“I was pleased to remain a debtor to Humboldt,” writes Agassiz, a sentiment which probably awakens more sympathy in the heart of the average undergraduate than it did in the bosom of Humboldt. A holiday which Agassiz spent with another great naturalist, Charpentier, was indirectly responsible for the beginnings of the glacial theory. Throughout Switzerland, you may find huge boulders known as erratic blocks. These blocks have a different geological ancestry from the rocks in the immediate neighbourhood. They did not grow like mushrooms, and they must therefore have been carried to their present position by some outside agency. In the eighteenth century, naturalists solved all these questions by _a priori_ theories, proved by quotations from the book of Genesis. The Flood was a favourite solution, and the Flood was, therefore, invoked to solve the riddle of erratic blocks. By the time that Agassiz had begun his great work, the Flood was, however, becoming discredited, and its reputed operations were being driven further afield. The discovery of the true solution was due, not to a scientist, but to a simple chamois hunter, named Perrandier. He knew no geology, but he could draw obvious conclusions from straightforward data without invoking the Flood. He had seen these blocks on glaciers, and he had seen them many miles away from glaciers. He made the only possible deduction--that glaciers must, at some time, have covered the whole of Switzerland. Perrandier expounded his views to a civil engineer, by name Venetz. Venetz passed it on to Charpentier, and Charpentier converted Agassiz. Agassiz made prompt use of the information, so prompt that Charpentier accused him of stealing his ideas. He read a paper before the Helvetic Society, in which he announced his conviction that the earth had once been covered with a sheet of ice that extended from the North Pole to Central Asia. The scepticism with which this was met incited Agassiz to search for more evidence in support of his theory. His best work was done in “The Hôtel des Neuchâtelois.” This hôtel at first consisted of an overhanging boulder, the entrance of which was screened by a blanket. The hôtel was built near the Grimsel on the medial moraine of the lower Aar glacier. To satisfy Mrs. Agassiz, her husband eventually moved into even more palatial quarters to wit, a rough cabin covered with canvas. “The outer apartment,” complains Mrs. Agassiz, a lady hard to please, “boasted a table and one or two benches; even a couple of chairs were kept as seats of honour for occasional guests. A shelf against the wall accommodated books, instruments, coats, etc.; and a plank floor on which to spread their blankets at night was a good exchange for the frozen surface of the glacier.” But the picture of this strange _ménage_ would be incomplete without mention of Agassiz’s companions. “Agassiz and his companions” is a phrase that meets us at every turn of his history. He needed