MATTER AND FORGE. 385 
the savage, and his sensations of muscular force, we pass 
on to the observation of force exerted between a magnet 
and rubbed amber and the bodies which they attract, 
rising, by an unbroken growth of ideas, to a conception of 
the force by which sun and planets are held together. 
This idea of attraction between sun and planets had 
become familiar in the time of Newton. He set himself 
to examine the attraction: and here, as elsewhere, we find 
the speculative mind falling back for its materials upon 
experience. It had been observed, in the case of magnetic 
and electric bodies, that the nearer they were brought to- 
gether the stronger was the force exerted between them; 
while, by increasing the distance, the force diminished 
until it became insensible. Hence the inference that the 
assumed pull between the earth and the sun would be 
influenced by their distance asunder. Guesses had been 
made as to the exact manner in which the force varied with 
the distance; but Newton supplemented the guess by the 
severe test of experiment and calculation. Comparing the 
pull of the earth upon a body close to its surface, with its 
pull upon the moon, 240,000 miles away, Newton rigidly 
established the law of variation with the distance. But on 
his way to this result Newton found room for other con- 
ceptions, some of which indeed, constituted the necessary 
stepping-stones to his result. The ona which here con- 
cerns us is, that not only does the sun attract the earth, 
and the earth attract the sun as ivholes, but every particle 
of the sun attracts every particle of the earth, and the re- 
verse. His conclusion was, that the attraction of the 
masses was simply the sum. of the attractions of their con- 
stituent particles. 
This result seems so obvious that you will perhaps wonder 
at my dwelling upon it; but it really marks a turning point 
in our notions of force. You have probably heard of 
certain philosophers of the ancient world named Demoo- 
ritus, Epicurus, and Lucretius. These men adopted, 
developed, and diffused the doctrine of atoms and mole- 
cules, which found its consummation at the hands of the 
illustrious John Dalton. But the Greek and Boman phi- 
losophers I have named, and their followers, up to the time 
of Newton, pictured their atoms as falling and flying 
through space, hitting each other, and clinging together 
by imaginary hooks and claws. They missed the centra.' 
