322 GEOLOGY, 



motion has long been a mooted question, and is still so regarded. The 

 main alternative interpretations that have been entertained are the 

 following: 



(1) In the early days of glacial studies De Saussure thought that 

 glaciers sUd bodily on their beds; 



(2) Charpentier and Agassiz referred the movement to the expan- 

 sion of descending water freezing within the glacier; 



(3) Rendu and Forbes, followed by many, perhaps most, modern 

 writers, beUeved ice to be viscous, and that in sufficiently large masses 

 it flows under the influence of its own weight, like pitch or asphalt ; 



(4) Others, reaUzing the fundamental d'fference between crystaUine 

 ice and a true viscous body, have fallen back on a vague notion of plas- 

 ticity which scarcely amounts to a definite hypothesis at all ; 



(5) Tyndall urged that the movement was accomplished by minute 

 repeated fracturing and regelation, appealing to the fact that broken 

 pieces of ice slightly pressed together at melting temperatures freeze 

 together, but neglecting the fact that this would destroy the integ- 

 rity of the crystals; 



(6) Moseley assigned the movement to a bodily expansion and con- 



Ueber das Wesen der Gletscher und Wintereise in dem Eismeer, Stuttgart, 1842. R. 

 Mallet, The Mechanism of Glaciers, Jour. Geol. Soc. Dublin, Vol. I, p. 317; On the 

 Plasticity of Glacier Ice, Jour. Geol. Soc. Dublin, 1845, Vol. Ill, p. 122; On the 

 Brittleness and Non-plasticity of Glacier Ice, Phil. Mag., XXVI, p. 586. James 

 Thompson, On the Plasticity of Ice as Manifested in, Glaciers, Roy. Soc. Proc, Vol. 8, 

 1857, pp. 455-58. J. Tyndall and T, H. Huxley, On the Structure and Motion of 

 Glaciers, Phil. Trans., 1857, Vol. CXLVII, p. 327. J. D. Forbes, Occasional Papers 

 on the Theory of Glaciers, Edinburgh, 1859. W. Hopkins, On the Theory of the 

 Motion of Glaciers, Phil. Trans., 1882, p. 677; Phil. Mag., 1863, Vol. XXV, p. 224. 

 J. Tyndall, Forms of Water, New York, 1872; The Glaciers of the Alps, London, 1861. 

 James Croll, On the Physical Cause of the Motion of Glaciers, Phil. Mag., 1869, Vol. 38, pp. 

 201-6. A. Heim, On Glaciers, Phil. Mag., 1871, Vol. 41, pp. 485-508; Handbuch der Glet- 

 scherkunde, 1885. H. Moseley, On the Cause of the Descent of Glaciers, Br. Assoc. Rept,, 

 1860, Pt. 2, p. 48; also Phil. Mag., 1869, Vol. 37, pp. 229, 363; Vol. 39, p. 241; Vol. 42, 

 p. 138; Vol. 43, p. 38. Ch. Grad, La Constitution et le movement des Glaciers, Revue 

 Sci., 1872. H. J. Rink, Danish Greenland, 1877. R. M. Deeley, A Theory of Glacial 

 Motion, Phil. Mag., 1888, Vol. 25, pp. 136-64. J. C. McConnel, On the Plasticity of an 

 Ice Crystal, Proc. Roy. Soc. London, Vol. 48, 1890, pp. 256-60; ibid.. Vol. 49, 1891, 

 pp. 323-43. O. Miigge, tJber die Plasticitat der Eiskrystalle, Nachr. k. Ges. d. Wiss., 

 Gottingen, 1895, pp. 1-4. R. M. Deeley and George Fletcher, The Structure of Glacier 

 Ice and its Bearings on Glacier Motion, Geol. Mag. (London), Decade 4, Vol. 2, 1895> 

 pp. 152-62. T. C. Chamberlin, Presidential address before the Geol. Soc. Am., BuU. 

 Geol. Soc. Am., Vol. VI, February 1895, pp. 199-220. Reid, Mechanics of Glaciers, 

 Jour. Geol., Vol. IV, 1896, p. 912. Erich von Drygalski, Gronland-Expedition der 

 Gesellschaft fiir Erdkunde zu Berlin, 1891-93, Vol. I, 1897. 



