425 
Geology of the Environs of Petersburg. 
road to Anteleva from Gatchina, and on the hills behind Lukozy, 
the quantity of fresh fragments of limestone is such that it must be 
in the neighbourhood. The rising level of the country favours this 
supposition ; but the valley is too much covered with alluvia to 
allow of accurate examination. 
DILUVIUM. 
Having thus described all those formations which occur in this 
district, and which belong to the class of Antediluvian depositions, 
the next which presents itself is that which is properly called 
Diluvian, and which, in contradistinction to the more modern 
accumulations or Alluvium, may be termed Diluvium or Diluvian 
gravel, by which latter name it has been long known, at least in this 
country. 
I need not say what is intended by this term ; it is meant to 
express that superficial deposit which covers every thing, and is 
composed of almost every thing. 
Its composition and thickness are very various : the latter 
amounting to thirty, forty, or even fifty feet. In some instances it 
The protrusion of an inferior bed through a superior one, where entirely owing to an 
elevation in the strata, independent of any denudation, is a circumstance of frequent 
occurrence, and which it is absolutely necessary to distinguish from the appearance of 
subjacent rocks, laid bare by simple denudation, without change of dip in their stratifi- 
cation. 
Denudation. Protrusion, 
3 h 2 
