641 
had it been proposed, than another seemed requisite to charac- 
terize the older slaty rocks, on which the newly-named Silurian 
system reposed. For these an eminent continental geologist sug- 
gested, in a letter to myself, the classical word “ Hercynian,” de- 
rived from the Hartz mountains, where the rocks might be pre- 
sumed, from their antique aspect and mineral character, to be of re- 
moter age than the soft argillaceous Silurian types of Britain. 
Alive, however, to the danger of mingling assumptions, drawn from 
lithological structure, with proofs derived from unequivocal suc- 
cession of organic remains, and knowing that in our own country 
there was, in fact, a vast mass of ‘slaty rocks on which the Silurian 
strata reposed, and which my friend Professor Sedgwick had long 
studied, I urged him in describing these rocks which he had made 
his own, to fix on a general British geographical name. He then 
adopted the name of Cambrian. Nothing precise was known’ at 
that time of the organic contents of this lower or Cambrian system, 
except that some of the fossils contained in its upper members at 
certain prominent localities were published, Lower Silurian species. 
Meanwhile, by adopting the word “Cambrian,” my friend and 
myself were certain, that whatever might prove to be its zoological 
distinctions, this great system of slaty rocks, being evidently inferior 
to those zones which had been worked out as Silurian types, no 
ambiguity could hereafter arise. On the other hand, the adoption of 
any term derived from a part of the continent, where we had not 
made ourselves masters of the true sequence, might involve the whole 
subject in confusion. This would in reality have occurred had the 
word “Hercynian” been selected, for subsequent researches have 
taught us, that the greater portion of oldest rocks of the Hartz are 
younger than the Silurian system, and that their antique impress is 
due to metamorphic action*. In regard, however, to a descending 
zoological order, it still remained to be proved, whether there was 
any type of fossils in the mass of the Cambrian rocks different from 
that of the Lower Silurian series. If the appeal to nature should 
be answered in the negative, then it was clear, that the Lower Silu- 
rian type must be considered the true base of what I had named the 
Protozoic rockst+; but if characteristic new forms were discovered, 
then would the Cambrian rocks, whose place was so well established 
in the descending series, have also their own fauna, and the paleozoic 
base would necessarily be removed to a lower geological position. 
In a very comprehensive memoir, recently read, which, when pub- 
lished, will throw a clear light over the ancient rocks of the lake di- 
stricts, as compared with their equivalents in Ireland, Wales, and Scot- 
that he had blotted out the very name of Silures from the face of the earth. 
A British geologist had, therefore, some pride in restoring to currency the 
word Silurian, as connected with great glory in the annals of his country. 
* See Geological Transactions, vol. vi. p. 288. 
+ Shortly afterwards Professor Sedgwick proposed the word “ Palzo- 
zoic”’ as a general name for all the older groups, which, preferring to my 
own, I immediately adopted as involving no theory, 
VOL, III. PART II. 3G 
