I had confined myself during the summer of 1857 to the Mer de Glace and its tributaries, desirous to make my knowledge accurate rather than extensive. I had made the acquaintance of all accessible parts of the glacier, and spared no pains to master both the details and the meaning of the laminated structure of the ice, but I found no fact upon which I could take my stand and say to an advocate of an opposing theory, "This is unassailable." In experimental science we have usually the power of changing the conditions at pleasure; if Nature does not reply to a question we throw it into another form; a combining of conditions is, in fact, the essence of experiment. To meet the requirements of the present question, I could not twist the same glacier into various shapes, and throw it into different states of strain and pressure; but I might, by visiting many glaciers, find all needful conditions fulfilled in detail, and by observing these I hoped to confer upon the subject the character and precision of a true experimental inquiry. The summer of 1858 was accordingly devoted to this purpose, when I had the good fortune to be accompanied by Professor Ramsay, the author of some extremely interesting papers upon ancient glaciers. Taking Zuerich, Schaffhausen, and Lucerne in our way, we crossed the Bruenig on the 22nd of July, and met my guide, Christian Lauener, at Meyringen. On the 23rd we visited the glacier of Rosenlaui, and the glacier of the Schwartzwald, and reached Grindelwald in the evening of the same day. My expedition with Mr. Huxley had taught me that the Lower Grindelwald Glacier was extremely instructive, and I was anxious to see many parts of it once more; this I did, in company with Ramsay, and we also spent a day upon the upper glacier, after which our path lay over the Strahleck to the glaciers of the Aar and of the Rhone. PASSAGE OF THE STRAHLECK. (14.) [Sidenote: A GLOOMY PROSPECT. 1858.]