354 EXPERIMENTAL INVESTIGATIONS. 



the practical difficulties, though undoubtedly not small, being, 

 in his opinion, by no means insurmountable. 



Electrical Mag.) p. 601. Jan. 1845. 



Mr. Grove communicated to the proprietors of the London 

 Institution, at this their first soiree for the season, some of the 

 leading discoveries in physical science during the past year. 



Of electrical subjects, M. Matteucci's researches were de- 

 scribed, with experimental illustrations ; as also the magnetic 

 note. In reference to the latter Mr. Grove detailed a curious 

 experiment that had occurred to him, and which bore greatly 

 on the subject. A glass tube, with plate glass at the ends, and 

 protected along its length with a copper jacket, was filled with 

 water, in which was suspended powdered magnetic oxide of 

 iron. On looking through the tube at distant objects a con- 

 siderable portion of the light was intercepted by the hetero- 

 geneous arrangement of the particles of the oxide ; but, on 

 passing a current through a coil placed round the tube, these 

 particles assumed a symmetrical character, and much more 

 light was transmitted. This experiment was alluded to as an 

 illustration of the molecular polarisation and vibration that is 

 attributed to the particles of an iron rod, when a musical note 

 is obtained under the influence of the current. 



[This result was the small outcome of a series of experi- 

 ments which ought to have led me to the discovery afterwards 

 made by Faraday. At the time I made the above experiment I 

 tried a tube having a coil of coated wire round it, and a Nichol's 

 prism at each end. The tube was filled successively with 

 various solutions, and I hoped to divert the plane of polarisa- 

 tion by passing a voltaic current through the coil. I failed 

 only because my coil was a single one, and not several times 

 reduplicated, as it should have been. I mentioned the experi- 

 ment at the time, to Mr. Gassiot, Faraday, and Pereira, and the 

 latter communicated it to the Managers of the London Insti- 

 tution. I subsequently observed that a plate of mica in vacuo 

 placed itself transversely to the line joining the poles of a 

 powerful electro-magnet, and was engaged on this when 

 Faraday published his paper on the magnetisation of all 

 matter, which included and explained the single case I was 

 working at.] W.R.G., 1874. 



