434 : RIESS ON THE INCANDESCENCE OF 
Tue MELTING-POINT CALCULATED FROM OBSERVED IN- 
CREASE OF TEMPERATURE. 
A thin platina wire inclosed in the ball of an air thermometer 
was taken of different length in four successive series of experi- 
ments, and the heat excited in it, by different discharges, vary- 
ing in power, of an electrical battery, was observed. This heat 
might have been calculated by the formula which I formerly 
established *, when the two constant quantities of the formula 
had been determined. The following sufficiently close accord- 
ance between the observation and calculation occurred. 
Temperature for unity of charge. 
Length of wire. Observed. Calculated. 
141°6 lines 0:270 C. 0°2688 
91°66... 0°338 0°3419 
48°75 w. 0°449 0°4461 
Bt by ieee 0°495 0°4953 
The shortest wire was still too long to be melted by the battery 
used ; I shortened the wire therefore to 15 lines, and was then 
enabled to fuse it with the quantity 38 of electricity contained 
in four jars, or with the quantity 42 contained in five jars. If 
the formula be applied to these cases, we obtain as the tempe- 
rature of the consumed wires 211°8 and 207-0 degrees of the 
centigrade thermometer, temperatures insufficient to raise to red 
heat, much less to fuse platina. . 
These temperatures could also be calculated from other obser- 
vations. There was constantly in all these experiments a thick 
platina wire forming part of the connecting circuit of the battery, 
the increased temperature of which was observed, that bearing, 
according to the formula mentioned, a definite relation to the 
rise of temperature in the thin wire. This calculation likewise 
corresponded sufficiently with the observation. 
Increase of temperature in the thin wire. 
Calculated from the increase of 
Length of wire. temperature in the thick wire. Observed. 
141°6 0°2792 0°270 
91°66 0°3346 0°338 
48°75 0°4427 0°449 
34°75 0°4906 0°495 
15°0 0°6792 
* Poggendorff's dnnalen, vol. xlv. p. 23. 
