ELECTRICITY. 



Chalk 



ELECTRICITY. The word electrici- 

 ty denotes a peculiar state, of which all 

 bodies are susceptible, and which is 

 supposed to depend upon the presence 

 of a substance called the electric fluid. 

 Some of its phenomena were known to 

 the ancients, particularly those attrac- 

 tions and repulsions which a piece of 

 amber, after being rubbed, exhibits, with 

 regard to hairs, feathers, and other small 

 bodies ; and the name electricity is de- 

 rived from the Greek word denoting 

 amber. 



This subject is so far from being well 

 understood, even at present, that there 

 is some difficulty even in classing the 

 facts. They may, however, be stated as 

 follows : A body in an electric state at- 

 tracts other bodies, and these become 

 electric by touching k, and are after- 

 wards repelled. Bodies are capable of 

 being electrified more or less strongly ; 

 and when the electric state is considera- 

 bly strong, the electrified body will 

 throw out luminous sparks or flashes, to 

 other bodies brought near it, and by that 

 means communicate the same electric 

 state to them, without actual contact. 



The means by which bodies are ren- 

 dered electric are so various, that it may 

 be asserted, perhaps without exception, 

 that every change, whether mechanical 

 or chemical, which can take place in 

 them, will at the same time produce elec- 

 tricity, or alter their electric state. When 

 one body is applied to another, and they 

 are afterwards separated ; or if they be 

 rubbed together ; or if their parts be 

 torn asunder ; or if they be heated ; or 

 cooled ; or evaporated ; or congealed ; 

 or fused ; or if any chemical combina- 

 tion be made to take place between 

 them , the signs of electricity become 

 manifest, though with differences of in- 

 tensity dependant on the nature of the bo- 

 dies, as well as of the processes and the 



circumstances; some of which have been 

 so far classed as to take the form of sci- 

 ence, while others remain to be develop- 

 ed by new researches. 



When the electric state is communica- 

 ted from one body to another, very strik- 

 ing differences are observed in its effects. 

 Some bodies become electrified only in 

 those parts which are near the place of 

 communication, and the electric state is 

 considerably permanent ; other bodies 

 transmit the electric energy from part to 

 part with great rapidity and facility. 

 The former of these have been called 

 non-conductors, and the latter conduc- 

 tors of electricity. From the properties 

 here described, it will easily be under- 

 stood, that a non-conductor cannot be 

 made to exhibit the electric state for 

 any perceptible portion of time, unless 

 it be supported by a non-conductor. In 

 this situation it is said to be insulated. 



The state of electricity which is pro- 

 duced by chemical changes in bodies 

 has, within a few late years, greatly en- 

 gaged the attention of the philosophical 

 world, under the denomination of GAL- 

 VANISM ; which see. 



It does not appear that the property 

 of conducting electricity depends alto- 

 gether on the nature or component parts 

 of the conductors themselves, but rather 

 on their state with regard to heat. Glass, 

 resin, baked wood, atmospheric air, and, 

 many other bodies, which are non-con- 

 ductors in the ordinary temperature 

 of the atmosphere, become conductors 

 when very hot ; and on the contrary, ice, 

 cooled to 13 below on Fahrenheit's 

 scale, has all the properties of non-con- 

 ductors. If we might generalize these 

 facts, analogy would lead us to an in- 

 duction, that, as the freezing points of 

 bodies differ so greatly among each 

 other, and in some, as in alcohol and the 

 gases, it can only be admitted by suppo- 



