Additmial Notes, 45$ 



a magnetic bar, and constipated in the other, and on this de* 

 peiids ibe exertion of its force. In other words, the con- 

 densation and motion of the magnetic fluid are subject to the 

 same laws, f mutatis yiiutandisj in the opinion of this phl- 

 lospher, as the electric fluid on the Franklinian theory, the 

 motion and sensible signs of which depend on the plus and 

 jiu'iius srates, or the deficiency and redundancy of the same 

 fluid in difl-erent bodies. 



Mag7ictical Theory of M. Prevost. 



Mr. Prevost, of Geneva, in a Dissertation on the Ori- 

 gin of jMsgr\etic Forces, expresses a belief that there are two 

 magnctk jluids, which, by their union, compose a third, 

 which he calls combined fluid. These two fluids, he thinks, 

 are both elastic like air; the particles of each attract each 

 od:ier, but those of the other kind most strongly. A strong 

 elective attraction of the combined fluid for iron decomposes 

 part of the fluid in the iron, and each of its ingredients oc- 

 cupies opposite ends of the bar. These bars then approach or 

 recede, according as the near ends contain a difl-erent or the 

 same ingredient. — See Essai sur VOrigine dcs Forces Mag^ 

 iietiques. 1788. 



Chemical Theory of Magnetism, 



Among other attempts to extend the bounds of Chemistry, 

 it has been lately proposed to place the magnetic fluid in the 

 list of its subjects. Accordingly, several writers have con- 

 sidered this fluid as a chemical agent, and explained its phe- 

 nomena on corresponding principles. Among these. Dr. 

 Darwin, in the Additional Notes to his T^empLe of Nature, 

 proposes the following hypothesis. 



1. Magnetism coincides with electricity in so many im- 

 portant points, that the existence of two magnetic ethers, as 

 well as of two electric ones, becomes highly probable, 



2. In a common bar of iron or steel, the two magnetic 

 ethers (which, for the greater ease of speaking, may be 

 called arctic ether and antarctic ethe)), exist intermixed, or 

 in their yieutral state: in this state, like the two clectiic fluids, 

 they are not cognizable by the senses. 



3. When these two magnetic ethers arc separated from 



