38 SCIENTIFIC AGRICULTURE, 



in two opposite states, viz : positive and negative. The terms 

 vitreous and resinous have also been used to designate these 

 t\vo states. 



The simplest manner of exciting or producing electricity is 

 by rubbing a piece of amber or sealing wax on dry cloth* 

 when it will be found capable of attracting light bodies, such 

 as feathers, bits of thread, paper, &c. The body so affected is 

 called an electric, and is said to be in a state of, .electrical 

 excitation. The sealing wax or amb^r in this case is in the 

 positive state, or is positively electrified, while the feather or 

 other substance attracted to it is in the negative state, or is 

 negatively electrified. It is impossible to develop one of these 

 states or phenomena without at the same time developing the 

 other also. After adhering to the electrical body for a few 

 seconds it will fall off, it being charged with electricity and in 

 the positive state like the electric : if the electric be excited 

 again, and the feather presented to it, it will be strongly 

 repelled and tend to fly off this is called electrical repulsion. 



The passage of the electric spark is instantaneous: it appears 

 also to be confined to the surface of bodies in its passage. 

 Bodies which allow electricity to pass over them are called 

 conductors: these are non-electrics, that is, they cannot be 

 excited by friction so as to produce electricity: on the con- 

 trary, those bodies which can be electrically excited will not 

 conduct the fluid; so that non-conductors are electrics, and 

 non-electrics are conductors. 



The electric spark fires gaseous mixtures, and is capable of 

 producing intense heat: electricity also decomposes solutions 

 of metallic oxides and salts. Some fishes, as the torpedo and 

 electrical eel, possess an electrical apparatus within their 

 bodies, which is capable of producing severe shocks upon 

 other animals ; and this is done, too, at the will of the fish. It 

 has been satisfactorily settled by Prof. Matteitcci, that electri- 

 city has nothing to do with the action of the nervous system 



