246, Canon Moseley on the "Veined Structure" 



of the Mer de Glace at Les Ponts moves at the same rate as that 

 of the side of the Geant does near the Tacul ; E 10 10' 10 D, fig. 3, 

 will then represent the side of the ice at A, fig. 2, or rather along 

 the neighbouring line 112 3; D 10 being the top or surface- 

 line, and E 10 the bottom one. 



We can have no observations on the motion of the bottom ice 

 elsewhere than at the sides of the glacier. Supposing, however, 

 that it bears elsewhere the same proportion to the surface-motion 

 as it does at the sides, it may be calculated that the mean annual 

 motion of the bottom ice at stations 12 and 13, where the sur- 

 face-ice moves fastest, is 457 links. In fig. 4 I have set off, on 

 the same scale as before, the depth G H of the glacier in links, 

 and from H the distances H 1, 1 2, 2 3, &c, each of 457 links, 

 to represent the mean annual motions of the bottom ice in suc- 

 cessive years at the stations 12 and 13, and, from G, G 1, 1 2, 2 3, 

 &c. to represent the corresponding motions of the top ice, and 

 from K corresponding distances to represent the motion of the 

 ice at 35 feet from the bottom. The curved lines 1 1, 2 2, 3 3, 

 &c. represent, therefore, on this figure, as the corresponding 

 lines did on the preceding, the positions of the ice at the ends of 

 ten successive years which at the beginning of them was in G H ; 

 so that if a boring had been made at that time at station 12 and 

 filled with sand, then the sand would at the end of one year have 

 been drawn out into the curve 1 1 (fig. 4), at the end of two 

 years into the curve 2 2, &c, and at the end of ten years into 

 the curve 10 10. And if a cut had been made across the gla- 

 cier in the line A B and filled with sand, or with water which 

 had frozen into a plate of transparent ice, then at the end of the 

 first year that sand or that transparent ice would have arranged 

 itself into a conoidal surface, of which 1 1 represents a hori- 

 zontal section at the surface (fig. 2), and H 11 (fig. 4) represents 

 a vertical section parallel to the axis of the glacier at station 12, 

 and E 11 a section at the side A, and so of succeeding years; 

 and at the end of ten years the plate of sand or of trans- 

 parent ice, which at the beginning filled the vertical cut at 

 A B, would have been drawn out and attenuated into the 

 surface whose horizontal section at the top is 10 10 (fig. 2), 

 its vertical section at the point of fastest motion 10 10 (fig. 4), 

 and its section at the side 10 10 (fig. 3). 



It will be observed of these surfaces, that they are of that 

 spoon-shape which Principal Forbes has described as character- 

 istic of the veined structure, that, as in that structure, their 

 frontal dip continually diminishes as they descend the glacier, 

 and that the surface indications of the structure are more ener- 

 getically developed at the edges than in the centre. If we con- 

 ceive a point in the channel of a glacier where such a cut is from 



