MURCHISON ON THE SILURIAN SYSTEM. 179 



any one, suppose otherwise than that he had then agreed ex neces- 

 sitate rei to the classification I had proposed, and which all my 

 contemporaries had adopted ? 



The present controversy, which on my part I now close, began 

 at the end of the year 1846, or eleven years after the promulgation of 

 the Silurian System in England, and four years after it had been ex- 

 tended and generally adopted. In the Supplement to his memoir of 

 1846, " On the classification of the fossiliferous slates of Cumberland, 

 Westmoreland, and Lancashire," Professor Sedgwick put forth opi- 

 nions which I was compelled to oppose ; because I foresaw, that if a 

 fossiliferous Cambrian group were to be formed by the abstraction of 

 a portion of the Lower Silurian, and the Wenlock shale thrown into 

 the Lower Silurian as a sort of make-weight to enlarge the Caradoc, 

 I might very soon be called upon for a farther concession, and be 

 asked to abrogate entirely the lower half of the system : this is lite- 

 rally what has followed. 



To that memoir* I therefore replied at the conclusion of a paper 

 on the Silurian rocks of Sweden f. To another and more elaborate 

 memoir ;j; by my friend I also replied § in the paper entitled " On 

 the meaning originally attached to the term ' Cambrian System,' and 

 on the evidences since obtained of its being geologically synonymous 

 with the previously established term ' Lower Silurian.' " 



To these two memoirs I refer young geologists for all that I could 

 say and which I then thought settled the question at issue. Five 

 years have elapsed during which I have published nothing on this 

 controversy. In the mean time, however, authors who have written 

 on palaeozoic geology, in every part of the world, have either gone on 

 with, or adopted my terminology ; and, what is most gratifying to 

 me is, that the Government Geological Surveyors have definitively 

 taken the same course, and have in accordance coloured all their maps 

 and sections, and have so named all the fossils of the great Museum 

 presided over by Sir Henry de la Beche. All the fossils of the re- 

 gion of Cambria or North Wales (down to the Lingula-beds inclusive) 

 are now classified as Silurian. 



But this band of able men have done much more. They have 

 sustained the value of my chief original sections. They, having also 

 used my keys, have decided, after years of hard labour in the field, 

 that the whole of the fossihferous strata of North Wales are repeti- 

 tions, by undulation, of certain Lower Silurian strata first described 

 by me in 1834, and of which detailed coloured sections were finally 

 published in 1838. Showing that my original unfossiliferous base, 

 the Longmynd of Shropshire, offers a more copious development of 

 the unfossiliferous rocks to which they now restrict the term " Cam- 

 brian," than any of the oldest slaty masses of North Wales, they 

 affirm, that, overlying such unfossiliferous greywacke on the west, and 

 in the order in which I have represented in coloured sections (' Silu- 

 rian System,' pi. 32. figs. 1, 2, 3), the Lower Silurian schists and 

 quartz-rocks of the Stiper stones and the Llandeilo series of Shelve 



* Quart. Journ. Geol. Soc. vol. ii. p. 106 et seq, t Ibid. vol. iii. p. 1 et seq. 

 X Ibid. vol. iii. p. 133, Dec. 1846. § Ibid. vol. iii. p. 165, Jan. 1847. 



