no WALTER AUBREY KIDD_, M.D., M.R.C.S., F.Z.S., ON 



but to see how piece by piece the purpose in creation is worked 

 out in the divinely-wrought preparation of environments for 

 organisms and organisms for environments is more conclusive 

 still, if not more interesting. The astronomer, chemist, physicist, 

 and geologist can give us expert information as to the secondary 

 causes by which this globe has passed from the molten and 

 liquid mass that it may have been 100 million years ago to 

 what it is to-day. The manner of production of the atmosphere 

 of our globe;, the oxygen probably derived from the living 

 processes of lowly plants (such as confervie) in the warm primeval 

 seas, may be expounded, but in all such cosmic matters which are 

 great enough to give him enough occupation, the scientificobserver 

 may be reminded of the old sayinj?, " Ne sutor ultra crepidam." 



The whole duty of the scientific man is to contribute his 

 quota of expert evidence in the subjects of his choice, and to 

 bring them to that great assize with which Philosophy is 

 concerned, and where her voice is ever the last to be heard. 



On former occasions I have dealt more fully with the known 

 geological history of the globe and the changing environments 

 in successive epochs.* It is not needful to do more here than 

 to refer to the warmth, equability, and homogeneous character 

 of the primary, the increasing definition of land and sea still 

 with excessive moisture, warmth, and equable conditions of the 

 secondary, closing with a period of greater cold and more severe 

 conditions of life, the slow development of more complex 

 climates, continental areas increasing by elevation, diminutiun 

 of the previous excessive warmth and moisture, more volcanic 

 action with its profound effects upon the face of the earth, the 

 gradual cooling of Pliocene times characteristic of the Tertiary 

 Period, until the present geological epoch was ushered in by the 

 glacial period of the Quaternary Age, this again subsiding and 

 allowing the present state of the globe, with all its adaptations 

 to man and the existing fauna and flora, to take its place. 



It is enough to state that the four successive groups of 

 environments, which we call geological ages, are wonderfully 

 matched by the plants and animals which in due time were 

 produced to fill them. We cannot conceive the tender infancy of 

 the living world to have arisen and have prospered even under 

 the guiding hand of the Creator during the glacial period, or that 

 the age of mammals could have been placed on the stage of this 

 world during the sub-carboniferous times, or the age of reptiles to 

 have found its suited home and cradle in the Laurentian period. 



Trans. Vict. Inst., vols, xxxii, xxxiii, xxxiv. 



