1859.] on the Veined Structure of Glaciers. 73 



veins of a more transparent character than tlie rest of the mass ; tlie 

 transparency being due to the fact that the air which gives to 

 the ice its whiteness has by some means or other been wholly or 

 partially ejected from the veins. These veins partake of the blue 

 colour of transparent ice, and, contrasted with the white ice in which 

 they are imbedded, often give to the substance a most beautiful 

 laminated appearance ; vast portions of many glaciers consist of this 

 laminated ice. 



The object of the discourse was to offer an explanation of this 

 veined structure of glacier ice. 



The theory of the veins which perhaps first presents itself to the 

 mind, and which is still entertained by many intelligent Alpine explo- 

 rers, is that the veining of the middle glaciers is simply a continuation 

 of the bedding of the nt^vt^ ; that not only do the annual snow-falls 

 produce beds of great thickness, but every successive fall tends to 

 produce a layer of less thickness, which layers, or rather the surfaces 

 separating them, ultimately appear as the blue veins. This theory, it 

 was admitted, demanded the most serious consideration : on the exposed 

 sections of the n^ve the lines of stratification were very manifest, and 

 exhibited in many cases appearances closely resembling that of the 

 veined structure. Indeed, it was with a view to examine this subject 

 more closely, that the speaker withheld his observations on the structure 

 of the Mer de Glace made in 1857, and betook himself once more to 

 the mountains during the summer of 1858 ; his desire being to settle 

 once for all the rival claims of the only two theories which then 

 deserved serious attention, namely those of pressure and of strati- 

 fication . 



In pursuance of this idea, he first visited the lower glacier of 

 Grindelwald, one of the most accessible, and at the same time most 

 instructive in the entire range of the Alps. Ascending the branch of 

 this glacier which descends from the Schreckhorn, the Strahleck, and 

 the Finsteraarhorn, he came to the base of an ice-fall which forbade 

 further advance. Quitting the glacier here, he ascended the side of 

 the flanking mountain, so as to reach a point from which the fall, and 

 the glacier below it, were distinctly visible ; and from this position he 

 observed the gradual development and perfecting of the structure at 

 the base of the fall. On the fall itself no trace of the transverse 

 structure was manifest ; but where the glacier changed its inclination 

 at the bottom, being bent upwards so as to throw its surface into a 

 state of intense longitudinal compression ; where, moreover, it had to 

 bear the thrust of the descending mass behind, the blue veins first 

 made their appearance. The base of the fall was a true structure mill, 

 where the transverse veins were manufactured, being afterwards sent 

 forward, giving a character to portions of the glacier which had no 

 share in their formation. 



The speaker afterwards examined the fall from the opposite side of 

 the valley, and corroborated his observations. It is difficult, in words, 

 to convey the force of the evidence which this glacier presents to the 

 mind of the observer who sees it ; it seems in fact like a grand labora- 



