254 THE POPULAR SCIENCE MONTHLY. 



entific era of the world's history. Newton, or rather Newton as de- 

 veloped by Laplace and the French school of mathematicians, entirely 

 changed the whole aspect of things. Laplace, with proprietj^, de- 

 scribed his great work by the title of ' Celestial Mechanics ' : the pur- 

 pose of the work, which it effected with singular skill, was the reduction 

 of the whole system of the heavens to the condition of an ordinary 

 mechanical problem — a problem, too, having the advantage that the 

 bodies concerned are all moving in vacuo, and that therefore there 

 are none of the difficulties of friction, resistance of the air, and the 

 like, which interfere with the easy solution of terrestrial dynamical 

 problems. To the mathematician the solar system is a set of small 

 bodies, which for some purposes may be even regarded as particles, 

 revolving in connection with one much larger and central body, under 

 the action of mutual gravitation according to a certain simple law ; 

 while the earth, regarded by itself and with reference to the phenom- 

 ena of its own revolution, is a rigid, slightly oblate spheroid, the motion 

 of which in given circumstances constitutes one of the prettiest prob- 

 lems of rigid dynamics. It is difficult perhaps for any one, who has 

 not gone through the study pesonally and practically, to conceive how 

 completely to the mind of a mathematician the solar system resolves 

 itself into a problem of bodies in motion in vacuo. But, as soon as 

 the mind apprehends the solar system thus, it has found an instance 

 of the uniformity of Nature upon a very large scale. The mathema- 

 tician who is capable of solving the problem of the planetary motions, 

 as Laplace and Lagrange solved it, or who knows anything of the 

 motion of a rigid body revolving as the earth revolves, finds himself 

 simply incapable of conceiving of anything but motion, according to 

 fixed law, being found in the solar system ; the uniformity of Nature 

 in this department presses itself upon him with a power which he can 

 not resist. 



A mathematician, for example, would find himself entirely pre- 

 cluded from sympathizing, in the most distant manner, with the view 

 expressed by Mr. Ruskin at the meeting of the Metaphysical Society. 

 The standing still of the sun, of which Mr. Ruskin speaks so pleas- 

 antly, means the stopping of the revolution of the earth, for the mo- 

 tion of the sun is only the earth's revolution ; consequently, what is 

 called the standing still of the sun involves tremendous dynamical 

 consequences, an utter disruption of everything upon the earth's sur- 

 face, a return of chaos, or I know not what. I am not criticising the 

 expression as to the sun standing still, used in the book of Joshua 

 without any attempt at scientific language. What the actual fact was 

 to which the language used refers, and what was the actual phenom- 

 enon, I can not undertake to say ; but if we adopt the phrase into 

 the language of the nineteenth century, and in that language speak 

 of the news of the sun standing still as a thing w^hich need not sur- 

 prise us, but which we have rather expected than otherwise, then I 



