196 FORMATIONS OF THE 
near Fort Berthold, where it is from four to six feet thick. I had not time to sub- 
mit this coal to a rigid chemical examination by combustion with copper scales. A 
preliminary examination showed it to be of a remarkable character. In burning, 
it emits a peculiar odour, and gives out but little flame. Its specific gravity is 1:33. 
Of volatile matter, there is 54-5, chiefly light carburetted hydrogen; of carbon or 
coke, 37-0; of coke itself, 45°5; of light green ashes, 8°5. A hundred grammes of 
nitre required 27-8 for deflagration; which, if 12 be taken as the amount necessary 
to deflagrate the same nitre, would give about 43 per cent. of carbon in both coke 
and volatile matter, and about 6 per cent. of carbon in the volatile matter alone. 
This coal does not present the appearance either of true lignite, or of brown coal. 
It has more the aspect of ordinary bituminous coal ; especially of the poorer varieties 
of splint or cannel coal. It is unlike them, however, in its elementary constituents ; 
for, when exposed to heat, little or no coal-gas is given out, but only a little car- 
bonic acid and light carburetted hydrogen. It smoulders away, more like anthra- 
cite; which, however, it does not resemble either in structure, lustre, or proportion 
of carbon. 
MAUVAISES TERRES, NEBRASKA. 
After leaving the locality on Sage Creek, affording the above-mentioned fossils, 
crossing that stream, and proceeding in the direction of White River, about twelve 
or fifteen miles, the formation of the Mauvaises Terres proper bursts into view, dis- 
closing, as here depicted, one of the most extraordinary and picturesque sights that 
can be found in the whole Missouri country. 
From the high prairies, that rise in the background, by a series of terraces or 
