and the Palceozoic System of England. 501 



suspecting that my proposed nomenclature had been most un- 

 warrantably tampered with), I was for some years perfectly un- 

 conscious of the fact, never having scrutinized the reduced map, 

 or read its definitions of the several geological subdivisions. 



Having before referred to this strange passage in the history 

 of a controversy, I should not again have taken it up, except to 

 introduce one or two remai'ks on the classification of the Go- 

 vernment Survey. — (1) Under the name Cambrian they include 

 only the Lower Cambrian group of the Tabular View {supra, 

 p. 362). (2) Under the name Lower Silurian they include 

 all the Middle Cambrian and nearly all the Upper Cambrian 

 groups of the Tabular View. (3) Under the name Middle 

 Silurian they include the Caradoc sandstone, as well as all the 

 groups I have since called May Hill sandstone. (4) Lastly, 

 they naturally adopt the Upper Silurian groups, about which 

 there never has arisen any doubt. 



In this scheme I think that the separation of the first and 

 second subdivisions into Cambrian and Silurian is unnatural ; 

 and that, so far, the nomenclature in the new work 'Siiuria' 

 (though wrong in principle) is more consistent than their own. 



In the next place, I think their second division has only been 

 established by a desertion of the principles which the Director of 

 the Survey has repeatedly advocated in the Geological Society, 

 with, perhaps, more energy than any other member of it, viz. 

 that in every new case of classification we must ground our 

 system on the succession of physical groups as well as on the 

 evidence of fossils. This true principle is also energetically 

 asserted by Sir R. I. Murchison in his Anniversary Address for 

 1842 (Proceedings, vol. iii. p. 649). "So long (he teaches us) 

 as British geologists establish a classification founded on the se- 

 quence of the strata, and the imbedded contents, .... so long will 

 their insular names be honoured with a preference by foreign 

 geologists. ^^ But was this plan pursued in the downward ex- 

 tension of the Lower Silurian groups, either by himself or by the 

 gentlemen of the Government Survey ? I am certain it was not 

 followed out by himself; and I think it was not followed out in 

 the Government Survey. They soon found that the " Silurian 

 System^ Vas on an erroneous base, and that the Llandeilo flag was 

 in a false relation to the " Upper Cambrian '' groups of South 

 Wales. But having reduced it to its right relation, they then de- 

 veloped it upwards through five or six thousand feet of strata, and 

 downwards through more than twice as many thousands, and so 

 elaborated their second division with a nomenclature which is 

 geographically incongruous, and had no primary reference to 

 the actual succession of physical groups; and they did this while 

 a truer and more philosophical nomenclature was before them. 



