This conglomerate is in nearly horizontal strata, which probably extend eastward below the chalk, while to the westward they lie upon rocks of a different nature, of which I shall afterwards speak. The town of Exeter is situated in a sort of hollow encircled by hills not very elevated, nearly all of the same height, and which become gradually lower as they approach the coast. I found one of these hills, situated eight or nine miles N. N. W. of Exeter, near the village of Thorverton, to be seven hundred feet above the level of the sea. This basin opens to the S. S. E. and, as is frequently the case in England, a river, which at the distance of a few miles from its mouth would deserve rather the name of a brook, suddenly enlarges near the sea to a considerable width. The Ex at the place where it flows into the open sea, suddenly again contracts, and forms a very narrow strait.
There are several quarries opened in the neighbourhood of Exeter, deserving the attention of the geologist: some of these I shall now enumerate.
The quarry of Heavitree is situated about a mile and a half from Exeter, on the road to Honiton. It is worked to the extent of a quarter of a mile in length, and at present, to the depth of about ninety or a hundred feet, in a plane intersecting that of the strata. The rock worked in this quarry is a conglomerate evidently stratified; the strata are from six to eight feet in thickness, and dip S.E. at an angle of about 15°. As long as this rock preserves the character of conglomerate, it is compact and tenacious, and according to the workmen employed in the quarry, it hardens more and more by exposure to the air. But as soon as it passes to the state of an arenaceous sandstone, it becomes tender and friable. It is very common to see blocks of it in this last state, and sometimes of great size, included in the middle of the conglomerate. The cement of this
