ELECTRICITY. 



465 



f.Miptife a heated body. In a second experiment made with the 

 "X- the same Copper crucible, and under the very same cir- 



> '>"'' cumstances, the electricity was at first negative at the 

 end of the first projection, but afterwards became posi- 

 tive, and remained so till the experiment was comple- 

 ted. 



In order to make the experiment witli a metal that was 

 not altered by the contact of water, Saussure employed 

 a crucible of very pure Silver, 2J inches in diameter at 

 top, 1^ inch in diameter at bottom, 12| inches high, 

 1 ' r line thick, and weighing 16 ounces. 



TABLE IV. Shoving the Electricity produced by the Evaporation of Water placed on a heated Crucible 



of pure Silver. 



In this experiment, the evaporation was very slow, 

 and the electricity, which was always very feeble, was 

 thrice negative, and thrice nothing during the interval 

 of 5 minutes and 6 seconds at the timeof the greatest heat. 

 In a second experiment with the same crucible, the eva- 

 poration lasted 6 minutes and 1.5 seconds, and the electri- 

 city wa also negative at the first projection, but it became 

 positive at the second projection, and vanished at the 

 third. In a third experiment, the electricity was 



stronger, and was at first negative, when the balls-of the 

 electrometer separated 3^ lines. It then was positive, 

 and the balls separated V^ths of a line, and at the third 

 projection it was still positive, and the separation of the 

 balls was so much as 6 lines. 



Saussure now employed a cup of White Porcelain, and 

 surrounding it with sand in a clay crucible, and having 

 brought it to a white heat, he kept it in the clay pot 

 during the experiments. 



TABLE V. Shouting the Electricity produced by the Evaporation of Water placed on a heated Crucible 



of white Porcelain. 



The rapidity of evaporation in the porcelain crucible 

 is very remarkable. Saussure repeated the experiments 

 twice with different porcelain crucibles, and obtained 

 tin- very same results, both witli regard to the evapora- 

 tion, an'l to the degree and kind of the electricity which 

 was produced. 



VOL. VIII. PART II. 



Saussure made his next experiments with Alcohol 

 instead of water. The following results were obtained 

 with the .silver crucible formerly used, and with the 

 same quantity, viz. 54 grains of distilled water. 





