410 



SCIENCE 



[N. S. Vol. XXVII. No. 



lengths of approximately 15 to 18 miles, 

 as shown by the extent of morainic de- 

 posits. Glaciation is not yet extinct. A 

 tiny glacier was seen at the head of Big 

 Timber and another in Sweetgrass Canyon, 

 and a third is reported by Assistant For- 

 ester Wilson at the head of Rock Creek. 

 Glacial topography predominates through- 

 out the southern section of the mountains 

 and occurs locally in the southern section. 

 Striffl and truncated valley spurs along the 

 sides of the canyons show that the ice must 

 have been 500 to 800 feet thick. The gla- 

 ciation succeeded a long erosion period in 

 which the region had reached an early 

 stage of peneplanation. It continued long 

 enough to form broad, deep troughs in the 

 weaker rocks and to produce much of the 

 sharp arete topography so characteristic of 

 the southern section of the mountains. 

 Later stream erosion has incised the glacial 

 deposits and in some cases the old troughs. 

 The papers were discussed by A. C. 

 Lawson. 



The following papers were read by title : 

 The Shaler Mountains, Unalaska, a Granite 

 Core to the Aleutian Islands: T. A. Jag- 

 gab, Jr., Boston, Mass. 



The Groivth and Destruction of Metcalf 

 Cone, Bogosloff Island, 1906-7: T. A. 

 Jaggar, Jr., Boston, Mass. 

 Then was read 



The Sandia Mountains: W. G. Tight, 



Albuquerque, N. M. 



The following papers were then read by 

 title: V 



The Geology of the Alaska Range: A. H. 

 Brooks, Washington, D. C. 



The Paleozoic and Associated Bocks of the 

 Upper Yukon Basin: A. H. Brooks and 

 E. M. Kindle. 



Discovery of Fish Remains in the Ordo- 

 vician of the Black Bills: N. H. Darton, 

 Washington, D. C. 



The next paper read was 

 The Topaz-hearing Rhyolite of the Thomas 



Mountains, Utah: Horace B. Patton, 



Golden, Colo. 



Extensive rhyolite flows occur in the 

 Thomas Mountains of Juab County, Utah, 

 associated with somewhat more basic erup- 

 tives. The rhyolite has been profoundly 

 affected by mineralizing vapors that have 

 removed all trace of dark-colored constitu- 

 ents and have caused the development of a 

 surprising number of topaz crystals, with 

 occasional garnet and specular hematite. 

 The topaz crystals occur, first, in litho- 

 physal cavities associated with quartz, and 

 are then mostly clear crystals having a 

 handsome brownish-yellow wine-color that 

 quickly disappears on exposure to direct 

 sunlight; second, imbedded in the solid 

 rhyolite and having frayed out ends but 

 fairly well developed prismatic faces. 

 These are brownish in color before exposure 

 to light, but are rendered opaque by 

 numerous enclosures of quartz crystals. 

 Similar crystals, but perfectly developed 

 and with double terminations, were found 

 imbedded in fragments of a very fine 

 grained rhyolite tuff, the fragments being 

 themselves inclosed in rhyolite. Discussed 

 by G. K. Gilbert. 



The next two papers were read without 

 break. 



Strata containing the Jurassic Flora of 

 Oregon: J. S. Dillee, Washington, D. C. 

 The Jurassic flora of Oregon has been 

 described and designated by Professors 

 Lester F. Ward and William M. Fontaine 

 in the II. S. Geological Survey Twentieth 

 Annual Report, pt. 2, p. 217 and Mono- 

 graph 48. The localities of its occurrence 

 have been greatly extended among the 

 Klamath mountains of California, and 

 several distinct faunas have been found at 

 different places in the same strata. On the 

 one hand it is clearly associated with a 



