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482 PHILOSOPHICAL TRANSACTIONS. [ANNO 17QQ. 



even the summits of these secondary mountains which contain the remains of tropi- 

 cal plants. The changes which these vegetables have suffered in their substance, is 

 almost total ; they commonly retain only the external configuration of what they 

 originally were. Such is the state in which they have been found in England, by 

 Llwyd ; in France, by Jussieu ; in the Netherlands, by Burtin ; not to mention 

 instances in more distant countries. Some of the impressions or remains of plants 

 found in soils of this nature, which were, by more ancient and less enlightened 

 ory otologists, supposed to belong to plants actually growing in temperate and cold 

 climates, seem, on accurate investigation, to have been parts of exotic vegetables. 

 In fact, whether we suppose them to have grown near the spot where they are 

 found, or to have been carried thither from different parts, by the force of an im- 

 pelling flood, it is equally difficult to conceive, how organized beings, which, in 

 order to live, require such a vast difference in temperature and in seasons, could 

 live on the same spot, or how their remains could, from climates so widely distant, 

 be brought together to the same place, by one common dislocating cause. To this 

 ancient order of fossil vegetables belong whatever retains a vegetable shape, 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 species and present state of the 

 trees which are the subject of this Memoir, and from the situation and nature of 

 the soil in which they are found, it seems very clear that they do not belong to this 

 primeval order of vegetable ruins. 



The 2d order of fossil vegetables, comprehends those which are found in strata 

 of clay or sand ; materials which are the result of slow depositions of the sea or of 

 rivers, agents still at work under the present constitution of our planet. These 

 vegetable remains are found in such flat countries as may be considered to be of a 

 new formation. Their vegetable organization still subsists, at least in part ; and 

 their vegetable substance has suffered a change only in colour, smell, or consistence ; 

 alterations which are produced by the developement of their oily and bituminous 

 parts, or by their natural progress towards rottenness. Such are the fossil vegeta- 

 bles found in Cornwall, by Borlase ; in Essex, by Derham ; in Yorkshire, by De 

 la Pryme, and Richardson ; and in foreign countries, by other naturalists. These 

 vegetables are found at different depths, some of them much below the present 

 level of the sea, but in clayey or sandy strata, evidently belonging to modern for- 

 mation, and have, no doubt, been carried from their original place, and deposited 

 there by the force of great rivers or currents, as it has been observed with respect 

 to the Mississippi.* In many instances however, these trees and shrubs are found 

 standing on their roots, generally in low or marshy places, above, or very little 

 below, the actual level of the sea. 



To this last description of fossil vegetables, the decayed trees here described certainly 

 belong. They have not been transported by currents or rivers ; but, though 

 standing in their native soil, we cannot suppose the level in which they are found, 

 * La Coudreniere sur les Depots du Mississippi. Journ. de Phys. vol. 21, p. 230. — Orig. 



