20§ Salter — Oji tJie May Hill Sandstone. 



mynd itself. And in Prof. Eamsay's short account of the Geology 

 of North Wales (vol. iv. Geol. Journ.) — to which, hy-the-by, he 

 makes but little allusion in the volume lately published — the rela- 

 tions of this Upper Caradoc were discussed by himself and Mr. 

 Aveline ; its unconformity recognized ; and its relative age (by the 

 fossils) given by Prof. Forbes and myself. But, by an accident, one 

 or two tyj)ical Lower Caradoc fossils were again wrongly quoted 

 from it, as had previously been done by Prof. Phillips. 



It was, moreover, known that these " Pentamerus beds, or Penta- 

 merus and Hollies Limestone " of the Silurian system (1839), were 

 equivalent in age to the " Clinton group " of America, which Prof. 

 Hall, in his Geology of New York (1843), had distinctly stated 

 appeared to lie on the eroded sui'faces of the underlying rocks, and 

 yet to contain a few, and only a few {Bellerophon bilobatus being the 

 chief) of their fossils. 



We ought not, therefore, to have been surprised to learn (when in 

 1853 Prof. Sedgwick and Prof. M'Coy read a paper before the Geo- 

 logical Society on the distinctness of the two rocks, " May Hill " and 

 " Caradoc "), that there must be a total difference in their age — only 

 to be expressed by the use of separate terms — the one being of the 

 age of the Bala rocks (Upper Cambrian of Sedgwick) ; the other a 

 Wenlock grit or sandstone. These are the Professors' own words. 



But this view of their total distinctness was not reconcileable with 

 the fact, that the author of the " Silurian System" had obtained a 

 mixed series from the typical locality where both were seen, viz., the 

 Hollies Limestone, near Acton Scott. It was resolved by the then 

 Director of the Survey, Sir H. de la Beche, that a survey should be 

 again made along the Wenlock valley (Apedale), and the veteran 

 geologist, Mr. Talbot Aveline, and myself, then assistant to Prof. Ed- 

 ward Forbes, were appointed to this duty. I wrote to Prof. Sedgwick, 

 telling him our object ; and his reply was, we should find them dis- 

 tinct and unconformable ; he had the previous year tried to ascertain 

 it. It was a cold spring in April, 1853, and not very pleasant 

 weather for tracing muddy brook sections in clay land ; but we had 

 thick boots and light hearts, and the primroses and early violets 

 were in full bloom. We found the unconformity first in the most 

 difficult of all the sections, viz., the Onny river at Cheney Longville. 

 And the slight discordancy (only a few degrees of angle) was only 

 discoverable by wading knee-deep along the shelves, and one at a 

 time hammering, while the other observed the line of contact from 

 the opposite bank. Prof. Eamsay joined us here, and confirmed 

 the unconformity by the same amphibious process. We need hardly 

 have given ourselves so much trouble ; for by proceeding north- 

 ward we found the Pentamerus beds and purple (Tarannon) shale, 

 thickening and thinning out, and forming "Jacob-stones." Every 

 cottage doorsill and well step was Pentamerus limestone, when we 

 hit upon the right line, which was no little trouble to do. 



Moreover, Mr. Aveline, being an old stager, had bethought him 

 that we must first gain a true section of the under rocks. This he did 

 readily by going from Horderly turnpike to Cheney Longville and 



