394 Prof. T. Sterry Hunt — On Cambrian and Silurian. 



mistakes, whicli are scarcely paralleled in the history of geological 

 investigation. 



It was thus that the Lower Silurian was imposed on the scientific 

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

 " would have accepted the Lower Silurian classification and nomen- 

 clature had they known that the physical or sectional evidence upon 

 which it was based had been, from the first, positively misunder- 

 stood"? Feeling that his own sections were, as has since been fully 

 established, free from error, Sedgwick naturally 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 entirely 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, vol. iv. pp. 212-223), when the perplexity in which the 

 relations of the Upper Cambrian and Lower Silurian rocks were 

 involved had not been cleared up by the discovery of Murchi son's 

 errors in stratigraphy, Sedgwick proposed a compromise, according 

 to which the strata from the Bala limestone to the base of the 

 Wenlock were to take the name of Cambro- Silurian ; while that of 

 Silurian should be reserved for the Wenlock and Ludlow beds, and 

 for those below the Bala the name of Cambrian should be retained. 

 The Ffestiniog group (including what were subsequently named the 

 Lingula-flags and the Tremadoc slates) would thus be Upper instead 

 of Middle Cambrian, the original Upper Cambrian being henceforth 

 Cambro-Silurian ; it being understood that, wherever the dividing 

 line might be drawn, all the groups above it should be called 

 Cambro-Silurian, and all those below it Cambrian. This compromise 

 was rejected by Murchison, who, in the map accompanying the first 

 edition of his Siluria, in 1854, extended the Lower Silurian colour so 

 as to include all but the lowest division of the Cambrian, viz. the 

 Bangor group. When, however, the relations of Upper Cambrian 

 and Silurian were made known by the discoveries of Sedgwick and 

 the Government surveyors, this compromise was seen to be uncalled 

 for, and was withdrawn in 1854 by Sedgwick, who re-claimed the 

 name of Upper Cambrian for his Bala group. 



In June, 1843, Sedgwick pi'oposed that the whole of the fossil- 

 iferous rocks below the horizon of the Wenlock should be designated 

 Protozoic, and on the 29th of November, 1843, presented to the 

 Geological Society an elaborate paper on the Older Palaeozoic (Proto- 

 zoic) Eocks of North Wales, with a coloured geological map. This 

 paper, which embodied the results of the researches of Sedgwick 

 and Salter, was not, however, published at length ; but an abstract of 

 it was prepared by Mr. Warburton, then President of the Society, with 

 a reduced copy of the map. (Proc. Geol. Soc, vol. iv. pp 212, 251- 

 268 ; also Geol. Journ., vol. i. pp. 5-22.) In this map of Sedgwick's 

 three divisions were established, viz., the hypozoic crystalline schists 

 of Caernarvonshire, the " Frotozoic," and the "Silurian." On the 



