60 



mentioned .1 greater proof still, which is the existence of u-on slabs, cast at 

 the Forge, In the place of tombstones, which are to be fovuid in the neighbouring 

 churchyards. 



A quarry of Downton Sandstone was first inspected. The lower strata 

 afford excellent building stone, but the thick upper one is useless, and immense 

 blocks of it lay scattered about in picturesque confusion. A pretty walk of half 

 a mile bi ought them to the site of the Tin Mill. Nothing remains of it now but 

 certain artificial walls and ground works. The object was not to see them but to 

 examine a very interesting geological formation admirably explained in these 



NOTES ON PASSAGE BEDS, AT TIN MILLS, DOWNTON. 



By KOBEKT LiGHTBODT, Esq., F.G.S. 



The section we see before us here, is a very fair illustration of the Passage 

 Beds between the Silurian, and Old Ked formations ; but, as there are no doubt 

 passage beds between most of the other formations, wherever the deposit was 

 continuous, it becomes needful^^to select some distinctive name to indicate this 

 particular series. Mr. Salter calls them Ledbury Shales, from the section at the 

 mouth of the railway tunnel at Ledbury, where the sequence of them, from 

 the Ludlow rocks to the Old Red, is better exhibited, probably, than elsewhere. 

 I should, however, have preferred to call them Tin Mill Sluiles, as they do not 

 show at Ledbury their usual lithological character of olive shales, but are 

 generally red or yellow. They contain, however, there, similar grey giit beds to 

 those found here, and in other places, but thicker, and the same prevalent 

 fossUs, such as Cephalaspis, Auchenaspis, Pterygotus, Eurypterus, Lingula, 

 and Beyrichia, but I have found here, a peculiar, and very solen shaped Orthonota, 

 wliich I believe is at present unique. Also, I have found a small Modiolopsis 

 here, and between Onibury and Norton, which I have not seen elsewhere. 



I am not aware that we find anywhere, but at Ledbury, the full sequence of 

 these beds, — probably from the softness of the beds immediately succeeding the 

 Downton sandstone admitting of their being easily washed away, and forming 

 hollows, covered by a thick soil, — but in some places owing to the occurrence of 

 faidts. At any rate, we have not yet traced the connection between the Downton 

 sandstone in the quarries we saw on our way from the bridge and these beds. 

 Nor yet is it visible in the road from Onibury to Norton, about half a mUe from 

 Onibury, where there is a tolerable section through these beds. Nor is it seen at 

 the]place of its original discovery at the south-east mouth of the tunnel at the 

 Ludlow Railway Station, where it appears to be cut off by a fault bringing in the 

 Old Eed'marl on 'its horizon. 



Another place in this neighbourhood where these beds are found, though 

 rather differing lithologicaUy, is on the riglit bank of the Teme, between the flour 

 mill at Ludford, and a point opposite iwhat was once a paper miU, and there they 

 are likewise observed at the same point as here. 



