412 
Proceedings of Royal Society of Edinlurgh. [july 2, 
force was measured by a quadrant electrometer, a Latimer-Clark cell 
being used as a standard. The resistance of the battery was small in 
comparison with that of the rest of the circuit, so that the quantity 
E was given by direct measurement of the difference of potential 
between the poles of the battery. 
The following table shows the result of one series of experiments. 
The first row gives the electromotive force in volts, and the second 
row gives the value of (u + p + expressed in ohms. 
1-5 1-90 2-41 3-04 3*1 3*7 7’8 9-2 
1600 455 251-80 197*30 159 124-5 50*4 41*7 
A graphical representation of these numbers is given in fig. 1. The 
curve in the diagram is drawn free-hand through the corresponding 
points, and is closely represented by the equation (3/ - 2)(£c - 1) = 336, 
where y represents a number in the second column above, and x 
represents the corresponding number in the first column. 
Another series of experiments (the total resistance in the circuit 
being increased) gave the numbers 
1-9 2-47 3-68 3-9 5-8 7*8 12-4 
517 230-20 101 87-7 64-7 53-1 48-4 
The graphical representation is given in fig. 2, the equation being 
(y-30)(^-l-6) = 144. 
Hence we may conclude that the excess of the total apparent 
resistance over a certain quantity is inversely proportional to the 
excess of the electromotive force over a definite value, 
I next sought to determine the immediate cause of the variation 
of the total opposition to the passage of the current. First, the 
electromotive force was kept practically constant, while the current 
density was altered by the introduction of additional resistances 
into the circuit. The first row gives the value of the electromotive 
force, the second gives the value of the current strength (the factor 
reducing the numbers to amperes being 0*267), and the third gives 
the value oi['R + p + — 
resistance. 
where E does not include the additional 
10-19 11-090 
0-61 0-566 
62-50 101 
12-84 
0-30 
132 
11-22 
0-223 
150 
11-48 
0-17 
211 
