Electro-Magnetic Experiments. 329 



Art. XI. — Electro-Magnetic Experiments; by Dr. G. Moll, 

 F. R. S. E. M. A. S. Professor of Natural Philosophy in the 

 University of Utrecht. 



(Communicated by the Author for Dr. Brewster's Edinburgh Journal of Science.) 



In the Transactions of the Society for the Encouragement of Arts, 

 Manufactures and Commerce, Mr. Sturgeon of Woolwich, has given 

 a description of an elegant and curious apparatus, with which many 

 striking electro-magnetic experiments may be performed. Among 

 these, is a soft iron wire, bent in the form of a horse-shoe, wound 

 round with copper wire. The ends of this copper wire, being made 

 to communicate with the opposite poles of a galvanic apparatus, the 

 iron becomes a strong horse-shoe magnet, capable of supporting a 

 heavy bar of iron. On lifting the connecting wire out of the cups, 

 the force is immediately destroyed, and again restored on plunging 

 the connecting wire of the battery again in the cups. 



This apparatus I saw in 1 828, at Mr. Watkins', curator of philo- 

 sophical apparatus to the London University ; and the horse-shoe, 

 with which he performed the experiment, became capable all at once 

 of supporting about nine pounds. 



I immediately determined to try the effect of a larger galvanic ap- 

 paratus on a bent iron cylindrical wire, and I obtained results which 

 appear astonishing, and are, as far as the intensity of magnetic force 

 is concerned, altogether new. I have anxiously looked since that 

 time, into different scientific continental and English journals, without 

 finding any further attempt to extend and improve Mr. Sturgeon's 

 original experiment. 



I procured from Mr. "Watkins a soft iron wire, bent in the shape 

 of a horse-shoe. The length of the horse-shoe was about eight and 

 a half inches, and one inch in diameter. A copper spiral wire was 

 twisted round this iron from right to left (sinislrorsum.) The diam- 

 eter of this wire was about one-eighth of an inch, and it v\'as twisted 

 or coiled eighty-three times round the iron. The ends of this wire 

 were made to plunge in cups filled with mercury, in which the con- 

 necting wires of the zinc and copper poles of a galvanic apparatus 

 were likewise immersed. 



