of Devonshire and Cornwall, 157 



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 ex- 

 tends 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 oxydule of Haliy) covered only at the surface with 

 a cap of gneiss or mica slate. Every inhabitant of the valley hav- 

 ing 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 endea- 

 vours 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, 



* Geographie Physique de Bergman. Journal dcs Mines. No. xvi. p. 58. 



