0. O. Marsh— Geology of the Uintah Mounfnh^^. 1'^ 



waters at temperatures of from 46° to 70° CentinniM- 

 t-'iice of apophyllite, natrolite and stilbite in tin- l;:i 

 tiarv limestones of Auvergne; apophyllite iiicru^- _ 

 wood, and chabazite crystals lining shells in a recent .i.i" ■-• iu 

 Iceland. The association of such hydrated silicates with < ui i i o- 

 clase, as already noticed (§ 13) and as described by S( iirm r. 

 where natrolite and orthoclase envelop each other. sIiowihl^ 

 their contemporaneous formation, with many otlicr l;i(t< oi' u 

 similar kind, lead to the conjecture that ortliiM-hisr. like l.rrvl 

 and quartz, and perhaps some other constituents of -.ininitu' 

 veins, may have crystallized in many ca.^^es ;it tempn-atuns uuK'h 

 lower than those determined by Sorby, and that the eon.liti.'ns 

 of their production include a considerable range of temj^era- 

 ture, a conclusion which is, however, probably true to some 

 extent, of zeolites also. 



It is proposed to continue the subject of granitic veins, and 

 in a third part of this paper to give some facts in the history of 

 i of Laurentian rocks. 



[To be continued.] 



Art. XXIX.— O^ the Geology of the Eastern Uintah Mountains; 

 by Professor O. C. Marsh, of Yale College. 



One of the Expeditions in the Kocky Mountain region, made 

 by the Yale College Scientific party during the past season, had 

 for its special object the study of the vertebrate remains of the 

 Tertiary deposits known to exist in the Green Eiver Valley, but 

 never carefully examined. During this investigation, while 

 endeavoring to reach the junction of the Grreen and White 

 Rivers, in Utah, the party passed along the base of the Eastern 

 Uintah Mountains, as well as over portions of the range ; and 

 as nearly all of tbis region was entirely unexplored, it is desira- 

 ble to note its more important geological features. 



The route pursued by our party on this expedition was from 

 Fort Bridger, in Wyoming, southeast by way of Henry's Fork 

 to the Green River; thence down the eastern side of tne river 

 to the great bend near the mouth of the Vermilion. Then 

 crossing to the western side, and passing over the eastern spurs 

 and foothills of the Uintah Mountains, we proceeded southward 

 to the mouth of the White River. After continuing up this 

 stream for about twenty miles, we returned directly to the Green 

 River, then proceeded to Fort Uintah, and from there struck 

 BprtWard over the Uintah range to Henry's Fork, and back to 

 -t'ort Bridger by our former route. As the country traversed is 

 entirely impassable for wac^ons, and it was only with considera 

 t>ie difficulty that a way for our 



r our pack-animals could be found, 



