1862.] HULL CAEBONIFEKOUS STRATA. 131 



mentary elements are situated at opposite extremities of the area 

 occupied by the Permian group. 



Fig. 1. — Comparative Sections in Oxfordshire and YorJcshire, showing 

 the Changes in the Sedimentary and Galcareovs Members of the Great 

 Oolite, when traced from South to North. 



Scarborough. / 



Wilts and _.,---"'"" "^Yt^^v^ 

 Orfordshire. ,-■-''' "" - o 



1. Cornbrash. =1. Cornbrash. 



2. Forest-marble. =2. Upper Sandstone and Shale. 



3. White Limestone, or Upper Zone of Great 1 ^ o T.ivvjesto 



Oolite. J ■ ^ ' 



4. Stonesfield Slate, or Lower Zone. =4. Lower Sandstone and Shale. 



(e.) To take another example of development, from opposite direc- 

 tions, of calcareous and sedimentary strata, we may select the Lower 

 Carboniferous Rocks of Belgium and Westphalia, which present phe- 

 nomena analogous to those of the same formations in our own country. 

 In Belgium the Coal-measures rest upon a thin floor of sandstone 

 representing the Millstone-grit. Below this is the Carboniferous 

 Limestone in great thickness, which in turn rests on a thin series 

 of shales. On tracing these strata north-eastward towards the vla- 

 ley of the Rhine, they are found to undergo marked changes in their 

 development, as shown by Sir R. Murchison and Prof. Sedgwickf. 

 The limestone thins away, while the grits and shales proportionably 

 expand. Thus it is found that the series which underlies the Coal- 

 measures of Westphalia resembles the Lower Carboniferous series of 

 Scotland, consisting of sandstones (Flotz-leerer Sandstein) and shales 

 with Posidonomya Becheri, the limestone itself having disappeared*. 

 These changes I consider to be intimately connected with those under- 

 gone by the same formations in Britain, and to be due to the same 

 general cause, namely, the northerly drift of sediment during the 

 Carboniferous Period. 



Similar illustrations might be multiplied, did space permit ; but, 

 without here entering further into the general principle, I will 

 merely state my belief that a comparison of the relative distribution 

 of the calcareous as distinguished from the argillo-arenaceous, or 

 sedimentary, strata of the Carboniferous, Devonian, and Upper Silu- 

 rian formations would show, as a general rule, that the regions of 

 maximum development of the one series are those of minimum de- 



* "Siluria" 2nd edit. p. 427. 



t Although there is a marked unconformity between the Lower and the Upper 

 Carboniferous Rocks of Westphalia, I do not consider it, of itself, sufRcient to 

 account for the interchange of development between the arenaceo-argillaoeous 

 and the calcareous strata. 



k2 



