40 EXPEDITION TO THE 



IS found in white efflorescences, so as to be annually col- 

 lected there by the colonists of Pembina ; notwithstanding 

 which, at that settlement, the price of this article is from 

 four to six dollars per barrel, weighing eighty lbs. One of 

 the residents on this river cleared five hundred dollars in 

 one winter by the salt which he collected. Probably by 

 boring to a small depth abundant springs would be obtain- 

 ed. We had no opportunity of ascertaining the geological 

 features of the country, having seen on the whole route no 

 rock in place, and but few rolled stones, none of which had 

 attained to any size. The soil of the prairies is occasionally 

 sandy, though this does not appear to be its prevalent cha- 

 racter ; it is rather a dry argillaceous ground, which, with- 

 in a few miles of the river and its tributaries, yields good 

 grass, but at a distance from it presents but a scanty growth. 

 We do not profess to be judges of prairie land ; but we ob- 

 served that where trees do grow, the soil appears extreme- 

 ly fertile. It is probable, that the fires, which annually 

 overrun these prairies, destroy all the vegetable matter, 

 and tend to keep the ground in an impoverished state. We 

 observed a very great difference in the soil of those parts 

 of the prairie from which the grass had not been burnt off 

 the preceding year. 



The causes of these conflagrations are numerous. The 

 Indian frequently sets the prairies on fire in order to dis- 

 tract the pursuit of his enemies by the smoke, or to de- 

 stroy all trace of his passage; to keep the country open, 

 and thus invite the buffalo to it ; to be able to see and chace 

 his game with more facility ; as a means of communicating 

 intelligence to a distance with a view to give notice to his 

 friends of his approach, or to warn them of the presence 

 of an enemy. The traders often burn the prairies with 

 the same view. Independent, of these, the fires of encamp- 



