244 Canon Moseley on the " Veined Structure " 



absence of longitudinal compression exists in many glaciers ; and 

 in such ice streams there is no transverse central structure deve- 

 loped. But let a circle be stamped upon the mud-stream near 

 its side; owing to the speedier flow of the centre, this circle must 

 be distorted to an ellipse, because the part of the circle furthest 

 from the side moves more quickly than the part nearest the 

 side. Hence we shall have an ellipse formed with its major axis 

 inclined downwards, indicating that the mud is compressed in 

 one direction and expanded in another. An exactly similar state 

 of things occurs in many glaciers : the ice near the sides is sub- 

 jected to a presure and tension like that here indicated ; and we 

 have marginal crevasses as the result of tension, while the veined 

 structure is, at all events, associated with the pressure"*. 



In all these theories a connexion between the differential mo- 

 tion of the ice of glaciers and the veined structure is supposed ; 

 but in none of them is it recognized that the one is a necessary 

 consequence and simple result of the other. It is the object of this 

 paper to show that the differential motion is constantly producing 

 in all parts of the ice those internal displacements which in certain 

 parts the veins make visible— so that, under assumed conditions, 

 the veined structure is a necessary result of the differential mo- 

 tion, and, conversely, the fact of the differential motion is proved 

 by the existence of the veined structure — and that the force, 

 whatever it may be, by which the first is produced is no other 

 than that which, through it, is the cause also of the second. 

 From this it follows that, as the differential motion is assumed to 

 be wholly in the direction of the length of the glacier, no lateral 

 motion of any kind, nor any lateral pressure, is necessary to that 

 structural process, going on in all parts of the glacier, of which, 

 in certain parts, the veined structure and the dirt-bands afford 

 the evidence. 



I have set off along the line AB ; fig. 2, the measurements of 

 Professor Tyndall, taken in links, across the Mer de Glace at 

 "Les Ponts^f. The stations where he put stakes are numbered 

 from 1 to 17. I have multiplied the mean daily motions of these 

 stakes, observed in iuches by Professor Tyndal!, by 365 ; and re- 

 ducing them to links, I have set them off from the same scale of 

 equal parts along the dotted lines drawn from the several stations 

 parallel to the length of the glacier ; the points 1', 2', 3', 4', &c. 

 show the terminations of these lines. 



If stones were placed on the surface of the glacier at the points 

 1, 2, 3, 4_, &c, and the ice retained the same mean daily motion 

 as was observed by Professor Tyndall throughout the year, then 



* Phil. Trans. 1859, part i. p. 282. 

 t Ibid. p. 266. 



