399 



Grove's Nitric-Acid Battery. 



Each set of elements in the battery were inserted in a glass ves- 

 sel with a stem 6 inches long ; the stems were carefully cleaned and 

 dried. These precautions, with the high chemical affinity of the 

 elements, raised the tension of each terminal, as denoted by gold 

 leaf electroscopes, to nearly that of the larger series of the water- 

 battery. A succession of spark-discharges could be taken between 

 the copper discs of my micrometer-electrometer, one disc being 

 attached to the zinc, and the other to the platinum end of the 

 battery. 



In the following experiments, the different vacuum-tubes were 

 introduced between one of the copper discs and the battery, as also 

 a galvanometer. By this arrangement the circuit could be gradually 

 completed without any risk of disarranging the apparatus, and the 

 spark discharged obtained before the copper discs of the micro- 

 meter-electrometer came into contact. 



" In 146, on the completion of the current, the discharge of the 

 battery passed with a display of magnificent strata of most dazzling 

 brightness. On separating the discs by means of a micrometer 

 screw, the luminous discharges presented the same appearance as 

 when taken from an induction coil, but brighter. On the copper 

 plate in the vessel there was a white layer, and then a dark space 

 about one inch broad ; then a bluish atmosphere, curved like the 

 plate, evidently three negative envelopes on a great scale. When 

 the plate was positive, the effect was comparatively feeble." The 

 preceding is an extract from notes made by the Rev. Dr. T. R. Ro- 

 binson, when he first witnessed the experiments in my laboratory, 

 on the 5th of August, 1859. With the same vacuum I have 

 always obtained similar results. 



In 187 and 196 (fig. 1, with carbon-balls in the tubes) the discharge 

 of the nitric-acid battery elicits intense heat, and probably changes 

 the condition of the vacuum. On the 5th of August, 1859, "the 

 discharge in 187 presented a stream of light of intolerable brightness 

 [I again quote from Dr. Robinson's notes], in which, through the 

 plate of green glass, with which he observed the phenomena, strata 

 could be observed. This soon changed to a sphere of light on the 

 positive ball, which became red-hot, the negative being surrounded 

 by magnificent envelopes, whilst with the horseshoe magnet the 



VOL. X. 2 F 



