216 TRANSFORMATION AND EQUIVALENCE OF FORCES. 



by rain, rivers, winds, waves, and ocean-streams, are the 

 indirect effects of solar heat. 



Thus the inference forced on us by the doctrine of trans- 

 formation, that the forces which have moulded and re- 

 moulded the Earth's crust must have pre-existed under some 

 other shape, presents no difficulty if nebular genesis be 

 granted ; since this pre-supposes certain forces that are both 

 adequate to the results, and cannot be expended without pro- 

 ducing the results. We see that while the geological 

 changes classed as igneous, arise from the still-progressing 

 motion of the Earth's substance to its centre of gravity ; the 

 antagonistic changes classed as aqueous, arise from the still- 

 progressing motion of the Sun's substance towards its centre 

 of gravity a motion which, transformed into heat and radi- 

 ated to us, is here re-transformed, directly into motions of the 

 gaseous and liquid matters on the Earth's surface, and indi- 

 rectly into motions of the solid matters. 



70. That the forces exhibited in vital actions, vegetal 

 and animal, are similarly derived, is so obvious a deduction 

 from the facts of organic chemistry, that it will meet with 

 ready acceptance from readers acquainted with these facts. 

 Let us note first the physiological generalizations; and then 

 the generalizations which they necessitate. 



Plant-life is all directly or indirectly dependent on the 

 heat and light of the sun directly dependent in the im- 

 mense majority of plants, and indirectly dependent in plants 

 which, as the fungi, flourish in the dark : since these, grow- 

 ing as they do at the expense of decaying organic matter, 

 mediately draw their forces from the same original source. 

 Each plant owes the carbon and hydrogen of which it mainly 

 consists, to the carbonic acid and water contained in the sur- 

 rounding air and earth. The carbonic acid and water must, 

 however, be decomposed before their carbon and hydrogen 

 can be assimilated. To overcome the powerful affinities 

 which hold their elements together, requires the expenditure 



