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Show APPENDIX NN. 1287 SKETCH OV LAKE TAHOE. Lake Tahoe lies in the heart of the Sierra Nevada, at an elevation of 6,202 f » et above the sea- level. It is one of the largest fresh- water lakes in the West, and, unlike many other Bheers of water, contains no islands. Lake Tahoe is inclosed by twopaallel ranges of grayish granite, called respectively the Eastern and Western Summits. Lake Tahoe is 21 miles long and 12 miles in the widest part. The breadth, however, varies greatly, the southern portion being much narrower than the northern. The shoro- liue is very diversified. The numerous bays, rocky promontories, bold headlands, estuaries, and beaches, oftentimes- covered with pebbles, remind one of a miniature ocean. Hot springs are found on the north side of Lake Tahoe, near Campbell's hotel. They rise in granite. Standing on the dock in front of the hotel, the observer may see bubbles of gas in several places rising in the clear water of the lake. One spring is inclosed by a brick wall about 3 by 4 feet. The temperature of the water in this spring is 132° F. A bath- house has been built near the hotel directly over another spring, having a temperature of 128° F. The spring- water contains solphydric acid. Lake Tahoe is remarkable for its great depth. It is probably the deepest lake in the United States. There are only two lakes iu Europe that are deeper than Tahoe, viz : Lago Mrfggiore and Lago di Como, iu Italy. The shallow water has an emerald- green color, which is more frequently observed on the southern and southeastern portions of the lake than elsewhere. The width of the emerald- green zone varies greatly. In some places this zone is nearly half a mile broad, especially in the shallow water of the southern part of the lake. Where the bottom slopes rapidly the emerald- green water extends only 100 to 150 feet from the Shore- Hue. The deep water is of elegant ultramarine- blue color. The transparency of the water is wonderful. According to experiments made by Prof. John Le Conte, a white object can be seen at a depth of 115 feet. The depth of the water at the line of junction of the ultramarine- blue and emerald* green colors is at least 100 feet. The temperature of Lake Tahoe, taken o? i the north shore in November, is 50° F. This lake does m *, rroezo in winter, and I am inclined to believe that there is but little variation of temperature, if any, throughout the year. The temperature of the deep Alpine lakes is 39* .2 F. at all seasons of the year. People living on the borders of the lake rarely bathe in it, even in midsummer. Soundings were mode in Lake Tahoe in November, 1875, by Messrs. John McKinney and Thomas Jackson, two of the oldest settlers in this section of California. The apparatus used belonged to the Coast Survey, and was forwarded from Oaklaud, by Prof. Joseph Le Conte. It consists of a hexagoually- shaped plumb attached to a rope about one- quarter inch in dia » eter. Rhombic pieces of brass are fastened to the rope at intervals of 100 feet. There is a bit of leather half- way between the pieces of brass, and the space between each bit of leather and brass is divided equally by a scrap of red cloth. By means of this apparatus many sonndings were taken along the State line, which rnns through the middle of the lake, and in the western part of this body of water from Emerald Bay to Observatory Point. The soumling- liue was not used at any place east of the State line. Supposing the reader to be familiar with the ontline of Lake Tahoe, and beginning at the southern end, the tirst sounding is 900 feet near the point where the State line trends to the southeast. Going northwards the depth increases steadily. Sonndings taken at five localities indicate a depth respectively of 1,385 feet, 1,405 feet, 1,524 feet, 1,600 feet, and 1,645 feet. The average depth of the lake measured along the State line, for 10 miles due north and south, is from 1,200 to 1,410 feet. Commencing on the western shore of the lake, near Emerald Bay, the tirst sounding is 750 feet. At Rubicon Point, 4 miles further north, the depth is 850 feet near the shore. This is owing to the fact that the face of this rooky headland slauts quite abruptly. At Meigs's Bay the depth is 750 feet, at McConnell's it is 700 feet, and Barton's Mills it is 330 feet. A short distauce eastward of the two latter places the lake deepens rapidly. Midway between the State line and the shore at MuConnell's, the sonnding taken was 1,506 fe> e. tf aud at a point a few miles north, opposite Barton's Mills, the sounding- line marked 1.540 feet. Keepiug tolerably near the shore wo have 772 feet as the next sounding north of Barton's Mill. The last observations to be mentioned were taken in the northwestern portion of the lake. In front of Tahoe City, the depth was found to be 312 feet; a little further east the sounding- line iudicat' d 1,350 feet, and still further near the State line it is marked 1,504 feet. Iu general it may be said that while the depth increases in the middle of the lake in going from south to north, it decrease** in the same direction in the western portion. Iu some places the sediment at the bottom adhered to the plumb, and the specimens thus brought up enable ns to form some idea of the lake- bed. Near Emerald Bay mica was found in the soundings in considerable quantities, evidently derived from the disintegration of the granitic rocks bordering the lake. But the most interesting sediment was obtained at a point near the deepest part of the lake, 3} miles southeast of the Warm Springs, and about 3£ miles northeast of Observatory Point. I have examined this sediment with the microscope and rind that it contains many species of Diatoms. Not being very familiar with the protophytes, I Bent some of the sediment to Prof. H. L. Smith, of |