252 



confined to the freedom of motion it gives to the particles, but to the 

 exaltation of the electrical energies of bodies, such as is well known 

 to take place in glass, tourmalin, and sulphur. The electricity of an 

 insulated plate of copper, and a plate of sulphur, was scarcely sen- 

 sible at 56 Fahr. to the condensing electrometer; at 100 they 

 affected the gold leaves without condensation ; they increased in a 

 still higher ratio as the sulphur approached its melting point ; and at 

 a little above that point, the two substances rapidly combine, and 

 evolve heat and light. In general, when the different electrical ener- 

 gies are equally strong, the combination seems to be vivid, the heat 

 and light intense, and the new compound is in a neutral state, as in 

 combustion, and the union of the strong acids with the alkalies ; but 

 when only the energy is strong, the effect is less vivid, and the com- 

 pound exhibits the excess of the stronger energy. 



Mr. Davy then considers the theory of the Voltaic apparatus ; and 

 remarks, that the above facts seem to reconcile Volta's own theory 

 with the chemical theory of galvanism. 



In a pile of zinc, copper, and water, the plates are in opposite 

 states of electricity ; and in regard to such low electricity, the water 

 is an insulating body. Of course, each plate produces an opposite 

 electricity upon the opposite plate, the intensity increasing with the 

 number, and the quantity with the extent of the series. Upon con- 

 necting the extreme points, the opposite electricities tend to produce 

 an equilibrium, which would cause the motion to cease : but the 

 fluid medium being composed of two elements possessing opposite 

 electrical energies, the oxygen is attracted by the zinc, and the hy- 

 drogen by the copper. Hence the balance of power is only momen- 

 tary ; for oxide of zinc is formed, and hydrogen is disengaged. The 

 electricity acquired by the copper is communicated anew to the zinc, 

 and the process continues as long as the chemical changes are carried 

 on. 



Neither the conducting nor solvent powers of the fluid mediums 

 are a principal cause of their activity ; for strong sulphuric acid has 

 very little activity in the pile. The effect of neutro-saline solutions 

 diminishes when troughs are used, according as their acid arranges 

 itself on the side of the zinc plates, and their alkali on the other ; 

 but the energy may be restored by agitating the fluids in the 

 cells. 



As sensible heat appears when an equilibrium is produced by small 

 metallic surfaces in the voltaic battery, the opposite states being 

 exalted, so if the decomposition of the chemical agents be essential 

 to the balance of the opposed electricities, the decomposition of the 

 saline solutions ought to be attended with an increase of temperature. 

 To water electrified in the gold cones by the power of 100 plates, a 

 drop of solution of potash was added in the positive cone : potash 

 immediately passed over, and in less than two minutes the water was 

 in a state of ebullition. When solution of nitrate of ammonia was 

 employed, the water was evaporated in three or four minutes with a 

 kind of explosive noise, and inflammation took place. The pure alka- 



