PREFACE. barbs 
friend had a Government Map of the Country we first glanced at, well marked and coloured, 
with references to his previous labours. I had been disappointed in my hope of procuring 
the map of the Geographical Survey as I passed through London, and I had no map what- 
ever with me of that part of the country; but I gradually learnt, on the spot, to understand 
what were the characters of such groups of Strata as were afterwards known to all British 
Geologists by the names Caradoc and Llandeilo rocks. 
As we advanced northwards and passed the limits of the published Ordnance map, | 
could then turn to good account my old field map; and when I found myself among the 
rocks I had hastily examined in the year 1832, I readily accepted my friend’s interpretation 
of the calcareous beds of Meifod, of the calcareous bands among the undulating rocks be- 
tween Meifod and Llanfyllin, and the still more astonishing groups which are displayed be- 
tween the Tannat and the Ceiriog. In these districts all the calcareous bands were counted 
as Caradoc. But my scepticism was alarmed before we reached the Ceiriog; because the 
calcareous bands, which descend from the northern end of the Berwyn chain into the valley 
of the Ceiriog—ranging about E.S.E., and nearly at right angles to the strike of the northern 
Berwyns—appeared to me, on almost certain evidence, to be only branches given off from 
Bala limestone. Here was a great difficulty. For if the Glyn Ceiriog limestone could not be 
separated from the calcareous bands we had left behind us, and if they were Caradoc, 
this limestone must be also Caradoc: and the natural conclusion drawn from my Sections was, 
that the Caradoc sandstone was exactly on the same parallel with the Bala limestone. But 
how could this be reconciled with the Silurian Sections of Murchison? For on his scheme, 
both the Caradoe and the Llandeilo groups were several thousand feet above the Bala 
limestone and its associated calcareous slates. To settle this difficulty we retraced our steps 
to Liangynog; and from thence we crossed the Berwyn Chain, marking its structure and the 
synclinal position of the Bala limestone by the way: and so we descended to some highly 
fossiliferous quarries in the limestone, which I had examined two years before. 
There we parted, never to meet again in North Wales. I gave my friend all the chief 
localities of the Bala limestone, in its long range towards the South-Eastern flank of the 
Jader Idris group. 
He did follow the line of the Bala limestone; but he gave me no information respecting 
his labours or his discoveries; nor did he tell me then, nor did I ever know, before the 
publication of the “Silurian System,” that every species of the Bala Limestone fossils, which 
we collected together, and all of which he carried away for examination, were well-known 
Caradoc species. 
We met, however, again after the end of the same summer, at Edinburgh, during the 
meeting of the British Association, and I naturally enquired what had been the success of my 
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