on the Elasticity of certain Metals. 359 
mean of the two temperatures at which the times of vibration 
were observed. 
TABLE 2. 
Decrease of the coefficient of elasticit: 
for 1° as func. of the coeff. of elast. at 0°. 
Calculated 
Temperature. " 
74° 0,00068 0,00068 +0,00000 
71 69 67 4. 2 
66 75 65 + 10 
60 56 62 _ 6 
54 50 60 - 10 
48 65 57 + 8 
42 ° 55 12 
37 53 53 + 0 
38 55 51 + 4 
28 48 49 — 1 
25 0,00052 0,00047 +0,00005 
The numbers of the second column can be regarded as the 
values of — > a for the temperature t of the first column. It 
will be observed that this mode of observation affords the de- 
crease of the modulus of elasticity for 1° with tolerable accu- 
racy, even for the times of vibration for two temperatures dif- 
fering only by a few degrees. (The greatest difference is 7°, 
the smallest 2°). This decrease for the brass wire is noticeably 
greater for the higher temperatures than for the lower. 
The numerical law of the variation is to be derived from all 
ee the observations. We seek to represent it by the formula 
ee, (l—a tbr), 
~~ It would obviously be more in accordance with the laws, of the 
1 e 
calculus of errors to determine the values of the coefficients ¢,, 
a and } by means of least squares from all the observed values 
of € or 5 for all temperatures. This would prove, however, 
when applied to all the series of observations, exeenve labo- 
: d her all 
variations from one day to another, probably in consequence of 
the considerable heating to which the wire 1s subjecte 
