It is now fifty years since Charpentier told us that the heaps of Northern boulders which stretch across the plains of Prussia and Saxony mark the ancient limits of the great glacier of Scandinavia, and that the smaller debris met with farther south represents the stuff carried on by the torrents that escaped from the margin of the ice. All this he explained to his incredulous contemporaries, and now after half a century of debate, in which every other conceivable mode of accounting for the phenomena has been tried, it seems to he agreed on all hands that he was right—right in every particular—but, strange to say, it appears to be now generally forgotten that he was the man to whom we owe the first sketch of this explanation.