Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/64

54

On the part of Dun How where the granite appears at the surface, and in a natural excavation, but which I believe has been enlarged by art, there is a brown sort of powder, said to be used by the inhabitants for the cleaning of plate. It feels rather soft to the touch; does not effervesce with acids; fuses per se, but not readily, into a greyish enamel.

All over the curragh, and on the beach also at Kirk-michael, a substratum of marl several feet deep, underlies a light and sandy soil.

B.-Vodden marl.

Calcareous marl of a light flesh colour, soft enough to be cut with a spade, feels almost greasy to the touch, basis extremely fine, texture dull and earthy; no other discernible particles in the mass but very small spangles of white mica; adheres to the tongue strongly, is soluble with a brisk effervescence in diluted muriatic acid, leaving a considerable residue readily fusible into a slightly magnetic olive enamel.

Kirk-Michael-beach.

Calcareous marl of a grey-reddish colour, not so soft as the preceding, owing to some sandy particles immersed in the basis; leaves in diluted muriatic acid a more abundant residue, not so easily fusible; the enamel of an olive-green colour.

There is another variety of calcareous marl in the same place of an ash-grey or of a dun colour.