REAPPEARANCE OF THE FORCE EXPENDED. 93 



dients is known, but all results from the operation of far-reaching and immutable laws. 

 In those remote times events were taking place, the application of which referred not 

 to things then existing, but to an hereafter. The earth, and the sea, and the air were 

 enlivened and invigorated by the sunbeams as they are now, but while present pur- 

 poses were subserved, the future also was not forgotten. In the twilight that then ex- 

 isted, as it does now, the wolf followed his flying prey, and by the light of the same 

 stars the royal tiger pursued his midnight maraudings. Nor is there anything op- 

 posed to the order of Nature in those things. Intellectual development can only take 

 place when a thousand natural conditions conspire. Reason and analogy would equally 

 lead us to suppose that, in a majority of those globes which are scattered through the 

 regions of space, those conditions are not attained ; that they are, as this earth was for 

 countless ages, a dungeon of pestiferous exhalations, and a den of wild beasts. And 

 yet the formative forces of Nature are at work ; the plastic fingers of light, each colour 

 producing its proper effect, are arranging, and decomposing, and modelling, and the 

 work which thus goes on in silence attains perfection in the lapse of ages. In those 

 planets, as in this, the atmosphere and the sea are finally brought to a proper constitu- 

 tion, and wild animals make their appearance, and then intellectual beings. For these, 

 whatever is wanted has been provided. And results which for so long a time have lain 

 dormant now come into use, just as those forces which in primeval ages were expended 

 by light in the reduction of carbon by leaves; carbon which has been buried in the 

 earth, in our times reappears again, and is, perhaps, occupied in driving the steam-ship 

 that carries these pages over the waves of the Atlantic Ocean. 



376. Two prominent facts must always be present to the mind of a natural philoso- 

 pher the indestructibility of matter, and the indestructibility of forces. Disappearances 

 of the one or of the other are only fictitious deceptions. Throughout the universe the 

 quantity of matter and the quantity of force remains forever unchanged. Material 

 atoms migrate from one condition to another, now putting on the form of a solid, 

 now of a liquid, now of a gas ; so also with forces, which are occupied in producing 

 sometimes one, and sometimes another effect ; but the quality of the former and the 

 value of the latter remains, under all circumstances, unchanged. And when such con- 

 siderations as those which are before us show that rays of light of different colours 

 have certain offices to discharge, and certain chemical effects to produce, affinities of 

 given intensities to overcome, molecules to group in determinate positions, these are 

 things which can only be done by the expenditure of a certain force ; but, though that 

 force be expended, it is not destroyed ; it is ready to reappear from its condition of trans- 

 mutation. In the same way that, all over the American Continent, at a certain period 

 .after the fall of the leaf the Indian summer sets in, and in the cold weather of winter 

 restores the warm days of July, the heat which is evolved from decaying leaves in the 

 forests being derived from the sunrays of the preceding summer, so also every ray 

 which has been expended, no matter of what colour it may be, or what has been the 

 chemical or physical result with which it has been connected, or what series of trans- 

 mutations it has passed through, is ready to be restored in its pristine energy, and give 

 rise to its equivalent mechanical effect. And hence we can see that although, so far 



