ON THE STRUCTURE AND MOTION OF GLACIERS 25 
hacked irregularly, so as to represent the dislocation of the ice in the 
glacier. Along the slope this hacking produced an irregular and 
confused distribution of the sand; but lower down, the patches of 
dirt 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 them- 
selves 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 regelation, without which it 
may be doubted whether the existence of a glacier would be at all 
possible, opens, in itself, a new field of investigation. This and other 
questions, introduced in the foregoing pages, must however be: dis- 
cussed with strict reference to the phenomena as Nature presents 
them. Much might be said even now upon these subjects, but the 
known liability of the human mind to error when speculation is 
substituted for observation, renders it safer to wait for more exact 
knowledge than to hazard opinions which an imperfect acquaintance 
with the facts must necessarily render to some extent uncertain. 
RovaL InsTITuTION, January 1857. 
