depth of one hundred and twenty-five feet. The most serious peril of the ascent was caused by the huge stalactites of ice, between the points of which he had to steer his way. Any one of them, if detached by the friction of the rope, might have caused his death. He afterward said: "Had I known all its dangers, perhaps I should not have started on such an adventure. Certainly, unless induced by some powerful scientific motive, I should not advise any one to follow my example." On this perilous journey he traced the laminated structure to a depth of eighty feet, and even beyond, though with less distinctness. The summer closed with their famous ascent of the Jungfrau. The party consisted of twelve persons Agassiz, Desor, Forbes, Heath, and two travelers who had begged to join them,--M. de Chatelier, of Nantes, and M. de Pury, of Neuchatel, a former pupil of Agassiz. The other six were guides; four beside their old and tried friends, Jacob Leuthold and Johann Wahren. They left the hospice of the Grimsel on the 27th of August, at four o'clock in the morning. Crossing the Col of the Oberaar they descended to the snowy plateau which feeds the Viescher glacier. In this grand amphitheatre, walled in by the peaks of the Viescherhorner, they rested for their midday meal. In crossing these fields of snow, while walking with perfect security upon what seemed a solid mass, they observed certain window-like openings in the snow. Stooping to examine one of them, they looked into an immense open space, filled with soft blue light. They were, in fact, walking on a hollow crust, and the small window was, as they afterward found, opposite a large crevasse on the other side of this ice-cavern, through which the light entered, flooding the whole vault and receiving from its icy walls its exquisite reflected color.* (* The effect is admirably described by M. Desor in his account of this excursion, "Sejours dans les Glaciers" page 367.)