44.1 



the remarkable circumstance exhibited in this specimen, that though 

 the change in the longitudinal fibres appears to be complete, yet the 

 medullary rays are still in their ligneous state; and on referring to 

 the specimen formerly described, Mr. Stokes has found some instances 

 in which a part of the medullary ray which passes through the petri- 

 fied portion has not been so completely changed as the surrounding 

 longitudinal fibres, or the part of the same ray which is more in the 

 centre of the petrified portion. 



Of the unpetrified part of the specimen, some portions are much de- 

 cayed and worm-eaten, while others are hard and apparently in good 

 preservation; the line of separation between the two conditions being 

 occasionally remarkably well defined. On submitting portions of 

 each to the action of muriatic acid, Mr. Stokes found that the decayed 

 part exhibited only a slight effervescence, while that which appeared 

 in good preservation gave off a much greater quantity of gas, and 

 chiefly from the inside of the larger vessels, as if they were coated 

 with an extremely thin layer of carbonate of lime. This fact, connected 

 with the medullary rays remaining in some instances unchanged, or but 

 partially changed, presents, as stated by the author, the first ocular 

 demonstration of progressive steps in the process of petrifaction. The 

 communication concluded with some observations on the fossil wood 

 of Allesley described in Dr. Buckland's paper, in some of the specimens 

 of which there are spindle-shaped portions similar to those in the 

 partially petrified wood of Buckeberg. 



" Description of a Raised Beach in Barnstaple Bay, on the north- 

 west coast of Devonshire," by the Rev. Professor Sedgwick, F.G.S,, 

 and Roderick Impey Murchison, Esq., F.G.S., was afterwards read. 



This raised beach is first seen at the northern extremity of the 

 blown sand-hills called Braunton Burrows, and thence may be traced 

 round the western end of Saunton Down, into Croyde Bay. After 

 meeting with some interruptions it reappears, and may be followed to 

 the face of the bold headland called Baggy Point, about three miles 

 from the place of its commencement, in situations where it is best 

 exposed, especially on the south side of Saunton Down, it puts on 

 the form of a horizontal under terrace, resting upon an indented 

 and irregular surface of the older formations, and abutting against 

 their component beds. It forms regular sea-cliff's, the stratification of 

 which is most distinct ; and the several beds may be traced by small 

 bands of shingles, by alternating courses of different degrees of fine- 

 ness, and by horizontal lines of division. In distinctness of stratifica- 

 tion it yields to no rock ; and as several parts of the cliff are in a state 

 of perfect induration, presenting regularly bedded masses of calcareous 

 grit and sandstone, the authors at first sight mistook it for a secondary 

 tormation. 



The bottom of this horizontal deposit is chiefly composed of indu- 

 rated shingles resting on the ledges of the older rocks, and filling 

 up their inequalities. These conglomerates or shingles are seldom 

 of great thickness, but in some places alternate two or three times 

 with beds of sand, so as to reach an elevation of eight or nine feet m 



