360 Mr. Horner on the Geology of the 



by the derivative rocks I have been describing, and all the different 

 modifications to be found in the district occur in this valley, and 

 the whole of the low hills are composed of them. In the bottom 

 of the valley there is a considerable tract of loose sand. On leaving 

 the grauwacke series near Dunster, we find at Carhampton a low 

 hill composed of a red argillaceous sandstone, and proceeding east- 

 ward towards Williton, either that sandstone, or a sandstone con- 

 taining rounded fragments of the grauwacke formation appears in all 

 those places where the ground is broken. At Tarr, Tor Weston, 

 and Vellow, the same conglomerate (or pebble rock) that I have 

 described at Alcombe, again appears. At Tor Weston the quarries 

 are situated near the top of a small detached hill, the conglomerate 

 forming beds of great magnitude. At Vellow there are sections of 

 it above 50 feet in height, and it rests here upon a bed of red clay. 

 There are distinct parallel lines which divide it into thick beds, 

 dipping northward about 10°. It contains here more fragments of 

 limestone than it does at Alcombe, and I found between the pebbles 

 in some places, small nests of hematite. It is covered as at Alcombe 

 by a sandstone, but of a different variety, being of a deep reddish 

 colour and full of fragments of grauwacke, and without any appear- 

 ance of copper or of sulphate of barytes. The same sandstone may 

 be seen in different places between Williton and Vellow, particu- 

 larly near the village of Sampford Brett. A little to the west of 

 Williton church, there is a reddish white sandstone, much harder 

 than any other I met with in this district. It occurs at the eastern 

 termination of the same ridge, on the west side of which the quarries 

 of conglomerate at Tarr are situated, and I think that it is very pro- 

 bably only a variety of that sandstone which covers the conglomerate 

 in other places. If it is stratified the lines of separation are very 

 indistinct. There are many perpendicular fissures in it; part of 



