42 SKETCH OF THE 



establish. These are very rare, and besides it is not impossible that the 

 shales in which these occur, may belong to an older class similar in posi- 

 tion to the rocks of the north of Germany, (see Conybeare and Phillips, 

 page 311,) which overly the coal measures. I have never seen any traces 

 of them in the well-marked sandstones or sandstone slates. 



Excepting in iron, the above series does not appear rich in metalli- 

 ferous substances, neither have I met with any variety of simple minerals 

 in it. I have occasionally seen, however, specimens of a fibrous variety 

 of quartz disposed in small veins, or rather laminae, interposed between 

 the strata; and Captain D. mentions the occurrence of a " fat yellow 

 clay," embedded in the sandstones. 



The next rock which claims our attention in the above series, is the 

 limestone on which this belt abounds, especially towards the north. I 

 have little to add to the description of its external appearance, mode of 

 occurrence, &c. as given by Captain Dangerfield ; and, if I shall have 

 occasion to differ from him respecting the age of this rock, I shall do so 

 with all humility, fully aware as I am of the difficulties attending this 

 branch of my subject. It is not improbable that two distinct varieties 

 of limestone may occur in this belt, the one belonging to the mountain 

 limestone formation, in which class Captain D. seems inclined to place 

 all the calcareous rocks of the portion of the district under consideration ; 

 but the one which I am about to describe overlies the sandstones and 

 sandstone slates, and I feel disposed to believe that it belongs to the 

 lias formation. Perhaps, too, in addition to the above, there may be a 

 formation of magnesian limestone of the English Geologists in the 

 magnesia limestones described by Captain D. On this point, however, 

 I can give no information, as I have only met with one variety character- 

 ised in every position, where I have had an opportunity of examining 



