THE STEUCTUEE AND MOTION OE OLACIEES. 
345 
the Grimsel or the Furka pass. ACLM is a box with a sluice front, which can be 
raised so that the fine mud within the box shall flow regularly into the trough, as in the 
Fig. 10. 
cases akeady described. The disposition of the trough will be manifest from the section, 
fig. 11. While the mud was in slow motion downwards, a quantity of dark-coloured 
Fig. 11. 
sand was sifted over the space ACEF, so as to represent the debris irregularly scattered 
over the corresponding surface of the glacier ; during the passage of the mud over the 
brow at EF, and down the subsequent slope, it was hacked irregularly, so as to represent 
the dislocation of the ice in the glacier. Along the slope this hacldng produced an 
kregular and confused distribution of the sand ; but lower down, the patches of dkt and 
the clean spaces between them gradually assumed grace and symmetry; they were 
squeezed together longitudinally and drawn out laterally, bending with the convexity 
downwards in consequence of the speedier flow of the central portions, until finally a 
system of bands was established which appeared to be an exact miniature of those 
exhibited by the glacier. On fig. 10 is a sketch of the bands observed upon the surface 
of the mud, which however falls short of the beauty and symmetry of the original. These 
experiments have been varied in many ways, with the same general result. 
In conclusion we would remark, that our joint observations upon the glaciers of 
Switzerland extended over a period of a few days only. Guided by the experience of 
our predecessors, much was seen even in this brief period ; but many points of interest 
first suggested themselves during the subsequent experimental investigation. While, 
therefore, expressing our trust that the substance of the foregoing memoir will be 
found in accordance with future observation, we would also express our belief in the 
necessity of such observation. Indeed the very introduction of the principle of regela- 
MDCCCLVII. 2 z 
