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PEOFESSOES TTNDAiL AXD HUXLEY OX 
irregular patches appear, and at others elongated spaces covered vrith dirt. Tovrards 
the bottom of the cascade the aspect changes; but still, were the eye not instructed 
by what it sees lower down, the change would have no significance. AMien the ice has 
fah'ly escaped from the gorge, and has hberty to expand laterally in the valley below, 
the patches of dht are squeezed by the push behind them, and drawn laterally into 
narrow stripes, which run across the glacier; and as the central portion moves more 
quickly than the sides, these strips of discoloration form curves which turn their con- 
vexity downwards, constituting, we suppose, the “Dud-Bands” of Professor Foebes. 
On the Grindelwald glacier, where one of us, in his examination of the bands, was 
accompanied by Dr. Hookee, this change in the distribution of the dirt, — the squeezing, 
lateral drawing act, and bending of the dirt patches below the bottom of the ice-fall, — 
was especially striking. 
Such then appears to be the explanation of the dirt-bands in the cases where we have 
had an opportunity of observing them. We have not seen those described by Professor 
Foebes, but the conditions under which he has obseiTed them appear to be similar. 
An illustration of the explanation just given is furnished by the dut-bands observed 
below the “ cascade ” of the Talefre. The character of this ice-fall may be inferred 
from the following words of Professor Foebes, and from the map which accompanies 
his ‘ Travels.’ “ The structure,” he says, “ assumed by the ice of the Talefre is extii’pated 
wholly by its precipitous descent to the level of the Glacier de Lechand, where it 
reappears, or rather is reconstructed out of the broken fragments according to a wholly 
difierent scheme.” One of the results of this “scheme” would, it is presumed, be a 
redistribution of the dut, and the formation of bands in the manner described. Those 
who consult the map will, however, see dirt-bands marked on the Glacier du Geant 
also, while no cascade is sketched upon it; but at page 167 of the ‘Travels,’ Professor 
Foebes, in referring to this glacier, says, “ I am not able to state the exact number of 
dirt-bands between the foot of the ice cascade opposite La Noire and the corner of Tre- 
laporte.” Here we are not only informed of the existence of a cascade, but are left to 
infer that the dut-bands begin to form at its base, as in the Glacier du Geant, and in 
those which have come under our own observation. The clean Glacier des Bossons, also, 
which was referred to by Professor Foebes, in one of his ear best letters, as afibrding no 
lodgement to the dirt, possesses its cascade (page 181), and here also we find (page 182) 
“ that the pecuhar phenomena of ‘ dirt-hands' on a great scale are not wanting, although 
from the dazzling whiteness of the ice they may be very easily overlooked.” Vde make 
these remarks with due reserve, not having yet seen the glaciers referred to. 
The explanation just given has been brought to the test of experiment. ABCD, 
fig. 10, is a wooden trough intended roughly to represent the glacier of the Phone, the 
space ACEF being meant for the upper basin. Between EF and GH the trough 
narrows and represents the precipitous gorge down which the ice tumbles, while the 
wide space below represents the comparatively level valley below the fall, which is filled 
with the ice, and constitutes the portion of the glacier seen by travellers descending from 
