurate determination. An average of the various measurements 

 that have been made of the present elevation of the Lahontan beach gives 

 4,378 feet, which is the nearest approximation we can make to its original 

 altitude. 



Besides the Lahontan beach there are three other water-lines of suffi- 

 cient importance in the history of the lake to deserve special designation. 

 One of these is a strongly defined terrace, 30 feet below the Lahontan beach, 

 and at the upper limit of a calcareous deposit, precipitated from the waters 

 of the ancient lake, which we have named " Lithoid Tufa"; we therefore 

 call this the "Lithoid Terrace." Its elevation is 500 feet above the 1882 

 level of Pyramid Lake. 



Another chemical deposit, known as " Dendritic Tufa," occurs in great 

 quantities in the same basin, and at its upper limit is bounded by a water- 

 line, usually but poorly defined, which we name the " Dendritic Teirace." 

 Its elevation is 320 feet above the datum plain just mentioned. 



•loSee prolile iu Plate XVIII. 



*'Its elevation was deteiniiui d Iiy haiometric readings at Reno and at the lake surface in June, 

 1884, and gave a dift'erence of level of 715.5 feet. The elevation of Keno, as determined by the Cen- 

 tral Pacific Railroad snrveys, is 4,497 feet. 



«U. S. Geological Exploration of the Fortieth Parallel, Vol. I, p. 507. 



