﻿Horace B. Woodivard — Notes on the Devonian Rocks. 451 



He descinbed the Old Eed Sandstone of Cockington as " chocolate- 

 coloured, micaceous, siliceous, and very compact sarLdstone." 



The fact that the Devonian slates and limestones in South Devon, 

 as well as in North Devon, are underlaid by beds resembling the 

 Old Eed Sandstone, is most important. Almost every writer speaks 

 of their mineralogical resemblance. So far as I know, the beds at 

 Cockington have yielded no organic remains, but I obtained some 

 obscure plant-like markings. 



We can draw no such close comparisons between the Devonian 

 Slates of South Devon and the Lower Limestone Shales, although 

 there are local resemblances. The former beds are, however, much 

 affected by cleavage. In West Somei'set some of the Devonian 

 slaty beds are much like the Lower Limestone Shales of the Mendip 

 Hills. 



When we come to the Devonian Limestone, we find a great and 

 striking mineralogical resemblance to the Mountain Limestone. Some 

 beds are of a dense blue colour, with few veins of calcite ; others 

 again are very freely veined with a fine network of spar, or contain 

 broad bands of crystalline matter. Beds of nearly white limestone 

 occur near Ideford, others again are Oolitic in structure. It may be 

 remarked, also, that many of the beds of Devonian Limestone, when 

 fractured, emit the same sulphurous smell as does the Mountain 

 Limestone ; while the slaty beds beneath sometimes exhibit similar 

 alternate bands and nodular beds of limestone. So that almost every 

 lithological feature that one may observe in the Mountain Lime- 

 stone of the West of England is repeated in the Devonian Limestone 

 of Devonshire. This reminds me that a few years ago, when writing 

 in conjunction with Mr. Bristow about the much-abused limestone of 

 Cannington Park, near Bridge water, we spoke of its striking re- 

 semblance in all particulars to the Mountain Limestone. I can 

 only add now that lithologically the Cannington Park Limestone 

 is as much like the Devonian as the Mountain Limestone.^ 



Sedgwick and Murchison noticed the occurrence of " thin laminee 

 of bright coal " in the limestone near Plymouth.^ Mr. Godwin- 

 Ansten too observed that " the limestone of the Ashburton band is 

 exceedingly carbonaceous, containing even seams of anthracite," and 

 he detected the same feature at Totnes. He considered the formation 

 of the carbonaceous matter to be due to marine rather than to ter- 

 restrial vegetation." 



The weathering of the Devonian Limestone is naturally similar 

 to that of the Mountain Limestone. Some ■ of the honeycombed 

 surfaces that may be seen on joints and exposed edges of the rock 

 in a quarry at Wolfsgrove Farm, near Kingsteignton, showed that 

 when fossils occurred, they stood out in relief in the cavities, 

 proving that here at least the phenomena resulted from the action of 

 atmospheric agents, and not that of snails. 



1 Geol. Mag., Vol. VIII. p. 500. See also Geol. of E. Somerset, etc. (Gaol. 

 Survey), p. 26. 

 ^ Trans. Geol. Soc. , 2nd series, vol. v. p. 651. 

 s Idem, vol. vi. pp. 461, 469. 



