240 Rev. James Yates on the Structure of the 



series of hills meets the eye, which is more interesting to the geological 

 observer, though of inferior elevation. Por^ as he stands upon the verge of 

 strata dipping east, he sees the hills alluded to dipping in different directions 

 according to the order of their arrangement, so as to form the basin, which 

 contains the coal field, situated on the confines of Shropshire and North 

 Wales. These hills are, 1st, those of Ness-cliff, whose escarpment is towards 

 the South-east; then Greensill; near it the Cleve, which rises with an even 

 slope terminated by a most distinct escarpment towards the east ; and lastly 

 the two ridges of Hawkstone, one to the north of the other. Thus the strata 

 of these hills together with those on which the spectator is situated, are seen 

 to converge so as to form a basin for the deposits of coal ; and they conse- 

 quently suggest to him the supposition, that as the rocks beneath his feet 

 belong to the millstone grit formation, those in the series of hills so connected 

 with them may probably belong to the same class of strata. 



The ridge, on the summit of which the race-course is situated, has a very 

 precipitous escarpment. Along its base flows a small river, called the Cyn- 

 lleth, and the grounds of Llanvorda, the residence of Mr. Henry Wynne, 

 occupy that part of it which lies to the south of the race-course. This escarp- 

 ment displays in regular succession the strata of the millstone grit formation. 

 The uppermost are found to consist of hornstone, which varies in its colour 

 and texture, sometimes becoming very fine and passing into perfect flint. It 

 divides by its cleavages into rhomboidal pieces, and has evidently supplied 

 many of the pebbles, both angular and rounded, which abound in the gravel 

 between this ridge and Oswestry. Below these strata is a bed, several feet 

 thick, of white sandstone. It consists of grains almost entirely siliceous, which 

 are for the most part cemented into a firm rock by a siliceous deposition : but 

 in many situations the texture of this sandstone is more loose and friable. In 

 some places it is spotted throughout its substance with black and brown oxide 

 of iron ; in others it contains the hollow impressions of entrochi. We then 

 come to a remarkable bed of indurated clay, generally of an ochre yellow 

 colour, though sometimes passing into bluish or brownish black. It is light, 

 and adheres to the tongue.. 



Below this are successive beds of sandstone, the thickness of which far 

 exceeds that of the upper beds, and sometimes amounts to several yards. 

 Some of them contain contemporaneous veins of silica, which are very con- 

 spicuous by their projection on surfaces exposed to the weather. Sometimes 

 the sides of these veins are exposed instead of their cross fracture. In these 

 cases they are striated like slickensides, but certainly not from the effect of 



