14 



Prof. BucKLAND and Mr. De la Beche on the 



have been derived. A bed of snow falling on a modern peat-bog-, and cover- 

 ing the upper portion of prostrate trees, whose lower portion has been sunk 

 by their weight into the substance of the peat, would represent the position 

 of the calcareous slate which immediately covers these fossil trees in Portland : 

 some of them extend to a length exceeding thirty feet, and bifurcate at their 

 upper end ; but the branches are not continuous to their extremities, and we 

 find no traces of leaves. The leaves and small branches, and exterior parts 

 of the trunks, had probably decayed, whilst they lay exposed to air on the 

 surface of the peat. Amid these prostrate trees, many of which attain three 

 and four feet in diameter, we find silicified stems of plants closely resembling 

 the modern Cycas and Zamia : these have been described by Prof. Buck- 

 land under the name of Cycadeoideae*, and are important, as indicating that 

 the temperature in which they grew was much higher than that of our pre- 

 sent climate. We find also, at nearly the same intervals at which trees are 

 found growing in a modern forest, an assemblage of silicified stumps or stools 

 of large trees, with their roots attached to the earth in which they grew. 

 These stumps are from one to three feet long : they are mostly erect, whilst 

 a few are slightly inclined. The black earth which contains their roots 

 seldom exceeds one foot in thickness ; the upper portions of the stumps, as 

 represented by Mr. Webster f, project upwards into the substance of the 

 superjacent stone (called "soft Burr" and "Aish"), which gives indication of 

 their presence by hemispherical concretions accumulated around the top of 

 each stump of wood|. 



Section of the Cliffy east of Lulworth Cove. 



Lower Purbeck beds 

 composed of c<dca- 

 reous slate of fresh - 

 water formation. 



Sift burr. 



Ancient forest in the dirt-bed. 



Portland stone of 

 marine formation. 



In the highly inclined strata of the cliff, about a furlong east of Lulworth 

 Cove, and represented in the above sketch, we find a considerable number 

 of these silicified stumps, some entirely laid bare by the washing of the sea, 

 others partly exposed and partly covered, and others still wholly encased with 



* Geological Transactions, Second Series, vol. ii. Part III. p. 395. 



t Ibid. vol. ii. Part I. PI. 6. fig. 3, 4. + See wood-cut at p. 13. 



