THEORIES OF FORMATION. 171 



the vegetation, of which we as yet know too little, and the 

 long continuance over the same areas of the same external 

 conditions. So far as we can judge of the character of the 

 vegetation (alliance to equisetums, clubmosses, tree-ferns, 

 swamp-pines, and the like), it by no means required a tro- 

 pical temperature for their growth and accumulation, but 

 rather a moist, equable, and genial climate, inundated river- 

 plains and morasses, low-lying deltas and sea-swamps and 

 these could be brought about by the terraqueous arrange- 

 ments of the earth's own surface, and without calling in the 

 aid of anything either preternatural or abnormal. We 

 say, " could be brought about by the terraqueous arrange- 

 ments of the earth's own surface," for it is not difficult to 

 conceive such a position of the land-masses as to receive 

 more heat from the sun and more warmth from oceanic cur- 

 rents, and such a lowness also of the terrestrial surfaces as 

 to offer few points of condensation to aqueous vapours, and 

 thus preserve a greater permanent amount of atmospheric 

 moisture. This moisture would act in a twofold manner 

 in promoting luxuriance of vegetable life first, by afford- 

 ing a full and direct supply for their growth ; and, second, 

 in lessening the radiation of heat from the land-surface, and 

 thereby greatly increasing the general temperature.* But 

 whatever the geographical conditions, they must have con- 

 tinued for long ages over the same areas to permit the ac- 

 cumulation of such a thickness of coals and sediments and 

 igneous eruptions as those which constitute the Carbonifer- 

 ous system. And these accumulations imply vast con- 

 tinents from which they were wasted, large rivers for their 

 transport, extensive deltas and sea- swamps for the growth 

 of coal-beds, frequent volcanic eruptions in or near the 



* For evidence of this peculiar effect of atmospheric vapour, see Profes- 

 sor Tyndall's reasonings and experiments in his ' Heat considered as a 

 Mode of Motion.' 



