THE SOURCE OF MAGNETIC VIRTUE. 177 



merely to transpositions of the pieces of the divided stone, 

 it is not necessary to trace them minutely here. The 

 conclusion is that the unlike poles attract because natur- 

 ally they desire to unite and make one; whereas the like 

 poles, also because of their nature, have no such desire. 



Peregrinus next remarks that some unlearned people 

 have supposed that the virtue by which the magnet attracts 

 iron is already existing in the mineral veins in which the 

 magnet is found; "whence they say that the iron is moved 

 to the poles of the earth because of the mines of the stone 

 there existing." But, he declares, the mines of the stone 

 are found in various places in the earth, and hence the 

 needle influenced by them should stand irregularly in dif- 

 ferent positions; which is not the fact. Now, he concludes, 

 "wherever a man may be he may see with his eyes this 

 motion of the stone, according to the place of its meridian 

 circle. But all meridian circles meet at the poles: where- 

 fore from the poles of the world the poles of the magnet 

 receive their virttie. ' ' 



He evidently regards the poles of the earth, and those 

 of the heavens, as in the same axial line, and attributes no 

 especial directive faculty to those of the earth. For, he 

 adds that the needle does not point to the Pole star, which 

 varies in place, but to the heavenly poles, thus showing 

 that he knew, possibly by means of astronomical observa- 

 tions, that the common opinion of his contemporaries, that 

 the position of the Pole star coincided with that of the 

 pole of the heavens, was erroneous. 1 



The first part of Peregrinus' letter, which I have now 

 reviewed, ends with the description of his first form of 

 perpetual motion, and this, as I have already stated, is 

 apparently based on the Archimedean sphere. He intro- 

 duces it as a means of showing how all parts of the 



1 This opinion, however, was not universal in the Middle Ages, as is 

 shown by a celestial globe (Cufic- Arabic) in the National Museum at 

 Naples which dates from 1225, and in which the Pole star is indicated 

 5>^ distant from the pole. 

 12 



