262 
HUGHES : ADAM SEDGWICK. 
These facts obviously account for the difficulties which have 
arisen from some observers recording that the base of the Poikilitic 
series graduated into the Carboniferous, while others saw a strong 
discordancy between the two. The confusion has been increased by 
an attempt to force the English classification into harmony with the 
as yet unestablished sequence of Germany, or the still less known 
deposits of Russia. 
" Each country, said Sedgwick, ought to be described without 
any accommodating hypothesis, according to the type after which it 
has been moulded. But in comparing the unconnected deposits of 
remote countries, we must act on an opposite principle ; learning to 
suppress all local phoenomena, and to seize on those only which are 
co-extensive with the objects we attempt to classify." 
Whatever therefore may be convenient in respect to the Dyas 
of Germany, or the Permian of Russia, all the attempts to bracket 
the magnesian limestone, and associated red marks of England 
with the carboniferous instead of making them the beginning of a 
new series, forming the base of the secondary rocks has been founded 
on stratigraphical mistakes and tends to perpetuate an unnatural 
classification. 
Another great paper written about this time was that on "The 
Structure of large Mineral masses," which the council of the Geologi- 
cal Society thought advisable to publish before its turn, because they 
considered it to be introductory to other papers of his they had in 
hand on the origin and structure of the older stratified rocks. 
Obviously it was of the greatest importance to point out the 
nature of concretionary action, and to distinguish indigenous 
segregation from the results of original mechanical accumulation. 
We are coQtinually reminded of the value of accuracy of observation 
on such points even in the discussions of to-day. He goes on to 
examine another series of phoenomena of no less importance which on 
various occasions he had commented upon before. The obliteration 
of the evidence of original stratification by a superinduced structure 
known as cleavage, and the relation of these to joints. When 
deposits which were laid more or less horizontally have been in after 
ages exposed to great lateral pressure (whether due to the heaving up 
