56 GEOLOGICAL QISTORY OF LAKE LAHONTAN. 



90 square miles. In the summers of 1859 and 18G3 it is reported by the 

 settlers in tlie valley to have become completely desiccated, leaving a broad 

 smooth jilain of cream-colored mud. Its average depth in the summer of 

 1877 is reported by Lieutenant Symonds''* to have been about 18 inches. 

 In 1882 its greatest dei)th was 4 feet, but the average, as nearly as could be 

 judged, did not differ much from the figures given for 1877. The outline 

 of the lake is indefinite, as its shores are usually low and marshy, and in 

 places form broad tule swamps. Its waters are quite strongly alkaline, 

 unfit for human use, and always of a greenish-yellow color, due to the im- 

 palpable mud held in suspension. A preliminary examination of tiie water 

 shows that it contains 0.0784 per cent, of saline matter in solution. Quali- 

 tative tests show tlie water to be alkaline and charged with chloride of 

 sodium, and carbonate and sulphate of soda, together with some potash 

 and magnesia. 



PYKAMID liAKE. 



Pyramid Lake was discovered January 10, 1844, by General Fr(^mont, 

 who first saw it from the mountains at its northern end. From the remark- 

 able form of an island near its eastern shore its discoverer gave it the name 

 which it now bears.^^ 



The accompanying map of Pyramid and Winnemucca lakes (Plate IX) 

 was made in August and September, 1882, by Mr. Johnson, and shows an 

 accurate outline of the lakes as they existed at that time. The soundings 

 indicated are from actual observation, the position of the boat at the time 

 of measuring the depth being determined with instruments stationed on 

 shore. The sublacustrine contour lines, drawn at intervals of 50 feet, are 

 in part conjectural, but are believed to represent approximately the topog- 

 raphy of the lake bottom. The north and south axis of Pyramid Lake is 

 30 miles in length ; in the widest part, near the northern end, its breadth is 

 12 miles; farther southward between Anaho Island and the southern end of 

 the lake it is conti'acted to about 5 miles. Its area in September, 1882, was 

 828 square miles. Our soundings determined that the greatest depth occurs 



«Aiiii. Rep. U. S. Geographical Surveys West of the 100th Meridian for 1878, p. 115. 

 ■^i^ Fremont's First ami Secouil Expeditions, 184-J-M;)-'44, y.. 216. 



