186 THE GEOLOGICAli AGE OF CENTEAL AJST) WEST COENWAXL. 



probably laid down continuously in our district, in other districts 

 can be subdivided into 



SMddaw Slates, 



Arenig and Stiper Stones, 



Lower Llandeilo, 



Llandeilo Flags, 



Caradoc Sandstone, 

 &c., &c., 



in fact representing the whole of the time — or a large portion — 

 from the top of the Lingula Flags to the bottom of the Llandovery 

 series.*' Once admit this, and the whole difficulty as to the 

 great thickness of the Cornish Lower Silurian series vanishes. 



Greological analogies should not be carried too far, but we 

 cannot help noticing those existing between the quartzj^te cairns 

 of the two Nare Heads, of Grorran, Gerrans and Caerhayes, with 

 those of the Stiper Stones. The resemblance is probably more 

 than a merely superficial one. The great silicification of certain 

 beds in the line of strike, and the association with intrusive 

 rocks as observed in several of the Cornish localities, may very 

 probably, we think, be connected with the intense volcanic 

 action which characterized the latter part of the Lower Silurian 

 period in the typical districts of Shropshire and Wales. The 

 rocks of the two districts have similar, if not always identical 

 fossils, their mineral composition and condition is the same, 

 and they have almost exactly the same line of strike. The 

 Cornish rocks dip to the E.S.E., the Stiper Stones nearly 

 W.N.W., the lines if produced being not much farther apart 

 than is the line of the Stiper Stones from that of the Lower 

 Silurian saddle of Merionethshire. 



Many interesting problems in relation to the rocks vinder- 

 lying the Cornish quartzytes remain to be solved. Prof. Sedgwick 

 visited the Lower Silurian rocks of Gerrans Bay, after Mr. Peach 

 had found fossils there, and satisfied himself that they were 

 really of Lower Silurian age, and that they appeared to rest 

 upon the rocks called Devonian further to the N. and N.W. 

 To explain this apparent anomaly, he suggested an inversion of 

 the strata — a not uncommon resource among geologists at the 



*Supposing — with many good autliorities — the Skiddaw Slates to be newer 

 than the upper Lingula Flags and older than the Lower Llandeilo. 



