After this interglacial there set in a period of renewed elevation in the Rocky Mountains and in the Labrador-Newfoundland centres, which brought about a recurrence of the glaciation. In the Rocky Mountains the ice was not so thick as in the preceding stage, but all the valleys were occupied to a considerable depth and the ice spread out to the eastward. The Labrador ice-sheets also developed again, forming the Illinoian glaciation, the moraines of which are found as far west as Illinois, but no moraines are known of this age due to the Keewatin ice-sheet. The latter developed later, and is classed by some American geologists as a separate glaciation, the Iowan, which is only certainly found in northern Iowa, but may be represented further east by a thin sheet of boulder-clay overlapping the Illinoian moraine. The supposed interglacial between the Illinoian and Iowan, the “Sangamon Stage,” is represented only by land surfaces formed of the Illinoian moraine and covered by the loess or locally by the equivalent of the Iowan moraine, and there is no evidence that the ice-edge retreated far. Other American geologists, including F. Leverett, do not recognize the existence of a separate Iowan glaciation, and as the amount of weathering and denudation undergone by the two moraines differs very little, this seems the more natural view. The natural explanation seems to be that this was another case of “glacial piracy,” the Keewatin ice-sheet, owing to its lesser snowfall, developing more gradually, and finally diverting the supply of moisture from the Labradorean ice-sheet, until it reached a maximum after the latter was already on the wane. Both these sheets of drift present similar flat features to the Kansan sheet, without morainic ridges.