ON STANDARDS OF ELECTRICAL RESISTANCE. 137 
positive and negative states, exhibiting no electrical symptoms whatever, and 
hence described as unelectrified, or containing no electricity. But, during the 
first moment of their junction, the conductor is found to possess certain new 
and peculiar properties: any one part of the conductor exerts a force upon 
any other part of the conductor; it exerts a force on any magnet in the 
neighbourhood; and if any part of the conductor be formed by one of those 
compound bodies called electrolytes, a certain portion of this body will be 
decomposed. These peculiar effects are said to be due to a current of elec- 
tricity in the conductor. The positive quantity, or excess, is conceived as 
flowing into the deficiency caused by the negative quantity ; so that the whole 
combination is reduced to the neutral condition. This neutral condition is 
similar to that of the earth where the experiment is tried. If the balls are 
continually recharged by the battery, and discharged or neutralized by the 
wire, a rapid succession of the so-called currents will be sent; and it is 
found that the force with which a magnet is deflected by this rapid sncces- 
sion of currents is proportional (ceteris paribus) to the quantity of electricity 
passed through the conductor or neutralized per second ; it is also found that 
the amount of chemical action, measured by the weights of the bodies decom- 
posed, is proportional to the same quantity. The currents just described are 
intermittent ; but a wire or conductor, used simply to join the two poles of a 
battery, acquires permanently the same properties as when used to discharge 
the balls as above with great rapidity ; and the greater the rapidity with 
which the balls are discharged, the more perfect the similarity of the con- 
dition of the wire in the two cases. The wire in the latter case is therefore 
said to convey a permanent current of electricity, the magnitude or strength 
of which is defined as proportional to the quantity conveyed per second. 
This definition is expressed by the equation 
c=2, . . . . . . . . . . (4) 
where C is the current, Q the quantity, and ¢ the time. A permanent current 
flowing through a wire may be measured by the force which it exerts on a 
magnet; the actual quantity it conveys may be obtained by comparing this 
force with the force exerted under otherwise similar conditions, when a 
known quantity is sent through the same wire by discharges. The strength 
of a permanent current is found at any one time to be equal in all parts of 
the conductor. Conductors conveying currents exert a peculiar force one 
upon another; and during their increase or decrease they produce currents 
in neighbouring conductors. Similar effects are produced as they approach 
or recede from neighbouring conductors. The laws according to which 
currents act upon magnets and upon one another will be found in the writings 
of Ampére and Weber. 
16. Meaning of the words ‘ Electromotive Force.’’—Hitherto we have spoken 
simply of statical effects ; but it is found that a current of electricity, as above 
defined, cannot exist without effecting work or its equivalent. Thus it 
either heats the conductor, or raises a weight, or magnetizes soft iron, or 
effects chemical decomposition ; in fine, in some shape it effects work, and 
this work bears a definite relation to the current. Work done presupposes 
a force in action. The immediate force producing a current, or, in other 
words, causing the transfer of a certain quantity of electricity, is called an 
electromotive force. This force is necessarily assumed as ultimately due to 
that part of a circuit where a “degradation” or consumption of energy takes 
place; thus we speak of the electromotive force of the voltaic or thermo- 
