212 



HOLTZ ELECTRIC MACHINE. 



maintained by friction with the rubber. When the dis~ 

 charging rod and ball are brought near the prime con- 

 ductor, as shown in the figure, a rapid succession of sparks 

 is produced, owing to the recombination of the separated 

 electricities. If another body is to be charged from the 

 prime conductor, the ball and rod may be turned aside. 

 The power of this machine is greater than that of the plate 

 or cylinder ma- 

 chine; it is less 

 affected by at- 

 mospheric moist- 

 ure, and is more 

 compact. 



349. The 



Holtz Electric 

 Machine. T h i s 



instrument is repre- 

 sented in Fig. 148. 



It contains two thin circular plates of glass, the larger of which is 

 held fast by two fixed pillars. The smaller plate revolves rapidly 

 very near it. There are two holes in the fixed plate near the 

 extremities of its horizontal diameter. To the sides of these open- 

 ings are fastened paper bands called armatures. Opposite these 

 armatures, and separated from them by the revolving plate, are 

 two metallic combs, connected respectively with the two knobs 

 shown in the front of the picture. One of these knobs is carried 

 by a sliding rod so that their distance apart is easily adjusted. In 

 using the machine, the knobs are placed in contact, one of the 

 armatures is electrified by holding against it an electrified sheet of 

 vulcanite, the handle is turned for a few seconds, and the knobs 

 gradually separated. A series of electric discharges between the 

 two knobs takes place. When this machine works well, it gives 

 results superior to either of those previously mentioned. It is, 

 however, peculiarly subject to atmospheric conditions, and is gen- 

 erally considered extremely capricious. 



. When used, any electrical machine should be free from 

 dust and perfectly dry. It should be warmer than the atmosphere 



