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stone. Mr. Lambert therefore infers, that the ore is more super- 
ficial, and he adds, there is no instance of its having been found at 
a greater depth than 200 yards from the surface. 
The lower parts of the fissures which traverse the limestone, are 
frequently filled with fragments of ore enveloped in a red earthy 
soil, and associated with angular as well as rounded fragments of 
limestone. In the alluvial detritus of the ravines, and the dry 
deltas at their mouth, fragments and masses of ore have been ex- 
tracted, often in considerable quantities, and at the Pecho de las 
Lastras to the extent of 100,000 tons. 
In the limestone mountains which stretch westward from the 
Sierra de Gador to Marbella, within forty miles of Gibraltar, lead 
ore is found in variable quantities, but not so abundantly as in the 
Sierra de Gador. 
In conclusion, Mr. Lambert observes, that the improvident me- 
thod of working the ore in that mountain is fast destroying the 
best mines ; that new trials have not been attended with anything 
like success; and that the hardness of the rock renders sinkings 
very expensive, and compels adventurers with limited funds to aban- 
don their undertakings, unless ore be speedily obtained. 
6. On the polished and striated surfaces of the rocks which form 
the beds of Glaciers in the Alps, by Professor Agassiz. 
This paper was accompanied by a series of plates intended to re- 
present the effect of glaciers upon the rocks over which they move. 
These effects, consisting of surfaces highly polished, and covered 
with fine scratches, either in straight lines or curvilinear, according 
to the direction of the movement of the glacier, are constantly found, 
not only at the lower extremity, where they are exposed by the 
melting of the glaciers, but also, wherever the subjacent rock is 
examined, by descending through deep crevices in the ice. Grains 
of quartz and other fragments of fallen rocks, which compose the 
moraines that accompany the glaciers, have afforded the material 
which, moved by the action of the ice, has produced the polish and 
scratches on the sides and bottom of the Alpine valleys through which 
the glaciers are continually, but slowly descending. It is impossible 
to attribute these effects to causes anterior to the formation of the 
glacier, as they are constantly present and parallel to the direction of 
the movement of the ice. ‘They cannot be considered as the effects 
of an avalanche, for they are often at right angles to the direction in 
which an avalanche would descend; they are constantly sharp and 
fresh beneath existing glaciers, but less distinct on surfaces which 
have for some time been left exposed to atmospheric action by the 
melting of the ice. In the valley of the Viesch, the direction of the 
scratches is from north to south, or towards the Rhone; the direction of 
those which accompany the glacier of the Rhone is from east to west ; 
that of those beneath the glacier of the Aar is first from west to 
east, as far as the Hospice of the Grimsel; and then from south to 
north, from the Grimsel to the Handeck. If we would account for 
these scratches by the action of water, we must imagine currents of 
