390 Geological Society. 



organic remains of that ancient group differ from those found above 

 the old red sandstone, the plants also, if ever discovered, will differ 

 as greatly. Considerable surprise was therefore excited when, 

 during the Presidentship of my predecessor in this chair, a letter 

 was read, addressed to him from Mr. De la Beche, stating that he 

 had found, near Bideford in North Devon, many well known coal 

 plants in the lower greywacke, or far down in the transition series*. 

 Such of the plants as were determinable had been identified by 

 Professor Lindley with species characteristic of the true coal 

 measures, and which had never been found elsewhere below the 

 coal. The anomaly, therefore, in the supposed position of these 

 fossils was so great, that between the ordinary geological site of 

 such remains, and that in which they were here inferred to present 

 themselves, there would be interposed if the series were complete 

 the whole of the old red sandstone, and at least the two upper forma- 

 tions of the Silurian system. When this point was considered, I 

 expressed to the Society my opinion, in common with Mr. Mur- 

 chison, as to the insufficiency of the proofs relied on by our 

 Foreign Secretary, and we felt that we had a right to call for more 

 conclusive evidence. The simple fact of shales having been found 

 charged with true coal plants, raised so strong a presumption in 

 favour of their belonging to the regular carboniferous series, that 

 the burthen of proof rested with him who wished to assign to them 

 either a higher or lower position. Our scepticism was regarded 

 by Mr. Greenough as implying too marked a bias for a preconceived 

 theory, and this he afterwards hinted in his Anniversary Addressf. 

 I may affirm, however, that in the first place it implied on my part 

 no distrust of Mr. De la Beche's skill or experience in geological sur- 

 veying, and that had Professor Sedgwick and Mr. Murchison ad- 

 vanced a similar opinion on analogous proofs, I should equally have 

 withheld my assent. Suppose, for example, they had announced to 

 us that they had found fossil fruits and leaves identical with those of 

 Sheppey in strata of the age of the white chalk with flints. I should 

 have demanded from them, in corroboration, the most clear, un- 

 equivocal, and overwhelming evidence. If it were a region of dis- 

 turbed and vertical strata, I should expect them first to have re- 

 sorted in vain to every hypothesis of inverted stratification with a 

 view of explaining away such an exception to the general rule. 



I might perhaps be told that we are unacquainted with the flora 

 of the upper cretaceous period, and I admit that we are as ignorant 

 of it as of that which belonged to the transition period j but when 

 we consider the contrast of the shells and other fossils of the 

 chalk and London clay, we naturally anticipate that if plants are ever 

 found of the precise age of our chalk with flints, they will not prove 

 to be of the same species as those of the Sheppey clay. There 

 is a like presumption from analogy against the conclusion that the 

 same vegetation continued to flourish on the earth from the period 

 of the lower greywacke to that of the coal, because we know that 



* Lond. and Edinb. Phil. Mag., vol. vi. p. 67. f Ibid., vol. vii. p. 162. 



