60 GEOLOGICAL HISTORY OF LAKE LAHONTAN. 



although without fresh water, and but scantily clothed with vegetation, is 

 one of the most instructive points about Pyramid Lake, and will well repay 

 a visit from the geologist or the artist. During the time that Lake Lahontan 

 had its greatest extent, Anaho Lshmd rose but a few feet above its surface. 



Pyramid Island, as determined by sights with an engineer's level from 

 Anaho Island, rises 289 feet above the lake ; the water near its base is from 

 150 to 175 feet deep As remarked by Fremont, its regular pyramidal form 

 and precipitous sides give it a striking resemblance to the great pyramids 

 of Egypt Its sides are somewhat convex owing to the immense accumu- 

 lation of tufa deposited upon them, and are difficult to scale. On the ac- 

 companying plate this island is represented as it appears from the neighbor- 

 ing shore 



The most picturesque portion of the shores of Pyramid Lake is at the 

 northern end, where a rugged cape, known as "The Needles," projects a mile 

 or more from the main land, and has near it many small islands of peculiar 

 and sometimes fantastic form. This group of spires, domes, and crags ex- 

 hibits rock forms of the most rugged description, and furnishes the grandest 

 display of tufa in all their varieties that is to be found in the Lahontan basin. 

 A general view of this picturesque point is given on the accompanying 

 plate, which is sketched from a photograph taken on the lake shore to the 

 westward of The Needles. The highest of the spire-like masses, rising 300 

 feet above the lake, is shown somewhat in detail in the illustration forming 

 Plate XIII. A photograph of one of the islands near The Needles, taken 

 from the peninsula, is given on Plate XXXVIII. Plate XXXIX also illus- 

 trates the remarkable towers and domes that the tufa deposits here simulate. 



On the northern side of the peninsula a numbei" of hot springs rise 

 from the bottom of the lake and along the base of the tufa crags, and are 

 forming a deposit of calcareous tufa beneath the lake surface. This accumu- 

 lation is soft and creamy white, and forms a more or less regular layer over 

 considerable areas. The hot water of the submerged springs rises from 

 many orifices, a number of which have built up tubular chimney-like 

 growths 5 or G inches high that sometimes look not unlike mushrooms, 

 but always liave one or more openings at the top, through wliicli the spring- 

 water issues The carbonate of lime is deposited when the hot spring-water 



