43 
plied dairy products and beef to the mission. The prairies in that vicinity 
yield excellent hay and grazing, and the Salt Plains have long been used for 
wintering horses. An old Indian informed the writer that in former times- 
the people at Salt River settlement, Fort Smith, and vicinity used to set out 
in late summer or early autumn with pack horses to hunt the buffalo south- 
ward to Pine Lake district and westward of it. They spent the winter in 
the interior upland, turning their horses loose to wander of their own accord 
out to the Salt Plains. The Indians returned with dog-teams in the spring, 
and the horses came through the winter in splendid condition. 
So far as they have been examined the prairies occur on clayey, lacus- 
trine soils which were formed in the post-Glacial lakes that stood at about 
the 1,000- and 800-foot levels. As noted in the summary of topography and 
geology, these soils occur chiefly in three districts. One is at the eastern 
base of Caribou mountains where the prairie extends in a northeast and 
southwest direction within the park area and is said to extend to the west- 
ward of the fifth meridian north of Peace river. The writer found north- 
eastern extensions of it about 25 miles north of the Peace, but has no pre- 
cise information as to whether it has representatives still farther northward 
and northwestward at similar elevations (54). Another prairie lies in a 
strip beginning a short distance north of Pine lake, in the Grassy Slough 
district, and reaching northwestward to the vicinity of Flatgrass lake near 
Little Buffalo river. A third is on the more or less level area between the 
Slave River lowlands and the Salt Mountain upland, and has long been 
known as the Salt Plain. The extensions of this and the preceding area 
beyond the Little Buffalo have not been ascertained, though the descriptions- 
of parts of that region by a few travellers seem to indicate that they are 
present there in some form (61, 48, 54). The presence of saline conditions 
in shallow depressions in the Salt Plain has already been discussed. 
Other occurrences of certain elements of the prairie vegetation are in 
small openings in the upland forests, observed mostly in the vicinity of 
Pine lake and in sink-holes that still have or have had in former times a 
water level that fluctuates greatly. 
It seems best, in the following discussion, to give more or less detailed 
descriptions of the several different types of prairie opening vegetation 
before attempting any correlation. Like the upland forests, the initial 
stages in their history are now lost, and there is only the most scanty 
evidence of the causes of their occurrence and the course of their develop- 
ment. Willow and poplar or spruce clumps seem to be encroaching slowly 
upon the open spaces, and appear to have done so within the memory of 
men. E. T. Seton notes a statement by an old Indian inhabitant that he 
could remember when the prairies near the Salt Mountain escarpment were 
larger than they were in 1907 (65) . Studies made by the writer in 1930 on 
soil sections show that the marginal poplar groves have not existed for 
very long upon the ground *they now occupy. There is very little humus 
or leaf mould, and so little rotten w r ood that it seems apparent that at least 
some of the groves are of comparatively recent development. However, the 
marginal districts of these openings show, in the aggregate, a very small 
encroachment. The prairie extends to the very base of the first slopes of the 
