Geology of England and Wales, i^c." 229 



united by an an argillaceous cement. These rocks con- 

 tain subordinate beds of coal and limestone ; the former 

 being thin and poor. Lead and copper and iron ores, sat- 

 in spar, bitumen, petroleum, naptha, and asphaltum, aUo 

 occur in the shale and grit. The fossils are similar to those 

 of the coal measures, and are of marine origin. Indeed, if 

 we may be allowed to form an opinion at the distance of 

 three thousand miles from these rocks, we should say, that 

 we can see hardly sufficient reason for separating them 

 from the coal formation. 



Carboniferous or Mountain Limestone. This rock occasion- 

 ally alternates with shale, grit and amygdaloid, and some of 

 its synonymes are metalliferous limestone, and entrochal, or 

 encrinal limestone. We cannot here enter into a particular 

 description of this interesting rock, but remark, that its strata 

 are often divided by thin partings of clay, and that it con- 

 tains nodules of chert, and is extremely cavernous. Be- 

 tween 60 and 70 caverns are mentioned, as existing in this 

 rock, in England and Wales; and also several subterrane- 

 an rivers. It is the grand depository of the English lead 

 mines. Various copper, iron, and zinc ores, fluor spar, calc. 

 spar,arragonite, selenite, carb. and sulph.of barytes, sulph. of 

 «!lrontian, also occur in it ; besides various minerals in the 

 accompanying toadstone. The organic remains are very 

 distinct from those in the oolitic series and the lias, and 

 belong, chiefly, to extinct genera. Vertebral animals are 

 rare ; but Zoophytes, Encrinites, Coralites, and Testacea 

 are numerous. The strata are often highly inclined and 

 contorted. 



Old Red Sandstone. This is a mechanical rock, consti- 

 tuted of abraded pebbles and masses of quartz, feldspar, 

 and mica; and containing fragments of clay slate, flinty 

 slate, t^c. "its colour is usually dirty iron-red or dark 

 brown, but sometimes passing into gray." From the new- 

 er red sandstone it may be distinguished by its greater con- 

 solidation, but it is not so easily discriminated from the 

 sandstones of the millstone grit series. It is, therefore, 

 highly probable, that many rocks have been denominated 

 old red sandstone, that really belong to formations widely 

 removed from it. It is often asserted, that coal is contain- 

 ed in, or lies beneath, o|d red sandstone. But the authors 

 of the work under consideration, will allow none to be 

 with propriety thus designated, unless it underlie the coal 

 formation. They regard even the red dead Iyer, (rothe 



