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XL 1 1. On Electromachines with Disks of Ebonite. 

 By Dr. L. Bleekrode*. 



[Plate III.] 



THE name " electromachine " is in Germany specially ap- 

 plied to electrical machines in which no friction is used 

 to generate electricity, but in its place a small quantity is in- 

 troduced into the apparatus to act by induction on metallic points 

 fixed before rotating surfaces, and this action is reinforced by 

 the peculiar arrangement of the machine. This principle was 

 first employed by W. Holtz, at Berlin, in 1865, in the con- 

 struction which bears his name. 



The object of the present communication f is to place before 

 the reader the results of an investigation of this machine, 

 which has led to the substitution of ebonite plates for glass 

 ones J. I had recourse to this material because the atmospheric 

 moisture in Holland (as it may also, perhaps, in England) 

 seriously hinders the activity of the apparatus, and in many 

 cases causes it not to work at alL But not only did this change 

 of material prove very useful ; I also found the machine, con- 

 structed on my system, to possess some very remarkable pro- 

 perties, different from those observed when glass disks are used, 

 and worth being more generally known § . 



I. The Electromachine of the First Species with ebonite disks. 



Description of the apparatus* — The electrical machine of the 

 first species, as it is commonly called^ consists of one fixed disk, 

 before which another somewhat less in diameter rotates rapidly 

 at a very short distance and passes along a set of horizontal 

 points fixed on conductors. I may suppose the construction 

 to be sufficiently known, as it is the same that was employed 

 by Borchhardt of Berlin ; it presents the simplest form, and 

 has spread widely over the continent. I have augmented the 

 surface of the paper armatures by extending them almost over 

 two opposite quadrants of the fixed disk, to the horizontal aper- 

 tures ; and I found it advantageous to cover the adhering 

 paper points with tinfoil. 



Remarks on ebonite. — It has been already observed that 

 the peculiar character of my machine is the substitution of 

 ebonite for glass, so that it is wholly composed of that sub- 



* Communicated by the Author. 



t A more detailed description of the apparatus with illustrations and the 

 results obtained, is published in Poggendorff 's Annalen, No. 10, 1875. 



\ My first machine with ebonite disks dates from the year 1873. 



§ The machine here described (and probably also a double machine) 

 will be seen working in the Loan exhibition at South-Kensington Museum 

 in London, having been sent by the makers. 



