METALLIC WIRES BY ELECTRICITY. 441 
Becquerel, to whom the bends in the wires were known, has 
endeavoured to establish a law for the shortening of platina wires 
in proportion to their diameters, assuming without further proof 
that the shortened wires had become thicker*. I have found it 
necessary to institute new experiments upon this subject. 
Experiment 5.—A platina wire, 0!02089 radius, the length 
of which, 42°66 lines, had been accurately determined, was fixed 
horizontally in the spring clamps of the connecting circuit. The 
quantity of electricity 5, collected in 4* jars, was discharged 
eleven times, and the quantity of electricity 7 was discharged 
six times through the wire. The discharges of the smaller quan- 
tity of electricity had no visible effect upon the wire; those of 
the larger quantity produced two deep bends. When the wire 
was drawn tight its length was exactly 42°63 lines, therefore the 
same as before the experiment. 
Experiment 6.—A platina wire of the same thickness was 
loosely laid in the clamps, and after each discharge drawn tole- 
rably tight and measured. 
Length of the 
Number Quantity 
wire in lines. 
of jars. of electricity. Appearance of the wire. 
38°16 
4* 10 Bends. 38°11 
me Sparks at the ends—bend. 37°86 
a5 The same. 37°76 
12 The wire slightly red-hot. S751 
te The same. 37°41 
14 Bright red heat 37°21 
The same. 36°86 
Here the wire was shortened 1°3 line; its jagged appearance, 
however, which could not be removed by drawing it tight, showed 
that the shortening was only apparent. After the wire had been 
drawn through the fingers, its leugth was 37°21, and after an- 
other smoothing 37°41. Even now the uneven surface of the 
wire could be seen and felt, and could only have been removed 
by pressure against a hard body. 
Experiment 7.—A platina wire of 0°0286 radius was heated 
to redness ten times by discharges; its length before the experi- 
ment was 77°5 lines, afterwards 72°3. The apparent shortening 
of 5°2 lines was removed by drawing it once through the fingers, 
* Poggendorff’s Annalen, vol. xlviii. p. 549. 
VOL. IV. PART XV. =: 21 
