378 Scientific Intelligence, 6fc. 



2. Cefn Caves. — Mr. Bowman described the Cefn Caves in 

 Denbighshire. They are situated in limestone. Their roofs are 

 covered with stalactites, and their floors with animal matter, princi- 

 pally the elytra of beetles, bones, and teeth. 



Tuesday y ^rd August. — On the Classificatio7i of the old Slate 

 Hock of Devomhire, with an explanation of the true position of the 

 Culm Deposits of the central portion of that County, by Professor 

 Sedgwick, and R. J. Murchison, Esq., V. P. R. S., &c. 



Mr. Murchison began by observing, that he was about to submit 

 a mere outline of a more detailed memoir on the physical structure 

 of Devonshire, which, in conjunction with Mr. Sedgwick, he pur- 

 posed to lay before the Geological Society of London. One object 

 they had in view was, to remedy the defects in existing geological 

 maps, as to colouring sub-divisions of formations ; and another, to 

 ascertain by actual sections, the true position of successive deposits, 

 and their natural sub-divisions, so as to bring them into comparison 

 with other con*esponding deposits, and to determine their true place 

 in the succession of British formations. By help of a section, the 

 following succession of deposits in the ascending order was deter- 

 mined : — 



1. A system of slaty rocks, containing a vast abundance of organic 

 remains, generally in the form of casts ; these rocks sometimes pass 

 into a fine glossy clay slate, with a true transverse cleavage — some- 

 times into a hard quartzose flag-stone, not unusually of a reddish 

 tinge, sometimes into reddish sand- stone, subordinate to which are 

 bands of incoherent shale. In North Devon, they are very seldom 

 so calcareous as to be burnt for lime, but in South Devon, rocks of 

 the same age appear to be much more calcareous. This series is 

 finely exposed in the Valley of Rocks, and the Valley of the Lyn, 

 but its base is no where visible in this line of section. 



2. A series of rocks, characterized by great masses of a hard thick- 

 bedded red sand-stone and red flag-stone, subordinate to which are 

 bands of red, purple, and variegated shales ; the red colour occa- 

 sionally disappears, and the formation puts on the ordinary appear- 

 ance of a coarse silicious gray wacke, subordinate to which are some 

 bands of slate, but too imperfect to be used for roofing. This system 

 contains very fine organic remains ; it is several thousand feet in 

 thickness, occupying the whole coast from the west end of the Valley 

 of Rocks in Combmartin, being thrown back by a dip into the cliffs 

 between Porlock Bay and Linton ; it re-appears in North Hill and 

 the Quantock Hills. 



3. The calcareous slates of Combmartin and Ilfracombe, of very 

 great aggregate thickness, abounding in organic remains, and con- 

 taining in a part of its range, at least, nine distinct ribs of lime- 

 stone, burnt for use. This lime-stone is prolonged into Somerset- 

 shire, and is apparently the equivalent of the lime-stone on the flank 

 of the Quantock Hills. 



4. A formation of lead-coloured roofing slate of great thickness, 

 and occupying a well-defined zone in North Devon, its up])cr bed 

 alternating with, and gradually passing into a great deposit of green, 

 gray and purple, or red sand-stone, and silicious flag-stone. These 



