1869.] 



by Magnetism and Heat. 



267 



coil by continuously heating the iron wire. In several experiments, by 

 employing twelve similar Grove's elements as a double series of six intensity, 

 an iron wire 1*56 millim. diameter was made bright red-hot ; and by keeping 

 the current continuous until the galvanometer-needles settled nearly at zero, 

 and then suddenly disconnecting the battery, the needles remained nearly 

 stationary during several seconds, and then went rapidly to about 10 : this 

 slow decline of the current during the first few seconds of cooling was 

 probably connected with the "momentary molecular change of iron wire" 

 during cooling which I have described in the preceding paper. The 

 irregularity of movement of the needles did not occur unless the wire 

 was bright red-hot, a condition which was also necessary for obtaining the 

 molecular change. 



The direction of the current induced by heating the iron wire was found 

 by experiment to be the same as that which was produced by removing 

 the magnet from the coil ; therefore the heat acted simply by diminishing 

 the magnetism, and the results were in accordance with, and afford a 

 further confirmation of, the general law, that wherever there is increasing 

 or decreasing magnetism, there is a tendency to an electric current in a 

 conductor at right angles to it. 



