138 PROCEEDINGS OF THE ACADEMY OP [1883. 



found in it, and I enumerate several additional ones in the present 

 article. 



Tlie Mud Lakes in tlie neighborhood south of Fort Bidwell lie 

 in a monoclinal valley of moderately inclined beds of a plutonic 

 outflow. The strata dip towards the Sierra Nevadas, westwards. 

 A high divide on the north separates these lake basins from that 

 of the Warner Lakes. As already remarked, it is possible that 

 they may have been connected by water, which occupied lower 

 lands to the eastward, but this point remains as yet unsolved. 



The four Warner Lakes occup^'^ a long valley, which trends 

 north and south. They are connected by a stream which flows 

 through a succession of swamps of Typha latifoUa. They abound 

 in fishes and fishing-birds. The valley is apparently a fractured 

 anticlinal, the strata dipping away from the lake on both the east 

 and the west sides. The rocks are a dark-colored basalt. At the 

 first and second lakes the western bluff is the higher, reaching, to 

 judge by the eye, nearly a thousand feet elevation at the lower 

 part of the third lake. At the northern part of the latter, at 

 Wilson's Ranch, the eastern bluff is the higher, reaching the 

 grand proportions of two thousand feet, estimated measurement. 



Summer Lake is eighteen miles long and six or seven miles 

 wide. The hills and bluffs of the western side probably reach a 

 thousand feet in elevation. Those of the eastern side are much 

 less elevated, and are separated from the water by a wide slope 

 of sand and alkaline earth and mud. The western range is 

 basaltic. At one point where the escarpment is especiall^^ steep, 

 the brown basalt is overlaid by a deposit of white pumice or 

 siliceous dust, which is worn into a picturesque sculpture by the 

 weather. 



I did not get a near view of Abert Lake, but it lies between 

 high basaltic bluffs, of which the eastern is the more elevated, 

 rising to a great height above the water. It is supplied with water 

 by the Chewaucan River, which is a large creek with a fine flow of 

 pure water. It abounds in fishes, especially the trout, Salmo 

 purpuratus. 



Silver Lake also lies in a valley with eastern and western walls 

 of basalt. The sti-ata of which the walls are composed, dip away 

 from each other here, as at Warner's Lake, producing the impres- 

 sion that the lake occupies a fracture in an anticlinal. A range of 

 hills, terminating at its eastern extremitj^ in a bluff, extends along 



