Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/169

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A. Of Mineral Beds.

A bed is the mass of a substance different from the rock or rocks of which the mountain is formed in which it occurs, but the direction and position of which are conformable with the strata of the mountain.

Mineral beds are of less extent and of rarer occurrence on the surface of the globe than mineral veins.

We seldom find mineral beds and mineral veins in the same district.

I know of no ores having been found in the form of beds in Cornwall.

There is at Torneo in Lapland, a mountain entirely composed of iron ore, and at Luleo in the same country, the mountain Gelliware is one mass of rich iron ore of a blackish blue colour, which extends like an irregular vein for more than a mile, and is three or four hundred toises in breadth.

I saw in the valley of Brozzo in Piedmont, five leagues west of Ivrea, at the height of four hundred and fifty-five toises above the level of the sea, a mountain almost entirely composed of very rich iron ore, (the fer oxydulé of Haüy) covered only at the surface with a cap of gneiss or mica slate. Every inhabitant of the valley having the right of working this mine, by paying a very small sum of money to the Commune, it cannot be expected that the mining operations are conducted with that method which is the result of theoretical and practical knowledge combined. Every one endeavours to dig out the greatest possible quantity of ore with the least possible trouble and expense to himself. Nothing can be more curious than the appearance of those galleries, if galleries they can