foi;mee glaciatiox of the tuolomne a^alley. 41 



present also the usual phenomena of former glacial action on a magnificent 

 scale. The main tributary of this river in the High Sierra is the so-called 

 South Fork, which heads in two streams, one coming down from the north 

 side of Mount Goddard, and the other from the north end of the Palisades. 

 The principal stream, receiving many tributaries, runs about fifty miles in a 

 direction parallel with the axis of the chain, or northwest, and then unites 

 with the North Fork, a much smaller branch coming down from the portion 

 of the ridge between lied Slate Peak and Mount Lyell. The total length of 

 the portion of the Sierra drained on its western slope b}' the San Joaquin is 

 between fifty-five and sixty miles This area has been but very imperfectly 

 explored by the Geological Survey ; but abundant evidences were obtained 

 of the former existence of glacial masses in this region, on a scale perhaps 

 even grander- than in the King's River area. In the valley of the San 

 Joaquin, on the South Fork, Professor Brewer inferred, from the position of 

 the old moraines, that the former glacier must have been at least 1,500 feet 

 deep, and eight or nine miles wide in its widest places. The length of 

 the whole South Fork glacier, measuring to the termination of the ice in the 

 Main Valley, must have been over fiftj^ miles. Neither in the case of the 

 King's nor the San Joaquin River glacier has the precise point of the valley 

 reached by the glacial mass at the time of its greatest extension ever been 

 ascertained. 



The formerly glaciated portion of the Sierra Nevada, which has been most 

 carefully explored by the Geological Survey, is that at the head of the Tuolumne 

 River. This region, from its importance as being in the most accessible part 

 of the range, near the Yosemite Valley, and consequently much more visited 

 by pleasure-travellers than the Southern High Sierra, was mapped on a 

 larger scale than the rest of the range,* and sufficiently studied to make it 

 possible to lay down the position and extent of the ancient glacial mass with 

 considerable approach to accuracy. 



The length of that part of the Sierra ^\■hic•h is drained by the Tuolumne, 

 measured parallel with the axis, is a little less than forty miles. The prin-. 

 cipal gathering-ground of the glacier was in the elevated plateau-like region 

 embraced between Cathedral Peak, Mount Conness, Mount Dana, and Mount 

 Lyell, forming an irregularly shaped area of some sixteen miles in length 

 and from six to ten in breadth. The lowest part of this area is a little less 



* This map, comiinsint; aljnut 2,300 squarB miles, and on a scale of two miles to an inch, accompanies the 4to 

 and Svo editions ol'the Yosemite Gniile-Book. A reduced iihotolithographir; copy, on a scale of three miles to an 

 inch, is also given in the 16mo edition of the same work. 



