ON ELECTRO-DYNAMIC INDUCTION. 15 



at the ending as to magnetize it to saturation, the indication of the galvanometer 

 was the same in both cases. 



42. Also, similar results were obtained in comparing the shock and the de- 

 flection of the galvanometer. In one experiment, for exaoiple, the shock was 

 so feeble at making contact that it could scarcely be perceived in the fingers, 

 but so powerful at the breaking of the circuit as to be felt in the breast; yet the 

 galvanometer was deflected about thirty-five degrees to the right, at the begin- 

 ning of the current, and only an equal number of degrees to the left, at the 

 ending of the same. 



43. In another experiment, the apparatus being the same as before, the mag- 

 netizing spiral and the galvanometer were both at once introduced into the cir- 

 cuit of the helix. A sewing needle being placed in the spiral, and the contact 

 with the battery made, the needle showed no signs of magnetism, although the 

 galvanometer was deflected thirty degrees. The needle being replaced, and 

 the battery circuit broken, it was now found strongly magnetized, while the 

 galvanometer was only moved about as much as before in the opposite direc- 

 tion. 



44. Also, effects similar to those described in the last two paragraphs were 

 produced when the apparatus was so arranged as to cause the induction at the 

 beginning of the battery current to predominate. In this case the galvanome- 

 ter was still nearly equally affected at making and breaking battery contact, or 

 any difference which was observed could be referred to a variation in the power 

 of the battery during the experiment. 



45. Another fact of importance belonging to the same class has been men- 

 tioned before, (24,) namely, that the actions of the currents of the third, fourth, 

 and fifth orders produced a very small effect on the galvanometer, compared 

 with that of the secondary current ; and this is not alone on account of the di- 

 minishing power of the successive inductions, as will be evident from the fol- 

 lowing experiment. By raising the helix from the coil, in the arrangement of 

 apparatus for the secondary current, the shock was so diminished as to be in- 

 ferior to one produced by the arrangement for a tertiary current, yet, while 

 with the secondary current the needle- was deflected twenty-five degrees, with 

 the tertiary it scarcely moved more than one degree ; and with the currents of 

 the fourth and fifth orders the deflections were still less, resembling the effect 

 of a slight impulse given to the end of the needle. 



46. With the light obtained from the foregoing experiments, I was led to 



