372 ANCIENT SUBMERGED FOREST. 



PI. 57, Fig. 3, exhibits similar stumps of trees rooted in 

 their native mould, in the Cliff immediately east of Lulworth 

 Cove. Here the strata have been elevated nearly to a angle 

 of 45*^, and the stumps still retain the unnatural inclination 

 into vv^hich they have been thrown by this elevation. 



The facts represented in these three last figures are fully 

 described and explained in the paper above referred to; 

 they prove that plants belonging to a family that is now con- 

 fined to the warmer regions of the earth, were at a former 

 period, natives of the southern coast of England.* 



As no leaves have yet been found with the fossil Cycadeae 

 under consideration, we are limited to the structure of their 



tions, marked in the stone, which surrounds a single stump, rooted in the 

 dirt-bed in the Isle of Portland. This very curious disposition has apparently 

 resulted from undulations, produced by winds, blowing at different times in 

 different directions on the surface of the shallow fresh-water, from the sedi- 

 ments of which the matter of this stratum was supplied, while the top of 

 this stem stood above the surface of the water. See Geol. Trans. Lond. N. 

 S. vol. iv. p. 17. 



* The structure of this district affords also a good example of the proofs 

 which Geology discloses, of alternate elevations and submersions of the 

 strata, sometimes gradually, and sometimes violently, during the formation 

 of the crust of our planet. 



First. We have evidence of the rise of the Portland stone, till it reached 

 the surface of the sea wherein it was formed. 



Secondly, This surface became for a time, dry land, covered by a tempo- 

 rary forest, during an interval which is indicated by the thickness of a bed 

 of black mould, called the Dirt-bed, and by the rings of annual growth 

 in large petrified trunks of prostrate trees, whose roots had grown in this 

 mould. 



Thirdly, We find this forest to have been gradually submerged, first be- 

 neath the waters of a fresh-water lake, next of an estuary, and afterwards 

 beneath those of a deep sea, in which Cretaceous and Tertiary strata were 

 deposited, more than 2000 feet in thickness. 



Fourthly, The whole of these strata have been elevated by subterranean 

 violence, into their actual position in the hills of Dorsetshire. 



We arrive at similar conclusions, as to the alternate elevation and depres- 

 sions of the surface of tiie earth, from the erect position of the stems of Ca- 

 lamites, in sand-stone of the lower Oolite formation on the eastern coast of 

 Yorkshire. (See JVIurchison. Proceedings of Geol. Society of London, vol. 

 i. p. 391.) 



