NATURAL PHILOSOPHY. 137 



the distances of the other planets, we have the ratio of densities; which 



coincide very nearly with the densities given by Laplace, in the third column. 



Distances. Density. Density from 



Miles. 73 Laplace. 



Mercury, 370,674 5 2.560 2.585 



Venus, 685,598 1-384 1.024 



Earth, 948,925 g 1.000 1.000 



Mars, 1,444.982 Jj J .687 .655 





Jupiter, 4,937,223 .192 .201 



Saturn, 9,048,712 j - .104 .103 



Uranus, 18,204,570 ^ .052 .218 



Neptune, 28,527,828 .037 



In Biot's Astronomy the density of Mercury, resulting from the diameter 

 and mass there given, is 3.097 ; but in the author from whom Olmsted copies, 

 it is put down as 1.12. Laplace is between them. 



It has been shown that the square roots of the distances of the planets are 

 inversely proportional to their velocity of revolution. Hence, the nearer a 

 planet approaches the sun, its velocity is more and more increased. At the 

 distance of one mile, therefore, from the sun, the velocity of the earth's revo- 

 lution around it would be nineteen miles per second, multiplied by the square 

 root of 94832572 miles, which equals 10 x 9744 = 185136 miles per second, 

 which is very nearly ihe estimated velocity of light. The atoms of terrestrial mat- 

 ter, therefore, if placed at the surface of the sun, would have a motion equal 

 to the velocity of solar light. 



If the resistance of atoms of matter retards the velocity of light and modi- 

 fies the force of gravity, the amount of such retardation ought to be in 

 some ratio with the number of atoms, or masses of the planets. It is found 

 that the sixth roots of the masses represent this retardation. The times of 

 rotation of the planets, therefore, should be in the ratio of the square roots 

 of the cube roots, that is, the sixth roots of the masses. 



Mass. Ratio. Times of rotation. 



6 / -- h. m. s. 



Mercury, V #465 = .715 or 33 29 09 



Venus, C \/lT322i3 = 1.048 " 22 55 57 



Earth, %/1.00(>00 = 1.000 " 24 00 00 



Mars, %/.12535 = .707 " 33 54 28 



Jupiter, . 7 7232 = 2.546 " 9 23 00 



Saturn, 6 \/ib3.4S990 = 2.169 " 11 07 00 



Uranus, \A.4994Q = 1.270 " 18 45 00 



Neptune, G ^2^2liTl = 1.147 " 20 56 32 



GROWTH OF A CRYSTAL. 



Mr. Xevil Story Maskelyne, in a paper read by him to the Royal Institution, 

 " On the Insight hitherto obtained into the nature of the Crystal Molecule by 

 the instrumentality of Light," in conclusion, says: 



In every case the growth of a crystal is an inexplicable thing, so long as 

 we endeavor to trace its cause to powers residing in, and confined to, the 



12* 



