596 WINTER'S ELECTRICAL MACHINE. 



the rubbers are to be put in the frame, one is placed on each side 

 of the plate, the two springs are pressed together, one with each hand 

 at the same time, so as not to break the plate by onesided pressure, 

 and in this manner they are pushed into their places. The felt of 

 the rubbers must be covered with a thin uniform layer of amalgam, 

 which is reduced to powder in a porcelain mortar (one of metal 

 would be spoiled), or between two small boards, and rubbed into 

 the felt with the finger. When the machine has been in use for a 

 considerable time, the amalgam should be renewed, the old layer 

 being previously scraped off with a knife. For the various experi- 

 ments on electrical distribution previously described the conductor 

 of this machine may obviously be used; for this purpose it is 

 cautiously raised from the support, and the small brass ball as well 

 as the collecting apparatus removed by turning the latter gently 

 from right to left. The collecting apparatus when put on again 

 afterwards must be carefully adjusted so as not to slant ; the plane 

 of each ring must be parallel to the glass plate. 



For the experiments just alluded to it is better to support the 

 conductor on a separate pillar of glass, provided with a foot. If 

 this cannot be done, the conductor may be used on the machine, 

 but must be turned round so that the horizontal opening which 

 passes through it may be parallel to the axis of the plate, and 

 not directed to the glass plate as it is usually. Lest the plate, by 

 being accidentally turned, should become electrified, and then by 

 its own state disturb the intended experiments with the conductor, 

 it is better to remove the rubbers at least an hour before the ex- 

 periments, so that the plate may resume completely its neutral 

 state. 



In using the machine all parts made of glass must insulate well, 

 they must therefore be quite dry. When the machine is brought in 

 the winter from a cold into a warm room, water is deposited upon 

 it, and this must be completely evaporated before the machine 

 can be used. The handle should never be turned wtile the plate 

 is still moist, or water will be forced into the rubbers, from which 

 it cannot be got rid of for a long time. To dry the machine it may 

 be placed at some distance from an open fire, but it should be 

 removed again for use. There is no particular advantage in having 

 the air which surrounds the machine very warm ; the action is best 

 when the machine is slightly warmer than the air, because in that 

 case there is the least tendency for moisture to be condensed upon 

 it. The action is also very good in a cold dry room, provided that care 

 be taken not to breathe upon the machine. The experiments with 

 the machine, and all oiher electrical experiments, generally succeed 



