440 THE INTELLECTUAL RISE IN ELECTRICITY. 



the two which is least moved; as when we call the attrac- 

 tion of sun and planet the attractive power of the sun. 

 Yet more correctly, he says, we should regard the force as 

 acting between the sun and earth, between the sun and 

 Jupiter, between the earth and moon, for both bodies are 

 moved by it, in the same manner as when tied together by 

 a rope, which shrinks on becoming wet, and so draws 

 them each one to the other. Equally true is this another 

 link forged of electrical and magnetic attractions; for al- 

 though as to the nature of this he has no hypothesis to 

 offer ("Hypotheses non fingo," is his motto everywhere), 

 yet concerning it he says, if we would speak more cor- 

 rectly, and not extend the sense of our expressions beyond 

 what we see, we can only say that the neighborhood of a 

 lodestone and a piece of iron is attended with a power, 

 whereby the lodestone and the iron are drawn toward each 

 other; 1 and the rubbing of electrical bodies gives rise to a 

 power whereby those bodies and other substances are mu- 

 tually attracted. Thus, we would also understand in the 

 power of gravity, that the two bodies are mutually made 

 to approach each other by the action of that power. 2 



Such was the first suggestion that the seat of electric 

 and magnetic forces is not in the electric, or the substance 

 attracted by it, or the magnet, or the iron, but in the in- 

 tervening medium; whatever the last may be. 3 



1 " I made the experiment on the lodestone and iron. If these placed 

 apart in proper vessels are made to float by one another in standing 

 water, neither of them will propel the other; but by being equally at- 

 tracted, they will sustain each other's pressure and rest at last in an equi- 

 librium." Principia cor. vi. 



2 Pemberton: A view of Sir Isaac Newton's Philosophy. London, 1728, 



254- 



3 " We may conceive the physical relation between the electrified bodies, 

 either as the result of the state of the intervening medium, or as the re- 

 sult of a direct action between the electrified bodies at a distance. If we 

 adopt the latter conception, we may determine the law of the action, but 

 we can go no further in speaking on its cause. If, on the other hand, 

 we adopt the conception of action through a medium, we are led to in- 

 quire into the nature of that action in each part of the medium. . . . 



If we now proceed to investigate the mechanical state of the medium 



