262 The Founders of Geology LECT. 



this unhappy controversy. 1 My only object in referring 

 to it is to point out how far we are indebted to Sedg- 

 wick for the establishment of the Cambrian system. He 

 eventually traced through a part of the Welsh border a 

 marked unconformability between the Upper Silurian for- 

 mations and everything below them, and he proposed that 

 his Cambrian system should be carried up to that physical 

 break and thus include Murchison's Lower Silurian forma- 

 tions. But as these formations had been defined strati- 

 graphically and palseontologically before he had been 

 able to get his fossils from North Wales examined, they 

 obviously had the right of priority. And the general 

 verdict of geologists went in favour of Murchison. 



While this dispute was in progress in Britain, a re- 

 markable series of investigations by Joachim Barrande 

 had made known the extraordinary abundance and variety 

 of Silurian fossils in Bohemia. This distinguished observer 

 not only recognized the equivalents of Murchison's Upper 

 and Lower Silurian series, but found below that series 

 a still older group of strata, characterized by a different 

 assemblage of fossils, which he termed the first or prim- 

 ordial fauna. It was ascertained that representatives of 

 this fauna occurred in Wales among some of the divisions 

 of Sedgwick's Cambrian system, far below the Llandeilo 

 group which formed the original base of the Silurian series. 

 Eventually, therefore, since the death of the two great 

 disputants, there has been a general consensus of opinion 

 that the top of the Cambrian system should be drawn at 

 the upper limit of the primordial fauna. 2 



1 I have already given a full and, I believe, impartial account of it in 

 my Life, of Murchison. 



2 It has been proposed by Professor Lapworth that the strata named 



