M. W. Holtz on a new Electrical Machine. 433 



their action*. At the same time I am engaged on the con- 

 struction of complex machines, which consist of a small machine 

 of the above construction, and a larger apparatus, whose coat- 

 ings are not kept in electrical tension by its own action, but by 

 that of the electrical machine. 



Figc 5, Plate V. shows such a one, as especially fitted for high 

 tension, and as constructed some time ago, with disks of 30 inches 

 diameter. The coating marked + must be supposed to be con- 

 stantly electrified, the conductor e, opposite to it, in contact 

 with the earth, and the conductor / with a larger conductor. 

 Although the insulation of this apparatus was extremely imper- 

 fect, I could obtain a striking-distance of 9 inches. For greater 

 quantity, instead of one, a larger number of elements had to be 

 used. In order to have as many as possible, I was at last obliged 

 to try to avoid the notches by alternately electrifying the coat- 

 ings negatively and positively. The liberation of electricity in 

 this case was effected by the tension of the coatingsf . 



1 have, however, already remarked that, by multiplying the 

 elements on a disk, the quantity is always increased only at the 

 expense of the striking-distance. If this is to be retained, the 

 disks must be increased in number, but removed so far that they 

 do not mutually disturb one another ; and this is more diffi- 

 cult of attainment with a high degree of tension than with a 

 low one. 



In any case it is to be remembered that the velocity of rota- 

 tion which can be attained with such a machine is materially 

 diminished by the increase of its dimensions, and that there- 

 fore the quantitative effect cannot be increased in the same de- 

 gree as the tension. 



* I have entrusted their construction to M. W. Schulz, mechanician, 

 Berlin. A machine like the above, but with better insulation, and more 

 convenient arrangement for experimenting, will cost about 25 to 30 thalers. 

 A larger table with wheel and treadle would increase the price about 15 to 

 20 thalers. 



t Last summer I had the opportunity of showing to Dr. Paalzow the 

 action of an apparatus which depended on the application of this principle. 

 Both disks were coated on their outside with tinfoil, and this coating was 

 divided by insulating spaces into a greater or smaller number of sectors 

 alternately joined with each other. Those of the fixed disk were positively 

 and negatively electrified by an ordinary electrical machine. To two suc- 

 ceeding ones conductors were opposite, which touched the rotating disk 

 with fine wires. If these were in connexion, and the disk rotated, all the 

 sectors when they passed those of the solid ones were discharged and again 

 charged. I have subsequently placed sixty such elements, in which the 

 coatings of the fixed disk were replaced by wires enclosed in glass, on a 

 smaller apparatus, and thus rendered it possible to electrify the disk, which 

 rotates twenty times in a second, 800 times. It is a defect in this and 

 other apparatus, that by their means only a comparatively small striking- 

 distance can be attained. 



