104 NOMOS. 



at Jupiter, through 18*00 feet at Saturn, through 

 12-05 feet at Uranus, through 13 '5 6 feet at Nep- 

 tune, through 2 '72 feet at the Moon, and through 

 459*47 feet at the Sun. These differences are ac- 

 counted for by saying that the gravity is directly 

 proportional to the mass of the gravitating bodies, 

 and not to their volume. Some of these bodies are 

 supposed to contain much less gravitating matter 

 than others, and for this reason they are lighter than 

 others. Indeed, if mass be compared with volume, 

 all the planets, except Mercury, as well as the Sun 

 and Moon, are lighter than the Earth, and some of 

 them much lighter. Taking the Earth as 1, Mer- 

 cury is 3*45, Venus 0-92, Mars 0-95, Jupiter 0*94, 

 Saturn 0*12, Uranus and Neptune 0*17, the Sun 

 0*26, and the Moon 0'62. The differences in gravi- 

 tating power, then, are accounted for by saying that 

 the power is directly proportional to the mass of the 

 gravitating bodies. If the mass were doubled the 

 weight would be doubled; if halved it would be 

 halved ; and so on. In the first case a body would 

 fall towards the Earth through twice 16*03 feet in 

 the first second, in the other case it would only fall 

 through 8*01 feet. All this has been determined 

 by experiments, as by those of Cavendish and 

 others. 



What, then, is the final conclusion of this magni- 

 ficent theory ? The conclusion is, that every particle 

 in the universe attracts every other particle with a 

 force which is directly proportionate to the mass of 

 the attracting particles, and inversely proportionate 

 to the square of their distance ; and that this attrac- 



