One friend, scarcely mentioned thus far in this biography, was yet, from the beginning, the close associate of Agassiz's glacier work. Arnold Guyot and he had been friends from boyhood. Their university life separated them for a time, Guyot being at Berlin while Agassiz was at Munich, and they became colleagues at Neuchatel only after Agassiz had been for some years established there. From that time forward there was hardly any break in their intercourse; they came to America at about the same time, and finally settled as professors, the one at Harvard College, in Cambridge, Massachusetts, and the other at the College of New Jersey, in Princeton. They shared all their scientific interests; and when they were both old men, Guyot brought to Agassiz's final undertaking, the establishment of a summer school at Penikese, a cooperation as active and affectionate as that he had given in his youth to his friend's scheme for establishing a permanent scientific summer station in the high Alps. In a short visit made by Agassiz to Paris in the spring of 1838 he unfolded his whole plan to Guyot, then residing there, and persuaded him to undertake a certain part of the investigation. During this very summer of 1838, therefore, while Agassiz was tracing the ancient limits of the ice in the Bernese Oberland and the Haut Valais, and later, in the valley of Chamounix, Guyot was studying the structure and movement of the ice during a six weeks' tour in the central Alps. At the conclusion of their respective journeys they met to compare notes, at the session of the Geological Society of France, at Porrentruy, where Agassiz made a report upon the general results of his summer's work; while Guyot read a paper, the contents of which have never been fully published, upon the movement of glaciers and upon their internal features, including the laminated structure of the ice, the so-called blue bands, deep down in the mass of the glacier.* (* See "Memoir of Louis Agassiz" by Arnold Guyot, written for the United States National Academy of Sciences, page 38.) In the succeeding years of their glacial researches together, Guyot took for his share the more special geological problems, the distribution of erratic boulders and of the glacial drift, as connected with the ancient extension of the glaciers. This led him away from the central station of observation to remoter valleys on the northern and southern slopes of the Alps, where he followed the descent of the glacial phenomena to the plains of central Europe on the one side and to those of northern Italy on the other. We therefore seldom hear of him with the band of workers who finally settled on the glacier of the Aar, because his share of the undertaking became a more isolated one. It was nevertheless an integral part of the original scheme, which was carried on connectedly to the end, the results of the work in the different departments being constantly reported and compared. So much was this the case, that the