46 
SYNOPSIS OF FORMATIONS. 
yet they have greatly narrowed their num¬ 
ber. A few y^ars ago the slate system of 
Cornwall^ in which the mineral veins occur, 
was announced to be primitive and devoid 
of organic forms. Subsequent observation 
has traced the structure of corals and shells 
up to the very walls of the metallic lodes, 
and shewn that the whole series was depo¬ 
sited coeval with the existence of marine 
animals. In like manner elsewhere, the 
result of minute observation has been to 
enlarge the boundaries of the world of an¬ 
cient life, and to diminish the lifeless terri¬ 
tory of pure physical force. 
The fossiliferous rocks and beds constitute 
a list formidable in the detail of its numbers, 
but not difficult to divide into a few leading 
groupes. 
If for instance we use a local illustration, 
and take the granite of the south western 
promontory of England as a base, we find 
inclining against it a series of coarse slates, 
including thin beds of limestone and re¬ 
mains of marine shells. The lower portion 
of this series is distinguished by one set of 
fossils, and named the Silurian system ; the 
