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WAVE-LIKE PROGRESS OF AN EPEIROGENIC UPLIFT.
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third distance of 74 miles to the international boundary. Its whole ascent thus in 224 miles is 175 feet, by a slope which increases from slightly less than a half of a foot per mile in its southern third to slightly more than one foot per mile in its northern third. This beach extends only a short distance farther north, having been formed when the ice-sheet lay there as the northern boundary of the lake; but the second of the Herman beaches, slightly lower and later, reaches as far northward as to the limit of my exploration, in the vicinity of Gladstone, Manitoba, and Riding Mountain, and in this distance of 308 miles, from Lake Traverse to the latitude of Gladstone, it has an ascent of 265 feet. In the four successive nearly equal parts of its extent from south to north, namely, 75 miles, again 75 miles, then 74 miles, and lastly 84 miles, it rises respectively about 35, 50, 80, and 100 feet; and almost the whole of this change of the old beach, from its horizontality at the time of formation, has been produced by the gradual uplifting of the lake basin while the ice-sheet was retreating from it.

The considerably later upper Norcross beach rises in these distances about 25, 35, 55, and 70 feet, amounting to 185 feet in the entire 308 miles. The upper Campbell beach as ascents of about 10, 15, 30, and 35 feet, or 90 feet in all; and the lowest of the three McCauleyville beaches, marking the latest stage of southward outflow of Lake Agassiz, ascends about 5, 10, 15, and 20 feet or a total of 50 feet. It is thus seen that far the greater part of the uplift of this area had been accomplished before the formation of the Campbell and McCauleyville beaches.

Beyond the limits of my leveling, portions of nearly all the shore lines of Lake Agassiz below those of the Herman series have been observed and mapped by Mr. J. B. Tyrrell, of the Canadian Geological Survey, at localities in northwestern Manitoba and eastern Saskatchewan, bordering the northern half of this lacustrine area.[1] From a careful comparison of the eleva-

  1. ↑ Geol. and Nat. Hist. Survey of Canada, An. Rep., new series, Vol. 3, for 1887-88, Part E, pp. 16, with map; Vol. 5, for 1889-90, Part E, pp. 240, with map, sections, and illustrations from photographs.
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