1846.] THE VEINED STRUCTURE EXAMINED AND ACCOUNTED FOR. 183 



of the intense pressure with which the whole mass of the glacier 

 is urged against the side of the valley ; but as the glacier is 

 finally compelled to move in the direction of the declivity from 

 E towards D, a longitudinal tearing force arises parallel to E D, 

 and the motion is facilitated by the formation of the veined struc- 

 ture already mentioned, for of longitudinal crevasses there are 

 absolutely none. Such crevasses as there are, are transverse to 

 the blue bands, shewing the usual direction of the tearing force 

 due to the lateral friction. But they are small and isolated. 



Now, in this case, the development of the structure is evi- 

 dently due to the projection at D, in contact with which it 

 terminates ; and though the whole glacier is more or less struc- 

 tured in the manner described and figured in my former work, 

 this remarkable development gradually ceases [in an upward 

 direction] about E, where the rush of the ice-current past the 

 promontory B has ceased to exert so palpable an effect. I can 

 positively state that no such unusual development of the structure 

 occurred opposite to B in 1842, and for this reason, that the glacier 

 lying then more in the trough of the valley, not being violently 

 pressed against the promontory B, and embayed in the height * 

 C, the friction and longitudinal tearing force was incomparably 

 less. I wish I could convey any adequate -idea of the beauty of 

 the ice for an extent of some hundred feet in length, and for a 

 comparatively trifling breadth between D and E. It resembled 

 the greenish-veined marble called by the Italians Cipollmo, 

 when of the highest perfection, and polished or wetted ; and it 

 was impossible to resist the wish to carry off slabs, and to per- 

 petuate it by hand specimens in cabinets. 



I did not, however, content myself with arguing the rela- 

 tive motions of the parts of the ice and embaying of the rest, 

 from the mere configuration of the ground. But I made the 

 following experiments, which proved that my first belief was 

 correct. 



The instrument [theodolite] being stationed at B [Plate 

 VIII. fig. 4], and a transverse visual line established with reference 



* [Evidently a misprint for bight, which is the word used in my original notes.] 



