of Devonshire and Cornwall. 99 



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 iji 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 fre- 

 quently 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 con- 

 tracts, 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 stra- 

 tified ; the strata are from six to eight feet in thickness, and dip S E. 

 at an angle of about 1 5% 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 com- 

 mon 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 



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