EXDucii.] WIND RIVER RANGE METAMORPIIIC ROCKS. G7 



certain zones, no applicable data upon this point conld be obtained. It 

 is evident that tlie processes producing metamoi'pliisni must Lave in- 

 volved a great many factors of enormous power. Certainly one or more 

 of these factors resulted in extensive stratigraphical disturbances. We 

 find that the granites are flexed and contorted in every possible direc- 

 tion. Within the main chain the stratoid segregation of the granites is 

 not very completely carried out. It may be noticed, however, that the 

 arrangement of constituent minerals indicates the former planes of strati- 

 fication. This feature is also demonstrated by the breaking of the 

 granite masses. They form sharp, angidar bowlders, frequently with 

 two parallel sides. Within the same block of granite often several litho- 

 logical varieties may be found. Inclosiu-es of micaceous or chloritic 

 schists, exposed as narrow, ramifying, or simple bands, denote the origi- 

 nal planes of stratification. Could they be hewn out of the block they^ 

 would form undulating tablets with parallel sides. As well as on a very 

 small scale, we may note the occurrence of this feature in so extensive a 

 manner that it affects the structure of the chain. Broken and displaced 

 by the violent contortions to which the masses were subjected during 

 and since their metamorphosis, the continuity of the entire system is now 

 no longer intact. It would require the most carefid examinations, con- 

 ducted on a liberal scale, as to time, to elicit evidence bearing upon the 

 former condition of this metamorphic area. I am confident that, to a 

 certain extent, these examinations could be successfully carried out. 

 The establishment of facts that their results Avould indicate could 

 fiu-nish us with a most accurate account of the earliest history of this 

 region. 



On the western slope of the main chain we have ample opportunity to 

 observe the weathering of these rocks. As a rule they are so firmly ce- 

 mentedby the metamorphosing influences that the local predominance of 

 one constituent or the other produces no marked result. Erosive agents 

 attack the granites but very slowly. Yf hile that exhibited by the sub- 

 sidiary range is deei)ly furrowed, looks old and weather-beaten, the gTan- 

 ites of the main chain have a comparatively fresh api)earance. Hard 

 and firm, they p^re, for long distances, very homogeneous. Breaks of the 

 original strata and inclosures of softer rock, iirovided they are of suffi- 

 ciently large extent, have been taken advantage of by erosive agents. 

 They probably have fii^st given impulse to the formation of depressions 

 that to-day exist as gulches and canons. Water and moving ice, with 

 their accompanying bowlders and gravel, both tend to smooth and pohsh 

 the gTanites. 



As we leave the crest of the mountains and proceed to the eastward, we 

 notice a general change in the character of the rocks. While they have 

 been massive and comi^act heretofore, they now show more decided 

 stratification, Aveather in sharp pinnacles, and form steep slopes or per- 

 pendicular walls. Ui)on examination we find that the purely granitic or 

 syenitic character has disai^peared to a great extent, and that we have 

 before us either schistose granites or tj^iical schists. It is this zone of 

 schists, essentially, that gives rise to the steep and precipitcuis eastern 

 slopes of the main cham. The schists may be traced for some distance, 

 but eventually their unity is broken and their place is supplied by other 

 rocks. Taking into consideration the stiaictural stratigraphy of the main 

 chain, we find that the beds dip steeply to the eastward. At some 

 localities the granitic masses are so homogeneous that no attempt at strat- 

 ification can be observed. It becomes veiy apparent, however, as soon 

 as we reach the schists. Few metamorphic regions can be foimd where 

 the stnictmal conditions of rocks remain imiform even for a short 



