MACKIK — REMNANTS OF THE FIRST LIFE-WOHLD. 137 
table of rock-group3, page 64, and the ideal diagramatic section at 
page 93, will already have done something towards this, but the more 
detailed view and remarks I am now about to add will still more ex- 
plicitly convey a correct idea of our starting point and its relations to 
these early deposits by which it was succeeded. 
OLD RED SANDSTONE. 
UPPER 
SILURIAN. 
LOWER 
SILURIAN, 
BOTTOM ROCKS 
J 
(Cambrian of Murchison, and of the 
Geological Survey, but only a part of 
the Cambrian of Sedgwick), 
reposing on 
GNEISS— FUNDAMENTAL ROCKS— GRANITE. 
Between the fundamental gneiss and granite and the lowermost 
beds of the Silurian formation are mountains of strata, about which, 
except for their mineral, domestic, or commercial value, little is 
generally known. Their accumulated thickness is calculated by 
thousands of feet, and they were formerly styled by geologists Azoic, 
under the belief that they contained no organic remains, and that they 
were formed before the dawn of life upon our globe. Those are the 
" Bottom Rocks," which form the subject of this chapter. 
{To he conlinucd.) 
0 
LUDLOW ROCKS. 
WENLOCK ROCKS, 
(including the Woolhope Limestone 
and Denbigh Grits and Shales.) 
UPPER CARADOC. 
May Hill and Llandovery Beds 
Beds of 
Passage. 
LOWER CARADOC, 
Caor Caradoc and Bala Rocks. 
LLANDEILO ROCKS. 
Cambrian 
of 
Sedgwick. 
