No. 3.] HUNT — ON CAMBRIAN AND SILURIAN. 293 



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

 errors in stratigraphy, Sedgwick proposed a compromise, accord- 

 ing 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 Siluriin should be reserved for the Wenlock and Ludlow 

 beds, and for those below the B ila the name of Cambrian should 

 be retained. The Festinios: group (including what were subse- 

 quently named the Lingult-flags and the Trcmadoc 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 miuht 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 color 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 withdrawn in 1854 by Sedgwick, who re-claimed the name of 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 B ila group. 



In June, 1843, Sedgwick proposed that the whole of the fos- 

 giliferous rocks below the horizon of the Wenlock should be 

 designated Protozoic, and on the 29th of November, 1843. pre- 

 sented to the Geological Society an elaborate paper on the Older 

 Paleozoic (Protozoic) Rocks of North Wales, with a colored 

 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. AVarburton, 

 then president of the society, with a reduced copy of the map. 

 [Proc. Geol. Soc. IV, 212 and 251-268 ; also Geol. Jour. I, 5-22.] 

 In this map of Sedgwick's three divisions were established, viz., 

 the hypozoic crystalline schists of Caernarvonshire, the " Proto- 

 zoic,'' and the " Silurian." On the legend of the reduced map, 

 as published by the Geological Society, these latter names were 

 altered so as read ^^ Loicer Silurian (Protozoic)'' and " Upper 

 Silurian.'^ These changes, in conformity with the nomenclature 

 of Murchison, were, it is unnecessary to say, made without the 

 knowledge of Sedgwick, who did not inspect the reduced and 

 altered map until it was appealed to as an evidence that he had 

 abandoned his former ground, and had recognized the equivalency 



