72 Geological Society '.-—the Rev. D. Williams on the 



exhibited in juxtaposition the several varieties of Cornish killas, pale 

 green, light blue, and purple volcanic ash andCoddon Hill grits (the 

 two latter containing plants), interstratified beyond any doubt among 

 the coral limestones, and these limestones inclosing carbonaceous 

 beds, underlaid and overlaid by thick accumulations of Coddon Hill 

 and floriferous grits. On the road by Grayleigh, and descend- 

 ing further on to Waddon Burton, Mr. Williams has traced these 

 alternations foot by foot, and he says the sequents are so manifestly 

 palpable in their interchanges, great and small, that nothing is left 

 for inference or conjecture. 



The inseparable connexion of the coral limestone and Cornish 

 killas with the floriferous series, he states, is also most plainly ex- 

 hibited to the N.E. of Kingsteignton, at Ashburton, Newton 

 Bushel, Abbots, and King's Kerswell, Marldon, Berry Pomeroy, 

 Higher and Lower Yalberton, and thence to Brixham and Berry 

 Head. At Meadfort sands, on the south, the author says, there is 

 a strange intermixture, yet in regular stratified order, of Cornish clay 

 slate, and buff- coloured, finely arenaceous beds inclosing shells and 

 corals, with true floriferous sandstones containing plants, also with 

 culmy slates, and strata of volcanic ash and coral limestones, forming 

 an anticlinal axis, ranging north and south, and throwing off the great 

 mass of the Torquay limestones to the east and west. 



To the east of Dartmoor, Mr. Williams has little doubt the same 

 alternations on a great and small scale occur, as far as the parallel 

 of Torquay, immediately to the south of which line, but west of the 

 bay, are said to be lofty conspicuous hills of the floriferous strata (No. 

 9), which he conceives " may be abruptions" ; but their bases are 

 commonly concealed by a thick mantle of new red sandstone. To 

 the west of Dartmoor, independent of what he believes to be an axis 

 of No 8, and forming the southern margin of the culm-trough, 

 Mr. Williams has been led to conclude, that the floriferous beds, by 

 other arcs of undulation, have broken through the thinner northern 

 border of the killas, throwing it off on each shoulder and intercepting 

 it in troughs. Instances of this, he says, are sufficiently appa- 

 rent on each side of a line drawn from Greston Bridge on the 

 Tamar, S.E. of Launceston, to Heath Field, north of Tavistock ; the 

 high central ridge consisting of floriferous and Coddon grits, flanked 

 on the north by undoubted killas and volcanic ash and breccia. To 

 the N.W., W.S.W., and S. of Greston Bridge, the floriferous 

 series is stated to be exposed in great force, extending almost un- 

 interruptedly in a straight line into the great bod)?- of the culm-field ; 

 but to the west it is said to be generally concealed by killas, though 

 a continuous contracted range branches off to the westward by 

 Lezant, Lawanick-down, and Alternau ; and it appears to be depressed 

 under, or to pass into the killas and speckled slates of Davidstow, 

 N.E. of Camelford. 



A small area of an inverted arc of undulation is exposed in and 

 around Tavistock ; and the floriferous grit, principally identified by 

 its associated slates, is stated to underlie the high killas range of 

 Whitcombe Down on the south ; and on the north to be laid open in 



