THIS CLASSIFICATION APPLIED TO GERMANY. 
2 * 
enforced in these words : “ To what extent the same species of shells which cha- 
acteiize the Lower Silurian rocks descend into the Cambrian system has not yet 
satisfactorily determined, nor can it be until the oldest fossiliferous rocks of 
umber land, Wales and Devonshire, are brought into close comparison, and their 
specific contents accurately determined.” (Sil. Syst., p. 308 .) 
Judging from their infraposition, their great thickness and distinct lithological 
c laracters, it was, indeed, presumed, chiefly from the analogies of the overlying 
eposits, that the lowest stage of these slaty rocks might be found to contain a class 
o organic remains peculiar to themselves. Subsequent appeals to nature have, 
pOw^er, decided otherwise. In the slaty tracts of Cumberland and Westmoreland 
ro essor Sedgwick has satisfied himself, that the earliest organic remains which 
e traced, are no others than those published from the Caradoc sandstone or 
uppeimost part of the Lower Silurian; the great subjacent series being filled up 
with igneous, crystalline slaty rocks. Again, having recently revisited North 
Wales, the structure of which he long ago described, and where the series is infi- 
nite y more developed, he has come to the conclusion, that the oldest tracts of that 
country do not contain any group of fossils differing from those of the Lower 
i unan type 1 . I n the mean time, through the valuable labours of Sir Henry 
to ^ UnqUe8ti0nabl 3 r tbe S-dogi-t after Mr. Jonathan Otley, who attempted 
■? r ”*■ ° f c— - *— — • l 
f essor Phillip® Mr T v, 7 S been worked out b T hilnself and other authors, including Pro- 
reader „ ^ “ "Vp" ^ ^ ‘ *” “ «*» »>»= .he 
m!“ r Proceedings of .he Geological Society of London and the Phi- 
■o Mr Wo! S T, <S o ' he G '”'“ SketCl ' ° f «” .he H*. Disttie. in a series of letter, 
«r! c T o T by Pr ° fe " r SedBWidi ’ 1842 >- '» »«*>■ Wele,, Mr. Bowman performed some good 
assumed 7 ? ,mS the 6XaCt CqU1V;lkntS of certain U PPcr Silurian rocks in a tract where they have 
g-j . ' " aty cbaracter ’ ^ r - U. Sharpe instituted certain tabular comparisons between the 
to off?" SI ° UPS ° f North Wales > Shropshire and the north of England. This is not, however, the place 
Ine . XaCt b i sf:or i ca l sketch of these labours, still less to enter upon any discussion of the relative 
there a ”* eau ’ lrs > 4,1 °f which more or less go to show, that despite of variations in mineral character 
()i <lre both Lower and Upper Silurian groups in all these tracts, 
the 'i the P , reSent occasion we would simply state, that as Professor Sedgwick led the way in deciphering 
with r a StlUCtUre of North Wales, so after a full re-examination of both countries he has shown, that 
there eXpfmS1 ° n ° f equivalents of the Ludlow and Wenlock rocks in the lake districts, there are 
that howT^Tfl™— 5 ° f h ' gher aDtiquity thaI * the V6ry Upper part of the Lower Silurian rocks , and 
great inf ^ . enng ln mineral characters and containing a few species hitherto undeseribed, all the 
term Low^ 8 ! aty “ ° f that and ° f N ° rth Wales are the equivalents of those to which the 
of London " ! Unan had beCn aPI>hed (sCe Map and TableS ’ Quartcrl y J °urnal of the Geological Society 
• 'o . i„ and memoir read before that Society, March 1845). 
