170 THE INTELLECTUAL RISE IN ELECTRICITY. 



stones are the most costly. A mode of testing the lode- 

 stone is now for the first time announced. The best 

 magnet, we are told, is that which will attract the 

 greatest weight of iron, and draw it most strongly. In 

 other words, Peregrinus considers not only the lifting 

 power of the stone, but the magnetic strength, and appar- 

 ently recognizes the difference between these effects. It 

 is difficult to believe that a thirteenth century mind is 

 evolving these concepts. Not until three hundred years 

 later did Baptista Porta and Cardan and other philos- 

 ophers of the time begin to measure the attractive force 

 by causing the magnet to draw iron suspended on a scale 

 arm. 



All of the foregoing is prefatory to his announcement 

 of greater discoveries. The ancient notions, as we have 

 seen, were that the Pole star governed the magnet; then, 

 that the Pole star influenced the magnetic mountains, 

 which, in turn, governed the magnet; then, that the mag- 

 net was controlled, not by the Pole star, but by all parts 

 of the celestial sphere, and, by their resultant action, the 

 needle was brought to the north and south position. 

 Peregrinus takes the next step forward, and reveals the 

 poles in the lodestone itself. There are two points in the 

 heavens, he says, of greater note than the rest, "because 

 the celestial sphere revolves about them as if it were on 

 pivots, one of which is called the Arctic or north pole, 

 and the other, the Antarctic or south pole." So in the 

 stone which he looks upon as an image of the celestial 

 sphere, u you must understand there are two points, the 

 one north and the other south." 



Bacon knew that different parts of the same magnet 

 would affect iron (as he supposed) differently, one attract- 

 ing, the other repelling; but he had no notion that these 

 parts had any definite position. Peregrinus not only tells 

 us that they have precise places as precise as the poles 

 around which the celestial sphere apparently revolves 

 but now proceeds to explain how they may be found. 



