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PEOFESSOES TTiS'DALL AXD HTXLET OX 
boxes, and after it had covered the bottom of the trough to some distance below the 
line ST, the end of a glass tube was dipped into a fine mixture of the red oxide of iron 
and water, and the two arms of the glacier were covered all over with small circles 
similar to those between the points ah and dV, The mud was then pennitted to flow, 
and the mechanical strains exerted on it were inferred from the distortion of the small 
circles. The figure represents the result of the experiment. The straight rows of 
cii’cles bent in the first place into curves ; at the point A both streams met, and by their 
mutual push actually squeezed the circles into lines. Along this central portion in the 
glacier itself the great medial moraine stands, and under it and beside it, as akeady 
stated, the lamination is most strikingly developed ; the blue veins being parallel to the 
axis of the glacier, or, in other words, coinciding with the direction of the central 
moraine. Midway between the moraine and the sides of the glacier the structure is 
very imperfectly developed, and the deportment of our model, which shows that the 
circles here scarcely change their form, tells us that this is the result which ought to be 
expected. It may be urged, that the structm'e is here developed, because of the sliding 
motion produced by the swifter flow of one of the glaciers ; but some of the experiments 
with the model were so arranged, that both of the branch streams flowed with the same 
velocity ; the distortions, however, were such as are shown in the flgiu’e. The case is 
precisely the same in nature. On reference to the map of M. Agassiz, we find a straight 
line set out across the Unter Aar glacier bent in three successive years into a cmwe; but 
on the central moraine, which marks the common limit of the constituent streams, we 
find no breach in the continuity of the curve, which must be the case if one glacier slid 
past the other. 
§ 6. On the DiTt-Bands" of Glaciers. 
Wherever the veined structure of a glacier is highly developed, the surface of the 
ice, owing to the action of the weather, is grooved m accordance uith the lamination 
underneath. These grooves are sometimes as fine as if drawn by a pencil, and bear in 
many instances a striking resemblance to those produced by the passage of a rake over 
a graveled surface. In the furrows of the ice the smaller particles of dirt prmcipally 
rest, and the direction of the furrows, which always corresponds with that of the blue 
veins, is thus rendered so manifest, that a practised observer can at any moment pro- 
nounce upon the direction of the lamination from the mere inspection of the smTac^ 
of a glacier. But besides these narrow grooves, larger patches of discoloration are 
sometimes observed, which take the form of cmwes sufilcient in uidth to cover himdreds 
or thousands of the smaller ones. To an eye placed at a suflicient height above a glacier 
on which they exist, their general arrangement and direction are distinctly visible. To 
these Professor Foebes has given the name of “ Du’t-Bands,” and the discovery of them, 
leading as it did to his theories of glacial motion, and of the veined structm'e of glacial 
ice, is to be regarded as one of the most important of his obseiwations. 
On the evening of the 24th of July he walked up the hill of Charmoz to a height of 
