THE 



GEOLOGICAL MAGAZINE. 



No. CXI.— SEPTEMBER, 1873. , 



I. — History of the Names Cambriajst and Silurian in Geology.^ 

 By Prof. T. Steery Hunt, LL.D., F.E.S. 



IT is proposed in the following pages to give a concise account of 

 the progress of investigation of the lower Palaeozoic rocks during 

 the last forty years. The subject may naturally be divided into 

 three parts : 1. The history of Silurian and Upper Cambrian in 

 Great Britain from 1831 to 1854 ; 2. That of the still more ancient 

 Paleeozoic rocks in Scandinavia, Bohemia, and Great Britain up to 

 the present time, including the recognition by Barrande of the so- 

 called primordial Palaeozoic fauna; 3. The history of the lower 

 Palseozoic rocks of North America. 



1. Silurian and Upper Cambrian in Great Britain. — Less than forty 

 years since, the various uncrystalline sedimentary rocks beneath the 

 coal-formation in Great Britain and in Continental Europe were 

 classed together under the common name of graywacke or grau- 

 wacke, a term adopted by geologists from German miners, and 

 originally applied to sandstones and other coarse sedimentary de- 

 posits, but extended so as to include associated argillites and 

 limestones. Some progress had been made in the study of this 

 great Graywacke formation, as it was called, and organic remains 

 had been described from various parts of it ; but to two British 

 geologists was reserved the honour of bringing order out of this 

 hitherto confused group of strata, and establishing on stratigraphical 

 and palgeontological grounds a succession and a geological nomen- 

 clature. The work of these two investigators was begun inde- 

 pendently and simultaneously in different parts of Great Britain. 

 In 1831 and 1832 Sedgwick made a careful section of the rocks of 

 North Wales from the Menai Strait across the range of Snowdon 

 to the Berwyn hills, thus traversing in a south-eastern direction 

 Caernarvon, Denbigh, and Merionethshire. Already, he tells us, he 

 had, in 1831, made out the relations of the Bangor group (including 

 the Llanberris slates and the overlying Harlech grits), and showed 

 that the fossiliferous strata of Snowdon occupy a synclinal, and are 

 stratigraphically several thousand feet above the horizon of the 

 latter. Following up this investigation in 1832, he established the 

 great Merioneth anticlinal, which brings up the lower rocks on the 

 south-east side of Snowdon, and is the key to the structure of North 

 Wales. From these, as a base, he constructed a section alono- the 

 line already indicated, over Great Arenig to the Bala limestone, the 

 whole forming an ascending series of enormous thickness. This 



' Reprinted from the "Canadiau Naturalist," new series, vol. vi, no. 3, p. 281. 



VOL. X. — NO. CXI. 25 



