30 
Geology and Physical Geography: 
continued for a long time after its descent in a state of ebullition, 
and was charged with a greater amount of mineral matter in solu- 
tion than at present. Natural chemical operations were iu & 
state of intense activity, aided by the heat. 
With the abatement of the surface-heat, the lower forms of 
marine organic life appeared, aud their remains were entombed in 
the accumulating sediments which wore laid down by the water 
upon the then thin crust of consolidated igneous matter. 
The continued cooling process, and the reduction of the ex- 
panding heat-force which liad partly counteracted the attraction 
of gravity, caused general shrinkage of the interior bulk ; the 
hardened crust, with its superimposed sedimentary layers, drawn 
centrewards by the attraction of gravity from within, and impelled 
by the atmospheric pressure from without, naturally sank, and in 
sinking became folded and corrugated through having to occupy 
a decreased area. It is easy to conceive that during such process 
the downward undulations of the sedimentary layers, together 
with the igneous crust on which they had been deposited, would 
be lowered to within the influence of the heated nucleus, by which 
the lower edges and folds of the broken and plicated strata would 
be fused, partly absorbed, and altered. Distinct from the heat of 
the internal mass, which would only radiate a short distance, heat 
generated by motion would no doubt play an important part in 
effecting alterations of the plicated strata. Such movements were 
probably repeated from time to time at different parts of the 
earth’s surface as further contractions took place. Besides move- 
ments resulting from general shrinkage, extraordinary pressure in 
one locality would cause an upward thrusting in another of the 
heated material, and the local transmutation thereby of the sedi- 
mentary rocks at the planes of contact. 
It is very improbable, as pointed out by Professor Jukes in his 
Manual of Geology, that the primeval igneous crust consisted of 
granite, as such a rock would not be ‘formed at the surface. Every 
vestige of the original crust has, in all likelihood, been re-melted 
and transmuted along with portions of the superincumbent sedi- 
mentary layers, and the granite, as we now sec it, is the product 
of the melted mass which has cooled at great depths beneath the 
surface. 
The above is at present the generally-accepted explanation as 
to the cause of the highly contorted and plicated state of the 
Older Palaeozoic rocks, and the previously noticed phenomenon of 
their being frequently found resting on edge against the granite, 
as well as their metamorphosed condition for a greater or less 
distance from their planes of contact with the latter. The out- 
lines of the theory as to origin having been so far enunciated, the 
Lower Palaeozoic strata will now ho more fully described, com- 
mencing with the metamorphic stratified rocks or crystalline 
