100 RECONNAISSANCE FROM CARROLL, MONTANA, 
selenite plates are found most abundantly near the level of the river, having been washed together 
here, but they occur also more or less frequently on the plains, twenty-five miles from the river, 
at a level nearly 1,000 feet above. 
The alkaline deposits scem to be particularly abundant in some layers, exuding from the 
bluffs along the river in long white lines. Considerable deposits of it are seen at various points 
on the banks of the river, and all the little dry creek-bottoms leading into the Missouri are white, 
as if frosted with it. The following is an analysis of a particularly-pure specimen of the alkali 
collected near Carroll. For this analysis we are indebted to Mr. Fred. P. Dewey, of the Sheffield 
Scientific School of New Haven, and we would here express our acknowledgments to him: 
Ee IL. Mean. 
Mg0O...... 11.69 11.91 11. 80 
Nay O xccc5 15. 81 16, 20 16. 00 
CaO) sesiaccs 0.53 0. 68 0. 60 
W515: Osmisiucs 0. 88 0. 88 0. 88 
S O3..-.--- 44,09 44,12 44,10 
Mt amie trace trace trace 
Ha Qiccccs 23. 09 23. 00 23. 05 
Tusoluble.. 3.29 By ot 3. 28 
OY. 3S 100. 06 99, 71 
As will be seen from this avalysis, the alkali consists essentially of the sulphates of sodium and 
magnesium; in fact, the amount of sulphuric acid given is almost exactly what is required to unite 
with the several bases. The presence of the lithia is also to be noticed. 
This alkali is a constant attendant of this member of the Cretaceous, wherever observed in the 
West, and is one of the causes of its barren character. The water of the Missouri is so entirely 
derived from pure mountain-sources—even the large rivers, as the Musselshell, which flow through 
the alkaline prairie, being nearly dry at their outlets—thbat it is little affected by the salt which is 
brought into it, though the white deposits on the alluvial banks show that the quantity is not 
small. 
These Cretaceous clays have a laminated shaly structure wherever exposed: they weather 
down so readily, however, that often only the rounded beds of clay are seen. These are so soft and 
yielding, that the foot sinks deeply into them, and they have much the feeling of a bed of ashes. 
In the neighborhood of Carroll, there is more or less of a scanty vegetation; but farther down the 
river, perhaps one hundred and fifty miles, there seems to be no vegetation whatever, and the 
appearance of these black clay-beds is desolate in the extreme. 
The height of the Cretaceous bluffs above the river is quite variable as viewed from the water ; 
but, when we examine the total elevation attained in passing back from the river, we find that it 
is remarkably constant. The Helena road at Carroll rises in two or three very steep pitches the 
greater part of its final ascent, and, within two or three miles of where the road leaves the valley 
the high plateau is reached, which is kept, with little change of level, beyond Crooked Creek. The 
height here, as given by an aneroid, is 665 feet. On the other side of the river, the height of the 
corresponding plateau is 680 feet; though in this case the final elevation was found a little farther 
from the river, the rise of the plain being more gradual after the first steep ascent had been made. 
The appearance of the surrounding country, as viewed from the top of the bluffs back of 
Carroll, is very forbidding. The whole landscape is of a somber, gray tint; the color of the soil and 
the sage-brush sparingly relieved by the dark green of the stunted pines that grow here and there 
ou the summits of the bluffs and along the little ravines. There is little vegetation, except the 
Artemisia, and, altogether, the region seems incapable of affording sustenance to man or beast. 
Notwithstanding its uninviting appearance, the neighboring country abounds in game. This region 
has been, and still is, though to a less extent than formerly, the favorite feeding-ground of a por- 
tion of the great northern herd of buffaloes: antelope are numerous on the plains, and mule-deer 
and elk are found in the pine-timbered ravines. Farther back from the river, in the hill-country, 
the big-horn, or mountain-sheep, and the grizzly bear occur, though nowhere numerous. 
On both sides of the Missouri, the high bluffs are cut into numberless ravines, which divide 
