APPENDIX TO THE EEPOET OF THE SECRETARY. G9 



ingly rough, but witli redeeming valley spaces abounding in good graz- 

 ing, while the hills are quite well wooded with coniferous forests. 



The southern flank of the Gros Ventre Mountains was traversed from 

 a point near where the Hoback's CaQon ridge first approaches this range, 

 thence east to the broad depression separating it from the northern 

 portion of the Wind Kiver Eange. In the west the culminating peak 

 rises into a bared Archaean cone, the primal rocks occurring at one or 

 two points farther east, where they have been laid bare in the deeper 

 caiious which all the streams penetrating the mountains from this side 

 have excavated. But for the most part this mountain front is heavily 

 plated with Pala?ozoic formations, iucludiug the Potsdam quartzite^ 

 Quebec limestones, the magnesian limestone, and the still heavier series 

 of Carboniferous limestones and saudstones, which latter forms the mass 

 of the eastern i)ortion of the range over to the divide at the head of 

 water flowing into Green EiA'cr. The Palseozoic rocks have been up- 

 lifted into great folds, with abrupt inclination on the southerly flanks, 

 contrasting with long declivities in the opposite direction, on which side 

 the range loses much of its rugged, imposing character. Here and there 

 patches of Mesozoic appear low in the south-side mountain flank, suc- 

 ceeded by the unconformable Tertiary beds descending into theHoback 

 and Green Eiver Basins. In some of the larger cahon mouths interest- 

 ing exhibitions of morainal and other glacial phenomena were first met 

 with. 



The work in the Wind Eiver Mountains was commenced towards the 

 northern end on the west side, and thence carried southwards, circum- 

 stances compelling a rapid march round via South Pass to Camp Brown, 

 from which point the work was prosecuted northwards along the east 

 ern flank of the range. 



In the vicinity of Green Eiver Caiion, on the west side of the Wind 

 Eiver Eange for a few miles, the outer barrier of the mountains preserves 

 a remnant of the Paleozoic formations. These deposits are very similar 

 to the corresponding formations in the Gros Ventre Mountains, and 

 identical with the much more extensive occurrence of strata of that era 

 on the east side of the range. They have been lifted high up on the 

 mountain with minor undulations, and, as seen from the open basin to 

 the southwest, they have the appearance of curving round the extremity 

 of the range. But the latter appearance was found to be deceptive, the 

 Archaean soon reappearing in the outer slope to the north of Green 

 Eiver Caiion, and thence continuing until all the more ancient rock 

 series is hidden by the Cenozoic and Post-Tertiary accumulations at the 

 northern end of the range. 



The brief visit paid to the summit of this portion of the Wind Eiver 

 Mountains aftbrded what is to the student of American geology a field 

 of greatest interest in the existence here of li\ing glaciers. The snow- 

 fields were found to be much more extensive than was surmised from 

 the distant views of the summit, and the ice-filled gorges, especially on 



