THE SUN COOLING OFF. 411 



limits of the- solar system be rained down upon the sun 

 without complete exhaustion ? The space inclosed by the 

 orbit of Neptune is not infinite. The supply of cosmical 

 matter is but a finite quantity. Time enough will drain 

 the bounds of the solar system of all its wandering parti- 

 cles of planetary dust. What then will be the fate of the 

 sun? 



The conviction can not be resisted that the processes 

 going forward before our eyes aim directly at the final ex- 

 tinction of the solar fire. Helmholtz says : " The inexora- 

 ble laws of mechanics show that the store of heat in the 

 sun must be finally exhausted." What a conception over- 

 shadows and overpowers the mind ! We are forced to 

 contemplate the slow waning of that beneficent orb whose 

 vivid light and cheering warmth animate and vivify the 

 circuit of the solar system. For ages past unbounded 

 gifts have been wasted through all the expanding fields of 

 space — wasted, I say, since less than half a billionth of his 

 rays have fallen upon our planet. The treasury of life 

 and motion from age to age is running lower and lower. 

 The great sun which, stricken with the pangs of dissolu- 

 tion, has bravely looked down with steady and undimmed 

 eye upon our earth ever since organization first bloomed 

 upon it, is nevertheless a dying existence. The pelting 

 rain of cos>mical matter descending upon his surface can 

 only retard, for a limited time, the encroachments of the 

 mortal rigors, as friction may perpetuate, for a few brief 

 moments, the vital warmth of a dying man. The time is 

 coming when the July sun will shine with a paler light 

 than he now gives us at the winter solstice. The nations 

 of men, if they still exist, will have emigrated from the 

 temperate to the equatorial regions. New diseases will 

 have diminished their numbers. Polar frost will have 

 crept stealthily and steadily from Behring's Straits to the 



