484 ELECTRICITY. 



applicable to all kinds of machines furnished with a glass 

 electric. 



' Moisture and dust, but particularly the former, be- 

 ing detrimental to the power of an electrical machine, 

 it becomes necessary to guard from both as much as 

 may be practicable ; hence, when not actually in use, 

 the electrical machine should be kept in a dry and clean 

 place, and at least the glass part of it should not be suf- 

 fered to remain dirty and soiled. If the machine has 

 been long neglected, the operator in order to render it 

 ready for use, must in the first place remove the rubber ; 

 he must then place the machine at a moderate distance 

 from the fire ; so as to render every part of it very dry, 

 but not too warm. This done, and the dust removed, 

 the glass part of the machine must be repeatedly rubbed 

 with a clean and warm handkerchief or towel ; the rub- 

 ber, likewise must be cleaned, removing all the old amal- 

 gam that may have adhered to it. The glass cylinder 

 or plate, in its rotation frequently contracts some dark 

 spots or concretions upon its surface, which tend to di- 

 minish its power. These spots which adhere pretty fast 

 to the glass, may be removed by applying a finger's nail 

 to each spot, or by rubbing them off with a piece of 

 coarse canvas. Previously to the replacing of the rub- 

 ber, the following operation generally contributes to in- 

 crease the excitation. It consists in touching the cylin- 

 der with the bottom of a tallow candle in streaks parallel 

 to the axis of the cylinder, then rub the cylinder again 

 with a dry and warm linen cloth; taking care that this 

 cloth be not very old, for in that case it is apt to leave 

 filaments about the glass, and about the rest of machine. 

 This done, the rubber is fixed in its place, and its sup- 

 port i.3 adjusted, so that the rubber may bear upon the 

 glass with a proper degree of pressure. Formerly the 

 amalgam, which greatly increases the power of excita- 

 tion, was spread upon the rubber, before the rubber was 

 put in its place ; but experience has shown, that it is 

 much better to fix the rubber clean in its place, and then 

 to apply the amalgam upon a piece of leather to the sur- 

 face of the cylinder while this is revolving in its usual 

 directions ; for by this means the revolution of the cylin- 



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