65 



ing in a later stratum, until at last, it appears utterly extinct. 

 "We see other limited durations appointed for the existence of 

 genera, families, and orders, so that analogy would make us infer 

 that it must be the same — for all groups of which in geological 

 strata we have, in a manner, witnessed the commencement. It 

 thus may be that classes, nay, the two kingdoms of animal and 

 vegetable nature themselves, — for these, after all, are but groups 

 of greater dimensions — as they have had in geological strata a 

 visible beginning, so must they also in process of time have their 

 due end. 



Nor need speculation cease here ; since it would surely be the 

 height of presumption to suppose that when all that organization 

 of matter which is dependent for existence on atmospheric air, 

 shall, with that gas, have passed away, other kinds of organic 

 beings may not remain, where atmospheric air has never existed, 

 or even where it may have ceased to exist. Nevertheless, it is 

 true that there is no vestige of material life having ever existed 

 on this terrestrial globe, except in connection in some way with 

 the atmosjihere, and dependent on it. Nay, it would appear 

 from observation, that the order of the creation of species — aye, 

 and perhaps the order of their extinction too — has been carried 

 on in point of time, with reference to the successive conditions of 

 the circumambient air. Thus, aquatic beings have preceded 

 terrestrial. But there is an exception, which, as usual proves 

 the rule ; and, pursuing the consequences legitimately to be 

 deduced from the above facts, we may, perhaps, be able to arrive 

 at the true reason for marine animals, ■warm-'blooded, like whales, 

 having been called into existence so late, when their proper food, 

 Mollusca and Crustacea, had, for ages before the earliest tertiary 

 period, abounded in the waters which then covered a great part 

 of the face of the earth. 



[2 plates.] 



Sydney : Charles Potter, Government Printer. — 1887 



