§ l&. THE PERMIAN FORMATION. 561 



conglomerate is made up in great part of pebbles, and frag- 

 ments of mountain limestone, millstone grit, coal-shale, and 

 other detritus of the strata on which it reposes ; and contains 

 fractured and water-worn bones of Saurians, teeth of fishes, 

 &c. It is well displayed, overlying the coal strata and 

 mountain limestone, near Clifton in the valley of the Avon, 

 and at Portishead, and other places in the vicinity.* 



In the central part of England, and extending from 

 the neighbourhood of Nottingham to the south-eastern 

 extremity of Northumberland, red marls and sandstones 

 form the lowermost strata of the Permian, and are regarded 

 as the equivalents of the Red-Iyer or Rothliegendes of Ger- 

 many ; a term applied to a group of red sandstones and 

 conglomerates, accompanied with porphyry, and basaltic and 

 amygdaloidal trap, that constitutes the base of the Permian 

 of the Continent. Upon these lower red sandstones are 

 yellow and reddish magnesian limestones, upwards of 300 

 feet in total thickness, corresponding with the Zechstein 

 of Germany. 



17. Magnesian Limestone or Dolomite. — The mag- 

 nesian limestone of England is regularly stratified, and, 

 when recently exposed, has a granular or saccharine 

 structure, with a glimmering lustre ; the colour is generally 

 either a pale fawn, salmon, or yellow, from hydrate of iron ; 

 or red, from oxide of iron. The hard varieties yield the 

 best building stone in England, j In many places the 

 limestone occurs in large concretional and botryoidal 

 masses ; the concretions varying from the size of small peas 



* The lower part of the strata marked Trias in the section of the 

 Mendips (Lign.l 18, p. 522), more properly belongs to this group ; the 

 dolomitic conglomerate very generally forms the immediate covering 

 of the older deposits in this part of England. 



f The New Houses of Parliament at Westminster are being con- 

 structed externally of magnesian limestone, from quarries at North 

 Anstone in Yorkshire, and near Worksop in Nottinghamshire. 



