2(i8 Mr. W. Sturgeon's Eluctro-ma^netieal Experiments. 



magnetic influence; thus vibrating, still describing a smaller 

 arc, anil approximating nearer the magnet. 



When it had become so feeble that the greatest distance 

 did not exceed 30°, I applied the lamp at the other extre- 

 mity. It was soon propelled to above 400° : and by keeping 

 the extremity of the wires warm (it is well known that zinc 

 would soon melt in a strong flame) I could keep it vibrating 

 at about right angles to the pole of the magnet ; lor when it 

 went further than 90°, the thermo arm became acted on by 

 the magnetic influence, and conspiring with the reaction of 

 the convoluted silk, the machine was frequently driven back 

 again 40° or 50°; but by keeping it moderately warm it was 

 kept at between 80° and 90° from the magnet. 



I now again changed the pole of the magnet, and took away 

 the htmp. The chemico action had now become so feeble as 

 to be just discernible. However, by applying the lamp it soon 

 acquired between 60° and 70°, and could be kept up to nearly 

 the lower point 



I have repeated the experiment, with the same success, in 

 about 6^ minutes each time. The copper wire was about 

 1-tiOth of an inch in diameter; and the zinc about twice that 

 thickness. 



When the lamp is applied before the chemico action gets 

 too weak, this thermo-chemical magnetic experiment, in minia- 

 ture, is most strikingly decisive. Not having it in my power 

 at present to carry on the experiment on a large scale, I am 

 not prepared to say how it might answer. 



All the phaenomena yet exhibited by the differently excited 

 wires, seeming to be so perfectly analogous in every other re- 

 spect than in the direction of their forces, I have, by parity 

 of reasoning, found no difficulty in producing a thermo rota- 

 tion by the influence of a central magnet. 



As this experiment seems to have baffled the exertions of 

 some of your scientific correspondents, it may perhaps be 

 considered of some importance in promoting the advancement 

 of the scieuce. 



I am yours, &c. 



Artillery Plnee, Woolwich, Wll. Sl'UKUKON. 



Feb. 1«, 1824. 



XLV. De- 



