20 



THE GEOLOGIST. 



porphyritic mass subsequently to its consolidation ;* then followed 

 the period of denudation; but all this was anterior to the com- 

 mencement of the conglomerate era, since pebbles of each kind of 

 granite occur in the Haldon beds, which belong to the base of the 

 red rocks of Devonshire. 



Should it be objected that the granites, though requiring great 

 pressure, were not necessarily formed beneath an accumulation of 

 rocky matter, but possibly under an equivalent depth of sea, it does 

 not appear that this can greatly aifect the chronology of the question, 

 at least by way of abridgment. Passing by all other considerations, 

 we should require a lapse of time sufficiently great to carry down the 

 area of, at least, central Devon, from the relatively high level at 

 which the culmiferous beds were certainly deposited, to an ocean 

 depth of enormous profundity ; and time enough, too, after the plu- 

 tonic masses had, at this depth, been called into existence, to bring 

 it up again within the influence of the waves, so that they might 

 detach samples of each kind of granite, to be transported to where 

 the conglomerate was being formed. 



Take what view of the case we may, an enormous period between 

 the culm and conglomerate series appears inevitable ; a period during 

 which great changes were effected within, and on, the crust of the earth 

 — changes which, from their nature, could not have been contempo- 

 rary, but must have followed each other in a definite and ascertained 

 order, and the greater part of which at least convulsion or cata- 

 strophe must have been powerless to produce or hasten. 



Unless we assume that a great chronological interval elapsed be- 

 tween the Carboniferous and Permian periods, — and to this palaeon- 

 tology appears to give no sanction,! — the facts of the case before us 

 seem to require the belief: — 



1st. That the granites of Dartmoor are not older, at most, than 

 the close of the Carboniferous period. 



2nd. That they had been stripped bare by denudation when the 

 materials of the red conglomerates were being brought together. 



3rd. That the red conglomerates and sandstones are not of higher 

 antiquity than the Lower Trias. 



4th. That the Permian period was of great duration. 



ON THE MODE OF FORMATION OF LIMESTONE 

 BANDS. 



By Rev. J. D. La Touche, Stokesay, Salop. 

 With a Note by J. W. Saltee, F.G.S., A.L.S. 



The existence of layers of limestone at various intervals among the 

 rocks, while in the intermediate strata there is a remarkable defi- 



* Trans. Gcol. Soc, 2nd scries, vol. vi. part ii. p. 477. 

 f Page's c Past aud Present Life of the Globe,' p. 114. 



