ESDucii.l STRUCTURE OF THE WIND RIVER RAXGE. G5 



not niifrequently the rocty faces are overhanging. As is usually the 

 case in mountains of so rugged a character, so here, too, "\ve find that 

 numerous ''ampliitheatres" have been formed. Steep slopes descend- 

 ing from three sides inclose a more or less regularly shaped area of small 

 extent. Enormous masses of avalauchial debris and numerous small 

 lakes render the scenery Avithin these depressions singularly wild and 

 beautiful. The canons on the east side of the main chain are very steep, 

 affording but rarely sufficient rooni on their Avails for the growth of tim- 

 ber. A series of caiions running i)arallel with this chain effectually pro- 

 duce its orographic separation Irom the second one. 



The chain of foot-hills directly east of the main- chain presents a some- 

 what different structure. Spurs starting li'om the latter are disconnected 

 by the formation of deep, precipitous " saddles." Eising from these the 

 foot-hills reach about to timber-line, or for several hundreds of feet 

 above it. Timber-line here follows an elevation of about 11,000 feet. 

 From these highest points the ridges, as well as the valleys between 

 them, extend eastward with but gentle sloi^es for some distance. After 

 that they fall off' steeply. Looking up toward the summit of the range 

 li'om the base of these foot-hills, little will be seen, therefore, but the 

 sharp ends of ridges jutting out in comparatively regular arrangement. 

 Often the valleys separating the higher portions of these cross-ridg^es 

 are swampy, affording an excellent abode for the millions of mosquitoes 

 which infest that region. A number of the ridges may be connected 

 with each other by elevated portions trending parallel with the main 

 axis of the range. Deep canons, cutting across the foot-hills, permit the 

 escape of di-ainage from between the first and second chains. Precipit- 

 ous and steep near their upi^er ends, they gradually widen and grow less 

 impassable. The streams passing through them receive large supplies 

 of w^ater from the ridges wdiich they separate. 



After the first imi^ulse of steep eastern descent is passed, the ridges 

 exhibit a more gradual slope in that direction. Secondaiy and teitiary 

 ridges are formed upon their slopes, and small streams flowing toward 

 the east are numerous. Owing to the character of the rocks, many lakes 

 have been formed, imparting a most ])leasing effect to the view. Follow- 

 ing the descent of the foot-hills, which gradually becomes more gentle, Ave 

 find (mrselves confronted by steep westerly sloj^es of outlying hills by the 

 third (jhain. The drainage of the secondary and tertiary ridges above 

 mentioned, here turns either to the north or south, joining forces with 

 those streams which have passed through the foot-hills in canons. In 

 one instance, that of Twin Creek, the presence of the thii"d chain forced 

 the main stream to make a considerable detom^ before it could resume 

 its easterly course. In speaking of the third chain in previous pages, it 

 has been compared to the characteristic " hog-backs " of other regions. 

 Both by their analogous position, and by their stratigTaphical condition, 

 is this analogy established. The once-continuous chain has been either cut 

 by the di*auiage, or the strata composing it have parted under the infiu- 

 ence of some enormous strain ; in the latter instance, causing, the forma- 

 tion of steep, narrow canons. We find the continuity broken only at 

 such points where important streams issue from the raoiuitains in their 

 course to the Iqw country eastward. This is esseutially a typical feature 

 of hog-backs, but the occiuTcuce here is on so grand a scale that the 

 term cannot appropriately be a])plied. While the western slopes of the 

 third chain are steep, those to the east are more gentle until arrested 

 by the superposition of younger sedimentary bluffs. 



Northwest of our district the western subsidiary range forms a por- 

 tion of the slope of the maui chain. Kear Mudd}- Creek the separaiion 

 5 G s 



