TRANSACTIONS OF TUB SECTIONS. 59 



of Valenciennes and Belgium terminates, as far as productive value goes, a few 

 miles west of Bethime. 



As the coal-measures thus thiu out towards the British Channel, though some 

 ti-aces of poor coal have been found near Calais, we have a clear demonstration 

 in the Boulonnais that no productive coal-measures are superposed to the carboni- 

 ferous or mountain-limestone. In other parts, indeed, of the same district, the 

 true Devonian limestone, with many fossils, as well as crystalline carboniferous 

 limestone are at once covered by oolitic and cretaceous rocks to the entire exclu- 

 sion of any workable coal. Judging, then, from the gradual deterioration and 

 extinction of the coal-beds as fhey approach the French side of the Channel, 

 I hold that there can be no reason to hope that better conditions can be looked 

 for throughout the southern counties of England. 



Looking, however, to the well-ascertained data that the secondary rocks of the 

 western and central parts of England which lie beneath the chalk, viz. the 

 Trias, Lias, and Oolites, thin out in their extension to the south-east, as well 

 proved by a memoir of Mr. Hull, still it is by no means improbable that the part 

 of the oolitic series which appears in the clifts north of Boulogne may be persistent 

 under the cretaceous and wealden rocks of Sussex and Kent. But the question is 

 What will the fundamental rocli: prove to be in these districts if it should ever be ■ 

 searched for? Reasoning from such data and the visible outcrops in the Boulon- 

 nais, my inference is that, if not in part Jm-assic, they will probably prove to be 

 a thin band of carboniferous limestone without any productive coal, or more pro- 

 bably Devonian rock only. So far, then, I agree with Mr. Godwin-Austen as to 

 paleozoic rocks (but unproductive of coal) being possibly found in the south-east 

 of England. 



Again, if we follow the course of tlie older rocks in France southwards from the 

 Boulonnais, everywhere Devonian rocks only have been found beneath the secondary 

 strata ; and, proceeding througli Normandy and Brittany, we find that the Jurassic 

 rocks repose at once on lower Silurian rocks to the total exclusion of everythino- 

 Carboniferous or even Devonian; whilst in the Channel Islands nothing but 

 crystalline rocks of granite, gneiss, and slate occur, with no signs of any Inter- 

 mediate strata between them and the Wealden and cretaceous rocks of the Isle of 

 Wight and Hampshire. 



Tracing the line of the older rocks which separate the south-eastern from the 

 south-western counties, we see the Devonian roclcs of the Qaantocli: Hills, in West 

 Somerset, at once overlaid by new red sandstone, oolitic, and cretaceous rocks, 

 without a sign of anything carljoniferous. When we advance northwards from the 

 Mendip Hills, the phenomena we there meet with are, it seems to nie, indicative 

 of the hopelessness of seeking for any productive coal-measures between these hills 

 and the Straits of Dover, i. e. in Wilts, Hants, Sussex, Kent, Surrey, J.Iiddlesex, 

 Essex, and Herts. For, on the west, the mountain-limestone forms" tlie outward 

 eastern girdle of the great Somerset and Bristol coal-basin from Wells and Elm, 

 near Fromc, on the south, to Chipping Sodlmry, Wickwar, and to near Tortworth 

 on the north. 



Throughout a distance of about 35 miles, the carboniferous limestone with traces 

 only_ of mill-stone grit, which is the unproductive bottom-rock of every coal- 

 bearing stratum in the south of England and Wales, is everywhere and at once 

 surmounted on the east by now red sandstone, or the lias and oolitic forma- 

 tions. It has been said that an exception to this ride occurs in the neighbour- 

 hood of Frome, where the unproductive limestone is said to exhibit an axial 

 foi-m with coal-measures on two sides. Not having been for many years in 

 that tract, I ask for information, and will only now say that, if the coal so 

 worked be not on the eastern flank of the limestone but on the southern side, and 

 is not seen to dip to the east and so pass under the secondary rocks, my reasoning 

 is unaffected. 



However this may be, we know that all along the remainder of the outcrop of 

 mountain-limestone which forms the eastern boundary of the Bristol coal-basin 

 the strata of that limestone are highly inclined to the west, thus passing under the' 

 Bristol coal-basin proper. Now, it is on the highly inclined and upturned edo-es of 

 tliat mountain-limestone that the secondary rocks lying to the east at once repose, 



