Dr. FiTTON on the Strata below the Chalk. 21 7 



Man-of-War Cove, PI. X. a. No. 10'.; and X. b. fig. 8. — In the isthmus here, which connects 

 with the main land a wide peninsular mass of Portland stone rising towards the south, many of 

 the beds are inclined backwards, and lean towards the chalk hills. A coating of reddish 

 gravel, from 3 to 6 feet thick, extends to some distance from the chalk along the top of the 

 isthmus, and is shown by the dotted line in fig. 8. The following are the strata at this place : 



Paces. 



1. Chalk. 



2. Green-sand , 35 



3. Wealden-clay and Sands. 



a. Dark clay, much mixed with sand ; and including a mass of ferruginous sand- "1 



rock, 4 to 6 feet thick : seems to represent the Weald clay j 



h. Light grey, and white sand 7 



c. Red clay, nearly vertical •, but inclining a little towards the chalk 10 



d. Grey, and brownish sand, including at top a conspicuous bed, of dark hue, which -1 



contains much lignite in large pieces. [The breadth of the isthmus here, at 1 40 

 the bottom, is about 150 paces from west to east ; at top about 40 paces.] . . J 



e. Dark red and variegated clay. A considerable depression here in the outline of 1 ,_ 



the cliff / ^Q 



Total, about 74 



4. Purheck strata. Upper calcareous beds much distorted. About the middle a bed ofi 

 oysters is conspicuous, which, as it rises, is divided like a Y, and one of the portions re- 1 30 

 fleeted back towards the chalk. Estimated thickness (probably less than the true) J 



5. Portland stone (estimated) 80 — 90 



(1 10.) Me of Poi^tland *. — The coast of Dorsetshire^, from the promontory 

 of Whitenore to Lyme Reg'is, forms the subject of a memoir by Dr. Buckland 

 and Mr. De la Beche, which is printed at the commencement of the present 

 volume : I shall not, therefore, give any general description of it ; but having 

 been favoured with a perusal of that valuable paper, L find it necessary to 

 mention some details respecting the appearances observable near the junction 

 of the Purbeck and the Portland formations, with a view to a comparison 

 of this part of the series in the interior, with that of the coast in England, 

 and in the Boulonnois. 



Mr. Webster, in his account of the strata above the Portland stonefj has 

 described a remarkable bed, called by the quarry-men the " Dirt " or '' Black 

 "dirt", which he found to contain portions of the trunks of silicified trees; 

 one of which he himself saw standing upright, and divided at the lower part, 

 " so as to give the idea of roots ". He states that these trunks were not found 

 in any other part of the series ; but not having seen any fossils in the beds 

 above the Portland stone, he expresses himself with caution as to the place 

 of the boundary between the Purbeck strata and the oolitic group beneath 



* The substance of this and the following sections, to (116.) inclusive, was read before the 

 Geological Society on the 13th of May, 1835 ; and is inserted here by permission of the Pre- 

 sident and Council. 



t Geol. Trans., 2nd Series, vol. ii. p. 39, &c.; read Nov. 1824. 



2f2 



