98 The Scottish Naturalist. 



have varied considerably at different times in composition and 

 in weight ; that our atmosphere has contained a much greater 

 proportion of carbonic acid or oxygen ; and our waters, aided 

 by excess of carbonic acid, and greater heat, resulting from 

 greater density of atmosphere, have contained a greater quantity 

 of lime, and other mineral solutions. 



Is the inference then unphilosophic, that living things which 

 are proved to have a circumstance-suiting power (a very slight 

 change of circumstances, by culture, inducing a corresponding 

 change of character) may have gradually accommodated them- 

 selves to the variations of the elements containing them, and 

 without new creation have presented the diverging changeable 

 phenomena of past and present organized existence ? 



The destructive liquid currents, before which the hardest 

 mountains have been swept and comminuted into gravel, sand, 

 and mud, which intervened between, and divided these epochs, 

 probably extending over the whole surface of the globe, and de- 

 stroying nearly all living things, must have reduced existence so 

 much that an unoccupied field would be formed for new diverging 

 ramifications of life, which, from the connected sexual system of 

 vegetables, and the natural instincts of animals to herd and 

 combine with their own kind, would fall into specific groups ; 

 these remnants in the course of time moulding and accommo- 

 dating their being anew to the change of circumstances, and to 

 every possible means of subsistence, and the millions of ages of 

 regularity which appear to have followed, between the epochs 

 probably after this accommodation was completed, affording 

 fossil deposit of regular specific character. 



There are only two probable ways of change ; the above and 

 the still wider deviation from present occurrence of indestructible 

 or molecular life (which seems to resolve itself into powers of 

 attraction and repulsion, under mathematical figure and regula- 

 tion, bearing a slight systematic similitude to the great aggrega- 

 tions of matter,) gradually uniting and developing itself into new 

 circumstance- suited living aggregates, without the presence of 

 any mould or germ of former aggregates, but this scarcely differs 

 from new creation, only it forms a portion of a continued 

 scheme or system. 



In endeavouring to trace, in the former way, the principle of 

 these changes of fashion which have taken place in the domi- 



