442 RIESS ON THE INCANDESCENCE OF 
after which it measured 75'9 lines. There is no doubt that the 
remaining loss of 1°6 line was occasioned by very fine bends. 
Experiment 8.—Lastly, I repeated the experiment upon an 
iron wire of 0'-0266 radius and 98-2 lines in length, and per- 
formed the experiment in the same manner as it had been done 
by others. The wire was loaded with a small pear-shaped 
weight (121 grammes), it was hung vertically, the point of the 
weight however was supported by a piece of metal with a hole 
in it. After the wire had been brought eight times to a mode- 
rate red heat by discharges it measured 90:7 lines, an apparent 
shortening had therefore taken place of 73 lines. By continued 
careful smoothing it was obtained of the lengths 95:2 and 96°5 
lines, so that there remained only 1:7 line as its decrease in 
length; a further straightening of the wire would doubtless have 
restored it to its former length, but could not have been effected 
without the aid of fire. 
The wires which served for the experiments 7 and 8 have 
been preserved: they appear under the magnifying-glass to be 
covered with a great number of minute bends, which easily ac- 
count for the apparent decrease in length of two lines. 
It follows from these experiments, that the shortening of wires 
and increase of their diameters, which have been accounted the 
effect of powerful electrical discharges upon them, does not take 
place in reality, and that the apparent shortening arises from 
bends which under certain circumstances are sufficiently small 
to escape a superficial observation. These less perceptible bends 
appear, with greater ones, in tightly-stretched wires when ex- 
posed to discharges which heat the wires to redness. In wires 
slackly suspended bends are effected, as was shown at page 439 
by electrical discharges, which even in complete darkness do 
not produce a red heat ; and these discharges would have sufficed 
to shorten the wires apparently, if the greater number of the 
bends had not been so marked as to render it impossible, on 
measuring, to overlook them. 
Amongst the effects of incandescence produced by electrical 
means, a lengthening of wires tightly stretched by weights has 
been noticed. Kinnersley first accomplished this by loading a 
harpsichord string twenty-four inches in length with a pound 
weight and making it red-hot by an electrical discharge, after 
which it was lengthened one inch*. Beccaria performed the 
* Franklin, Experiments and Observations, 3rd ed. p. 399. 
