Limestones of South Devon. 731 



1821 on a parallel with the old red sandstone, having taken for his base line 

 the limestone of Namur, the true representative of the mountain-limestone. 

 (Annals of Phil. 1821, June, p 465.) 



Mr. Conybeare, in " The Outlines of England and Wales" (note, p. 468, 

 1822), gives the following list of the formations beneath the coal strata of 

 Belgium and the North of France, with English equivalents, the former 

 being extracted from IVT. d'Omalius d'Halloy's Memoire sur la Geologic du 

 Nord de la F" ranee, (Journal des Mines, tome 24, 1806.) 



Belgium, &c. England. 



Coal strata The same. 



Shale and grit Millstone grit and shale. 



Limestone alternating with slate-clay Carboniferous limestone. 



Red and variegated grits alternating with slate-clay ^ 



Yellow granular quartz > Old red sandstone. 



Grit and breccia J 



Clay-slate Transition slate. 



Thus placing all the beds between "the limestone alternating with slate- 

 clay " and "the clay-slate " in the old red sandstone. 



This arrangement M. Rozet appears to have followed in his description of 

 Belgium, as he refers the psammites, &c., between the black limestone and 

 the schists, to the old red sandstone ; alluding at the same time to the account 

 of that formation, in The Outlines of Mr. Phillips and the Rev. J. Conybeare. 

 (Ann. des Sciences Nat., tome 20, p. 146, 1830.) 



It was, 1 believe, at the Reunion extraordinaire of the Geological Society 

 of France, at Mezires, in September 1835, (Bulletin Soc. Geoi. de France, 

 tome vi. p. 345, 183.5,) that the first attempt was made to compare the Bel- 

 gian formations with the Silurian system of England. At that meeting. 

 Dr. Buckland drew up a table in which the following equivalents are given : 



Systeme calcareux superieur. Mountain-limestone. 



(Old red sandstone wanting.) 



Systeme quartzo-schisteux superieur The Ludlow rocks. 



Systeme calcareux inferieur The Dudley and Plymouth rocks. 



Systeme quartzo-schisteux inferieur The Caradoc sandstone. 



Builth and Llandeilo flags wanting. 



With respect to the above comparisons it should be remembered, that in 

 1835 the Silurian system had not been made known in its full details, the 

 fossils having been determined only in part ; and the resemblance of the Bel- 

 gian corals to Dudley species, justified a comparison of the calcareous strata 

 of M. Dumont's systems with the Dudley and Wenlock limestones. 



During the discussions which took place on the identity of the English and 

 Belgian formations, M. Constant Prevost stated, that the calcaire bleu of the 



VOL. V. SECOND SERIES. 5 B 



