462 Dr. Faraday's Researches in Electricity. 



the magnetic force, let us now remark what occurs at the 

 moment of its cessation; for during its continuance there is 

 no change. If, then, after the magnetism has been sustained 

 for two or three seconds, the electric current be stopped, 

 there is instantly a strong action on the bar, which has the 

 appearance of a revulsion (for the bar returns upon the course 

 which it took for a moment when the electric contact was 

 made), but with such force, that whereas the advance might 

 be perhaps 15° or 20°, the revulsion will cause the bar occa- 

 sionally to move through two or three revolutions. 



2316. Heavy glass or bismuth presents no such pheno- 

 mena as this. 



2317. If) whilst the bar is revolving from revulsion the 

 electric current at the magnet be renewed, the bar instantly 

 stops with the former appearances and results (2310.), and 

 then upon removing the magnetic force is affected again, 

 and, of course, now in a contrary direction to the former re- 

 vulsion. 



2318. When the bar is caught by the magnetic force in the 

 axial or equatorial position, there is no revulsion. When in- 

 clined to these positions there is; and the places most power- 

 ful in this respect appear to be those most favourable to the 

 first brief advance (2313.). If the bar be in a position at 

 which strong revulsion would occur, and whilst the mag- 

 netism is continued be moved by hand into the equatorial or 

 axial position, then on taking off the magnetic force there is 

 no revulsion. 



2319. If the continuance of the electric current and conse- 

 quently of the magnetism be for a moment only, the revulsion 

 is very little, and the shorter the continuance of the magnetic 

 force the less is the revulsion. If the magnetic force be con- 

 tinued for two or three seconds and then interrupted and in- 

 stantly renewed, the bar is loosened and caught again by the 

 power before it sensibly changes its place; and now it may 

 be observed that it does not advance on the renewal of the 

 force as it would have done had it been acted on by a first con- 

 tact in that place (2310.) ; i. e. if the bar be in a certain place in- 

 clined to the axial position, the first supervention of the mag- 

 netic power causes it to advance towards the axial position; but 

 the bar being in the same place and the magnetic power sus- 

 pended and instantly renewed, the second supervention of force 

 does not move the bar as the first did. 



2320. When the copper bar is immersed in water, alcohol, 

 or even mercury, the same effects take place as in the air, but 

 the movements are, of course, not to the same extent. 



2321. When plates of copper or bismuth, an inch in thick- 



