ammed hj the method of reflection. Secondly, a needle already 

 deflected 30° or 40° has lost its delicacy in showing any minute 

 increase or diminution in the intensity of the current ; thirdly, 

 the greatest objection to this method is this very feeble induced 

 current that can be sent through the great resistance of the 

 battery m the circuit of the secondary wire ; finally, the manner 

 ot reading the galvanometer indications is entirely too gross. 



Faraday also (Exp. Kes. 3186) approximately showed that when 

 a magnet is quickly introduced into a wire loop or quickly 

 withdrawn from the same that the currents induced in the latter, 

 as measured by an ordinary galvanometer, are of the same in- 

 tensity; but a deflection on such an instrument cannot be read 

 closer than 15', while in my experiments I have shown with 

 more refined apparatus that magneto-electric waves can be evol- 

 ved not difiering more than 20" in the deflections which they 

 produce. 



Though ignorance of seioTur cxcusi'^ one no more than i'mo- 

 ranee of the law, yet T m.n rnniirL th;,r thi^ npiMn.tus was 

 devised and the results obt. 11 M. I Mh |m|, | ^ .,^ , ■ ..i, ',t Kuadav's 

 work in the same direction. ' ' " 



Those who would use th I- '. . - ,' i • •nrlcctric 



'rthe 



rises and falls with the saim 1„. de- 



vised of keeping tlie wire^ and th<' -aKannnu'tcr n<'cdloh at a 

 constant temperature while we altered that of the inducing 

 magnet a refined method would present itself for the determin- 

 ation ot the variation of the force of magnets with the tem- 

 perature. Probably the effect of the heat upon the wire circuit 

 could be tabulated and eliminated from the results of such ex- 

 periments, thus leaving a residual which will express the effect 

 ■ ™t^^''l^^^;e on the magnet. Or, a differential apparatus 

 might be devised, consisting of two magnets with two wire 

 circuit^s passmg through a diff"erential galvanometer. Having 

 brought the mduced currents of the two magnets to equal ac- 



temperature of one of the magnets, ascertain its efl'ect with 

 great precision ; and it could be expressed in the length of re- 

 ma "ets^^^^"^^^^ ^^^^^ *^ balance the disturbed equality of the 



