SCIENCE AND PSEUDO-SCIENCE. 215 



In the first place, Newton defined the laws, rules, or observed order of 

 the phenomena of motion, which come under our daily observation, 

 w T ith greater precision than had been before attained ; and, by follow- 

 ing out with marvelous power and subtilty the mathematical conse- 

 quences of these rules, he almost created the modern science of pure 

 mechanics, In the second place, applying exactly the same method 

 to the explication of the facts of astronomy as that which was applied 

 a century and a half later to the facts of geology by Lyell, he set him- 

 self to solve the following problem : Assuming that all bodies, free 

 to move, tend to approach one another as the earth and the bodies on 

 it do ; assuming that the strength of that tendency is directly as the 

 mass and inversely as the squares of the distances ; assuming that the 

 laws of motion, determined for terrestrial bodies, hold good through- 

 out the universe ; assuming that the planets and their satellites were 

 created and placed at their observed mean distances, and that each 

 received a certain impulse from the Creator will the form of the or- 

 bits, the varying rates of motion of the planets, and the ratio between 

 those rates and their distances from the sun which must follow by 

 mathematical reasoning from these premises, agree with the order of 

 facts determined by Kepler and others, or not ? 



Newton, employing mathematical methods which are the admira- 

 tion of adepts, but which no one but himself appears to have been able 

 to use with ease, not only answered this question in the affirmative, 

 but stayed not his constructive genius before it had founded modern 

 physical astronomy. 



The historians of mechanical and of astronomical science appear to 

 be agreed that he was the first person who clearly and distinctly put 

 forth the hypothesis that the phenomena comprehended under the 

 general name of "gravity " follow the same order throughout the uni- 

 verse, and that all material bodies exhibit these phenomena ; so that, 

 in this sense, the idea of universal gravitation may, doubtless, be prop- 

 erly ascribed to him. 



Newton proved that the laws of Kepler were particular conse- 

 quences of the laws of motion and the law of gravitation in other 

 words, the reason of the first lay in the two latter. But to talk of 

 the law of gravitation, alone, as the reason of Kepler's laws, and still 

 more as standing in any causal relation to Kepler's laws, is simply a 

 misuse of language. It would really be interesting if the Duke of 

 Argyll would explain how he proposes to set about showing that the 

 elliptical form of the orbits of the planets, the constant area described 

 by the radius vector, and the proportionality of the squares of the 

 periodic times to the cubes of the distances from the sun, are either 

 caused by the " force of gravitation " or deducible from the " law of 

 gravitation." I conceive that it would be about as apposite to say 

 that the various compounds of nitrogen with oxygen are caused by 

 chemical attraction and deducible from the atomic theory. 



