Mr. J. Ball on the Veined Structure of Glaciers. 265 



of years before, to direct attention to those smaller accumula- 

 tions that are found on slopes and depressions of the Alps, not 

 far below the region of the neve. I do not now speak of those 

 small patches of permanent neve which have scarcely any mea- 

 surable motion, one of which, close to the summit of the Faul- 

 horu, was very carefully studied by that good observer M. 

 Charles Martins ; and of which, as far as I can judge from the 

 lithograph, an example is given in plate 9 of Forbes^s ' Travels 

 through the Alps.' I speak of true glaciers of the second order, 

 such as the Kaltwasser Glacier above the pass of the Simplon, 

 the motion of which was measured by Professor Forbes. Ex- 

 amples may be found on all the higher parts of the Alps, but 

 most commonly on mountains of 10,000 or 11,000 feet in 

 height : they possess an appreciable, though slow, onward 

 motion ; and the neve becomes completely transformed into 

 glacier ice. Such glaciers are usually of very moderate depth, 

 and are nearly free from crevasses ; so that the only favourable 

 opportunity for obtaining a view of their internal structure is iu 

 places where they come to an end over an edge of steep rocks, 

 and the successive portions of the glacier break away as they 

 advance over the edge. In every instance of this nature, where 

 I have been able to approach the ice, I have seen indications of 

 a structure quite undistinguishable from the ordinary veined 

 structure, formed in planes sensibly pai-allel to the bed of the 

 glacier. I would strongly recommend those who desire to ap- 

 proach glaciers, however small they may be, in such situations, 

 to be on the ground early in the morning, before the sun has 

 had time to loosen impending fragments of the glacier. Failing 

 this precaution, considerable risk attends such inquiries. 



In tlie cases to which I refer, it has appeared to me that it is 

 diflScuIt to conceive the action of any pressure adequate to deve- 

 lope the veined structure. The only pressure, indeed, that can 

 be called into play is that compounded of the weight of the 

 upper portion of the ice pressing on the lower, together with that 

 which Professor Tyndall has shown to exist where adjoining 

 portions of a glacier move with unequal velocity. Whether 

 the amount of these two forces combined can be sufficient to 

 generate the veined structure in a glacier but thirty or forty 

 feet deep, where the absolute rate of advance is very small, and 

 the diflercntial motion is still smaller, seems to me very ques- 

 tionable. If it be so, the structure so developed should, at all 

 events, be confined to the lowest beds of such glaciers ; but, as 

 far as my observation has gone, this is by no means the case. 

 The structure has appeared uniform throughout the thickness 

 of the glacier. Pending further inquiry on this branch of the 

 •subject, I shall venture to believe that in these cases the veined 



I'hil. May. S. 4. Vol. 1 7. No. 114. April 1 859. T 



