ELECTRO-MAGNETISM. 



81 



ducfor round a magnet, are phenomena 

 also naturally resulting from the verti- 

 ginous circulation of the two fluids. 



(239.) The mutual attractions and re- 

 pulsions of parallel conductors, are at 

 once referred, as in the former case, to 

 the action of parallel magnets having 

 their poles in the same or in opposite 

 directions. If, for example, the electro- 

 magnetic current be moving in the same 

 direction in two parallel conducting 

 wires, the stream of austral magnetic 

 fluid belonging to one wire will be flow- 

 ing in the same direction as the boreal 

 magnetic fluid belonging to the other 

 wire, in that part which is adjacent to 

 it ; and, on the other hand, the direction 

 of the boreal fluid of the former will co- 

 incide with that of the austral fluid of 

 the latter wire, in the adjacent part. 

 According to the known laws of mag- 

 netic action, attraction must be the 

 result of such a state of things ; for the 

 boreal and austral fluids attract one an- 

 other. If W and w, Jig. 152, represent 

 sections of the conducting wires in both 

 of which the current of positive elec- 

 tricity is descending, the arrows in the 

 circumference of the outer dotted circles 

 Fig. 152. 



A A, will point out the directions in 

 which the austral magnetic fluids cir- 

 culate on the surface of the wires ; and 

 those on the inner circles B B, the di- 

 rections in which the boreal fluids cir- 

 culate, and it will be seen that in the 

 parts p and q, when they are nearest to 

 each other, the austral fluid in the one 

 is moving in the same direction as the 

 boreal fluid in the other, and we may, 

 therefore, expect that they will attract 

 each other. 



(260.) If the electric currents be 



moving in contrary directions in the 



two wires, as represented in a similar 



manner \nfig. 153, opposite effects will 



Fig. 153. 



result ; for in that case both the streams 

 of austral fluid are moving in the same 

 direction in the adjacent parts of the 

 wires, and must consequently repel one 

 another ; and the same thing happens 

 with regard to the streams of boreal 

 fluid, which flow in the contrary direc- 

 tion to those of the austral fluid. 



(261.) Such, then, is the hypothesis 

 that has been, after proper emendations, 

 made to correspond with the pheno- 

 mena, and which may be assumed as a 

 correct representation of them. It must, 

 at the same time, be admitted to be an 

 exceedingly strained and artificial hy- 

 pothesis, at variance with the analogy 

 of all other physical forces, and repug- 

 nant to our ideas of that simplicity 

 which seems to pervade all the opera- 

 tions of the material world. All other 

 known accelerating forces, emanating 

 from a certain point, and exerted upon 

 another point, act in the direction of the 

 line joining these two points. Such is 

 the case with the electric and with the 

 magnetic actions, in all the cases that 

 belong exclusively to the one or the 

 other of these two classes of phenomena. 

 When two conducting wires, bent into 

 helices, act upon one another, which 

 they do in a manner that imitates 

 very exactly the mutual action of two 

 magnets, the action is purely electri- 

 cal, and is exerted in the lines of di- 

 rection that join the acting points. 

 The same is the case with two magnets, 

 when magnetism alone is concerned. 

 But when a helix and a magnet act 

 upon one another, and present the very 

 same phenomena as in either of the pre- 

 ceding cases, the theory assigns a tan- 

 gential direction to the forces then called 

 into operation. That a mode of action 

 which is simple and intelligible in the 

 case of actions either purely electric or 

 purely magnetic, should be so suddenly 

 and so completely changed when the 

 electric and magnetic fluids act mutu- 

 ally upon one another, would be a 

 strange and scarcely conceivable ano- 

 maly in physical science. 



(262.) We may avoid all these diffi- 

 culties by adopting the theory of electro- 

 magnetism devised by the genius of 

 Ampere, and ably supported by his 

 mathematical, in conjunction with his 

 experimental researches. Of this theory 

 we shall proceed to give an account. 



2. Electro-Dynamic Theory of 

 Ampere, 



(263.) The phenomena relating to the 

 G 



