﻿W. J. 8onas — On Evolution in Geology. 3 



Velocity of the Earth'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 anhydride. All sedi- 

 mentary rocks must ixltimately 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 

 anhydride 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 

 anhydride extracted from the atmosphere, and, by calculating the 

 quantity of carbonic anhydride 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 anhydride, 

 i.e. about -3 ttoo-o part of the whole amount of this gas at present 

 existing in the atmosphere. The Laurentian formation of Canada 

 alone covers 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 anhydride stored away in these Laurentian 

 limestones alone exceeds by four times the quantity of carbonic 

 anhydride at present existing in the atmosphere ; or, in other words, 

 that if it could be again restored to the air, it would increase 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 

 of this carbonic anhydride 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 carhonic 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 



