Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/114

 102 containing a few laminæ of calcareous spar, and some crystals of quartz. This last rock forms the roof of the mine, the saalbände consists of a calcareo-manganesian amygdaloid. As to the floor of the mine, it is not known of what it consists, as the vein, which appears to be of considerable magnitude, has not been cut through. Its direction is from E. to W. dipping N. with an inclination of three feet in six. Of the black oxide of manganese, several varieties are met with, together with ferriferous carbonate of lime. The red argillaceous sandstone occupies the surface of the country from Upton Pyne to Thorverton.

There are three or four quarries at Thorvenon, and these not far distant from each other. They are all in the same rock, viz. a calcareous amygdaloid, the nature of which, however, varies considerably in different places. In some places, the nodules are small, and very closely united in clusters in the base, forming nearly a homogeneous mass, with here and there nodules of a much larger size than the rest imbedded in it. In other places the nodules are about the bigness of a pea, all of the same size, and consist of rhomboidal sparry laminæ There are other places where the base of the amygdaloid has the appearance of a sand stone in which a small number of calcareous nodules are imbedded, externally coloured green by the steatite, and exactly resembling those which enter into the composition of some of the amygdaloids of Derbyshire, and of the Pentland hills near Edinburgh.

The country between Exeter and Plymouth by Chudleigh, Ashburton, and Ivy-bridge, is quite hilly, the whole being a continual