88 PHYSIOLOGY OF LIFE. 



a distance of only three inches. A similar experiment 

 had been made by Descartes. I concluded, therefore, 

 said Brugmans, that if the iron plates were interposed 

 between the magnet and the needle lengthways, instead 

 of breadthways or right across, the action of the magnet 

 on the magnetic needle would, in consequence of this 

 great increase of resistance, become still weaker, or per- 

 haps evanescent. But not less to my surprise than my 

 admiration, I found that the power of the magnet was so 

 far from being diminished by this change in the relative 

 position of the iron -plates ; that, on the contrary, it now 

 extended to a far greater distance than when no iron at 

 all was interposed. Some time after the same philosopher, 

 out of several iron bars, the sides of which were an inch 

 broad each, composed a single bar of the length of more 

 than ten feet, and observed the magnetism make its way 

 through the whole mass. But, in order to try whether 

 the action could be propagated to any length indefinitely, 

 after several experiments with bars of intermediate lengths, 

 in all of which he had succeeded, he tried a four-cornered 

 iron rod, more than twenty feet long, and it was at this 

 length that the magnetic power first began to be diminished. 

 So far Brugmans. 



But the shortest way for any one to convince himself 

 of this relation of the magnetic power would be, in one 

 and the same experiment, to interpose the same piece of iron 

 between the magnet and the compass needle first breadth 

 ways -, and in this case it will be found that the needle, 

 which had been previously deflected by the magnet from 

 its natural position at one of its poles, will instantly re- 

 sume the same, either wholly or very nearly so then to 



