STATIC AND DYNAMIC ELECTRICITY. 2OQ 



cause serious injury, if not death. The battery can be charged from the 

 machine by a chain fastened to the central ball, while a second chain connects 

 the exterior of the box and all the outside of the jars, 

 by means of the handle, to the ground 



When electricity is at rest it is termed " static 

 electricity," and when in motion " dynamic " electricity. 

 The latter treats of electric currents which can be sent 

 through wires or chains. We can keep this current 

 moving by means of a machine, and the battery called 

 a Voltaic battery, from Volta. We will describe it 

 presently. Electric currents can be measured, for they 

 may be of different strengths according to the battery, 

 and they are measured by the GALVANOMETER. Elec- 

 tricity can therefore be transferred and carried by the 

 conducting substances, and much heat will be engendered as the " electric 

 fluid " passes along a wire. Lightning frequently fuses bell-wires as it 

 passes, and when we touch upon Galvanism or Dynamjcal Electricity we 

 shall hear more about it. 



By the Electric Machine we can obtain some very powerful currents of 

 electricity; we can produce many pleasing effects, and perform a number 

 of experiments, such as making balls or figures of pith dance, and several 

 other easy and entertaining tricks, which will be found in books more specially 

 devoted to the entertainment of young people. 



We have now given some explanation of the manner in which electrical 

 phenomena can be produced, viz., by the Electric Machine and by the Leyden 

 Jar, but we must not expect to find any electricity inside any charged body. 

 It has been proved that all the electricity is upon the surface of bodies, even 

 if in varying quantity, and that equal quantities of electricity are always 

 produced when bodies are excited by friction, but the kinds are different. 

 The rubbing body is of one kind, the body rubbed another, and consequently 

 the forces neutralize each other. The two forces or kinds of electricity we 

 have seen repel or attract each other, and we can imagine the farther they 

 are apart the less will be the force, and the rate of diminution of force, according 

 to distance, is ascertained by an ingenious apparatus called a " Torsion " 

 Electrometer, which was constructed by Coulomb, and was frequently used by 

 Faraday. 



Perhaps some people may not be aware of the term " torsion." It 

 means twisting, and " the torsion of a thread suspended vertically is the force 

 tending to twist the lower extremity when the upper end is turned through 

 an angle." This instrument is really an Electromoter, and is not considered 

 suited to beginners, and it is scarcely accurate in its workings. We need 

 not therefore describe it in detail. There are some excellent Electromoters, 

 the Elliott being, we believe, the best for use. A full and detailed descrip- 

 tion of the Quadrant Electromoter will be found in Mr. Gordon's treatise on 

 Electricity. 



