Prof. T. Rupert Jones—Notes on a Well at Wokingham. 421 
along its boundaries ; and I regard the chert pebbles above described 
as relics of such rocks, they having been separated out from the 
mother-limestone by the delicate sifting power of running water. 
The shaly rocks of the Harwich deep boring probably belong like- 
wise to the Carboniferous period, and those of Meux’s Brewery are 
true Devonian. The recent deep boring at Turnford also discovered 
Devonian rocks, and that at Ware Silurian (Wenlock Limestone), 
and the relations of these beds are such that, as Mr. Etheridge 
writes, “Should the dip of these Hertfordshire Silurians prove to 
lie to the south, we may anticipate the more ancient series further 
north towards Cambridge.”! The dip of the Hertfordshire Silurians 
is proved to lie to the south, and thus we find the details of the 
ancient barrier, so far as yet known, strongly supporting our 
independent conclusions that the more ancient Paleozoic pebbles 
were derived from this source. And at this period the old dividing 
ridge must have been suffering active marine denudation from waves, 
and the wash of strong currents between the two N. and S. seas; 
the advancing waters steadily widening the gaps in the old barrier 
as it gradually disappeared beneath the sea surface. The conditions 
were therefore peculiarly favourable to the formation of pebble beds, 
and then it'was that our Upware and Potton pebbles were formed, 
the Jurassic ones mainly from the western shores in Cambridgeshire 
and Bedfordshire, and the Carboniferous and older Paleozoic from 
the destruction of the ancient barrier.” The Rhyolite pebbles may 
have been obtained, like many of the quartzites, indirectly through 
the New Red Sandstone. 
Lastly, inquiring what we can learn from these fragments as 
relics of beds since destroyed by denudation, we find the Jurassic 
chert pointing to the former existence of Jurassic limestone near to 
this area, and the abundance of Mountain Limestone chert proves 
a great denudation of the Carboniferous formation. But little 
evidence appears bearing upon the question whether Coal-bearing 
beds now form part of the Paleozoic ridge; but the more ancient 
pebbles testify to the existence of the older Silurian and Cambrian 
rocks beneath the Cretaceous series near Cambridge, as independ- 
ently predicted by Mr. Etheridge. 
The almost exclusive presence of chert in the Portlandian pebble 
beds of Berkshire suggests that only the Carboniferous rocks were 
exposed to denudation in Upper Jurassic times, the Mountain Lime- 
stone wrapper being not yet eaten through so as to expose the more 
ancient core-rocks of the axis. 
VI.—Nore on tHe WELL LATELY sUNK AT WoxRINGHAM, Burks. 
By Prof. T. Rurerr Jonzs, F.R.S., F.G.S. 
TTAVING been favoured by Mr. T. M. Quill, who has of late 
successfully completed an artesian well at Wokingham, with 
opportunities of examining the specimens brought up from the well, 
and with his own notes on the progress and results of the boring, 
1 Popular Science Review, 1879, vol. iii. p. 293. 
2 Mr. J. J. Harris Teall suggested, in 1875, that the Lydian stone came from 
Paleozoic rocks to the east.—Sedgwick Prize Essay, 1875, p. 38. 
