352 CAMBRIAN AND SILURIAN IN EUROPE. [XV. 



at Gwastaden in Breconshire, and to the west of Llandovery in 

 Caermarthenshire ; constituting an underlying series of con- 

 torted slaty rocks many thousand feet in thickness, and desti- 

 tute of organic remains. The position of these rocks in South 

 Wales was, however, to the northwest, while the strata of the 

 Longmynd, as we have seen, appear to the east of the fossilif- 

 erous formations. 



In the L. E. & D. Philosophical Magazine for July, 1835, 

 Murchison gave to the four formations above named the des- 

 ignation of Silurian, in allusion, as is well known, to the an- 

 cient British tribe of the Silures. It now became desirable to 

 find a suitable name for the great inferior series, which, accord- 

 ing to Murchison, rose from beneath his lowest Silurian forma- 

 tions to the northwest, and appeared to be widely spread in 

 Wales. Knowing that Sedgwick had long been engaged in 

 the study of these rocks, Murchison, as he tells us, urged him 

 to give them a British geographical name, Sedgwick accord- 

 ingly proposed for this great series of Welsh rocks the appro- 

 priate designation of Cambrian, which was at once adopted by 

 Murchison for the strata supposed by him to underlie his Silu- 

 rian system. (Murchison, Anniv. Address, 1842 ; Proc. GeoL 

 Soc., III. 641.) This was almost simultaneous with the giving 

 of the name of Silurian, for in August, 1835, Sedgwick and 

 Murchison made communications to the British Association at 

 Dublin on Cambrian and Silurian Rocks. These, in the vol- 

 ume of Proceedings (pp. 59, 60), appear as a joint paper, 

 though from the text they would seem to have been separate. 

 Sedgwick then described the Cambrian rocks of North Wales 

 as including three divisions : First, the Upper Cambrian, which 

 occupies the greater part of the chain of the Berwyns, where, 

 according to him, it was connected with the Llandeilo forma- 

 tion of the Silurian. To the next lower division, Sedgwick 

 gave the name of Middle Cambrian, making up all the higher 

 mountains of Caernarvon and Merionethshire, and including 

 the roofing-slates and flagstones of this region. This middle 

 group, according to him, afforded a few organic remains, as at 

 the top of Snowdon. The inferior division, designated as 



