THE PLUEAL1TY OF WORLDS. 



55 



the least informed, that the brightness of light will then depend upon the mag- 

 nitude of this foramen. Granting that there are two eyes, in one of which the 

 pupil is twice as large as it is in the other, the organ being in all other respects 

 the same, then it is evident that one would admit twice as much light as the 

 other. If, then, the large pupil was exposed to light of only one half the in- 

 tensity or brightness of that to which the smaller one is exposed, then the two 

 lights would appear to these eyes of the same brilliancy, although in fact, one 

 would be only half as bright as the other. What, then, shall we say of the 

 planets ? Grant that the pupils of the eyes of all creatures endowed with 

 vision upon them are enlarged in their opening according as the planets are 

 more removed from the sun and diminished as they are nearer to that luminary, 

 and the whole difficulty arising from the varying intensity of light will vanish. 

 The inhabitants of all the planets will, in fact, enjoy days of the same bright- 

 ness, notwithstanding the extreme difference of their distances from the sun. 



In considering closely the physical powers of locomotion and strength con- 

 ferred upon animals on the surface of the earth, we find that they have certain 

 limitations ; that animals are capable of exercising the powers of locomotion 

 for certain periods of time, varying, it is true, among individuals, but still in 

 the main comprised within certain narrow limits. We find that after the lapse 

 of certain intervals, bodily repose is wanted. But besides the disposition to ac- 

 tivity and locomotion and the alternate want of rest, animals in general have 

 also other physical wants and capabilities of enjoyment which are periodical. 

 Thus they are capable of wakefulness for certain periods, after which recurs the 

 physical want of sleep. 



Now upon a general survey of the creation, it is found that the average pe- 

 riods which must regulate the intervals of labor and rest, of wakefulness and 

 sleep, corresponds in the main with those which regulate the alternations of 

 light and darkness. In the vegetable kingdom we find prevailing also peri- 

 odical functions, certainly not so obvious and apparent, but not on that ac- 

 count the less interesting, which are ascertained to have the same close 

 alliance with the period that regulates the returns of light and darkness. 



Plants undergo certain changes and suffer certain effects, in the presence 

 of solar light, which are different from, and in some respects contrary to, those 

 which they undergo in its absence. These changes are essential to the vege- 

 table health of the creature ; without them the tribes of plants would be 

 extinct. The duration of these operations is just as essential as their alterna-. 

 tions. Light must be present a certain time and neither more nor less ; and its 

 absence must be equally regulated by limits, otherwise the plant must perish. 

 There is, then, it is evident, an essential relation between the functions and 

 qualities of the vegetable kingdom between the power of activity, the suscep- 

 tibility of enjoyment and the physical wants of animals, and the periods which 

 separate light from darkness ; but what are those periods ? What is the 

 mechanical expedient to which He has resorted to accomplish his inscru- 

 table purposes, who divided the light from the darkness, and " saw that it 

 was good" Nothing can be more simple. Nothing can be more beautiful. 

 Nothing can be more admirably perfect. While the globe of the earth makes 

 its annual course round the sun, it has at the same time a spinning motion, on 

 a certain diameter, as an axis, in virtue of which it successively exposes all 

 parts of its surface to the light and warmth of the sun. Each complete rota- 

 tion is accomplished in the space which we call twenty-four hours ; subject to 

 a variation which we shall notice hereafter. All points on our earth are alter- 

 nately exposed to and withdrawn from the solar light ; the average intervals 

 being twelve hours. 



Now when we reflect on the close, the exact correspondence between these 



