44 GEOLOGICAL SURVEY OF THE TERRITORIES. 



that tliere is much excellent grass land among the granite ridges. The 

 patches of Pliocene marl here and there aid in smoothing the rougher 

 portions of the surface. That portion of Madison Valley immediately 

 west of Virginia City is about seventy-five miles from north to south, 

 and ten miles from east to west, closing up at the south end and forming 

 a fine canon through gneissic granites at the north end. These granites 

 are mostly feldspathic, the feldspar predominating, and in most in- 

 stances composed only of feldspar and quartz, with iron diffused through 

 the mass. This valley, at one time in the past, formed the bed of one of 

 the great chain of fresh water lakes, as is shown by the lake deposits 

 which underlie the upper terraces, and jut up against the mountains on 

 either side. This deposit is also covered in some places with a bed basalt. 



CHAPTER III. 



FORT ELLIS— :MYSTIC LAKE— SOURCE OF THE GALLATIN— TRAIL CREEK- 

 CROW AGENCY AND FIRST CANON— EXIT OF THE YELLOWSTONE. 



Fort Ellis is located on the east bank of Mill Creek, one of the sources 

 of the East Fork of the Gallatin, and from its position, overlooks one ot 

 the most beautiful valleys in Montana. It is surrounded on the east 

 and north sides by ranges of the hills and mountains which form the 

 divide between the waters of the Yellowstone and Missouri Elvers. 

 After our long journey across the dry plains from Salt Lake Valley, we 

 found this point a most agreeable resting-place. Every courtesy we 

 could desire was extended to us by the officers. Captain J. C. Ball, at 

 that time in command, during the temporary' absence of Colonel Baker, 

 afforded us every facility to aid us in our preparations for our explora- 

 tions up the Yellowstone, and his suggestions, from long experience in 

 western campaigns, were of the highest value to us throughout the trip. 

 Indeed, the favors that we received at this post, both going to and 

 returning from our Yellowstone exploration, were indispensable to our 

 complete success. Fort Ellis, although considered one of the extreme 

 frontier posts, and supposed to be located among hostile tribes of In- 

 dians, really commands the valleys of the Yellowstone and the three 

 forks of the Missouri, the finest and most productive portion of Mon- 

 tana. It is a very pleasant station, surrounded with beautiful scenery, 

 with a climate that can hardl}^ be surpassed in any country. Streams 

 of pure water flow down the mountain sides, cutting their channels 

 through the plains everywhere. The vegetation is most abundant. 

 Bozeman is a pretty town, with about fivehundredinbabitants, situated 

 three miles below, surrounded on every side with well-cultivated and 

 productive farms. It is most probable that within a short period the 

 Northern Pacific Kailroadwill pass down this valley, and then its beauty 

 and resources will become apparent. 



The drainage of the Gallatin is composed of a large number of little 

 streams that rise in the great divide for a distance of eighty to one 

 hundred miles, and each of these little streams gashes out a deep 

 gorge or canon in the mountain sides. The geology is thus rendered 

 comparatively simple in general terms, and yet in its details it is 

 remarkably complicated. Two forces seemed to have operated here 

 to give the present configuration to the surface, and whether they 

 may have acted synchronously or at different periods, or both, is not 



