LAKES OF THE LAHONTAN BASIN. 59 



ally composed of sand or gravel in which the shells of fresh water gastero- 

 pods were frequently obtained. At a distance of a few rods from land the 

 bottom invariabl}' became muddv, excepting in sheltered bays, where the 

 littoral deposits had a greater breadth than when the lake margin was pre- 

 cipitous. In all the central portions of the lake the bottom is of fine tena- 

 cious mud, either gray in color or intensely black, and having the odor of 

 sulphuretted hydrogen The samples of black mud when dried in the open 

 air lost their inkiness as well as their odoi', and became identical with the 

 gray mud occurring in other localities. 



In the southern portion of the lake the water is slightly discolored, and 

 is charged with a multitude of shining particles that are rendered visible 

 when a ray of light is passed through it. The lack of transparency is appar- 

 ently due to the suspended silt bj-ought down by the Truckee River. In the 

 northern part of the lake the water becomes wonderfully clear, and at some 

 distance from land of a deep blue color. On looking down into the waters 

 from the neighboring hills the color appears almost black, or black tinged 

 with deep blue. Neai- shore, especially where the bottom is of white sand, 

 the water presents a clear greenish-blue tint, as is the case on nearly all 

 lake shores where the bottom is light colored. When thrown into breakers 

 by strong winds it exhibits a play of colors that is only rivaled in beauty 

 by the surf of the ocean. 



The largest and most attractive islands in the lake are Pyramid and 

 Anaho, which rise in its southern portion near the eastern shore. Anaho 

 Island, as determined by engineer's level, is 517 feet above the water level 

 of 1882, and is surrounded by water from 150 to 300 feet deep. We pre- 

 sent an accurate map of it, prepared in August, 1882 (Plate II), from which 

 future changes in lake level may be determined. When seen from a dis- 

 tance the island presents a convex outline due to the deposition of vast 

 amounts of tufa at certain horizons. A broad terrace has been carved all 

 around it at an elevation of about 100 feet above the lake, and forms a ped- 

 iment for the extremely rugged crags that are piled upon it. The contour 

 formed by the water line of this terrace is indicated by the lower of the 

 three dotted lines on the map ; the next above marks the water level at the 

 dendritic stage ; and the highest of all is the Lahontan beach. This island, 



