Prof. T. G. Bonney— Welsh Pre-Cambrian Rocks. 303 
Carnarvon road. Nothing, however, that I have seen, after a 
careful re-examination (in company with Mr. Houghton) of the 
whole district, causes me to doubt the general correctness of my 
original reading. Jt seems to me not only simpler than that of 
Prof. Hughes, but also in accordance with the microscopic structure 
of the rocks ; while his requires the identification of rocks which have 
only superficial resemblances and real differences. 
I turn, in conclusion, to Prof. Hughes’s recent paper on Anglesey, 
read before the Geological Society on the 25th of February.’ Here, 
after establishing by fossil evidence a very important point, viz. the 
existence of Tremadocand Arenig beds in that island, he proceeded to 
identify what he terms the “ gnarled schists” with the Bala series of 
the mainland—supporting this view by the assertion that the 
appearance of metamorphism, which had hitherto led every one to 
bestow the name of schists on these beds, was only superficial and 
illusory; for in reality they were but slightly altered. To this 
series he referred the beds on the northern shore of the Menai Straits, 
in the neighbourhood of Valley and Holyhead, and in other places 
which I have not visited. Now, I do not pretend to have examined 
every rock in these two districts; but I have seen a good deal of 
them, and have investigated microscopically specimens which appear 
similar to those exhibited at the Society’s meeting by Prof. Hughes. 
For example, as types of the beds in the former district, I have had 
slices cut from two schists, one from very near the Menai Bridge, 
another from a quarry just outside that village, on the Beaumaris 
road; and from two rather chloritic-looking massive rocks, one 
beyond Glyn Garth on the same road, another by the shore, about 
300. yards from the gas works, west of the bridge. Without 
discussing the details of their mineral composition, it is enough for 
my present purpose to say that all four are metamorphic rocks in the 
fullest sense of the word, no certain trace being now left of their 
original constituents. Again, I have examined the dull lead-coloured 
or greenish schists from the shore south of Valley station (near the 
serpentine), and on the neighbouring island reached by Four Mile 
Bridge ; these also, like the others, are true foliated rocks. Again, 
I have examined a contorted hornblendic schist from near Holland 
Arms, and a contorted lead-coloured schist collected near to the 
road going from Holyhead to the Stack Rocks—-these are very highly 
altered. In short, if all these are not as much metamorphic rocks as 
any mica-schist from Scotland or Switzerland, then I have yet to 
learn what constitutes that class of rock.2 With the evidence of the 
microscope in this direction, and evidence in the field at best (as 
Prof. Hughes seems to admit) far from strong, we are, I think, 
justified in refusing to recognize Bala Beds, whether altered or 
unaltered, in the Anglesey schists. 
1 Published while this paper is passing through the press in vol. xxxvi. of the 
Quarterly Journal (p. 237). The author, however, has almost suppressed the portion 
of the paper in which this theory was enunciated (see p. 183 of this Magazine), 
2 Knowing that Mr. 8. Allport had also examined some of these rocks, I wrote to 
ask his opinion. He indorses my view, especially as to the Holyhead schists, which 
he has recently studied, in the strongest terms. 
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