and Electro-magnetism. 



19 



number of times round the iron ring, on a space equal to the 

 distance between those lifters; then continuing its course round 

 the second iron, it was again brought round the ring to the 

 third lifter, and so on ; the turns of the helix round this ring 

 were of course all in one direction. I took the whole apparatus 

 asunder at this time, with a view of making another alteration 

 (that occurred to me) when my attention should be direct- 

 ed, at a leisure hour, to another branch of the same sub- 

 ject ; and from that day have not put the machine together, 

 or tried any further experiments that way. There is a cir- 

 cumstance connected with electro-magnetism, or I should say, 

 in the making of temporary magnets by means of electri- 

 city, which has been overlooked as yet, but which is beautifully 

 explained by this momentary action which has been disco- 

 vered by Mr. Faraday: I mean, in the case when a weight is 

 suspended to one of these magnets, and the current of electri- 

 city suddenly reversed, the poles of the magnet are changed, 

 yet the weight will not fall off ; this fact is well known : but 

 what follows, I believe, is not, — That at that moment, and but 

 for a moment, it will lift a considerably greater weight than 

 what it could keep suspended with- 

 out this reversal of the poles, and ** 

 which is caused by the momentary l| 



reaction and action of the magnet ^ X 



and wires. The magnet I made, 

 which was but small, would lift a 

 weight for a moment from the di- 

 stance of half an inch, which it would 

 not keep suspended if there was a 

 bit of wood \ of an inch thick be- 

 tween it and the weight. 



In the sketch given of the wheel 

 in my former paper there was an 

 error ; as the board on which the 

 lifters was fastened, was parallel to 

 the wheel, and the magnets were 

 made fast in the wheel as here shown, in a direction perpen- 

 dicular to that board. 



Dublin, March 13, 1833. 



fl 



■■in I 



In the hurry of writing the above letter, I fear I have not suf- 

 ficiently explained the nature of the last experiment described 

 in it. As it is difficult to perform the experiment satisfactorily 

 when the magnet and weights are in contact (although it is 

 shown by the weight not falling off when the poles are revers- 

 ed, when yet the weight is actually separated and falls a small 



D2 



