Mr. LyelPs Address, 391 



in the course of the intervening epochs the testacea, zoophytes, fish, 

 and other classes of organic beings were several times changed. 



In regard to the proofs relied on by Mr. De la Beche, I should 

 observe that he never attempted to show that the plant-bearing 

 shales at Bideford were interstratified with rocks charged with 

 shells or other fossils known to belong to rocks older than the old 

 red sandstone. 



Since writing the above sketch of the different views recently 

 published of the structure of Devonshire, I have received a letter 

 from Mr. De la Beche, from which I am happy to learn, that it is 

 his intention before concluding his report on the Ordnance Map 

 of Devon, to reexamine Devonshire. He is far, he says, from 

 pretending that his first views were perfect, and if he finds rea- 

 son to modify any of them, he shall not hesitate to announce the 

 change of opinion. In the mean time he no longer contends that 

 the culmiferous strata are referable to the lower graywacke, and 

 considers the point of difference to lie within a narrower compass, 

 namely, whether the culm beds are to be considered as upper gray- 

 wacke or coal. This question, on which he is not yet satisfied, evi- 

 dently appears to him of much less theoretical importance than, I 

 confess, it does to me. It is fair, however, that I should state the 

 arguments which influence his mind. If the plants, he says, found 

 at Bideford in the culmiferous series should belong to strata more 

 ancient than the old red sandstone the fact would not stand alone, 

 for he has lately received a letter from M. Elie de Beaumont, de- 

 tailing analogous phaenomena in Brittany. It is stated that the grey- 

 wacke there closely corresponds in general character with that of 

 Devon, the upper part like the Devonian series containing anthra- 

 cite. With this anthracite or culm are found at Montrelais, Chatelai- 

 son, and other places, fossil plants, the greater part of which are 

 identical with those in the coal measures ; but there are others which 

 have not hitherto been detected in the latter rock. Patches of true 

 coal measures rest in unconformable position upon these upper 

 graywacke beds of Brittany. Now I regret that I have not seen 

 any printed account of the geology of this part of France ; for until 

 we learn whether the plants in question are associated with true Si- 

 lurian fossils, the testimony is quite incomplete. We know not, 

 for instance, whether the plant- bearing series in question is old red 

 sandstone or a Silurian formation, or wliether it is a lower part of 

 the true carboniferous system of which the strata had been disturbed 

 before a higher portion was superimposed. 



Similar remarks hold in regard to the observations made by 

 M. Virlet in the Dictionnaire d'Hist. Naturelle, where in his late 

 article " De I'Origine des Combustibles Mineraux," he speaks of 

 certain carboniferous deposits of Ireland, (those alluded to by Mr. 

 Weaver before mentioned,) as well as others examined by M. Voltz 

 in the Black Forest, also the culm beds of Brittany, and those of 

 the department of La Sarthe, as all belonging in age to the newest 

 transition formations, " terrains de transition les 'plus recens.''* 



Mr. De la Beche alludes to another discovery of coal plants 



