204 Salter — On the May Hill Sandstone. 



evident enough, after 1853, that these localities must be revisited ; 

 and the last official act that I remember of Sir H. de la Beche was a 

 kindly "God-speed" to Mr. Aveline and myself. We set out in 1857 

 for a fresh boundary line from Builth to Marloes Bay. But this 

 journey (the results of which Sir Henry did not live to see) gave us 

 a much more difficult task. Instead of soft shale, limestone, and 

 sandstone, we had to draw a boundary between hard cleaved slate, 

 and hard cleaved gritty slate ; and the solemn pipe often assisted 

 our deliberations. We traced the whole boundary together ; found 

 there were two Pentamerus series — one upper, with Wenlock fossils 

 and Pentameri, lying unconformably upon a lower, full of Caradoc 

 fossils and Pentameri — just such a mixture as had been at first 

 supposed in Shropshire, but had turned out untrue. Here it was true 

 enough ; and many a long day was spent in deciding which was the 

 upper and which the lower. For when two slates, one only a little 

 more gritty than the other — tilted together, and bent and broken 

 together, and cleaved in the same direction — have to be distinguished 

 in a cultivated country, all I can say is that, if any one thinks 

 geology is easy work, let him try that sort of thing. 



However, in course of time it came all right. There was a May 

 Hill rock, which began at Builth and swept on, in thick or thin 

 patches, as far as Llandeilo, lost there, and again coming out to sea in 

 the fullest force at Marloes Bay and Wooltack Park. Cleaved and 

 tilted as they were, there could be no doubt of them. Professor 

 Eamsay joined us at Marloes Bay, and accompanied us back to 

 Haverfordwest. 



And under these Lower Pentamerus beds at Haverfordwest, and 

 on the rolling hill tops north of the Towy, and thence to Llando- 

 very, we sought to find the boundary between these Loicer Llando- 

 very rocks (as Sir E. Murchison calls them) and the true Caradoc 

 beneath. To me they seemed conformable ; but Mr. Aveline after- 

 wards by himself did find, in tracing them painfully in detail, and 

 following them northward and westward, that the lower beds were 

 sometimes a little discordant on the Caradoc. I believe no one but 

 himself could have proved it. But it must be true, or there is little 

 faith in fossil evidence, for the change in the fauna is sudden and 

 considerable. 



This account, rather briefly and imperfectly given, is all that I 

 remember of the history of the May Hill and Llandovery rocks ; but 

 it may, perhaps, be enough to show how the observations of many 

 men and many minds must concur, before the hypothesis is reached — 

 which, as our old chief. Sir Henry, used to say, is the " peg to hang the 

 facts upon." Sir E. Murchison had traced the course of the " Penta- 

 merus beds" around the Longmynd and Shelve country without 

 dreaming they were other than part of the true Caradoc. The Survey, 

 misled by the supposed admixture of types, could get no further than 

 an Upper and Lower Caradoc. Hall had noticed, but failed to see the 

 full significance of the unconformity in New York. Pouring rain 

 had beaten Sedgwick and M'Coy in their gallant attempt to take the 

 Wenlock Valley by storm in 1852. And neither Swedish nor Eussian 



