ELECTRIC POWER. 213 



Care must be taken to leave them in the mercury long enough 

 to produce a perfect equilibrium of temperature, and afterwards 

 to draw them out very slowly. The same bodies continue to 

 become electric by the blow, or by quick immersion in 

 temperatures superior to the degree at Which their power 

 begins to be produced. It is remarked, nevertheless, that as 

 these bodies and the mercury arrive at much more elevated 

 temperatures, their electric power becomes weak, and at last 

 disappears, even bf biisk immersion, at 80°. c and 100°. c. 



We may, therefore, establish it as a principle, that these four Generalresult. 

 bodies are" not electrical in mercury, when they are of the 

 same temperature with it, and care is at the same time taken 

 that no mechanical pressure be exerted, except that of the 

 proper weight of the fluid upon the immerged body ; and that 

 even in the case when the immersion is effected with a strong 

 pressure, these two united actions do not produce any electrical , 



effect where the temperatures are equal, and are above 10°. c. 

 and under 80 '. c. 



II. The effects are not the same with regard to cotton, paper, Electricity 

 silk, and wool, for I have found these very electrical by the paging cot- 

 three immersions, and at all the degrees of heat between 10°. ton, paper, 

 c. and 80°. c. They continue to be electrical even below 10°. fo l merco™. 1 ' 

 c. j but by loweiing the temperature more and more; cotton is Here the ef- 

 found to have its power extinguished in mercury at 3°. c. after I^n^d bv° 

 remaining in it ten minutes j paper is also extinguished at 1°. c. the tempera- 

 after fifteen minutes j silk at 0°. c. after an hour and a half 5 * ure '^ tdiffer 

 " '■ from the pre- 



and lastly, wool between 5°. and 6°. c. after remaining near ceding. 



two hours. 



These four bodies are also extinguished, like the preceding, 

 at elevated temperatures, and it is even remarked with regard 

 to cotton and wool, that their power disappears at 60°. c. 

 This arises from the humid principle of these bodies, which 

 becomes fluid at that degree of heat. 



It is very observable, that these bodies should also be electric 

 by emersion, when they are at the same temperature as the 

 mercury at all the degrees of the thermometer, in which their 

 power is not extinguished, whereas, the contrary takes place 

 with regard to all the preceding bodies. Their calorific fluid 

 has, therefore, more natural tension than that of the four first 



bodies, 



