SYNOPSIS OF THE BRITISH STRATA. 35 
Obs.—No fossils have been detected in these rocks: but the intense 
igneous action which the masses appear to have undergone, may have 
obliterated all evidence of animal and vegetable structures, should 
any have been present, as well as the lines of stratification. By the 
aid of the microscope, we may yet perhaps solve the mystery which 
shrouds the origin of these rocks, and the student may take up the 
investigation with the certainty of obtaining much valuable informa- 
tion, even should the search for organic structures prove abortive. 
It is not, however, improbable that the siliceous frustules of diato- 
maceze may have escaped destruction, and remain to reward the 
researches of some skilful and patient observer. 
Volcante Works. (Wond. p. 815.) 
The products of subterranean fire or heat, erupted from 
profound depths through fissures in the Earth’s crust, whe- 
ther in ancient or modern times. 
Subdivisions—1. Trap, Basalt, Toadstone, Volcan-tuf ; 
the erupted materials of ancient extinct volcanoes. 
2. Lavas, Scorie, Pumice, Ashes; ejected by modern 
volcanoes. 
Obs.—These igneous products are of all ages, and they traverse 
alike the hypogene rocks and the older and newer sedimentary de- 
posits. Their characters, and the effects they have produced, are 
considered in the work to which reference is made. 
By a reference to the geological map of England ( Wond. 
pl. i. vol. i.), it will be seen, that the several formations 
appear on the surface in a somewhat chronological order, as 
we pass from the eastern or south-eastern part of the Island 
to the west or north-west. Thus the principal Tertiary 
deposits are situated in the eastern and south-eastern parts ; 
and proceeding towards the north-west, we traverse suc- 
cessively the Secondary—the Chalk, Oolite, Lias and Trias ; 
then the Palawozoic—Permian, Carboniferous, and Devonian ; 
next the Silurian and Cambrian ; and at length metamorphic 
and primary rocks appear. It is this distribution of the 
