UPPER CHALK. 
77 
Buckliind, which, if not satisfactory, is at least 
more worthy attention than any other hypothesis 
that has been suggested. 
“ It does not,” he remarks, “ appear possible 
that the flints could have been formed by infiltration 
into pre-existing cavities, according to the theory 
of Werner, like the regularly disseminated geodes 
of the trap rocks ; since this hypothesis, in the case 
of chalk, would im})ly the anomaly of there having 
once existed uniformly over many hundred square 
miles, as many strata of air bubbles as there are 
of flint, alternating with tlie chalk ; and of which 
air-holes not one was left empty, or partially filled ; 
whilst, on the otlier hand, many of the nodules 
could not have been formed in sucli air-holes, as 
they entirely derive their shape from some extra- 
neous bodies affording a nucleus to the silex that 
has incrusted them.* Assuming that the mass 
wliich is now separated into beds of chalk and 
flint, was, previously to its consolidation, a com- 
pound pnlpy fluid, and that the organic bodies 
now enveloped in the strata were lodged in the 
matter of the rock, before the separation of its 
calcareous from its siliceous ingredients, the bodies 
thus dispersed throughout the mass would afford 
nuclei, to which the flint, in separating from the 
chalk, would, upon the principle of chemical affinity, 
have a tendency to attach itself. The chalk and 
flint proceeded through a contemporaneous process 
of consolidation ; the separation of the siliceous 
from the calcareous ingredients liaving been modi- 
fied by attractions, which drew to certain centres 
♦ Geological Transactions, vol. iv. p. 422. 
