M. Quetelet's Memoir of Prof. Moll. 295 



an electric current exercises on the magnetic needle, opened 

 a new field, upon which the philosophers of all natiotis eagerly 

 entered, and which soon, thanks to their united efforts, was 

 as much cultivated and as productive as anj' other part of the 

 vast domain of natural philosophy. Our colleague was not 

 one of the last to put his hand to the work, and he communi- 

 cated in the Journal de Physique * the different results at 

 which he had arrived by repeating and extending the experi- 

 ments of the Danish physicist. He endeavoured to show that 

 there is a difference of action in chemical and magnetic phse- 

 nomena, according as the electricity is developed by simple 

 contact, or by the appai-atus of Wollaston. He was occupied 

 for several years in these researches. 



The English experimentalist Sturgeon had made known, 

 in 1826, that a bar of soft iron bent into the form of a horse- 

 shoe and covered with a spiral wire of copper, becomes a 

 powerful magnet as soon as the extremities of the wire are 

 placed in contact with the poles of a galvanic pile, and that 

 it instantaneously loses its power as soon as the contact ceases. 

 In an experiment made in England, and at which M. Moll 

 was present, one of these temporary magnets bore nine 

 pound weight. Our colleague resolved to make the experi- 

 ment on a larger scale. For this purpose he used a plate of 

 zinc of a surface of eleven square feet, dipping into a nar- 

 row copper vessel, and he put the poles of this element of 

 a galvanic pile in connexion with the ends of a copper wire 

 rolled 83 times around a soft iron bent into the form of a 

 horse-shoe and weighing five pound. As soon as the con- 

 tact was established the iron was able to bear 50 pound, 

 and it was even possible to carry the charge to 76 pound. 



Not content with these first results, M. Moll had an iron 

 constructed of 29 pound weight ; and with the same galvanic 

 element which he had used at first he made it bear 295. 



1 repeated these different experiments with M. Lipkens, 

 inspector-general of ordnance ; the results to which we came 

 have been recorded, together with an extract from M. Moll's 

 work, in volume vi. of the Correspondance Mathematique, 

 p. 327. We were at the same time led to investigate the 

 most advantageous proportions which it is proper to "■ive 

 to the horse-shoe and to the voltaic element in order to pro- 

 duce the maximum of effectf. Expressing his desire to see 



» By M. Dc Blainville, v. xcii. p. 295, 309 and 311. 



t Correspondance Malk., vol. vii. p. 54, and following. This is perhaps 

 the place to complain of an error in an Italian Journal, made to the 

 prejudice of our colleague. In page 6.'J and following of vol. iii. of the 

 Annali delle Hcicnze of Fadua, we read an article directed against the 



