ELECTRICITY. 



463 



Experi- 

 ments of 

 Sauisure. 



F>e:rip;ive the first, however, it appeared to be negative, but in the 

 Electricity. o ther two it was decidedly positive. In order to account 

 ^ for this result, they conjectured that the cooling pro- 

 duced by evaporation had increased the signs of posi- 

 tive electricity more than the evaporation had diminished 

 them. M. Volta assisted at these experiments. 



The same subject was more deeply investigated by 

 Saussure, who has given a full account of his experi- 

 ments in his t'oi/age dans leu Alpes. Volta having ob- 

 served that the electricity produced by evaporation was 

 always negative, Saussure attempted to repeat the ex- 

 periment, by throwing a mass of red-hot iron into a 

 small quantity of water in a coffee-pot with a large 

 mouth, and suspended by silk strings. He found, 

 however, that the electricity thus produced was nega- 

 tive. This result being quite opposite to that of Volta, 

 lie varied the experiment in the following manner. He 

 insulated a small chafing-dish by silk cords, and placed 

 upon it the coffee-pot, with a small quantity of water. 

 One electrometer was connected with the chafing-dish, 

 and another with the coffee pot, and when the water 

 had continued for a few minutes to boil strongly, both 

 the electrometers exhibited signs of negative electricity, 

 as in the experiments of Volta. He found also that the 

 evaporation produced by the effervescence of iron in 

 sulphuric acid, and by the effervescence of chalk in the 

 same acid, likewise gave negative electricity. 



In order to account for the positive electricity gene- 

 rated in the first experiment, M. Saussure conjectured 

 that the intensity of the heat to which the water was 

 exposed by the contact of a body brought to a white 

 heat, was the cause of the electricity produced by the 

 evaporation, and that a combination wag then formed, 

 by which a new quantity of the fluid was developed. 

 The quantity of electricity was so great in the ex- 

 periment, that the balls of the electrometer were sepa- 

 rated to the greatest possible distance. In order to ve- 

 rify this conjecture, that the electricity was produced 

 in some way or other by the combustion of the water 

 or the iron, .Saussure tried to procure positive electricity, 

 by moderating the heat of the iron. Into a large in>u- 

 lated iron crucible, five inches high, four in diameter, 

 and six lines thick, and made red-hot, he threw small 

 quantities of water successively, till the crucible had the 

 degree of heat sufficient to make water boil. The elec- 



tricity produced at each projection of the water was care- Descriptive 

 fully observed, and destroyed. The electricity which was ^ 

 exhibited was always positive. It was very strong at the Expert 

 first projection, and gradually diminished to the twelfth, merits of 

 when it was scarcely perceptible. In the repetition of Saussure. 

 this experiment, Saussure found that when a small 

 quantity of water was thrown into the crucible the mo- 

 ment it was taken from the fire, and while it had a pale ' 

 red colour approaching to white, he never could obtain 

 any indication of electricity. 



In order to examine the relations which existed be- 

 tween the periods of evaporation and the production 

 of electricity, M. Saussure made a great variety of expe- 

 riments. His apparatus consisted of a well-baked ves- 

 sel of clay, 4 inches in diameter, and 15 lines thick, 

 which he insulated upon a clean and dry goblet of glass. 

 Upon the vessel of clay he placed a crucible, or any 

 other body powerfully heated, and by means of a wire he 

 connected this crucible with the electrometer. Fifty- 

 four grains of distilled water were thrown 'upon the 

 heated crucible, and by means of a time-piece and an 

 electrometer he observed the period of evaporation, and 

 the degree of electricity that was produced. The results 

 which he obtained are given in the following Tables. 



'Yhejirtt column of all the tables contains the number 

 of projections of water that were made. The second the 

 number of minutes and seconds that had elapsed from 

 the commencement of the experiment, or from the time 

 of the first projection to that of the corresponding pro- 

 jection. The third column expresses in seconds the 

 time which was necessary to reduce the 54- grains of 

 distilled water to the state of vapour. Thefoiirth ex- 

 presses in lines and tenths of a line, the distance of the 

 balls of the electrometer. The jift h marks the charac- 

 ter of the electricity which was produced ; and the 

 sixth contains general remarks on the state of the cru- 

 cibles, the vapours, and the noise which was made du- 

 ring evaporation. This noise undergoes great varia- 

 tions. It is almost nothing when the metal is very hot, 

 and it increases as the metal becomes colder, and dissi- 

 pates more readily the projected fluid. 



The following Table contains the results which were 

 obtained, when the crucible was made of forged Iron, 

 24 inches in diameter, 22 lines high, 2 lines thick, and 

 weighing 25^ ounces. 



TABLE I. Shewing the Electricity produced by the Evaporation of Water placed on a heated Crucible of Iron. 



