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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 8, 



an opportunity of examining the spot from which they came. Having 

 now had the advantage of doing so in company with James Smith, 

 Esq., of Jordan Hill, I shall proceed to describe the order and nature 

 of the beds presented in the natural transverse section formed by the 

 ravine. 



The cliff was roughly estimated, by help of an aneroid barometer, 

 at the height of 130 feet. In the descending order the beds are dis- 

 posed as follows : — 



1 . Basalt, accurately described by Mr. Mills as having " horizontal 

 divisions and vertical joints," taking the form of rude pillars. This 

 bed of basalt is thicker on the western than on the eastern side of 

 the ravine, and appears to consist of two sheets, separated by a thin 

 seam of highly vitrified matter or obsidian. Mr. Mills's estimate of 

 the thickness of the basalt may be tolerably correct, viz. 30 feet. 

 The jointed character of this basalt renders it peculiarly liable to the 

 disintegrating effects of weather. The bottom of the ravine is covered 

 with its fallen blocks. 



2. The first leaf-bed, a thin seam, about a foot thick, of shaly 

 matter, bearing impressions of leaves and stems of plants. 



3. A bed of volcanic ashes or tuff ; being an ashy paste full of white 

 angular fragments or lapilli, disposed in a manner characteristic of 

 erupted volcanic matter, and closely resembling, as I am informed 

 by Sir C. Lyell, similar products found in Mont D'Or in Auvergne. 

 It appears to me to resemble very closely also some of the tuffs in those 

 remarkable ravines across which the road passes from Castel a Mare to 

 Sorento, in the vicinity of Naples and Vesuvius ; and, further, it was 

 recognised by Mr. Smith, of Jordan Hill, as very similar to some of 

 the volcanic products of the island of Madeira. This bed varies much 

 in the fineness or coarseness of its component fragments ; at some 

 points consisting of close fine-grained matter, with white specks 

 more or less abundantly interspersed ; at others presenting an ex- 

 ceedingly coarse texture, the paste containing large fragments of a 

 pumiceous matter, with the white lapilli of corresponding size. But 

 there is one peculiarity of a remarkable character ; the whole of the 

 beds, although not far removed from the horizontal, dip slightly 

 towards the S.E. or landward end of the ravine ; and upon the dip, 

 this bed of tuff passes into a conglomerate of flints, cohering by a 

 cement so tenacious, that the flints themselves frequently break rather 

 than quit their matrix. These flints present, when wet and freshly 

 broken, the most brilliant tints of red and orange, and are evidently 

 more or less in a burnt condition. Some of them, however, are less 

 altered than the rest in texture and colour. One specimen I obtained 

 from external appearance alone was easily identified as an unequivo- 

 cal chalk flint ; and after I had shown it at the late meeting of the 

 British Association, a fossilized organism was discovered in it, which 

 placed this conclusion beyond a doubt. The white lapilli, throughout 

 the whole course of the bed, are generally siliceous ; although some 

 of the minuter particles have the appearance of unaltered chalk. 



4. The fourth band in the descending order is the second leaf-bed ; 

 that which is by far the richest in vegetable remains. It is about 



