THE SOLAR SYSTEM AND ITS NEIGHBORS. 617 



to be measured by 15,000,000 of our unit-bars, together making a bar 

 of solid steel whose section would cover 15,000,000 square miles, more 

 than four times the area of the United States. The wires, such as we 

 supposed to hold the moon, would, in the case of the earth and sun, 

 be almost as close as the blades of grass on a lawn. 



Without going any further into calculations, it is enough to say 

 of the other planets, that Mercury is held to its duty by 6,590,000 of 

 our unit-bars ; while Venus, being nearly as large as the earth, and so 

 much nearer the sun, requires the united strength of nearly 23,000,000. 

 Mars is smaller, and more remote, and therefore needs only some 

 811,500 such bands to hold it to its course ; for, strange as it may ap- 

 pear, and however unlike other sovereigns, the sun holds its subjects 

 in obedience the more easily, the greater their distance from the cen- 

 ter of the system, provided, of course, that their importance other- 

 wise is the same. But still, distant as it is, Jupiter's immense mass 

 demands incomparably the strongest measures to keep it in check ; 

 nothing less than 170,000,000 of those bands of steel will overcome 

 its wandering tendencies. Saturn, being a lighter weight, is more 

 easily guided 15,000,000 suffice for that. Uranus and Neptune are 

 of little account as compared with Jupiter ; 588,000 for the one and 

 282,000 for the other are all that are needed to restrain their vaga- 

 ries. 



If, now, we turn to the planets, and study their influence, we shall 

 find them pulling and tugging at each other with forces that, but for 

 compensations planted in the system itself, would tear it to pieces ; 

 but, like the armed men of Cadmus, these forces destroy each other. 



However difficult it may be to conceive of such an amount of power 

 as the sun puts forth, we are so accustomed to regard that body as the 

 governing center of our part of the universe, and have heard so much 

 of its vast size, that we are prepared to accept almost any statement in 

 regard to it. But as to the planets we do not realize their size, and we 

 seldom think of their exerting any influence on the earth or on one 

 another. That they do exert such an influence we know, for astron- 

 omers have told us of perturbations thus produced ; but, then, very 

 few of us connect such statements with the tiny specks which we see 

 in the heavens. Yet their influence is no trifle. Mercury, which is 

 too small and too near the sun for most of us to have seen, draws the 

 earth when in mean perigee with a force small indeed when com- 

 pared with those which we have been considering, but large enough 

 to break 232,390,000 bars one foot square ; Venus pulls with a force 

 of 11,175,000,000 ; Mars pulls enough to overcome the united strength 

 of 590,680,000 ; while Jupiter draws away with a steady tug of nearly 

 23,000,000,000 ; and even Neptune, 2,700,000,000 miles away, and 

 utterly invisible to the naked eye, still has sufficient energy to drag 

 our earth toward it with force able to snap 27,000,000 such bars. 

 Besides these, which are only the interplay of forces between our 



