Salter— On the May Sill Sandstone. 203 



Slretford Bridge ; then by tracing the Caradoc divisions northward 

 — some five or six very distinct ones — we found that they were suc- 

 cessively each and all overlapped and covered up by the Pentamerus 

 limestone and grit, all the way ujd to the Wrekin, where, indeed, 

 they lie on the very lowest beds, or Shineton shales and slates, which 

 I take leave to call the top of the Llandeilo Flags proper, and believe 

 this to be their true position. 



However, the unconformity was fully proved ; and a pleasant bit 

 of geology it proved when the snow was gone from all but the 

 Longmynd top. I shall not easily forget the hot day we finished at 

 the Wrekin. Professor Eamsay and Mr. Aveline had been up before ; 

 but nothing would do but I should drink at the Eaven's Cup ; and I 

 shall remember that, for it had been artificially filled that day, and 

 not with pure water. 



On going to the Hollies Farm, in a pelting snow shower, I found 

 the source of all the error. The house is built on true Caradoc fiag3, 

 so calcareous and so full of Caradoc or Bala fossils, that they might be 

 burnt for lime ; and a little further down the brook, the Pentamerus 

 limestone crosses, thick enough to tempt them to use it for the kiln. 

 But the walls of the now deserted kiln were built of the Caradoc 

 flags from the house quarry, while the May Hill or Pentamerus 

 limestone had been burnt. The fire had calcined both, and frag- 

 ments of each, found in the kiln, had been most innocently and unsus- 

 pectingly gathered by the Silurian chief, and figured together by 

 accurate James Sowerby ! Who was to blame ? Not Sowerby, for 

 he rightly named the fossils from the " Hollies." Scarcely Murchi- 

 son, for who could dream that two limestones of such different age 

 were calcined in the same kiln by accident ? Not the farmer, who 

 was wise enough to build his kiln of the firmer and less valuable 

 stone. It was a chapter of accidents, such as has often happened 

 before and will again. But there was no longer any doubt as to the 

 supposed admixture, and the experimentum crucis had been made in an 

 old lime kiln. 



Henceforward all was plain sailing. The Upper Caradoc was 

 abolished, for the May Hill Sandstone had acquired its right meaning ; 

 and as fossils were abundant in it, we easily rearranged the drawers 

 of the Museum in accordance with the new facts. But this was not 

 all. Professor Sedgwick and myself had shewn in 1845 (Quart. 

 Geol. Journ.), as the result of our summer's work in North Wales in 

 ]843, that the fossils of the uppermost portion of the Bala (or 

 Caradoc) rocks in Montgomeryshire were full of these same Penta- 

 meri and of other fossils, Petraice, Atrypa reticularis, etc. These in 

 many places were found (and more have been found since) to range 

 along the border of the Upper Silurian rocks. In South Wales Sir 

 Eoderick had described them from near Llandovery, from Haverford- 

 west, from Marloes Bay ; and they were included in what was then, 

 indeed, a heterogeneous assemblage, under the tenn of Llandeilo 

 Flag. I examined the country, from Builth to Carmarthen, in 

 1846, made easy then by the accurate map ; and recognised, of 

 course, the Upper Caradoc, as we then had begun to call it. It was 



