Correspondeiice — Mr. J. R. Dakyns. 573- 



the rocks affected by great movement range from the Archgean to the 

 Lower Coal-measures, the Upper Coal-measures and Permian rest 

 relatively undisturbed on the denuded rocks of the range : thus the 

 range is a member of the Hercynian system produced during Coal- 

 measure time, and probably the two approximately rectangular 

 directions of movement were practically contemporaneous and were 

 produced during the limited interval between the deposition of the 

 Lower and Upper Coal-measures. There is no evidence to prove 

 that the Malvern and Abberley Hills formed part of a coast-line 

 against which the Triassic beds were deposited ; for the Upper 

 Bunter Sandstone forms the base of the Trias throughout the district 

 and rests unconformably on the Haflfield Breccia, together with, 

 which it passed unconformably over the site of the West of England 

 Chain. The present position of the Permian and Trias on the east 

 of the hills is due to a post-Liassic fault of moderate downthrow,. 

 which tends to run parallel to the western front of the old range. 



THE LIMESTONE KNOLLS OF CRAVEN. 



Sir, — According to Mr. Marr the limestone knolls in Craven, 

 are due to the rock having been squeezed up, under intense lateral 

 pressure, through the overlying shale. If this be the case, we- 

 should find the knolls most pronounced where the pressure has 

 been greatest. Now the pressure, as proved by excessive folding,, 

 was gTeatest along what is now the Skibeden Valley, between. 

 Skipton and Wharfedale, but there are no knolls there. The knolls 

 are confined to the region of Thorpe, where the rocks are not 

 much folded and have therefore not suffered great pressure. As- 

 the knolls, then, do not occur where, according to the theory of 

 Mr. Marr, they ought specially to be found, the theory cannot be 

 true. J. E. Dakyns. 



Pex-y-Gwrych, Llanbekis. 

 November 3, 1899. 



SUBMERGED PHYSICAL FEATURES OF THE MEDITERRANEAN 



BASIN. 



Sir, — Since my return from the Continent I have been engaged 

 in tracing out the physical features, by means of isobathic contours, 

 of the western portion of the Mediterranean, and not without some- 

 interesting results. Considering the essential difiierence in the 

 physical conditions of the Mediterranean and the Atlantic — that 

 is, of an inland sea, with numerous large islands, and the 

 vast sweep of an ocean almost unbroken through a thousand 

 miles from the British Isles to the Straits of Gibraltar — we may 

 well be prepared for differences in the submerged features of each ;. 

 although it may be assumed that any changes of level which the 

 eastern borders of the Atlantic can be shown to have undergone 

 have been shared by the western portions, at least, of the Medi- 

 terranean. The great changes of level, amounting to thousands of 

 feet vertical, which are indicated b}' the slopes of the continental 

 platform and its intersection down to its very base of 1,000-1,500" 



