INTRODUCTION. xlix 
In a paper, above mentioned, read before the Geological Society (May, 1838) I exhibited 
many of my best Cambrian sections, described them in detail, and followed them into the con- 
clusions to which they led. The paper was not printed; because the upper groups of the 
sections could not be reconciled to the lower groups of the “Silurian System *.” A part of 
one paragraph of the abstract published in the Proceedings (Vol. 1. p. 679) is as follows: 
“Many of the fossils of the Upper Cambrian System (i.e. the Upper Bala rocks of the 
above Tabular View) are identical in species with those of the lower division of the Silurian 
System; nor have the true distinctive characters of the groups been well ascertained.” 
Again, in the next paragraph, are these words :—*“ At the north end of the Berwyn chain the 
Upper Cambrian System appears to pass by insensible gradations into the lower division of the 
upper System (the Caradoc sandstone).” The section here alluded to provoked some discussion. 
Professor Phillips believed it true, and that it gave the full sequence of the Cambrian 
series. But if it were true, and a complete section, it was (for reasons above stated) in 
direct antagonism with the sections of the Lower Silurian groups (Caradoc and Llandeilo). 
Nor was this the only difficulty. The beds of sandstone and conglomerate, at the base of 
the Denbigh flag, were at that time considered by me as Caradoc; yet were they represented 
in the sections as unconformable to all the beds of the Bala group. Had my paper of 1838 
been published, it would have anticipated by four years what was proved (certainly on fuller 
and clearer evidence) by Mr Salter and myself, in 1842 and 1843. 
When it appeared (after 1842) not that my Cambrian sections were wrong in principle, 
but that the Caradoc and Llandeilo groups had been erroneously packed in the “Silurian 
System,” and were by a positive blunder in the published Silurian sections, at the very 
least, five or six thousand feet out of their true place in the general section of North 
Wales; I was perfectly ready to admit them into the Upper Bala group; and, by way of an 
equitable, and (as I thought) generous, compromise, to withdraw the name Upper Cambrian, 
and to define the group by the name Cambro-Silurian. My friend, however, with what I think 
very bad judgment and very bad taste, and without a syllable of communication to myself, 
had previously brushed out the whole of his Silurian base line, and incorporated all 
Cambria in Siluria! 
Strange as I thought this step, when I first became acquainted with it, a year or two 
after it had been taken, it was far distanced by the President of the Geological Society ; 
who undertook to abridge, for the Proceedings of the Geological Society, and also for the 
first Volume of its Journal, the two long papers which recorded the best part of the 
work done by Mr Salter and myself in North Wales, during the Summers 1842, 1843}. I 
was very grateful to Mr Warburton for undertaking this task, while I was engaged in 
duties which kept me away from Cambridge and London; but while the abridgment was 
? sections were 
* The reconciliation was impossible (as the event proved), simply because the “ Lower Silurian’ 
misinterpreted by the author of the “ Silurian System.” 
+ See the Proceedings of the Geological Society, Vol. iv. p. 251; and Quarterly Journal of the Geological Society, 
Volt ps6: 
g 
