350 Dr. L. Bleekrode on Electromachines 



of electricity that remained on the disks was sufficient to pro- 

 duce energetic sparks after a few revolutions of the disk. Neu- 

 tralizing was in most cases effected when the horizontal con- 

 ductors were brought into close contact and the disk was 

 caused to rotate in the opposite direction to the former. 



II. The Double Electromacliine ivith ebonite disks. 



The double electromachine consists of a combination of one 

 fixed disk, on each side of which a somewhat smaller disk can 

 rotate *. As the construction I have adopted is new, it may- 

 be useful to elucidate the description by a sketch in a hori- 

 zontal projection (PI. III. fig. 1). 



Description of the apparatus. — On a wooden frame are fixed 

 two pillars of ebonite, a and b. They bear two sets of hori- 

 zontal conductors, c, d, and c J , d' ; the latter are provided 

 with electrodes, e and /, which can be put at different distances 

 from another ; g and </ are vertical metallic rods, which, when 

 in contact with e and /, serve to convey the two electricities to 

 other apparatus. M is a wooden column, which holds the 

 horizontal axis A, a fixed steel rod on which an ebonite cylinder 

 is caused to rotate by means of a band and wheel, N. This 

 cylinder carries the two movable disks of ebonite, p and q, 

 pressed together by small plates n and n 1 and the screw z ; be- 

 tween them stands fixed on the board the disk k, which is retained 

 in its position by screws Z, l', and t (fig. 2). A large aperture 

 in its centre permits the axis A to rotate without communi- 

 cating its motion to it. Finally, in h h and h' h' the two diame- 

 tral or inclined conductors are shown, which can be moved to and 

 fro if necessary. One (h h) is fixed on an ebonite ring, the other 

 on the axis; r r and / r are two sets of paper armatures; fig. 2 

 shows their arrangement, near the apertures o and o', on the 

 fixed disk. All the parts are so adjusted that they may be 

 easily removed ; therefore the conductors c and c', d and d! 

 are separately screwed to the columns a and b ; and when the 

 screw z is loosened the disks can be taken away from the 

 axis. 



Exciting the machine. — This is effected in the same way as 

 in the former apparatus, and as quickly. A peculiar method 

 for bringing it into an active condition consists in causing the 

 disks to rotate rapidly, rubbing one of them at the same time 

 with the hand. It then becomes electric by friction ; this is 

 sufficient to produce a stream of sparks between the electrodes, 

 and then the hand need no longer be applied. 



* The first double electromacliine was constructed by Dr. P. Kaiser, 

 and described in Les Mondes, 1869. Another construction, also very 

 powerful, was published by Prof. PoggendorfTin bis Annalen, 1871. 



