—ideapemenalimaiee iia 
PLASTER OF PARis. 185 
to be of trap and greenstone. From the wa- 
ters of Red River to the southwest corner of 
Missouri, throughout the range of the Ozark 
mountains, granite, limestone, flint and sand- 
stone prevail. But much of the middle por- 
tion of the Prairies is without any apparent 
rocky foundation—we sometimes travel for 
ays in succession without seeing even as 
much as a pebble. 
On passing towards Santa Fé in 1839, and 
‘returning in 1840, I observed an immense 
range of plaster of Paris, both north and south 
of the Canadian river, and between thirty and 
fifty miles east of the United States western 
boundary. The whole country seemed based 
upon this fossil, and cliffs and huge masses 
of it were seen in every direction. It ranges 
from the coarsest compact sulphate of lime or 
ordinary plaster, to the most transparent 
sum or selenite, of which last there is a great 
abundance. By authentic accounts from 
other travellers, this range of gypsum extends, 
in a direction nearly north, almost to the Ar- 
kansas river. 
Of metallic minerals, iron, lead, and per- 
haps copper, are found on the borders of the 
Prairies ; and it is asserted that several speci- 
mens of silver ores have been met with on 
our frontier, as well as about the Witchita and 
the Rocky Mountains. Gold has also been 
found, no doubt, in different places; yet it is 
questionable whether it has anywhere been 
- discovered in sufficient abundance to render it 
worth the seeking. Some trappers have report- 
te 16* ° 
