Electricity. 



silver 100, and their resistance to the 

 silver 1: 



Electrical Conducting Power of Metals. 



345 

 of a current, calling 



The conducting power is decreased in all in the same proportion by 

 increase of heat. The resistance of any conductor to the passage of any 

 body through it tends to arrest part of the motion of that body so that 

 it comes out at a slower rate and in diminished volume. This loss of 

 motion in the passage of the body reappears in the shape of heat. Thus, 

 electricity being convertible into heat, it is proved to be a motion of 

 .some thing or substance. It has been shown that the speed of induction 

 when allowance is made for the resistance of the conductor is practically 

 the same as that of light, from which it has been concluded by some 

 physicists that the two are different sorts of motion of one and the same 

 substance, Ether. 



The units of measurement for electricity and magnetism are units of distance, weight 

 and time, as follows: the Centimetre, C., = nearlv 4 inches; the Gram, G., = 15 and 4-10 

 grains : the Second, S. These are called the C, G, S units. A force which acts on one 

 gram for one second of time, and imparts to it a velocity of one centimeter per second, is 

 the unit of force, and is called one Dyne. It takes about 455 thousand dynes to equal a 

 pound Avoirdupois- ThetmzY of magnetism, or magnet pole of unit force, is one that 

 when placed (in air ) one centimeter from a similar pole of equal strength, it repels it 

 with the force of one dyne. The amount of work required to move a body one centime- 

 ter against the force of one dyne, is called an erg; and it is the unit of work. 



The measure of the quantity of electricity is the same as that of magnetism, that is, it 

 is the quantity of electricity which, at a distance of one centimeter, will repel an equal 

 quantity with the force of one dyne. As this unit is too big, the practical unit is assumed 

 .at one-tenth of this absolute unit, and is called the Coulomb. The absolute unit of cur- 

 rent is one of such strength that when one centimetre length of its circuit is bent into an 

 ;arc of one centimeter radius, the current in it exerts a force of one dyne on a unit mag- 



