138 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25, 



alluded to, the Coniston grits had no physical representative among 

 the typical upper Silurian groups. I ascertained, moreover, in the 

 year 1845, that the Coniston limestone, at its south-western extre- 

 mity, was actually so interlaced with the green slates and porphyries 

 of the great central system of the Cumbrian mountains, that it could 

 not, at least on physical evidence, be separated from them. Hence I 

 gradually came back nearly to my first interpretation of the phseno- 

 mena. 



The Coniston limestone I again considered as a true Cambrian 

 rock, and the equivalent of the Bala limestone ; and its fossils have 

 within the last three or four years been arranged by Professor M*Coy 

 in conformity with this view. But the Cardiola-flags still presented 

 a great difficulty, as I had never seen the Cardiolce but among 

 rocks supposed to be upper Silurian : and, if possible, to clear away 

 this difficulty was one of my objects in my visit, during the past sum- 

 mer, to the flagstones near Horton in Ribblesdale. 



On writing to Professor M'Coy on the propriety of classifying the 

 Coniston flags with the upper Bala group, and the Coniston grits with 

 the Caradoc sandstone, I had a reply in which he used the following 

 words : — " I by no means think that we have yet fossil evidence 

 enough for determining zoologically the age of the flags and grits in 

 question ; nor the age of similar beds in a few other localities which 

 in our MS. lists stand as doubtful ; and I am glad you are collect- 

 ing more evidence. Meanwhile your field-impressions, I have little 

 doubt, will prove correct." At the same time I may remark, that 

 neither he nor 1 had a shadow of doubt that the Coniston limestone was 

 the equivalent of the Bala ; and this conclusion necessarily influenced 

 our opinion respecting the age of the Coniston flags and Coniston 

 grits. If the Coniston limestone and flagstone could be brought to 

 the parallel of the upper Bala groups, it followed almost of necessity 

 that the Coniston grits, geologically and physically, must be the exact 

 equivalents of the Caradoc sandstone ; and thus would a great physi- 

 cal difficulty be removed ; and the Westmoreland series would agree, 

 stage by stage, with the successive groups in North Wales, and with 

 the successive stages of the Silurian rocks, as they had been made 

 out by the author of the * Silurian System.' 



Knowing the importance of these determinations, I engaged, during 

 last autumn, my friend John Ruthven to re-examine, at his leisure, 

 all the fossil-bearing quarries in the Coniston grits and flags ; and I 

 hope, before long, to receive from him such a series of fossils as 

 will settle the zoological evidence bearing on the exact age of the two 

 last-mentioned groups, and put an end to any remnant of doubt as 

 to that essential point. 



About five weeks after my return to Cambridge I received (Nov. 

 6, 1851), unexpectedly and to my great pleasure, a note from Mr. 

 Salter (on whose authority the lists of Westmoreland fossils given in 

 my previous papers, in 1845-1846, had been made out*), containing 

 the following critical remarks : — *' In your most complete list of 



* See also * Letters on the Geology of the Lake District.' Hudson, Kendai, 

 1842. 



