BOOK III 
THE CAMBEIAH VOLCANOES 
CHAPTER IX 
CHAEACTERISTICS OF THE CAMBRIAN SYSTEM IN BRITAIN 
Tile Physical Geography of tlie Cambrian Period — The Pioneers of Palaiozoic Geology in 
Britain — Work of the Geological Survey in Wales — Subdivisions of the Cambrian 
System in Britain. 
leaving the investigation of the pre-Cambriaii rocks and entering upon 
that of the Palaeozoic systems, that is, the great series of sedimentary for- 
mations which include the earliest records of organized life upon the surface of 
the globe, the geologist feels much as the historian when, quitting the domain 
of legend and tradition, he can tread firmly in the region of documentary 
evidence. Prom the bottom of the Cambrian system upward through the 
long series of geological formations, the chronicle, though often sadly in- 
complete, is usually clear and legible. As we follow' the lowest fossili- 
ferous strata across a territory, we recognize that they bear witness to the 
same processes of denudation and deposition wliich have been going on 
uninterruptedly on the face of the globe ever since. The beds of conglo- 
merate represent the gravels and shingles of old coast-lines and river-beds. 
The sandstones recall the familiar features of sandy sea-bottoms not far 
from land. The shales bear witness to the fall of fine sediment in stiller 
water, such as now takes place in the deeper parts of seas and lakes. Not- 
withstanding their vast antiquity, the strata themselves exhibit no exceptional 
peculiarities of origin. They seem to be just such familiar deposits as are 
gathering under fitting conditions at the present time. 
Some writers have speculated on the far greater intensity of all geo- 
logical activities in the early times of the planet’s history. But if we may 
interpret the record of the stratified formations by the phenomena of to- 
day, there is for these speculations no confirmation in tlie sedimentation of 
the oldest stratified deposits. It is of course quite intelligible, if not prob- 
