﻿Sorace B. Woodward — Notes on the Devonian Rocks. 449 



noting a few facts in tlie local geology, some remarks be made on 

 the work that has been clone, so that if possible more labourers may 

 be tempted to come into the field. 



During a year's residence at Newton Abbot (1874-75), while 

 engaged in the revision of the boundaries of the Secondary and 

 newer deposits, I was enabled to gather a few facts which may be 

 of interest concerning the succession of the Palasozoic rocks in that 

 neighbourhood ; but I should mention that my work was restricted 

 to the older rocks immediately bordering the Secondary strata, as a 

 revision of the Palseozoic rocks is postponed, so far as the Geological 

 Survey is concerned, -until the Six-inch Ordnance Maps are issued. 



The published maps of the Geological Survey show but two 

 general divisions in the Devonian rocks, the slaty group having one 

 colour, and the limestones another. The relations of these are not 

 exhibited, and one might conclude that the limestones occurred at 

 dilFerent horizons as great lenticular or isolated masses. A careful 

 examination of the ground, however, soon dispels this notion ; and 

 when the boundaries are traced out, it will be found that the fre- 

 quently abrupt terminations of the limestone are due to well-marked 

 faults. Wherever positive evidence was to be obtained, a definite 

 sequence in the Devonian rocks was manifest — the limestones form- 

 ing an upper group, the slates a middle one, and red sandstones a 

 lower group. It must be admitted that this positive evidence is not 

 often obtained in sections actually showing a junction or super- 

 position, but it is very clearly established when the beds are traced 

 out over the ground. The relation of the rocks to the form of the 

 country is very clear, and the actual boundary-line between the lime- 

 stones and the slates beneath may usually be defined within a few 

 feet. When, as is often the case in some limestone quarries, the 

 dip of the beds cannot be distinguished amidst the cleavage and 

 jointing, the general inclination can be determined when the 

 boundary with the slates has been drawn, according as the line 

 runs a long way or but a short distance into the ravines and valleys 

 that intersect the escarpments. In this way the little masses of 

 limestone mar Woolborough and the slates of Abbots Kerswell, as 

 noted by Jukes and Dr. Holi, can be readily correlated with the 

 Devonian limestones and slates, instead of being classed with the 

 Culm-measures, as represented on the Geological Survey Map. 

 These beds are abruptly faulted against the Culm-measures on the 

 west. 



The slates may be clearly traced beneath the limestone south- 

 east of Daccombe, at Barton, Anstey's Cove, Wickaborough, and 

 other places. The boundary with the red sandstones beneath is not 

 so well marked, for the lithological characters are not so sharply 

 defined, nor have we the benefit of the springs which are thrown off 

 at the junction of the slates with the limestone. 



The relations of the red sandstones to the beds above are, how- 

 ever, well shown at Cockington. A quarry about a quarter of a mile 

 north-east of Livermead shows beds of red sandstone dipping a little 

 to the east of north, while further west they are shown dipping a 



DECADE II. — VOL. IV. — NO. X. 29 



