1821 .] Red Rock Mark, or Newer Red Sandstone, 257 



the other fragments imbedded in the red marie were of a forma- 

 tion contemporaneous with itself."*^ A minute and accurate 

 inspection of the coast between DawHsh and Teignmouth must, 

 however, I think, convince us of the truth of the commoner, or 

 at least earlier, opinion which regards them as derived from the 

 breaking up of the inferior strata. Other fragments imbedded 

 in the marie are greywacke, or compact sandstone. F'. Compact 

 greywacke, of a dirty-white, much ironshot, having the aspect of 

 a sandstone with a very small intermixture of argillaceous matter. 

 F'^. Compact greyivackej quartz more predominant, and closely 

 aggregated ironshot throughout of a reddish-grey. F^. Same, of 

 a greyish-black, w^ith contemporaneous veins of white quartz., 

 G'. Black compact siliceous rhck, of a very close texture, resem- 

 bling lydian stone. G-. The ^ame intersected in all directions 

 by small veins of ragged quartz, so as nearly to resemble a brec- 

 cia, occasional cavities filled with brown manganese ochre. 

 H. Small fragments, apparently of the reddish greywacke slate,. 

 provincially termed shillat. This list might hi\ increased by the 

 enumeration of some more trifling varieties in the compact grey- 

 wacke. Calcareous rock. IK Semicn/stalline limestone, of a 

 dirty-white, without organic remains. (Near the headland 

 termed the parson and clerk.) P. Dark grey limestone, without, 

 organic remains, near Teignmouth. P. Same, full of coralloids. 

 Same spot. 



It may be added, that insulated fragments, and occasionally 

 crystals of semivitreous felspar are met with in the marly beds. 

 A pit near Exeter afforded me an interesting specimen of three 

 macles united in a single groupe. Generally this variety of fel- 

 spar seems to have resisted the action of those causes which 

 have produced the disinte2:ration of its parent rock. 



The fragments which I have attempted to describe are, for 

 the most part, mixed promiscuously in the same strata. Occa- 

 sionally particular substances predominate, but rarely, or never 

 (as far as my observation went) to the total exclusion of all 

 others. The porphyritic and quartzose fragments have usually 

 their angles but slightly rounded ; in some cases, not even per- 

 ceptibly so. The calcareous portions have generally more the 

 appearance of being worn (as would from their softness be the 

 case) by attrition. These facts, added to the consideration that 

 the porphyritic or felspathic portions bear no resemblance to the 

 onty solid rock which appears to be subordinate to this forma- 

 tion (namely, the amygdaloid of Thorverton) will, perhaps, be 

 sufficient to establish the mechanical origin of the breccia in 

 question. We shall then have to inquire whence its contents 

 might be derived. 



The calcareous fragments bear a resemblance sufficiently close 

 to the limestones of Chudleigh and Babicomb. A Hmestone 



* See Dr. Kidd's Essay, p. 109. I have every reason to believe that in this opinio* 

 »y respected friend was by no means singular. 



New Series, vol. i. r 



