124 ELEMENTS OF STATIC ELECTRICITY. 



He then says : 



" Topler has recently rejected his system and adopted mine, 

 because it is simpler, and, at the same time, more effective. The 

 application of the pointed combs and the non-covered movable 

 discs is also my invention, since the Topler machine had only the 

 tin-foil coverings and sliding springs. (Schleifende Federn.) 



11 1 had been accustomed to the same, indeed, already ; although 

 not with independent acting, influence machines, but rejected 

 them on account of the smaller spark-length. 



" Topler has also lately adopted my principle of the pointed 

 combs, and the non-covered discs ; but so far modified, that besides 

 the pointed combs and non-covered discs, he yet allows to act, at 

 the same time, small pieces of tin-foil (or pieces of metal), and the 

 sliding springs. This has the advantage that the machine excites 

 itself, and is less sensitive to moisture ; but also the great disad- 

 vantage, that the sparks become shorter, and a constant reversal 

 of current follows. Besides, a certain mechanic, Voss, also claims 

 this machine, so modified, as his merit ; but unquestionably Topler 

 was the first who showed that influence machines, with metallic 

 covering and sliding springs, excite themselves. 



" The entire form of the machine, its symmetrical construction, 

 the one-sided support of the axis, the application of a sheath 

 running upon a pin fastened on one side, the application of the 

 so-called rotary diametrical (double) pointed combs, the applica- 

 tion of the so-called condensers (small Leyden jars) for increase of 

 spark-length, is all mine, as published in the year 1869, by Professor 

 Poggendorff (PoggendorfFs Annalen, vol. 136, page 171). 



" Yours truly, DR. W. IIOLTZ." 



The " sliding springs " mentioned above, doubtless 

 refers to a style of construction in which the springs 

 glide continuously over the surface of the glass ; essen- 

 tially different, and differing in its effect, from that of 

 the brushes, which touch only the raised centers of the 

 carriers, and are wholly insulated from the glass; 

 giving alternate contact and insulation, making induc- 

 tion much more effective. The latter construction is 

 attributed to Voss. 



