548 1'1-(JKA OF 'lllE NAKA.Mli: (llv'oll". 



inadc ill August iiiul Septemher down the Missouri River from Fort 

 IJcntou to Bismarck ; but observations that were made upon the Lara- 

 mie strata as seen at difi'ereut jtoints, and upon tlie vegetable remains 

 fbiiiid in tlieni during that journey, may titlingly be recorded here. 



This formation was tirst met with as the .hidith River group, near 

 Birch Greek, about 100 miles below Fort Benton. It here presented 

 the massive sandstone stratum at its base similar to that of the Bitter 

 Creek dejiosits and appeared about COO feet above the river, resting 

 upon the Cretaceous. Above this sandstone a few plant remains were 

 found in a soft, whitish-gray marl bed, too imperfect for specific identi- 

 fication, but showing the presence of Equisetum and coniferous and 

 moiiocdtyledonous jilants. 



Before reaching this point, and much of the way from Coal Banks, an 

 extensive system of dikes of micaceons basalt was observed cutting 

 th rough the white Cretaceous sandstone in all directions and forming 

 pictuies(iue objects along the river. These seemed to disappear as the 

 Judith River beds came into view, leaving the question of their age 

 lelative to that of these beds unsettled ; but at a point IS miles below 

 Ciaggett a single one of these dikes was observed to rise entirely 

 through the Cretaceous and Laramie strata, both of which were here 

 exposed, thus proving conclusively that the ujithrow of lava which 

 produced these dikes occurred posterior to the deposit of at least a large 

 portion of the Judith River strata. 



From a point about fifteen miles below (iraiid Lsland, where the Judith 

 River group may be said to end, to the Muscle Shell, where the Fort 

 Union group proper may be said to begin, no Laramie strata can lie 

 seen, and for much of the distance from the mouth of the Muscle Shell 

 to Poiilar Creek, 100 miles above the mouth of the Yellowstone, they 

 merely cap the hills or are wanting altogether. Below Poplar Creek they 

 come down to the level of the river, and some twenty or thirty miles below 

 that point fossil plants were found, including Populus and other Dico- 

 tyledons, as well as Conifers, at three different horizons in the cliffs on 

 the right bank of the river. At other points between this and Fort 

 Union, stems of cane and Equisetum were common, but no rich plant 

 beds were found. The Laramie hills here often form nearly ])erpeiidic- 

 ular walls along the south bank of the river and thick beds of coal 

 may be traced for great distances. Much of the Carbonaceous rock 

 has been burned ; and at one point the fire was still burning, the rocks 

 in the vicinity of a smoking crevasse being hot, but no actual ignition 

 being visible from without. The progress of this combustion could often 

 be easily traced along a vertical escarpment and the lines clearly seen 

 which were formed by its cessation. At one place the transition from 

 brick red to dark slate color was abrupt along a vertical line extending 

 from toj) to bottom of a wall several hundred feet high, forming a very 

 striking contrast. 



At a point about thirty miles below Fort Buford an interesting bed of 



