286 Correspondence—Prof. Edward Hull. 
Having been answerable for the theory which attributes the origin 
of these pebbles (I mean the quartzite pebbles chiefly) to the Old Red 
Sandstone of Scotland—to which they bear a remarkable resemblance 
—I wish now to state that I have abandoned the view of their 
North British origin altogether in favour of that proposed by Mr. 
J. W. Harrison, who considers them to have been derived from the 
concealed ridge of older Palzozoic rocks, which we now believe to 
underlie the Mesozoic strata of the Centre and Hast of England. 
At the time I suggested the Scottish source, I was freshly and vividly 
impressed with the resemblance of the reddish or “liver-coloured”’ 
quartzite plebbles to those of the Old Red Conglomerate of the Lesma- 
hago and other districts. But Iallalong felt the difficulty (on which 
Mr. Harrison lays just stress) that the number and size of the 
Bunter pebbles decreases from the Central District of England towards 
the North-west, which ought not to be the case if they had had the 
origin I attributed to them. Further reflection leads me to think 
that the objection is fatal to the view either of myself or of Professor 
Bonney, notwithstanding the microscopic resemblance which he 
points out to the quartzites of the Highland rocks. Indeed, it is 
difficult to picture to one’s self how the pebbles could have “ got 
round” the promontory and barrier formed by the Silurian rocks 
of the S. of Scotland without having been very thickly strewn over 
the submerged tract of the N.E. of Ireland and of N. Lancashire ; 
but such pebbles are almost entirely absent from the Bunter Sand- 
stone of Antrim and Downshire.' 
A reference to Plate IX. of my Paleeo-physiographical maps will 
assist in making this tolerably clear. The ridge of old rocks which 
occupies the Eastern Counties and ranges as far North as a line drawn 
from the Wash to the mouth of the Avon, shown on the map, very 
probably contains beds of quartzite, porphyry, and hornstone, etc., 
such as are found in the Bunter of Staffordshire; and the supposition 
of such a source seems to be attended with less difficulty than that 
of any other yet proposed. 
5, RacLAN Roap, Dustin, Epwarp Huvtut. 
5th May, 1883. 
ON THE SO-CALLED PLANT-FOSSILS FROM CENTRAL WALES. 
Sir,—In his recent communication on this matter (GEOLOGICAL 
Macazine, April, 1883, p. 192) Mr. W. Keeping expresses the opinion 
that Nematolites Edwardsii “is a Coralline Alga.” That object has 
formerly been described as “solid bodies of pale-chocolate colour 
and earthy constituency.” Now, it seems difficult to understand 
why a Coralline Alga should be more easily converted into earthy 
matter of pale-chocolate colour than branched burrows and tunnels 
of annelids should be filled up by such a sediment, and I consequently 
fail to see any evidence whatever why the opinion which has been 
expressed in my former communication should be altered. As to 
Nematolites dendroideum, I have not hitherto said anything on it, and 
1 It may be objected, truly, that the stage of the “ Pebble Beds”’ is but sparingly 
represented in N.E. Ireland. 
