446 RIESS ON THE INCANDESCENCE OF 
Number Quantity Increase of temperature 
of jars, of electricity. in thermometer. 
3 Fb 20°0 
io 20°0 
i 11°0 20°6 
3 ie 20°4 
It follows, therefore, that the incandescence of a wire, as also 
its increase in temperature, depends upon the square of the 
quantity of electricity divided by its intensity. If therefore the 
quantity of electricity and the number of jars necessary to pro- 
duce incandescence in a wire has been ascertained, the magni- 
tude of that product is established, and it is easy to calculate 
what number of jars are required for a certain quantity of elec- 
tricity to produce incandescence in a similar wire. In the ex- 
periments 9 and 10, the mean of that product is = 31:0, ac- 
cording to which the quantities of electricity for 2,3, 4,5, 7 jars, 
would be 
ro 9°6 11°0 12°4 14°7. 
In experiment 11, the product 18 gives for 3 and 7 jars the 
quantities 7°4 and 11:2 of electricity. These calculated quanti- 
ties of electricity approach as nearly to those which were ob- 
served as could be expected from the manner of conducting the 
experiments. But the law thus deduced is confirmed in a far 
more exact manner by the observations on the thermometer, 
which, for experiments of this kind (when the susceptibility of 
the eye and the amount of light may materially modify the ap- 
parent effects), showed for all the discharges a surprising uni- 
formity. My former experiments proved* that the increase of 
temperature in a wire of constant dimensions, forming part of 
the connecting circuit, was in proportion to the square of the 
quantity of electricity multiplied by its intensity, and we might 
therefore have deduced the law mentioned, simply from the ob- 
servations on the thermometer, without having measured the 
quantity and intensity producing each separate discharge. But 
this double confirmation was not superfluous, because hitherto, 
where the laws regulating the rise in temperature of the con- 
necting circuit have been applied, no part of the circuit was 
heated to any considerable extent. 
In the sequel also the effects of the current of discharge will 
be compared with the amount of heat which it produces; for 
* Poggendorff’s Annalen, vol. xl. p. 342. 
