FORMER CxLACIATION NORTH OF BEAR RIVER. 59 



reached an altitude great enough to warrant the expectation that traces 

 of former ghxciation might be met with. The most elevated region exam- 

 ined by Mr. Goodyear was about the head of the North Fork of the Middle 

 Fork of the American, where he made several barometric observations at 

 stations between 5,000 and 7,000 feet above the sea-level. The highest point 

 reached was Bald Mountain, with an altitude of 7,091 feet.* This region lies 

 south of the Central Pacific railroad, and nearly west of the upper part of 

 Lake Tahoe. In spite of its great altitude, however, Mr. Goodyear's notes 

 do not mention any glacial scratches or polished surfaces as existing in the 

 region explored by him. A large portion of this district, it is true, is covered 

 with volcanic debris ; but the valleys are mostly cut down deep into the 

 granite or slate ; and the rock would in many places have been of a texture 

 and hardness favorable to the preservation of glacial markings. This is 

 especially the case in tlie vicinity of the Canada Hill and Bald Mountain 

 Range, where a kind of quartz-rock predominates, which may be presumed 

 to have had all the qualities necessary for retaining either striations or 

 polished surfaces. The reason why the glacier descended to so much lower 

 altitudes on the line of the railroad, as mentioned above, must have been 

 that tliere was a more extensive gathering-ground for the glacial mass, 

 at a high altitude, in the upper basin of the North Fork than there was at 

 the head of those branches of the Middle Fork which chiefly drain the region 

 explored by Mr. Goodyear. 



From Bear River north no indications have ever been observed, by any 

 member of the Geological Corps, of extensive glaciation. During the con- 

 tinuance of the Survey, Sierra County was but very hastily and imperfectly 

 explored, and the higher part of it was not visited at all'. Plumas County, 

 however, was examined with some care by the writer, during the summer 

 of 1866, from Quincy to Lassen's Peak, which forms the extreme northwest 

 corner of the county. Nowhere in the course of this exploration were any 

 clearly defined traces of former glaciation observed, in spite of the \evy con- 

 siderable elevation of the valleys and the surrounding ranges. Even the 

 higher latitude seems not to have been efficient in aiding to bring about in 

 this part of the Sierra those climatological conditions necessary to the forma- 

 tion of glaciers of importance. 



During the summer and autumn of 1879 the higher portions of Sierra and 

 Plumas counties were explored by Professor Pettee, as already mentioned, 



* See Ta1)le of Barometric Altitudes, appended to gravel volume. 



