Life Changes on the Globe. 327 



and existing causes; but, notwithstanding" the exhaustive 

 reasonings which that distinguished philosopher embodied in a 

 most fascinating style, it has been customary to represent the 

 earlier epochs of our globe as periods of such continuous 

 violence as to make us exclaim with Isabel, " nothing but 

 thunder," and it has also been common to exalt negative evi- 

 dence to a most unwarrantable position in the scale of proof. 

 To get the world made and unmade as quickly as impatient 

 professors desired, it was necessary to fancy that, comparatively 

 speaking-, no great while had elapsed since it "wandered 

 lonely as a cloud" in the nebulous form. Condensation 

 followed almost as rapidly as the drops fall from the con- 

 densed steam of the locomotive, and it spun round as a fluid 

 fiery mass, getting sufficiently crusted at the surface to be a 

 convenient lodging for such forms of life as require what the 

 gardeners call a strong "bottom heat/'' Hadiation enabled 

 more and more of the molten material to become solid, and 

 colder creatures appeared upon the scene. Still the central 

 fires maintained their sway, every volcano was their outlet, 

 and where no lava streams could burst forth, continents were 

 upheaved with all the facility which characterizes the elevation 

 of bubbles on the surface of a baking pie. These high-pressure 

 movements soon exhausted and absorbed successive races of 

 organized existences, and when the earth had been tossed and 

 tumbled about, so that " chaos was come again," a fresh exer- 

 tion of creative energy upraised new forests, and caused new 

 creatures to bound or crawl beneath their shade. One apparent 

 advantage of this school of geology was its supposed power to 

 exhibit the first dawn of life, and the successive catastrophes by 

 which systems were swept away, and a higher fa una and flora 

 convulsively introduced. The general results of this mode of 

 philosophizing are thus stated by Professor Huxley, the words 

 in brackets being added by ourselves.* 



" Animals and plants began their existence together, not long 

 after the commencement of the deposition of the [earliest known] 

 sedimentary rocks, and then succeeded one another in such a 

 manner that totally distinct faunas and floras occupied the whole 

 surface of the earth, one after the other, and during distinct epochs 

 of time. 



" A geological formation is the sum of all the strata deposited 

 over the whole surface of the earth during one of these epochs ; a 

 geological fauna or flora is the sum of all the species of animals or 

 plants which occupied the whole surface of the globe during one of 

 these epochs. 



" The population of the earth's surface was at first very similar 

 in all parts, and only from the middle of the Tertiary epoch 

 onwards began to show a distinct distribution in zones. 



Quarterly Journal of the Geological Society, May 1862. 





