44 GLACIAL AND SURFACE GEOLOGY OF THE PACIFIC COAST. 



Valley. This has been sufficiently described in the Yosemite Guide-Book ; 

 but a few words must here be added in regard to the interesting glacial 

 features of this curious locality. The Hetch-IIetchy is about fifteen miles 

 northwest of the Yosemite, and is similarly situated with reference to the 

 crest of the Sierra, from which its upper end is about twenty miles dis- 

 tant. Both these valleys have been lakes in former times, and the Hetch- 

 Hetchy still becomes one not unfrequently, the gorge below it being too 

 narrow to carry off all the water at the time of the melting of the snow in 

 the spring. The bottom of the valley is about 3,650 feet above the sea, or 

 about 300 feet lower than the Yosemite. Unlike the latter, it is separated 

 into two pretty distinct divisions by a precipitous spur of granite, which pro- 

 jects out from the southern side, and the sides of this mass, as well as the 

 walls of the valley, are beautifidly scored and polished up to a height of at 

 least 800 feet above the level of the river. The walls of the Hetch-Hetchy 

 are nearly 2,000 feet iu height, and very precipitous, with but a small 

 amount of talus at the bottom, as is the case in the Yosemite. No doubt 

 the exact thickness of the glacier by which it was formerly filled could be 

 accurately determined by careful examination. From the observations of 

 Mr. Iloffinann, by whom this interesting locality was first made known to the 

 public, it appears that below the Hetch-Hetchy the trail runs for some dis- 

 tance along- the top of a moraine, at an elevation of 1,200 feet above the 

 level of the i-iver. The valley has not been explored below the Hetch- 

 Hetchy for the purpose of ascertaining the exact point to which the Tuo- 

 lumne glacier descended at the time of the greatest extension of the ice ; 

 but it must have reached nearly or quite down to the junction of the South 

 Fork. In that case the total leno-th of the mass of ice would have been 

 about fifty miles ; it was certainly over forty. The width must have been 

 more than four miles at some points in its course, and it may in places have 

 exceeded six. 



Between the San Joaquin and the Tuolumne rivers is the Merced, the 

 glaciation of whose v.alley is next to be discussed. This stream is more in- 

 terQsting than any other in the High Siei'ra, because it is the only one much 

 seen in the upper part of its course by travellers and tourists, since it runs 

 through the Yosemite Valley, the one feature of Californian scenery which 

 attracts universal attention. It is the more desirable that the glaciation of 

 the Merced Valley, including the Yosemite, should be somewhat minutely 

 described, because there seems to be a strong feeling, in California at least. 



