Taylor — Drift of Lancashire and Norfolk. 283 



All seem to have come from a less distance than those of Lancashire. 

 Mr. Hull gives the percentage (as determined by Professor Eamsay) 

 of rock fragments found in the Upper Boulder-clay at Gorton, in 

 Lancashire, as follows {vide Oeol. of Country around Oldham : Memoirs 

 of Geological Survey/) : 



Silurian Grits 

 Felspar Porphyry 



Felstone 



Carboniferous Grits 



per cent. 



37 

 31 



2 

 14 



pel' cent. 



Granite 6 



Porphyritic Conglomerate 4 



Carboniferous Limestone 3 



Ironstone 2 



In this case the Silurian Grits, vs^hich are most abundant in the 

 Upper Boulder-clay of Lancashire, may be taken to represent their 

 having been conveyed from a distance (the Silurians of Cumberland 

 and north of Lancashire) equivalent to the distance of the source of the 

 Oolitic pebbles found in the Upper Boulder-clay of Norfolk (the 

 Oolite of Yorkshire). The greater percentage of igneous boulders 

 found in the Lancashire Drift beds may arise from the fact of their 

 being nearer to their parent rock than those of the corresponding 

 beds in Norfolk. The small percentage of boulders of local rock 

 (sandstone) in Lancashire, as compared with the much greater per- 

 centage of flint boulders in Norfolk, may arise from the different 

 nature of the two parent beds whence both were derived. It would 

 be much easier for marine or glacial agency to disintegrate the Chalk 

 and liberate the enclosed flint nodules, than it would be to break up a 

 sandstone bed and to roll the fragments into boulders. But these 

 exceptions seem to me to carry out the analogy between the northern 

 and eastern deposits instead of detracting from their relation. 



Mr. Binney very justly remarks ^ on the varying nature of the beds 

 which compose the various members of the Drift or Quaternary 

 formation. The same feature is, more or less, common in Norfolk, 

 although it is not so decidedly shown as in Lancashire, owing to the 

 absence of high hills, along whose base, ia the North, the various 

 drift beds usually split up into almost unrecognisable portions. At 

 Sprowston in Norfolk, iu the Upper Boulder-clay, there are thin seams 

 of sand intercalated, in which Mr. T. G. Bayfield and myself found 

 numerous fragments of marine shells, among others of Cyprina 

 Islandica and Astarte borealis. But both in Lancashire and in Norfolk 

 these local deposits do not affect the general features of resemblance 

 so broadly manifested in both districts. 



I remain, etc., 



John E. Taylor. 

 Norwich, May Sth, 1867. 



BALA AND HIENANT LIMESTONES AT MYNTD FRON FRYS IN 



GLYN CEIRIOG. 



To the Editor of the Geological Magazine. 



Deae Sib, — I am glad to find Mr. Salter calling attention in this 



month's Magazine to one of the most interesting spots in North 



Wales — especially so to students of the Lower Silurian group. 



1 See Geol. Mag. Vol. IV., May, 1867, p. 231. 



