Communication in the Phil. Mag. for December 1836. 59 



has magnetized a closed circuit knows that this is not the case. 

 The following experiment will set this point at rest : take a 

 bar of steel, A B, and bend 



another of the same size and ' ' > i > 



length into a square. Mag- ^ 

 netize the straight bar by draw- 

 ing it lengthwise over one of 

 the poles of a magnet ; move 

 the same pole the same num- 

 ber of times round the square ; , 



break the bar into four equal parts and the square at the corners, 

 and the bar C D will be stronger than either portion of the 

 straight bar. I formerly stated, and again repeat the affirma- 

 tion, that if Mr. Rainey's explanation be admitted, it v;ill 

 completely overthrow the Newtonian law c^f the perfect equa- 

 lity of action and reaction. '* I had always considered," con- 

 tinues Mr. Rainey, " that law as applicable only to mechanical 

 forces, and not extending in the least to those physical phasno- 

 mena, the acting cause of which is altogether unknown. 

 Suppose a number of pieces of steel, properly tempered, and 

 for convenience made into the form of the common horseshoe 

 magnet, and one of them magnetized to saturation ; now, by this 

 one let all the others be magnetized, and afterwards let them 

 be put together, and the process of magnetizing be performed 

 repeatedly upon each of the rest, and it will be found that each 

 magnet possesses nearly, if not quite as much magnetism as the 

 one employed in the first instance, that is, as the prime motor 

 itself. This fact can scarcely be doubted, although it is at va- 

 riance with the Newtonian law of the perfect equality of action 

 and reaction as applied to mechanical forces, as no force can 

 be supposed capable of generating, under the same circum- 

 stances, a force greater than itself" It is but too obvious from 

 this quotation that Mr. Rainey has not read the Principia 

 with any degree of attention, as he has entirely mistaken the 

 meaning of the law in question. The acting cause of universal 

 attraction is as much unknown as that of any other physical 

 phaenomena, yet the law holds as much in this case as in the 

 case of a man pulling a boat against a stream. The second part 

 of the preceding paragraph is exceedingly unfortunate as an il- 

 lustration of a fact at variance with the Newtonian law. No- 

 thing could be more conclusive in its favour. The following 

 illustration would be equally applicable : suppose a number of 

 pieces of wood placed at the mouth of a river, and suppose 

 they are of such a size, that a man, after fixing a rope to one of 

 them, is just able to pull it a mile against the stream and fix it 

 to a tree growing by the side of the river ; and suppose that he 



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