Structure and bedding on the Great Aletsch Glacier 391 45, 46. Structure and Stratification on the Furgge glacier 394 47. Diagram illustrating Differential Motion 395 48, 49. Diagrams explanatory of the formation of Ripples 400, 403 50, 51. Appearance of a prism of ice partially liquefied by Pressure. 410 52, 53. Figures illustrative of compression and liquefaction of ice. 411 54, 55. Sections of White Ice-seams 414 56, 57. Variations in the Dip of the Veined Structure 414, 415 58. Section of three glacier Crumples 416 59. Wall of a crevasse, with incipient crumpling 416 60. Plan of a Stream on the Glacier du Geant 418 61. Plan of a Seam of White Ice on ditto 418 PART I. CHIEFLY NARRATIVE. Ages are your days, Ye grand expressors of the present tense And types of permanence; Firm ensigns of the fatal Being Amid these coward shapes of joy and grief That will not bide the seeing. Hither we bring Our insect miseries to the rocks, And the whole flight with pestering wing Vanish and end their murmuring, Vanish beside these dedicated blocks. Emerson GLACIERS OF THE ALPS. INTRODUCTORY. (1.) In the autumn of 1854 I attended the meeting of the British Association at Liverpool; and, after it was over, availed myself of my position to make an excursion into North Wales. Guided by a friend who knew the country, I became acquainted with its chief beauties, and concluded the expedition by a visit to Bangor and the neighbouring slate quarries of Penrhyn. From my boyhood I had been accustomed to handle slates; had seen them used as roofing materials, and had worked the usual amount of arithmetic upon them at school; but now, as I saw the rocks blasted, the broken masses removed to the sheds surrounding the quarry, and there cloven into thin plates, a new interest was excited, and I could not help asking after the cause of this extraordinary property of cleavage. It sufficed to strike the point of an iron instrument into the edge of a plate of rock to cause the mass to yield and open, as wood opens in advance of a wedge driven into it. I walked round the quarry and observed that the planes of cleavage were everywhere parallel; the rock was capable of being split in one direction only, and this direction remained perfectly constant throughout the entire quarry. [Sidenote: CLEAVAGE OF SLATE ROCKS.]