492 Prof. Sedgwick on the May Hill Sandstone, 



sical, or sectional, evidence on which it was based had from the 

 first been positively misunderstood? I cannot answer such a 

 question in the affirmative. 



When the progress of information proved that the Caradoc 

 group had in many places been misinterpreted, and that the 

 Llandeilo group had been placed at the base of the " System '' 

 by a great misconception of the Llandeilo section, one might 

 have looked for some modification of the nomenclature. On the 

 long run it would have been wise for the Author of the " System '' 

 to have changed his nomenclature : but for present advocacy it 

 would have been unwise ; for those who have accepted and used 

 a nomenclature never willingly change it. And in geology, as 

 in every thing else, to prevent the inconvenience of change, many 

 men will abide in a false position and sometimes even acquiesce 

 in a gross absurdity. A bad rule, however, for scientific progress. 



The Silurian nomenclature professed to be at once geographical 

 and sectional : and how was it to preserve its character with the 

 destruction of its base and its sudden extension over Cambria ? 

 It became geographical by absorbing Cambria into Siluria ; and 

 finally, it became sectional by making the great Cambrian series 

 the equivalent of the " Llandeilo formation V Greater geogra- 

 phical and sectional portents were never brought forth during the 

 history of physical science. The nomenclature does not mask, 

 but greatly exaggerates the incongruity of the scheme ; and it 

 contains within itself the inevitable elements of its own de- 

 struction. 



The Corndon sections are appealed to in defence of the clas- 

 sification and nomenclature. Unfortunately, the fossiliferous 

 beds of Coradon were called Llandeilo flag ; and hence, if the 

 typical Llandeilo gi'oup had a wrong place in the Cambrian series, 

 the Corndon beds could not have a right one. It is mere 

 mockery to compare the Corndon series with that of the Tabular 

 View, and to set it up as the Cambrian type. Its parts are de- 

 fective in succession, obscure in detail, and have only been put 

 into an hypothetical co-ordination with the lower groups of the 

 true and typical series of Cambria. 



The only real argument for the "Lower Silurian'^ nomen- 

 clature is derived from the so-called Lower Silurian fossils. They 

 are unquestionably Cambrian. How could they be otherwise, 

 being taken from a low Upper Cambrian sub-group. But to argue 

 from the fossils only without an appeal to co-ordinate sections, is 

 to desert the first principles on which the ' Silurian System ^ had 

 its legitimate claim for our acceptance. As a matter of fact, the old 

 Cambrian types of the Caradoc sandstone were gained by a false 

 step over the May Hill beds; and as for the Llandeilo fossils 

 they became Silurian only by the greatest sectional mistake the 



