vi The Cambrian and Silurian Systems 263 



By this arrangement, Sedgwick's name is retained for 

 an enormously thick and varied succession of strata which 

 possess the deepest interest, because they contain the 

 earliest records yet discovered of organized existence on the 

 surface of our globe. It was Sedgwick who first arranged 

 the successive groups of strata in North Wales, from the 

 Bala and Arenig rocks down into the depths of the Har- 

 lech anticline. His classification, though it has undergone 

 some slight modification, remains to this day essentially as he 

 left it. And thus the name which he selected for his system, 

 and which has become one of the household words in geo- 

 logical literature, remains with us a memorial of one of the 

 most fearless, strenuous, gentle and lovable of all the master 

 minds who have shaped our science into its present form. 



By the establishment of the Cambrian and Silurian 

 systems a vast stride was made in the process of reducing 

 the chaos of grey wacke into settled order. But there still 

 remained a series of rocks in that chaos which could not 

 be claimed as either Cambrian or Silurian and did not 

 yield fossils which would show them to be Carboniferous. 

 Before any dispute arose between Sedgwick and Murchison 

 as to the respective limits of their domains in Wales, 

 they were led to undertake a conjoint investigation which 

 resulted in the creation of the Devonian system. The 

 story of the addition of this third chapter to early 

 Palaeozoic history may be briefly told. 



by Murchison Lower Silurian and claimed by Sedgwick as Upper Cam- 

 brian, should be taken from both and be given a new name, " Ordovician." 

 But this proposal is fair to neither disputant. By all the laws that 

 regulate scientific priority the strata which were first separated by 

 Murchison and distinguished by their fossils, should retain the name of 

 Lower Silurian which he gave them. 



