lg2 On a Suhmarhie Forejl 



■We muft neccflarily recur to that period in the hiftory of 

 our planet, when the furface of the ocean was at Icaft fo 

 much above its prefent level as to cover even the fummits 

 of thofe fetondarv mountains which contain the remains of 

 tropical plants. The changes which thefe vegetables have 

 fiiffercd in their fubftance is almoft total ; they commonly 

 retain only the external configuration of what they were. 

 Such is the ftate in which they are found in England by 

 Llwyd; in PVance by Juffieu; and in the Netherlands by 

 Burtin; not to mention inftanccs in more diftant countries. 

 Some of the impreffions or remains of plants found in foils 

 of this nature, which were, by the more ancient and 

 enlightened oryftologifts, fuppofed to belong to plants 

 aflually growing in temperate and cold climates, feem, on ■ 

 acQurate invefligation, to ha\e been part of exotic vege- 

 tables. In fact, whether we fuppofc them to have grown 

 near the fpot where they are found, or to have been carried 

 tliitiicr from different parts by the force of an impelling 

 flood, if is equally difficult to conceive how organized 

 beings, wliich, in order to live, require fucli a vaft differ- 

 mce in temperature and in feafons, could live on the fame 

 fpot, or how their remains could (from climates fo widely 

 diftant) be brought together in the fame place bv one com- 

 mon diflocating caufe. To this ancient order of foffil vege- 

 tables belong whatever retains a vegetable fliape, found in 

 or near coal mines, and (to judge from the places where 

 they have been found) the greater part of the agatized 

 woods. But from the fpecies and prefent ftate of the trees, 

 which arc the fubje6t of this memoir, and from the fitua- 

 tian and nature of the foil in which they are found, it feems 

 very clear that they do not belong to the primeval order of 

 vegetable ruins. 



The fecond order of foflil vegetables, comprehends thofe 



which are found in the ftrata of clay or fand ; materials 



which are the refult of flow dcpofitions of the fea and of 



rivers, agents ftill at work under the prefent conftitution of 



9 our 



