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200 With this Martian information, received some years ago, it is pleasing now to see that Earthly knowledge is gradually catching up. For that increased precipitation could account for it, the evidence of pluvial eras in the

equatorial regions, contemporaneous with glacial periods, indicates. But another and probably the chief factor involved was not a generally increased precipitation, potent as that would be, but an increased snow deposit due to temporary elevation of the ground.

For it now appears that there was no glacial epoch. Our early ideas inculcated by text-books at school received a rude shock when it appeared that the glacial epoch was not, as we had been led to believe, a polar