GEOLOGICAL SURVEY OP THE TERRITORIES. 25 



traces of abundant fossils, as broken crinoidal remains and other mollus- 

 ea. It vreathers so as to expose upon its sides small flinty masses of chert. 

 This bed passes up into a light-gray limestone with drnsy cavities, and 

 breaking into irregular fragments in the direction of stratification, a 

 form of fracture common to the Carboniferous rocks. The dip of this 

 bed is 31°. Obscure traces of fossils are seen. These layers continue 

 on up, divided by thin partings ; others are solid, from 6 to 20 feet in 

 thickness. Then comes a bed without distinct lines of stratification, 

 often assuming the form of a sort of conglomerate, with masses of lime- 

 stone on all sides, cemented together with sulphate of lime ; dip, 20°. 

 There is then a return to the former condition of a yellow limestone. 

 It is full of dog-tooth spar and seams of crystalline matter. I should 

 estimate the limestone to be about 500 feet in thickness. 



"On the right side of the Gallatin, and dipping eastward from the 

 caiion at an angle of 8°, is a bed of yellow-gra,y sandstone and marl. 

 It does not quite conform to the Carboniferous limestone, though dipping 

 in the same direction. The Gallatin Fork, from its mouth to the i)oint 

 where it issues from the mountains, is about fifty miles, flowing through 

 a beautiful valley well fringed with cotton wood trees, mostly bitter Cot- 

 tonwood. The upper portion of this valley has been most beautifully 

 smoothed by the erosive action of water, leaving a space between the 

 base of the mountain-ridges and the upturned edges of the sedimentary 

 rocks of twenty or thirty miles which is smooth like a lawn. The Car- 

 boniferous rocks present a series of mouoclinals of the most interest- 

 ing character. Underneath them is a series of rocks, which seem to 

 represent the Potsdam sandstone. It is the most variable series which 

 I have yet seen. In order of descent we have a reddish, rust-colored 

 rock, mostly fine grained, compact, quartzose, siliceous, almost the 

 appearance of a metamorphic rock. It is sometimes made up of an 

 aggregation of grains of quartz. Beneath is a series of thin strata of 

 dark steel-gray micaceous sandstone, sometimes becoming a fine aggre- 

 gation of water-worn pebbles and dark-brown clay-slate, gradually 

 passing down into what appears to be a true eruptive rock, with verti- 

 cal seams of white quartz running through it. I am inclined to think 

 that the erupti\'e rocks have been thrust in between the partings of 

 rock, so that we have a bed of eruptive rock, and then a layer of the 

 sandstone, and so on alternating. 



"From the Gallatin we passed up one of the little forks emptying 

 into that river, over Carboniferous rocks, on to the source of Smith's or 

 Kame's River, which empties into the Missouri below the gate of the 

 mountains. Reaching the vicinity of the mountains, we find that the 

 basaltic or eruptive rocks prevail to a very large extent over all others. 

 On a little branch flowing into Smith's River near its source, we find a 

 dark steel-brown bed, 50 feet in thickness, a fine conglomerate at base, 

 but gradually growing coarse until toward the summit it is composed of 

 large angular blocks of mixed gray basalt, aggregated with a reddish 

 material. The beds dip northeast 45°. The imbedded masses are more 

 or less water-worn. This bed seems to continue a long distance, and is 

 sometimes vertical ; sometimes the pebbles are as much worn as those of 

 the little streams; and it seems to me that they have been changed since 

 deposition, for they now partake much of the color and character of the 

 matrix, except that they are much harder. The basaltic rocks along 

 our route are developed to an enormous extent, and present every variety 

 of texture, that which yields readily to atmospheric agencies predom- 

 inating. 



" July G. — Passing along the Smith's River, I saw this series of curious, 



