260 Mr. Knox on the Direction and Mode of 



the late experiments of Fechner and Peclet, have fully established. Fechner* 

 has proved (having shown that the same experiment was incorrectly tried by 

 Delarive), that when potassium, or sodium, are brought into contact with pla- 

 tinum, electrical development takes place without chemical action. Pecletf has 

 proved that electrical excitation is caused by the contact of platinum and gold, 

 wherk chemical action could not take place. In support of the opposite opinion 

 is the experiment of Delarive,| who found, that when chlorine gas is passed 

 through an insulated copper tube, the condenser exhibits electrical develop- 

 ment, which, he remarks, decreases when chlorine, unmixed with atmospheric air, 

 is employed, and also when the chemical action between the chlorine and copper is 

 violent ; circumstances which admit of a simple explanation by the contact theory, 

 according to which the air receives an electrical charge from the chlorine while in 

 contact with the copper, which charge so much of the gas as combines with the 

 copper loses. The same explanation may be given to the experiments of Peclet,§ 

 who has satisfactorily shown that the presence of moisture is necessary in order 

 that the oxidation of the amalgam on the rubber of an electrical machine should 

 develope electricity, the aqueous vapour in this case receiving the charge. 

 Experiments, then, having proved, that contact and not chemical action causes 

 the development of electricity, the question arises, how are we to explain the 

 phenomena ? When two atoms unite, it is difficult to avoid the conclusion, that 

 the compound atom (molecule) must have oppositely electrical surfaces. Two 

 such polarized molecules approaching cause a disturbance to take place in the 

 electrical ether, which disturbance is propagated by induction to a distance; but 

 when the molecules approach sufficiently near to combine, the two oppositely 

 electrical surfaces of one molecule coming in contact with the two oppositely 

 electrified surfaces of the other, no development of electricity can take place, 

 the electrical states becoming completely disguised ; and such a supposition is 

 borne out by every fact in crystallography, which shows that the molecules have 

 poles. The particles being compound molecules should have poles likewise ; and 

 when they unite, or chemical combination takes place, there should be no de- 

 velopment of electricity ; and, consequently, when oxygen unites with zinc (as in 



* Phil. Mag. vol. xiii. 1838. f Annales de Chimie, fom. Ixxi. p. 80. 



X Bib. Univer. N. S. torn. iii. kj Annales de Chimie, torn. Ixxi. p. 83. 



