1821.] Mr. Weaver on Floetz Formations. 243 



In the British Isles. 



In no part of the world, perhaps, are the mutual relations of 

 these three formations more fully displayed, in their distinct order 

 of progression, and in their various states of association, than in 

 England, Scotland, and Ireland. A general view of those rela- 

 tions will tend to show that these formations must be considered 

 as collectively constituting one group of the same era ; and the 

 whole series, whether in complete or incomplete progression, are 

 always found reposing on transition, or on primary tracts, or on 

 both of these conjointly. 



1 . Ireland. — In those parts of Ireland, of which I have given 

 an account (Geol. Trans, vol. v), the formations of old red sand- 

 stone, limestone, and coal, are separate and distinct, the lines of 

 division between them being broadly marked. This example 

 may be considered as affording the perfect type of the series in 

 their distinct order of succession. It may, however, be remarked, 

 that the old sandstone being there of unequal distribution, the 

 limestone formation is, in certain parts of its extent, in direct 

 contact with transition, and in others with primary tracts. 



This latter fact may be observed also in the north-west of 

 England, where the carboniferous limestone nearly encircles the 

 transition and primary tracts of Cumberland, Westmoreland, and 

 Lancashire, the old red sandstone intervening in few instances. 

 In other quarters again, the carboniferous limestone is altogether 

 wanting, the coal formation being directly and conjointly in 

 contact with old red sandstone and with transition rocks ; or the 



explored. The term has, in consequence, been misapplied in other tracts; and hence 

 also it has been supposed, that the old red sandstone, which precedes it in the order of 

 formation, must be a greywacke, or transition. But the real transition limestone of 

 Werner is found more particularly in association with clayslate, and with the true grey- 

 wacke of that naturalist, e. g. in the HarU. J On the other hand, however, if the 

 limestone in question (the English mountain limestone) be not the transition limestone 

 of Werner, neither is it his first floetz limestone. It so happened, that in the tracts 

 which came under the immediate consideration of the Freyberg Professor, in the north 

 of Germany, the limestone, which is there associated with the old red sandstone, is 

 found only in inconsiderable subordinate beds, incidentally disposed in that formation ; 

 and hence, if not entirely overlooked, it was not raised by him to the rank of a distinct 

 formation ; and hence also the application by him of the term fimt floetz limestone to 

 that limestone in Germany, which, in respect to age, appears to correspond with what 

 has been designated in England by the name of the magnesian limestone formation. § 

 Even the greatest men are subject to error, when information proves defective ; but in 

 the researches of the naturalist, the authority of names, however high, ought never to 

 outweigh the cogency of facts. 



■f- This term, which has been introduced by Prof. Buckland and the Rev. W. Cony- 

 beare, appears very appropriate, as distinctive of this associate of the great coal forma- 

 tion. 



t Or, as included in group No. 23 of Mr. Greenough's Geological Slap of England 

 and Wales ; a truly spirited work, by the execution of which, a most important service 

 has been rendered to geology. 



§ Included in group No. 17 of Mr. Greenough's Geological Map. Wherever, in the 

 following pages I may have occasion to refer to that map, I shall in general mention the 

 numj>e» of the group, with the initials G- M. only, 



B 2 



