between the Permatieiit and the Electro-Magnet. 83 



iron in the peculiar manner which constitutes magnetism, can- 

 not decompose and arrange the electricity belonging to the 

 lifter without suffering a corresponding diminution, and the 

 more difficult the arrangement in the lifter so much greater 

 will be the diminution of power in the electro-magnet. Again, 

 if the electricity in the electro-magnet be easily arranged by 

 the induction of the voltaic helix, it will be easily forced back 

 to its natural state by the reaction of that belonging to the 

 lifter. Hence it follows that when the induciiig power of the 

 electro-magnet is very great (which it is when the lifter is in 

 contact with its ends) it will possess sufficient power to van- 

 quish the coercitive force of the lifter, arrange by induction a 

 large portion of the electricity of the lifter, and thus exhibit 

 powerful attraction. When the lifter is removed to a certain 

 distance, one tenth of an inch for example, the power of the 

 electro-magnet being much diminished in consequence of the 

 distance, whilst the difficulty of overcoming the coercitive 

 force of the lifter is increased, the efi^ect will be very small 

 compared with the former. For if the inducing power be 

 only equal to the coercitive force of the lifter, no attraction 

 whatever will take place; and hence the impossibility of mag- 

 netizing a large bar of steel tempered as hard as possible, by 

 means of a small permanent magnet with a soft temper. 



Now, if the coercitive force of the electro-magnet be in- 

 creased, which is done either by employing a long magnet, or 

 using hard iron or untempered steel, such a magnet will 

 suffer a less diminution by the reaction of the lifter in the case 

 of increased difficulty of arrangement in the lifter, than in 

 the case of the short electro-magnet of pei'fectly soft iron. 



In the case of the permanent magnet of tempered steel, the 

 electricity belonging to it was arranged with dijjlcidly, and 

 after repeated touches of another magnet, and consequently it 

 ■will easily vanquish the coercitive power of a piece of soft 

 iron, and induce a magnetic state upon it, whilst the peculiar 

 arrangement of its own electricity will remain nearly un- 

 changed. Hence its attractive powers will diminish nearly as 

 the squares of the distances of the soft iron from its poles, or 

 imaginary centres of accumulation, a law which cannot exist 

 in the case of the electro-magnet the electricity of which is so 

 easily put in motion round the elementary molecules of the 

 iron by the reaction of the lifter. 



In the explanation given by Mr. Rainey the lifter is sup- 

 posed to react powerfully on the electro-magnet so as to in- 

 crease its power, a supposition which cannot possibly be ad- 

 mitted. For the electro-magnet must, in the first place, give 

 the lifter all its magnetic power, consequently the power of 



K 2 



