678 Professor Sedgwick and R. I. Murchison, Esq., on the 



exactly like bands of coal-grit. They are often gray, or brownish gray, and sometimes greenish 

 gray, and are occasionally stained by red haematitic joints. And on the north side of Portledge 

 Bay there is a series of sandstones and alternating shales of a deep red colour, which produce a 

 distinct feature in the county, and may be traced for many miles along the strike, all the way 

 preserving their peculiar mineral character. 



The system is traversed here and there by quartz veins, sometimes passing in well-defined 

 transverse lines, and sometimes reticulated through the whole mass of the rock. Many of the 

 thick gray beds exhibit, on their weathered and water-worn surfaces in the sea cliff, a number of 

 spherical light-coloured spots, indicating an approach to a concretionary structure. Specks of sil- 

 very mica are disseminated through many of the masses, on lines parallel to the bedding ; and 

 sometimes the mineral becomes so abundant that the rock has a flaggy structure, and resembles 

 the coarse flagstone, so commonly used as a roofing slate in all our coal countries. The thinner beds 

 alternate with, and pass into, a laminated arenaceous shale, with fine ripple marks at the partings. 

 This last variety is sometimes (for example, on the coast of Bideford Bay, south of the Popple 

 Bank,) continued through a thickness of many hundred feet; with hardly an interruption from 

 the thick hard coarser beds of sandstone. 



The sliales vary from a sandy, micaceous, laminated flagstone, to a soft slate-clay, not distin- 

 guishable from a common shale of our true coal-measures. Sometimes they exfoliate into innume- 

 rable thin flakes ; sometimes their weathered surfaces decompose into thin transverse prismatic 

 masses, like the forms of starch. Many of them are pyritous, and are coated superficially with a 

 white efflorescence or with brown ferruginous stains, precisely in these respects resembling coal 

 shales. Among them are, here and there, dark carbonaceous bands which stain the fingers, generally 

 in the form of mere laminae ; and near the junction of the shales with the harder flagstones, the dark 

 laminae often contain innumerable obscure vegetable impressions much discoloured by decompo- 

 sing pyrites: occasionally, but more rarely, the dark shales contain glossy plates, having the lustre 

 of plumbago, in which case they seem to pass into the state of culm. The best examples of these 

 glossy plates are, however, seen in the shales of the lower culm group already described. 



Impressions of plants are also found occasionally among the strong beds of sandstone ; for ex- 

 ample, in a quarry by the road-side about half-way between Barnstaple and Bideford*. In 

 Ugbrook Park, near Chudleigh, there is a large development of culm sandstone as coarse as mill- 

 stone grit, and passing into a conglomerate form ; and over it are some beds of more thin-bedded, 

 gray sandstone, not to be distinguished from a coal-measure sandstone, and containing very fine 

 vegetable impressions, among which are well-marked Calamites. Indeed, through the whole of 

 the upper group we are describing, vegetable impressions, though rarely so perfect as to give 

 anything like specific characters, are extremely abundant. 



Nodules of clay-ironstone are occasionally associated with the hard beds of sandstone ; and 

 sometimes they occur in beds, or rows, subordinate to the shaly bands. Among the accidental 

 beds we may also notice calcareous shale passing into thin, impure bands of limestone, of which 

 vre saw an example near Hatherleighf. All the beds above described are intersected by nume- 



* These gritstones may be called the upper culm grits, to distinguish them from the coarse 

 grits of the lower division, in which we never discovered any Calamites. The upper grits are 

 diffused through the whole upper division of the series, but perhaps abound most in the part 

 that first succeeds the black limestone and shale. 



t See the section from the Foreland to the granite of Dartmoor. (PL LI., fig. 1.) Similar 



