360 Prof. Sedgwick on the May Hill Sandstone, 



one palseozoic system. For example, Favosites alveolaris, and 

 F. Gothlandica, Stenopora fibrosa, Spirigerina reticularis, and 

 Lepagonia depressa are all found in the Bala group ; yet three 

 of them rise into the Devonian series, and the remaining two 

 rise into the Carboniferous. And this list of common species 

 might, I doubt not, be considerably increased. There is, then, 

 no incongruity, and certainly no risk of error, in applying the 

 term system to all the palseozoic rocks ; while there is some in- 

 congruity, and (as wc know from experience) a great risk of 

 error, in applying the definite term system to great groups of 

 rocks, such as the Carboniferous, Devonian, and Silurian. The 

 use of the word series, in describing the subdivisions of the 

 palaeozoic system, is by no means an innovation ; but is, on the 

 contrary, a return to the language formerly in very common use 

 among the members of the Geological Society ; as any one may 

 see on turning over the pages of their early volumes. 



Among the most exact continental writers, the word ter- 

 rain is used for collective, and sometimes imperfectly-defined, 

 groups of rocks ; while the word systeme is applied to the sub- 

 ordinate and well-defined groups, whether natural or artificial. 

 This sense of the word system is consistent and philosophical, 

 and can seldom lead to mistakes of interpretation. But in Eng- 

 land the word system has frequently been used in a loose and 

 ill-defined sense ; sometimes being applied to certain well-defined 

 groups, on evidence partly physical and partly palseontological ; 

 sometimes to utterly undefined groups, on evidence purely palse- 

 ontological. And hence has been introduced an incongruous 

 nomenclature, which is sometimes geographical, sometimes palse- 

 ontological, and sometimes neither geographical nor palseonto- 

 logical. By adopting a definite nomenclature before we are 

 well acquainted with the physical and palseontological phsenomena 

 on which it must ultimately rest, we inevitably retard the pro- 

 gress of geology, and damage its scientific language. For no 

 one who has prematurely adopted a definite nomenclature is 

 ever very willing to change it ; and it is notorious, that men are 

 far more ready to distort new facts so as to fit them to an 

 accepted nomenclature, than to modify and improve their 

 nomenclature so that it may meet the demands of advancing 

 knowledge. 



The rocks of England are now so well known, that a pretty 

 good classification of them (from the oldest Cambrian to the 

 newest Tertiary) might be grounded on physical evidence only. 

 In like manner (so soon as the long succession of physical 

 groups is known) a good classification of the whole English 

 series might be made on purely palseontological evidence. The 

 one would represent a vast succession of physical conditions, the 



