PORTLAND EOCKS OE ENGLAND. 



213 



the sand becomes much more argillaceous, but is not retentive of 

 water, which bursts out above some sandy-clay beds crowded with 

 the usual fossils of the Kimmeridge Clay. The line between the 

 two formations is, perhaps, somewhat arbitrary ; but the porous or 

 non-porous nature is of some consequence, and the fossils suddenly 

 cease above the water, except in the doggers. This latter fact is of 

 no consequence palseontologically, as it may simply prove that the 

 percolating waters have removed the fossils ; but it adds to the proof 

 of the lithological change. Including all this, the total thickness at 

 the north of Swindon may be estimated at 50 feet, which is pro- 

 bably not leyond the truth. Mr. Godwin-Austen's section at 

 Bourton makes this only 7 feet with a query. I did not see it there ; 

 it may have thinned in that direction, but scarcely to so great an 



I must here confess that I was in error about the Kimmeridge 

 Clay at Swindon being all Lower Kimmeridge. The sandy beds at 

 the top belong to the Upper by their fossils ; those belonging to it 

 are such of the list on p. 211 (Q. J. G. S. vol. xxxi.) as occur in the 

 general list with W. only against them. The same may be said of 

 the clay at Hartwell ; it is Upper Kimmeridge ; the fossils recorded 

 7. c. p. 212, only prove its relation to the Lower Kimmeridge. The 

 range of these sandy beds, and the fossils here and elsewhere found 

 in them, prove them to correspond to the strata cibove the first paper 

 slab of the typical section. This error was corrected by the perusal 

 of M. S^mann's statements. Unfortunately, from their misnaming 

 these beds Portlandian, I had not read MM. De Loriol and Pellat s 

 work, in which these statements are made. A further examination 

 of the beds, however, has made me fully concur in them. 



OoGfordshire. 



In this county there is no place where the whole of the Port- 

 landian rocks can be seen in one section, and no special feature is 

 presented by those that are visible ; hence the chief importance here 

 is the means of connexion afforded between the counties of Wilts and 

 Bucks. The various members of the formation dip gently to the 

 east, and are overlapped unconformably by the ferruginous sands of 

 a later period ; so that one has to traverse miles m order to pass 

 through a comparatively small thickness, and we must wait for the 

 interpretation of the sections till Buckinghamshire has been ex- 

 amined. T i • 



The uppermost beds of the Portland here shown spread out m a 

 broad area by the viUages of Great Hazeley and Great Milton. _ The 

 section at the former place has been admirably described by Dr. Fitton, 

 who saw a lower bed of stone than is now visible ; and I need only 

 point out the general characteristics for the sake of comparison. The 

 base of all these quarries (PI. YIIL fig. 7) is a yellow sand (4), not m 

 the least glauconitic, which extends downwards some 10 or 12 feet. 

 In this must be contained the lower bed of stone mentioned by Dr. 

 Fitton. The lowest stone (3) now seen is a shell-brash limestone, 

 mostly devoid of fossils, least compacted at the top, but hardening 



