ascent and descent as far as the neighbourhood of Ivy—bridge. The red argillaceous sandstone continues from Exeter for some miles on that road; it is succeeded near Chudleigh by a vast number of flint pebbles, which appear to be scattered over the surface of the ground: I was not able to stop to examine them more attentively: but between Chudleigh and Ashburton, there occurs a blue compact limestone, traversed by numerous veins of calcareous spar. At every step the extremities of the strata of this rock may be seen cropping out, and fragments of it are mixed with the soil. In the neighbourhood of Ivy-bridge a formation commences, which as will afterwards be shewn, occupies a prodigious extent in this part of England: I mean the slaty and compact grauwacke. At Plymouth, however, the cliffs on the shore are of limestone; which as I examined them leisurely, and as they appear to me to excite some degree of interest, I shall describe more minutely.
The range of tolerably high cliffs, which extends from Stonehouse Pool, between Plymouth and Plymouth Dock, and thence along Catwater, ascending the right bank of the Plym as far as the Flying bridge, together with Mount Batten, and probably also the Island of St. Nicholas, are formed of a compact limestone. It occurs in strata rising N.N.W. at an angle of about 65°; it breaks with a semi-conchoidal fracture into large flakes, is of a yellowish-white colour, and, when quarried, is blasted with gunpowder. I did not discover in it any impressions of organic bodies, and I did not hear that they have ever been found in it; at least, if any do exist, they are very scarce. It contains several cavities lined with calcareous spar, or with stalactites, and filled with an ochreous earth. It is frequently also traversed by veins of calcareous spar of a wedge shape, wider at the bottom than at the top, and which generally occupy the whole height of the cliffs. On the side of Catwater, this limestone
