All of the region about Winnipeg, in the Red River country, covering great areas of hundreds of miles in extent, is a level plain only lacking the coloring to give to one passing through it the effect of a great unruffled sea. There is no doubt but that all of this region was the bottom of a great lake at some period when the ice was receding. And this accounts for the great depth of black soil that we find in this and other regions. The soil was a water deposit, such as may be found in the bottom of any shallow lake or pond to-day, and thus many thousand years ago provision was made for the fertile areas which to-day are feeding the world with wheat. We can imagine that during this period the water that flowed off through the great Mississippi must have been of enormous volume as compared to the present time. A large portion of the delta of the Mississippi which now is a part of the States of Louisiana and Mississippi was carried down during the ice-melting period. Dr. Wright--as we have before stated--has estimated that there are a million square miles of country that has been covered to an average depth of fifty feet with glacial drift. A very large amount of the earth that was spread over the northern portion of the United States by leveling down hills and mountains in the northern country and scooping out the great lakes has been carried much farther than to the margin of the ice sheet. And I have no doubt but that a great portion of Louisiana and western Mississippi is made of earth carried down largely during the period of melting ice and deposited in this great delta. Imagine the effect that would be produced by the giving way of an ice dam or a great number of them at different periods, that would allow a body of water as large or larger than Lake Michigan to be drained off in a comparatively short time. When we think of it in this light the great delta of the Mississippi is easily accounted for. There are evidences of a great lake in the Red River country of the Northwest that is much larger than any of our greatest lakes. The shores of this lake--the bed of which is now dry land and the heart of a great agricultural region--are well defined and have been surveyed and mapped out. When this great body of water was released it was to the northward. For this reason it was undoubtedly held for a much longer time than some of the lakes to the southward where the ice melted sooner. CHAPTER XXVIII. SOME EFFECTS OF THE GLACIAL PERIOD.