W. J. Sollas — On Evolution in Geology. 
3 
Velocity of the Harth' s Rotation. — The retardation of the earth’s 
rotation, owing to the drain upon its energy in supplying the work 
done by the tides, has not yet, perhaps, been accurately estimated 
as to its amount, but as to its existence there can be little or no 
doubt. From this it follows that the rate of rotation of the earth 
was greater in the earlier stages of its history, and has continually 
decreased from then to the present day. 
Chemical Energy. — The Chemical energy which chiefly concerns 
us here is the unsatisfied affinity of carbonic anbydride. All sedi- 
mentary rocks must ultimately be traced to an igneous source, and 
those strata which are composed of carbonates must, in the long 
run, have resulted from the combination of the original carbonic 
anbydride of the atmosphere with the constituent of some igneous 
rock. 
Confining our attention to carbonate of lime, it is clear that 
every bed of this material bears testimony to so much carbonic 
anbydride extracted from the atmosphere, and, by calculating the 
quantity of carbonic anbydride which any given limestone bed con- 
tains, we determine by how much the atmosphere of our planet has 
been deprived by it of that constituent. Thus one cubic mile of lime- 
stone contains about four thousand million tons of carbonic anbydride, 
i.e. about 3 u } ,ö ö pari of the whole amount of this gas at present 
existing in the atmosphere. The Laurentian formation of Canada 
alone covets an area of 200,000 square miles of the earth’s surface, 
and contains limestone beds amounting altogether to 4000 ft. in 
thickness. Proceeding on the assumption that this is the average 
thickness, which of course it is not, it is easy to determine that the 
quantity of carbonic anbydride stored away in these Laurentian 
limestones alone exceeds by four times the quantity of carbonic 
anbydride at present existing in the atmosphere ; or, in other words, 
that if it could be again restored to the air, it would iucrease the 
existing per-centage therein from -04 to - 2 per cent. ; and when we 
consider all the calcareous rocks of the Silurian, Carboniferous, 
Triassic, Jurassic, Cretaceous, and Eocene formations now exposed 
at the earth’s surface, and the unknown beds of limestone, probably 
surpassing all these in thickness and extent, now buried beneath the 
sea, then we have abundant testimony to the extraordinary richness 
pf this carbonic anbydride gas in the original atmosphere of the 
earth, before it had been extracted, by virtue of its affinity for 
the lime of calcic silicates, and imprisoned in the solid form in 
limestone strata. And the same evidence moreover shows that 
it has been continually diminishing in amount from the earliest to 
the most recent geologic times. 
Influence of increased Solar and Terrestrial energy on the rate of 
Geologic Change. 
1. Disintegration by carbonic anhydride. — One does not know what 
Proportion of the carbonic anhydride which is effective in the dis- 
integration of rocks is directly dissolved by rain-water from the 
