6 S 6 THE POPULAR SCIENCE MONTHLY. 



of heat and cold at different periods of the year would be fatal to 

 life. If the orbit of Jupiter were as eccentric as that of Mercury, 

 the attraction of the larger planet would cause the smaller to change 

 their approximately circular orbits into very long ellipses ; such 

 would be the disturbance that they would fall into the sun or fly off 

 into remote space. The moon would approach nearer and nearer to 

 the earth with every revolution ; the year would change its character; 

 violent heat would succeed to violent cold ; the planets would come 

 nearer and nearer ; we should see them portentous in size and aspect, 

 glaring and disappearing at uncertain intervals ; tides, like deluges, 

 would sweep over whole continents ; and, finally, the fall of the moon 

 or one of the planets to the earth would result in the absolute anni- 

 hilation of both of them. 



Another reason for supposing that the solar system is the result 

 of one separate act of creation is, that all parts of it are subject to 

 one uniform law that of gravitation. By that law every particle 

 of matter attracts every other particle with a force directly propor- 

 tionate to its mass. This force varies as the inverse square of the 

 distance : that is, if the attractive force of a given mass at one mile 

 were called 1, at two miles it would be 2 X 2 = 4, or | of 1, and so 

 on. This law of the inverse square, as it is called, is but the mathe- 

 matical expression of a property which has been imposed upon mat- 

 ter by the Creator. It is no inherent quality, so far as we know. It 

 is quite conceivable that the central law might have been different 

 from what it is. There is no reason why the mathematical fact should 

 be what it is except the will of the Being who imposed the law. Any 

 other proportion could equally well be expressed mathematically, and 

 its results calculated. As an instance of what would occur if any 

 other proportion than the inverse square were substituted as the at- 

 tractive foi*ce of gravity, suppose, at distances 1, 2, 3, the attractive 

 force had varied as 1, 2, 3, instead of the squares of those numbers. 

 Under such a law any number of planets might revolve in the most 

 regular and orderly manner. But under this law the weight of 

 bodies at the earth's surface would cease to exist ; nothing would fall 

 or weigh downward. The greater action of the distant sun and plan- 

 ets would exactly neutralize the attractive force of the earth. A ball 

 thrown from the hand, however gently, would immediately become a 

 satellite of the earth, and would for the future accompany its course, 

 revolving about it in the space of one year. All terrestrial things 

 would float about with no principle of coherence or stability they 

 would obey the general law of the system, but would acknowledge no 

 particular relation to the earth. It is obvious that such a change 

 would be subversive of the entire structure and economy of the world. 

 From these and similar considerations, it follows that, although other 

 laws are conceivable under which a solar system might exist, the 

 solar system, such as we know it, could only exist under the actual 



