540 PROCEEDINGS OF THE ROCHESTER MEETING 



Professor A. C. Lawson was named by the chairman a committee of 

 one to draft suitable resolutions with reference to the death of Professors 

 Joseph Le Conte and E. A. Claypole. 



The Section, on motion, instructed the Secretary to send a telegram 

 of greeting to the Geological Society in session at Rochester, New York. 



An election for officers for the ensuing year was then held, resulting 

 in the election of Mr H. W. Turner as Chairman of the Section and 

 Mr A. C. Lawson as Secretary. 



The Secretary was instructed to prepare a list of members of the 

 Section— that is, of Fellows residing in North America. west of the 104th 

 meridian. 



An Executive Committee, consisting of the Chairman of the Section, 

 the Secretary, and Professor J. C. Merriam, was appointed to care for 

 the interests of the Section when not in session. 



The following papers were then read : 



AN INSTANCE OF VARIABILITY IN A BOCK MAGMA 

 BY H. W. TURNER 



Abstract published in Science. 



FOST-TERTIARY ELEVATION OF THE SIERRA NEVADA 

 BY H. W. TURNER 



In the Yosemite quadrangle only one of the Neocene streams, the Tuolumne, can 

 be traced by its gravels. The reason of this is that only in the Tuolumne basin 

 were there extensive lava flows, which filled the Neocene drainage and preserved 

 the gravels underneath. Even here the gravels and overlying lavas have been 

 largely eroded. 



The Neocene channel can be traced from the ridge east of Piute creek, west to 

 the north of Rancheria mountain, thence down Deep canyon, from which point it 

 may have gone down Rancheria creek or over through what is now Tiltill valley, 

 thence over the site of the Hetch Hetchy, reaching the south side of the present 

 Tuolumne canyon to the w r est of Hog ranch. The bench, with an altitude of about 

 8,000 feet to the east of Rodgers canyon, pretty certainly represents a portion of the 

 Neocene Tuolumne basin, but except near Rodgers creek the lava covering has been 

 entirely removed. 



Going w T est we find the lava covering well preserved on the spur east of Piute 

 creek, but no gravels are exposed, but the V-shaped channel is clearly evident on 

 the slope toward Piute creek. To the west of this creek is an even better section 

 of a lava-filled, V-shaped channel, and in this case the river gravels are to be seen 

 perhaps 50 feet in thickness at the bottom of the channel. A short tunnel was run 

 in here many years ago, presumably for placer gold in the gravel. Besides abun- 

 dant lava pebbles, there are numerous pebbles of slate and metamorphic lavas 

 such as make up the mass of mount Dana, and one pebble w T as found of epidotifer- 

 ous sandstone, precisely like the rock of the summit of Dana. 



