172 THE INTELLECTUAL RISE IN ELECTRICITY. 



Here was still another advance. The idea that the 

 lodestone somehow influenced the space between itself 

 and the iron had been in existence from the time of 

 Lucretius. But this in its latest form implied simply that 

 the intervening air " consented " to the passage of the 

 magnetic virtue, and thus the lodestone became, as it 

 were, permitted to draw the iron. But Peregrinus goes 

 far beyond that or any other earlier theory of the magnetic 

 influence. He sees for the first time that the lodestone 

 not only attracts the iron over the intervening space be- 

 tween them, but compels the iron to take a definite position 

 in that space. In other words, he perceives that when his 

 little needles are placed at the poles of the stone they stand 

 erect, while elsewhere they stand more or less inclined. 

 That was the first definite recognition of the directive 

 action of the magnetic field of force: the first revelation of 

 the direction in which the strains and stresses therein are 

 exerted, shown by the turning of the little bits of iron in 

 response thereto, as an anchored boat swings to the tide, 

 or a weathercock to the wind. 



Having found the position of the poles, the next step 

 is to distinguish one from the other. "Take," says 

 Peregrinus, "a wooden vessel, round, like a dish or platter, 

 and put the stone in it so that the two points of the stone 

 may be equidistant from the edge; then put this in a larger 

 vessel containing water, so that the stone may float like a 

 sailor in a boat." There must be plenty of room in the 

 large vessel, so that the one containing the stone may not 

 meet the side and so have the free motion impeded. Then 

 "the stone so placed will turn in its little vessel until the 

 north pole of the stone will stand in the direction of the 

 north pole of the heavens, and the south pole in that of the 

 south pole of the heavens;" and if it be removed from 

 this position, it will return thereto u by the will of God." 

 "Since the north and south parts of the heavens are 

 known, so will they be known in the stone ; because each 

 part of the stone will turn itself to its corresponding part 



