THE OVERLAND BOUTE— OGDEN TO SAJSf FRANCISCO. 197 



Truckee Kiver from Lake Talioe down to Boca or beyond is a 

 favorite resort of fishermen in summer. Camps and a number of 



small hotels afford stopping places that are easily 



reached from the California, side of the mountains. 



oSa^^S^^^^ The route from Polaris (milepost 211) to a point near 



Emigrant Gap and Towle, on the west side of the 

 Sierra, hes in the Tahoe National Forest. 



4 



Exposures of the thinl}^ and regularly bedded lake deposits con- 

 tinue and may be seen in a cut just west of Boca. Here is a la^^er 

 of white diatomaceous earth, which includes fragments of leaves and 

 stems and is believed to have been laid down in quiet water. 



Near the town of Truckee the valley broadens considerably and the 

 river terraces become very distinct. To the north a branch lumber 

 railroad climbs the edge of one of the terraces, exposing in deep cuts 

 loose white bedded gravels and other stream deposits corresponding 

 in age to the Pleistocene lake beds observed lower down the range. 



From Truckee, the last town passed on the climb to the summit, a 

 narrow-gage railroad runs up the main river valley to Lake Tahoe 



(15 miles) and a short lumber road goes north to 



Truckee. 



Ilobart Mills, but the latter does not carry passengers. 



Elevation 5 S20 feet, rj.^^^^ j^ ^^^^j^ ^f interest froui ahnost every pohit of 



Omaha 1,574 miles. 



view to be seen in crossing the Sierra Nevada, and 

 mau}^ features of geology, physiography, forestry, and history which 

 can here be only briefly noted. Beyond Truckee the evidences of 

 glacial action become apparent. The Sierra down to an elevation of 

 5,000 feet was long buried under ice. The grinding of this moving ice 

 mass T^-idened the bottoms of the canyons, smoothed off and steepened 

 their sides, and removed enormous amounts of loose rock and soiL 

 To a large extent, however, the ice protected from water erosion 

 the area that it covered. Moraines composed of rough and angular 

 but not watcr-roimded bowlders of all sizes, mixed with finer 

 detritus and sand, were deposited by the ice tongues that pro- 

 jected down the valley, pai'ticularly at their ends and along their 

 sides. The lower valleys which the ice did not reach differ in form 

 from those that were glaciated. Below the glaciated region the 

 valleys are narrow and V-shaped in cross section, but the glaciated 

 valleys are broader and U-shaped and many of them are characterized 

 by nearly level stretches occupied by meadows (filled-in lakes), 

 separated by rocky portions of steeper grade. At Truckee lake 

 beds and stream terraces of the lower river course, the records of work 

 by water, join moraines, the records of work by ice. The upper part 

 of the town is built on the lowest identifiable portions of these gla- 

 cial deposits. (See PL XLIV, B,) The canyon of Truckee River 

 between Truckee and Lake Tahoe has evidently never been glaciated, 



