BLAKE ! EAST YORKSHIRE. 
17 
certainly established, by an account of the peculiarities which 
attach to the several formations in this district. 
The great separating formation which lies between East 
and "West Yorkshire, and spreads out in the wide intervening 
plain, is the Trias. The hypothesis of Prof. Ramsay — founded 
partly on the colour, and partly on the absence of marine 
remains — that this is a deposit in a great inland salt lake, is 
well known ; and the general characters of the Trias are not 
different in Yorkshire from those elsewhere. If we accept 
this hypothesis, we must conclude that the boundary of this 
inland sea was some little distance north of the Tees, and that 
the effects of the elevation of the carboniferous rocks were 
not yet manifested in the separation of the East Yorkshire 
area ; for the Keuper marls have a uniform development 
throughout. 
The uppermost portion of the series differs in a remarkable 
manner from its development to the south. The great masses 
of black shales and limestones which form the massive of the 
Bhcetic Alps, and have there a thickness of more than 1,000 
feet, have dwindled to 100 ft. before they reach our shores ; 
and the further north we go the more feeble they become, till, 
from the neighbourhood of Gainsborough to the Humber, 
and throughout Yorkshire, they are almost unrecognisable ; 
and the particular stratum which usually renders them so re- 
markable — that thin zone of phosphatic nodules, associated with 
innumerable bones, the reliques of some sudden catastrophe, 
known as the bone bed — is not to be traced. All this may 
have been caused by the gradual elevation of the base 
on which the Trias rested, and we may thus approximate to 
the date at which the Yorkshire area was separated from the 
southern. 
That the two areas were ever absolutely cut off from each 
other, so that no community of fauna could exist, is of course 
negatived by the identity of successive zones of life through 
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