target="_blank" rel="nofollow" href="#u09502267-2a80-4c2a-ada7-e9317a0ade6d">27.—Veined Structure of Glaciers.376
General appearance; Grooves upon the glacier; first observations; description by M. Guyot; observations of Professor Forbes; Structure and Stratification; subject examined; Marginal Structure; Transverse Structure; Longitudinal Structure; experimental illustrations; the Structure Complementary to the Crevasses; glaciers of the Oberland, Valais, and Savoy examined with reference to this question
28.—The Veined Structure and Differential Motion.395
Marginal Structure Oblique to sides; Drag towards the centre; difficulties of theory which ascribes the structure to Differential Sliding; it persists across the lines of maximum sliding
29.—The Ripple Theory of the Veined Structure. 398
Ripples in Water supposed to correspond to Glacier Structure; analysis of theory; observation of the MM. Weber; water dropping from an oar; stream cleft by an obstacle; Two Divergent lines of Ripple; Single Line produced by Lateral Obstacle; Direction of ripples compounded of River's motion and Wave motion; Structure and Ripples due to different causes; their positions also different
30.—The Veined Structure and Pressure. 404
Supposed case of pressed prism of glass; Experiments of Nature; Quartz-pebbles flattened and indented; Pressure would produce Lamination; Tangential Action
31.—The Veined Structure and the Liquefaction of Ice by Pressure.408
Influence of pressure on Melting and Boiling points; some substances swell, others shrink in melting; effects of pressure different on the two classes of bodies; Theoretic Anticipation by Mr. James Thomson; Melting point of Ice lowered by pressure; Internal Liquefaction of a prism of solid ice by pressure; Liquefaction in Layers; application to the Veined Structure
32.—White Ice-Seams of the Glacier du Géant. 413
Aspect of Seams; they sweep across the glacier concentric with Structure; Structure at the base of the Talèfre cascade; Crumples; Scaling off by pressure; Origin of seams of White Ice
33. 419
Glacier du Géant in a state of Longitudinal Compression; Measurements which prove that its hinder parts are advancing upon those in front; Shortening of its Undulations; Squeezing of white Ice-seams; development of Veined Structure
Summary 422
ILLUSTRATIONS.
The Mer de Glace.—Showing the Cleft Station at Trélaporte, the Echelets, the Tacul, the Périades, and the Grand Jorasse.Frontispiece
Fig.Page
1. Ice Minaret14 2. Diagram of an angular reflector16 3, 4. Boats' sails inverted by Atmospheric Refraction35 5. Wave-like forms on the Mer de Glace43 6. Glacier Table44 7. Tributaries of the Mer de Glace53 8. Magnetic Boulder of the Riffelhorn143 9, 10, 11, 12. Luminous Trees projected against the sky at sunrise180, 181 13. Snow on the Pines201 14, 15. Snow Crystals214 16. Chasing produced by waves233 17. Diagram explanatory of Interference234 18. Interference Spectra, produced by DiffractionTo face 235 19. Moraines of the Mer de Glace" 264 20. Typical section of a glacier Table266 21. Locus of the Point of Maximum Motion286 22. Inclinations of ice cascade of the Glacier des Bois313 23. Inclinations of Mer de Glace above l'Angle314 24. Fantastic Mass of ice316 25. Diagram explanatory of the mechanical origin of Crevasses318 26. Diagram showing the line of Greatest Strain319 27a, b. Section and Plan of a portion of the Lower Grindelwald Glacier322 28. Diagram illustrating the crevassing of Convex Sides of glacier323 29. Diagram illustrating test of viscosity326 30, 31, 32, 33. Moulds used in experiments with ice346-348 34. Liquid Flowers in lake ice355 35. Dirt-bands of the Mer de Glace, as seen from a point near the FlégèreTo face 367 36. Ditto, as seen from les Charmoz" 368 37. Ditto, as seen from the Cleft Station, Trélaporte" 369 38. Plan of Dirt-bands taken from Johnson's 'Physical Atlas'374 39. Veined Structure on the walls of crevasses381 40. Figure explanatory of the Marginal Structure383 41. Plan of part of ice-fall, and of glacier below it (Glacier of the Rhone)386 42. Section of ditto386 43. Figure explanatory of Longitudinal Structure388 44. Structure and bedding on the Great Aletsch Glacier391 45, 46. Structure and Stratification on the Furgge glacier394 47. Diagram illustrating Differential Motion395 48, 49. Diagrams explanatory of the formation of Ripples400, 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-seams414 56, 57. Variations in the Dip of the Veined Structure414, 415 58. Section of three glacier Crumples416 59. Wall of a crevasse, with incipient crumpling416 60. Plan of a Stream on the Glacier du Géant418 61. Plan of a Seam of White Ice on ditto418
PART I.
CHIEFLY NARRATIVE.
