204 THIRTEENTH LETTER ON GLACIERS. [1846. 



face farther up ; and, in examining a number of the crevasses, I 

 could not see any engorged in the ice. The explanation seems 

 to be, that these stones are actually introduced into the ice by 

 friction at the bottom of the glacier, and forced upwards by the 

 action of the frontal resistance which produces the frontal dip of 

 the veined structure, and they are finally dispersed on the sur- 

 face by the melting of the ice. What is here supposed to occur 

 is illustrated by an ideal section of the glacier of the Rhone, 

 Plate VIII. fig. 7, where the curves of ejection are identical with 

 those of forced separation, causing the frontal dip of the veined 

 structure ; and this view is confirmed by what I have often 

 observed, particularly on the Glacier of Bossons, that the veined 

 structure in contact with the lateral moraines becomes soiled, 

 and that dirt and stones may be traced along the course of the 

 structural bands from the moraine to a considerable depth in the 

 ice. The action there is in the horizontal plane, what we here 

 suppose to take place in the vertical, and which the now esta- 

 blished retardation of the lower strata permits us to assume as 

 exactly a similar action. I have no doubt that a similar expla- 

 nation applies to the glacier of the Nant Blanc, and to other 

 glaciers.* 



Before closing this already too long letter, I wish to record 

 an observation already made by me in 1844, but which I hesi- 

 tated to publish because the sketch representing it was made 

 from memory, and not upon the spot ; but I have now verified 

 it both in the same and another locality. It is represented in 

 Plate VIII. fig. 5, where b d is part of the wall of the glacier 

 which is about to turn at a considerable angle with its former 

 direction (it is at the well-known part of the Mer de Glace named 

 IS Angle). I knew, from long experience, that the ice here pre- 



* It will be seen that this explanation will give an elevatory force to the ice 

 containing blocks similar to that which De Charpentier (Essai sur les Glaciers, 

 25) ascribed to the expansion of the frozen water. It will also be seen that it 

 renders a perfect account of the " veins of the debris of rocks '' in glaciers, particu- 

 larly near their lower extremities, which that ingenious author has attempted to 

 account for (unsatisfactorily, I think) by the transporting action of streams of water. 

 (Ibid, 27.) 



