40 



HISTORY OF ASTRONOMICAL DISCOVERY. 



GRAVITY, subject to the two conditions, that its force is directly as the mass of the bodies, 

 and inversely as the square of the distance. It extends to the confines of the system, and 

 acts as a mighty invisible chain to keep the primary bodies in brotherly relationship to 

 each other, and in mutual subjection to the central luminary. And who can trace its 

 operation without recognising a Supreme Potentate, who appointed to the sun his place, 

 launched the planets in the depths, obedient to a law which has preserved the family 

 compact originally established unbroken through the long series of ages ? 



It must, however, be borne in mind that the attraction between bodies is mutual, pro- 

 portioned to their masses and distances. While the sun attracts the planets towards 

 himself, they also attract the sun, though their effect is comparatively small, owing to the 

 vastness of the solar mass. The planets likewise act upon each other ; and as their relative 

 distances are perpetually varying, certain perturbations are caused in the system, which, 

 though minute in each particular case, become considerable by accumulation, and yet are 

 ultimately corrected and repaired by the same cause that produces them. Newton left to 

 posterity the task of thoroughly investigating these inequalities, of showing them to be a 

 result of the law of gravitation, and establishing the permanence of the system, notwith- 

 standing the accumulating influence of its internal disturbances. He himself had no 

 gleam of the latter truth, but seems to have entertained an opinion that the irregularities 

 occasioned by the mutual action of the planets and comets would probably go on increasing 

 till the system either wrought out its own destruction or received reparation from the 

 direct intervention of its Creator. But Euler, Clairaut, D'Alembert. Lagrange, and 

 Laplace have demonstrated the problem that the perturbations of the planets are periodic 

 in their nature, that accurate compensation for them is laid up in store, so that the system 

 is not arranged upon a principle of self-destruction. The elements of disorder and decay 

 are removed from it. The very conditions of its existence guarantee its stability till the 

 will of the great Ruler shall be expressed to the contrary. When an end shall come to 

 its present constitution, that will not be the effect of its own faulty architecture, but of 

 the fiat of OMNIPOTENCE. 



The house of Newton at Woolsthorpe, now the homestead of a farmer, has been in the 



ownership of persons 

 anxious to protect it, 

 and preserve every 

 relic of its former oc- 

 cupant. Stukeley thus 

 described it in 1727: 

 "'Tis built of stone, 

 as is the way of the 

 country hereabouts, and 

 a reasonable good one. 

 They led me up-stairs, 

 and showed me Sir 

 Isaac's study, where I 

 suppose he studied 

 when in the country 

 in his younger days, 

 or perhaps when he 

 visited his mother from 

 the university. I ob- 

 served the shelves were 

 of his own making, being pieces of deal boxes which probably he sent his books and 



Koom in which Newton was born. 



