1835.] BecquereTs Traitt Experimental, Sfc. 147 



negative in the charcoal, and the same effect was exhibited in the 

 combination of hydrogen with oxygen, but a negative result was 

 observed in the flame occasioned in the latter union. Becquerel 

 shews, however, that this subject requires further elucidation. 

 Water exhibits no sign of electricity when evaporation commences ; 

 but when it contains strontian or other bases, the vessel holding the 

 solution becomes positive, and the vapour of the water negative. 



A source of electricity analogous to that of chemical action is the 

 decomposition of oxygenated water, or peroxide of hydrogen, a sub- 

 stance discovered by M. Thenard. All the metals, with the exception 

 of iron, tin, antimony and tellurium, tend to induce the separation of 

 the elements, and the phenomena dependent upon the contact of the 

 metals, and the peroxide proceed from its decomposition and from the 

 oxidation of the metal. When an oxide is brought in contact with 

 the peroxide, for example oxide of silver, two phenomena occur, 

 which give origin each to contrary currents which tend to destroy 

 each other. 



4. With regard to the electrical effects produced in capillary action, 

 it appears that when muriatic acid acts upon spongy platinum, the 

 latter is at first positive and then negative immediately after. The 

 reverse occurs with nitric acid. It is obvious that acid is at first 

 absorbed and gives rise to heat, which occasions thermo-electric 

 effects ; but the elevation of temperature is not the only cause of the 

 phenomenon, for if the platinum is removed in the case of the nitric 

 acid, although a new immersion produces no effect, by heating and 

 re- immersion in the acid, the current proceeds from the acid to the 

 spongy platinum, and continues in this direction until the tempera- 

 ture be equalized in all parts. The direction of the current is the 

 same as that of a secondary current produced by concentrated acid. 

 Hence, the first current proceeded from the action of the acid and 

 platinum, but we are ignorant if it proceeds from a slight alteration 

 which the platinum may experience from contact with the acid. 



5. Electricity may be elicited from all bodies if properly isolated 

 by pressure. Five substances thus pressed acquire opposite states. 

 All vitreous crystallized substances such as sulphate of lime, fluor, 

 spar, &c, when pressed on a disk of cork are electrified positively ; 

 while fruits such as the orange, under the same circumstances com- 

 municate to the cork an excess of electricity. 



The disengagement of electricty by pressure is modified by several 

 causes, as the conductibility of bodies and heat. The author des- 

 cribes minutely an apparatus for determining the intensity of the 

 electricity developed by pressure, with which numerous trials 

 have been made on different bodies. The result of these shew that 

 the electrical intensity is proportional to the pressure, that is to say, 

 that if the pressure is doubled the intensity is likewise double ; at 

 least this law holds good as far as a pressure of 10 Kilogrammes 

 (22 lbs. loz. ldr.) 



In connexion with the effect of pressure, cleavage is noticed. 

 When a plate of mica is rapidly cleaved in a dusk place, a feeble 

 phosphoric light is observed. On examination each of the separated 

 porti ons is found to possess an excess of opposite electricities. 



l2 



