1911-12.] On the Torsional Oscillations of Magnesium Wire. 249 
was found to be impossible, as the wire broke even when a very small 
amount of stretching was produced. The magnesium wire was next sub- 
jected to rapidly alternating rotational strain for different periods of time, 
and the results were as follows 
Time. 
a. n. 
First experiment 
30 min. 
f 8 *289 
\ 11 -289 
Second experiment . 
. 210 min. 
( 8 -232 
1 11 -228 
Thus it appears that the twisting does not affect the constants to a great 
extent. The change in the value of n in the two cases is quite certain, but 
the values of n got in successive experiments may differ to some extent in 
the second place after the decimal point. 
(iii.) Another portion of the 
wire was next 
fixed between two clamps, 
and was subjected to periodic extensional 
stress (see J. B. Ritchie, 
Proc. Roy. Soc. Edin ., 1911). The results were 
as follows : — 
Time. 
a. 
n. 
30 min. 
f 8 
113 
•247 
•208 
ISO min. 
S 8 
1 13 
•239 
•233 
As it is quite possible that there may be 
a slight error even in the 
second figure after the decimal point, these values differ so little from one 
another and from the preceding 
that we may say that the effect of fatigue 
on unheated magnesium wire does not decidedly alter the constants. 
(iv.) A length of the wire was next placed 
in an electric furnace and 
heated to various temperatures. 
The following 
were the results : — 
Temperature. 
a. 
n. 
100° C. 
{ll 
•243, -269 
•276, -279 
250° C. 
jii 
•243 
•250 
350° C. 
i 8 
tn 
•190 
•280 
450° C. 
i ii 
in 
•112, 121 
•266, -260 
500° C. 
i 11 
ii 
•060, -080 
•140, *138 
The second series of values under the heading n refer to the results of 
duplicate experiments. The constants are not greatly affected until a 
temperature of about 350° C. is reached. At higher temperatures the 
value of n falls continuously in the case of small oscillations. In the case 
