ERRORS RESPECTING THE CLASSIFICATION OF TRANSITION ROCKS. 83 



remains occur ; for, among the secondary strata, abounding in such 

 remains, we often meet with alternating beds, in which they are nev- 

 er found ; but we do not, on that account, class them with primary 

 rocks. In arranging transition rocks, I most decidedly, place the 

 English mountain limestones among them, as I have done in the 

 former editions of this work. I know no circumstance in Geology 

 that evinces more strongly the tenacity with which errors are cher- 

 ished, when they have been some time entertained, than the deter- 

 mination of English geologists to separate mountain limestone from 

 transition limestone, — in opposition to analogy, and to the universal 

 opinion of geologists on the Continent. This separation, as a mere 

 matter of classification, would be in itself of little importance ; but, 

 it has tended, more than any other circumstance, to perplex both 

 foreign and English geologists, in their attempts to assimilate the rock 

 formations of England, with those on the continent of Europe. 



When a general attention was first excited, in this country, to the 

 study of Geology, access to the Continent was extremely difficult, 

 and we were left to explore, as well as we could, the geology of our 

 own island, enlightened only by the dark-lantern of German Geog- 

 nosy. Many characters were given of transition rocks, or floetz or 

 parallel rocks, founded on local observations in Germany, which did 

 not apply to the rocks in other countries : it was found that the char- 

 acters of our metalliferous limestone did not agree very well with 

 either, and therefore English geologists have retained the name of 

 mountain limestone ; and the appellation of transition limestone was 

 restricted to a lower bed, small in extent, and comparatively unim- 

 portant. When I first visited the Continent, and examined the cab- 

 inets of some eminent geologists, I was particularly struck with find- 

 ing the analogues of our principal beds of mountain limestone, ex- 

 hibited as types of true transition limestone. On ray return to Paris 

 the following year, I took specimens of our mountain limestone from 

 Derbyshire, Westmoreland, Somersetshire, and Wales ; and also of 

 the lower limestones from Shropshire and Devonshire ; and present- 

 ed them to MM. Brongniart and Brochant. The whole of the spe- 

 cimens they recognised as transition limestones, and selected the en- 

 crinal and dark madrepore mountain limestones, as the true types, 

 par excellence, des Calcaires de Transition. 



The following arrangement of transition rocks comprises the low- 

 est rocks in which organic remains occur, and those which are me- 

 t£tlliferous or are associated with metalliferous rocks : — 



TRANSITION CLASS (conformablc). 



1. Slate, including flinty slate and other varieties. 



2. Greywacke and greywacke-slate, passing into old red sand- 



stone. 



3. Transition limestone. Mountain limestone. 



