ELECTRIC POWER. C Z\J 



' friction, if the action be continued, but is again extinguished 

 if allowed an interval of repose. Bin at length, after five 

 minutes alternate frictions, and intervals of repose, it becomes 

 permanently electric, however great the interval between the 

 friction. It may be conceived that this effect arises from the 

 glass being a bad conductor, and allowing the heat produced 

 by the friction to pass with difficulty to the centre of its sub- 

 stance. 



Not only cold extinguishes the electric power, but an ele- The excita- 

 vated temperature has the same effects. Heat is no Jess effi- tl !jc poweVis* 

 cacious in changing the nature of electricity ; and in order to extinguished 

 ascertain this, I varied, or rather repeated, the beautiful expe- aho bv heat 

 riment of two skeins of silk performed by Beegman, in 

 which we see that each of two skeins perfectly alike, becomes, 

 in its turn, negative, and the other positive, when by the friction 

 to which they are subjected, more heat is given to one than 

 the other, and, consequently, more tension tolts electric fluid. 



VIII. Though the effects of heat and cold appear to me to Experiments 

 be well shewn by the immersion of idio-electric bodies in JigJ^JJS 

 mercury j nevertheless, as this kind of electrization gives a mere contact 

 mechanical pressure of mercury against the immersed body, ° .^ ie,< V 1 v 

 Idetermined to put the influence of temperature in a clearer mersion. 

 point of view, by attempting to obtain the electric state by the 

 mere contact of these bodies with the mercury. The following 

 weie the results : 



1. Amber, sulphur, and glass, put into contact with mercury, Amber, sul- 

 and without any pressure, do not become electric, while at „\^ m d 

 the same temperature as the fluid. But they become so 



when heated by the hand, and the slightest difference of tem- 

 perature is then sufficient for the purpose, particularly when 

 the air is becoming cold, and the barometer stands high. 



2. I have always found cotton, paper, silk, and wool, elec- Cotton, paper, 

 trical by contact, whatever attention I have bestowed to bring silk > and wool, 

 them to an equal temperature with the mercury, provided they 



be always kept closed in a bottle of caustic lime. 



3. The electricity produced by contact, is always stronger The el. is 

 the greater the interval of temperature between the two bodies Plater, the 

 which touch; yet, if the bodies be heated above 75°. c. and they interval of 

 be applied upon mercury, they acquire no electricity, and do temperature, 

 not resume their power until a little cooled. 



Vol. XXXIV— No. 158. Q 4. The 



