MAESHES IN MANITOBA. 587 



of the marsh lands, worthless before they are drained, but afterward very- 

 valuable. 



Several of the prairie marshes of Manitoba, lying west of the Red 

 River and on both sides of the Assiniboine, range in extent from 20 to 75 

 square miles, namely, the marsh in which Tobacco Creek is spread out and 

 lost east of Pomeroy; the great marsh similarly formed by the waters of 

 the Boyne River and Elm Creek, extending 15 miles from west to east, with 

 a width of 3 to 6 miles, overflowing southeastward to the Red River by 

 the Riviere aux Gratias; the Squirrel Creek marsh, lying close south of the 

 White Mud River, between Westbourne and Woodside, formed by Image, 

 Beaver, Squirrel, Pine, and Silver creeks, which come from the northeastern 

 slope of the Assiniboine delta; and the Big Grass marsh, extending more 

 than 20 miles from south to north, with a width of 3 to 5 miles, in which 

 the White Mud and Big Grass rivers are lost or flow sluggishly through 

 a broad, quaking morass, with shallow, rush-filled lakes along its axial 

 portion. 



Commonly the water of the marshes is supplied almost wholly by 

 inflowing streams and by rainfall, but in some instances they receive a 

 large part of their water from springs. Multitudes of copious springs of 

 fresh water, issuing from thick beds of sand and gravel which eastward 

 are overlain by till, form the very remarkable boggy tract, a half mile to 

 1 mile wide, which extends about 9 miles from south to north along the 

 highest shore of Lake Agassiz in Aki'on and Tanberg, Wilkin County, Minn. 

 Unlike the level marshes before enumerated, tliis tract lies on a slope which 

 descends 20 to 40 feet upon the width of the marshy gi-ound from east to 

 west. On such a slope the marsh can be maintained only by the constant 

 issuance of spring water through all portions of its bed. (See pp. 286, 385.) 



In several other marshes of smaller extent, as on the Salt Cooley and 

 Salt River, near Ojata, tributary to the Turtle River, and on the Forest 

 and Park rivers, it is known that saline spi-ings come up within the area of 

 the marshes, because, although the streams flowing into them are fresh, the 

 outflowing water is brackish. 



Throughout nearly all the part of the Red River Valley where brack- 

 ish water is found by the artesian wells, and where it infrequently outflows 



