292 THE CANADIAN NATURALIST. [Vol. vi. 



Llandeilo ; 2, Cambrian (= Caradoc or Bala) ; 3, Wenlock and 

 Ludlow ; 4, Old Red sandstone ; the Caradoc or Bala beds 

 being repeated on the two sides of the anticlinal, but in great 

 part concealed on the south-east side by the overlapping May Hill 

 or Upper Llandovery rocks. These latter, as has been shown, 

 form the true base of the upper series which, in the Silurian 

 sections, was represented by the Wenlock and Ludlow. Murchi- 

 son had, by a strange oversight, completely inverted the order of 

 his lower series, and turned the inferior members upside down. 

 In fact, the Llandeilo flags, instead of being, as he had main- 

 tained, superior to the Cambrian (Caradoc or Bala) beds, were 

 really inferior to them, and were only made Silurian by a great 

 mistake. The Caradoc, under different names, was thus made to 

 do duty at two horizons in the Silurian S3stem, both below and 

 above the Llandeilo flags. Nor was this all, for by another error, 

 as we have seen, the Caradoc in the latter position was made to 

 include the Pentamerus beds of the unconformably overlying 

 series. Thus it clearly appears that with the exception of the 

 relations of the Wenlock and Ludlow beds to each other and to 

 the overlying Old Red sandstone, which were correctly deter 

 mined, the Silurian system of Murchison was altogether incorrect, 

 and was moreover based upon a series of stratigraphical mistakes, 

 which are scarcely paralleled in the history of geological investi- 

 gation. 



It was thus that the Lower Silurian was imposed on the scien- 

 tific world ; and we may well ask with Sedgwick, whether 

 geologists " would have accepted the Lower Silurian classification 

 and nomenclature had they known that the physical or sectional 

 evidence upon which it was based had been, from the first, po- 

 sitively misunderstood." Feeling that his own sections were, as 

 has since been fully established, free from error, Sedgwick na- 

 turally thought his name of Upper Cambrian should prevail for 

 the great Bala group. Hence the long and embittered discussion 

 that followed, in which Murchison, in many respects, occupied 

 a position of vantage as against the Cambridge professor, and 

 finally saw his name of Lower Silurian supplant almost etitirely 

 that of Upper Cambrian given by Sedgwick, who had first rightly 

 defined and interpreted the geological relations of the group. 



In a paper read before the Geological Society in June, 1843, 

 [Proc. Geol Soc. IV, 212-223] when the perplexity in which the 

 relations of the Upper Cambrian and Lower Silurian rocks were 



