M. Henrici on the Theory and Application of Electricity, 169 



difficulty to and fro. By carefully moving this gold leaf, it 

 was very easy to place it in such a position that it should be 

 attracted by the strip of zinc only when negatively, and the 

 strip of silver only when positively electrified. As it was 

 electrified by induction, on removing the electrifying bodies 

 (sealing-wax and glass gently excited by friction) the opposite 

 attraction to that produced by the approximation of them took 

 place if an attraction had been thus produced. In my opinion 

 we have here no ambiguity. There is scarcely occasion to re- 

 mark, that the apparatus was enclosed in a glass vessel. As 

 the normal attraction ensued only when the gold leaf was in 

 a certain position {i. e. exactly midway between the arms of 

 the compound strip), the small intensity of the electricity of 

 contact is perfectly intelligible. Thus if the gold leaf be ap- 

 proximated to either arm, its free electricity will overpower 

 the weak electricity of contact of this arm, and act upon it by 

 induction, whence attraction between the two must always 

 ensue, as the experiment indicates. I have some hopes of 

 being able to obtain a comparative admeasurement of the in- 

 tensity of the electrical effects of contact by this method. 



4. It is well known that free electricity appears in many 

 chemical processes. Thus the fumes of burning potassium 

 are positive, whilst those of burning phosphorus are negative*. 

 Are we hence to conclude that the atoms of the potash con- 

 tain positive electricity and those of the phosphoric acid nega- 

 tive electricity in excess ? Certainly not. We must merely 

 consider that if the fumes of potassium appear positively elec- 

 trical, the burning potassium itself must possess negative elec- 

 tricity ; the conclusion that the potassium contained prepon- 

 derance of negative electricity would thus be arrived at. How- 

 ever, the phosphorus, which by combustion must possess posi- 

 tive electricity, as the phosphoric acid appears negative, might 

 be regarded as a body containing positive electricity predomi- 

 nantly. There is no doubt that the electricity which appears 

 in these experiments is first produced in the act of combustion ; 

 perhaps it arises from the violent separation of the burnt par- 

 ticles from those still unburnt. Besides, this spontaneously 

 disappears in a very short time, even when it is not purposely 

 annihilated, and the precipitated fumes then indicate no fur- 

 ther trace of free electricity ; the chemical attraction, therefore, 

 of the potash for the phosphoric acid cannot depend upon the 

 action of free opposite electricities with which their atoms are 

 said to be endowed. Neither can we suppose that any latent 

 electricity exists in them, for such would be unable (if so ca- 

 pable per se) to exert any outward action. If, nevertheless, 

 we were to attribute free electricity to the atoms of bodies, and 

 * Berzelius, Lchrbuch der Chemie, ii'" auf. S. 103. 



