27 
Fic. 4.—Section showing the approximate relative thickness of the British 
Sedimentary Rocks. 
Tertiary or Cainozoic . 
Secondary or Mesozoic jeer 
Triassic. 
Permian. 
Carboniferous. 
Devonian. 
Silurian. 
Primary or Paleozoic . 
“Cambrian 
