NATURAL PHILOSOPHY. 117 



merit suggested, it was believed, by Sir John Hcrschcl, and performed by 

 Professor Daniell. The carbon terminals of a battery of forty cells of Grove 

 were brought within one eighth of an inch of each other, and the spark from 

 a Leyden jar was sent across this space. This spark bridged with carbon 

 particles the gap which had previously existed in the circuit, and the bril- 

 liant electric light due to the passage of the battery current was immediately 

 displayed. 



2. The magnified image of the coal points of an electric lamp was pro- 

 jected upon a white screen, and the distance to which they could be drawn 

 apart without interrupting the current was noted. A button of pure silver 

 was then introduced in place of the positive carbon, a luminous discharge 

 four or five times the length of the former being thus obtained. The silver 

 was first observed to glow, and afterwards to pass into a state of violent ebulli- 

 tion. A narrow dark space was observed to surround one of the poles, cor- 

 responding probably with the dark space observed in the discharge of Ruhm- 

 korff's coil through rarefied media. 



3. The action of a magnet upon the splendid stream of green light obtained 

 in the foregoing experiment was exhibited. A small horseshoe magnet of 

 Logemann was caused to approach the light, which was bent hither and 

 thither, according as the poles of the magnet changed their position: the 

 discharge in some cases formed a magnificent green bow, which on the fur- 

 ther approach of the magnet was torn asunder, and the passage of the cur- 

 rent thereby interrupted. It was Davy who first showed the action of a 

 magnet upon the voltaic arc. The transport of matter by the current was 

 further illustrated by a series of deposits on glass obtained by Mr. Gassiot 

 from the continued discharge of an induction coil.* 



4. A discharge from RtihmkorfT's .coil was sent through an attenuated 

 medium and the glow which surrounded the negative electrode was referred 

 to. One of the most remarkable effects hitherto observed was that of a 

 magnet upon this negative light. PI ticker had shown that it arranges itself 

 under the influence of the magnet exactly in the direction of the magnetic 

 curves. Iron-filings strewn in space, and withdrawn from the action of grav- 

 ity, would arrange themselves around a magnet exactly in the manner of 

 the negative light. An electric lamp was placed upon its back; a horseshoe 

 magnet was placed horizontally over its lens, and on the magnet a plate of 

 glass: a mirror inclined at an angle of 45 received the beam from the lamp, 

 and projected it upon the screen. Iron-filings were scattered on the glass, 

 and the magnetic curves thus illuminated were magnified, and brought to 

 clear definition upon the screen. The negative light above referred to arranges 

 itself, according to Pliicker, in a similar manner. 



5. The rotation of an electric current round the pole of a magnet, dis- 

 covered by Mr. Faraday in the Royal Institution, nearly forty years ago, was 

 next shown; and the rotation of a luminous current from an induction coil 

 in an exhausted receiver, by the same magnet, was also exhibited, and both 

 shown to obey the same laws. 



6. Into a circuit of twenty cells a large coil of copper wire was introduced, 

 and when the current was interrupted, a bright spark, due to the passage of 

 the extra current, was obtained. The brightness and loudness of the spark 

 were augmented when a core of soft iron was placed within the coil. The 

 disruption of the current took place between the poles of an electro-magnet; 

 and when the latter was excited, an extraordinary augmentation of thekv.irl- 

 HCSS of the spark was noticed. This effect was first obtained by Page, and 



