80 
stone, the method of classification previously employed with so much 
success for the QOolites. It is truly remarkable, that Nature has 
placed in this our corner of the world, series, probably the most 
complete which exist, of both these groups of strata; and as the 
Oolites of England have long been the type of that portion of Euro- 
pean geology, the Silurians of Wales may perhaps soon be recog- 
nized as the standard members of a still more extensive range of 
deposits. As if Nature wished to imitate our geological maps, she 
has placed in the corner of Europe our island, containing an Index 
Series of European formations i full detail. 
The Carboniferous, Old Red, Silurian and Cambrian systems have, 
by many writers, up to the present time, been all comprehended in 
the term “transition rocks”, so far as that term has been used with 
any definite application at all. The analysis of this vague group 
into these distinct portions removes the confusion and perplexity 
which have hitherto prevailed in this province of geology. Prof. 
Sedgwick has further proposed to apply the term Paleozoic, and 
Mr. Murchison that of Protozoic, to the rocks which constitute the 
Cambrian and Silurian systems. 
How far these appellations are useful, we shall see when we have 
had speculations presented to us in which they are familiarly used ; 
for necessity is the best apology, and convenience the best rule, of 
innovations in scientific language. In the names applied to the 
members of the Silurian system, Mr. Murchison, following those 
examples of geological nomenclature which have been most clearly 
understood and most generally adopted, has borrowed his terms from 
localities in which standard types of each stratum occur. If the 
Silurian system be as exclusively diffused as some indications seem 
to imply, we may find the Ludlow Rocks in Seandinavia, and 
the Caradoc Sandstone even in Patagonia. Whether a like identi- 
fication of the more ancient rocks of the Cambrian series with the 
lowest formations of other countries be possible, may perhaps be 
(for the present) more doubtful. 
I have spoken of Mr. Murchison’s work as if it had formed part 
of our Proceedings, ‘as indeed almost every part of it has done, al- 
though it now appears in a separate form. And I will add, that it 
is impossible not to look with pleasure upon the form in which the 
work appears, enriched as it is in the most liberal manner, with 
