20 Mr. Weaver on the [July, 



sandstone and porphyry, and presents in its roof only alternating 

 beds of slate-clay and carbonated shale, the former containing 

 numerous impressions of ferns. Thin beds of coaly shale, beds 

 of quartzy sandstone passing into granular quartz, of large- 

 grained conglomerate (coal measure conglomerate), and of fetid 

 limestone also, are met with in the midst of the slate-clay before 

 the coal is attained."* 



On the other hand, it is equally certain, that Continental 

 geologists have misconceived, in some instances, the purport of 

 the language employed by English writers. Hence has arisen a 

 double confusion ; when, after all, if the language of each had 

 been correctly apprehended, there would have been as little 

 discrepancy in description as there is in the appearances of 

 nature, since the facts themselves are perfectly reconcileable to 

 each other. 



To attempt to clear away difficulties and dispel obscurity is 

 both an irksome and ungrateful task ; and the love of truth 

 alone has impelled me to it. If it shall be found that I have 

 in any degree succeeded in throwing a clearer light upon a com- 

 plicated subject, my purpose will be fully answered. The 

 researches of M. Constant Prevost, an eminent French geologist, 

 and FMGS. who is at present engaged in examining the geolo- 

 gical relations of this country with a critical eye, will, I have not 

 a doubt, conduce to the same desirable end. 



I have upon former occasions remarked, that all the esta- 

 blished relations of the old red sandstone, carboniferous lime- 

 stone, and coal formation, to each other, as founded upon the 

 researches and descriptions of naturalists in different countries, 

 prove that they constitute one group of the same era ; yet vary- 

 ing much in the modes of their association, as being found in 

 one tract distinct from, and in another more or less interstratified 

 with each other. The following view, which may be of some 

 value in reference to practical and economical purposes, will be 

 found to embrace a summary of those relations. 



1. Old red sandstone, carboniferous limestone, and the coal 

 formation, in separate and distinct succession, not interstratified 

 upon their several confines ; e. g. the general case in Ireland. 

 This may be considered as the distinct type of the series. 



N. B. The bed of sandstone and conglomerate, found in some 

 tracts interposed between the limestone and the coal measures, 



* P. 207. " Souvent le grand depot de houille n'est pas recouvert de porphyre et de 

 gres rouge. Souvent il est place dans les basins entour£s de collines de gres rouge et de 

 poq>hyre, et n'offre dans son toit que des couches alternantes d'argile schisteuse (schie- 

 ferthon), tantot gris-bleuatre, tendres et remplies d'empreintes de fougeres, tantot com- 

 pactes, carburees (brandschiefer) et pyriteuses. Des minces strates de gres charbonneux 

 (kohlenschiefer), de gres quartzeux passant au quartz grenu, de conglomerat a. gros 

 fragmens (steinkohlen-conglomerat), et de calcaire fetide, se rencontrent au milieu du 

 schiefgrthon ava;it qu'on atteigne la houille." 



