of Edinburgh , Sess ion 1885—86. 
689 
Professor F. Guthrie on Eutexia,* which appears to have important 
relations to the phenomena recorded in this communication. 
The first alloy tested was SnPb 3 . The change in resistance in 
this case took place by two distinct falls with a space between 
them where the resistance changed very much less rapidly. This 
exjDeriment was repeated several times, and the same result was 
always obtained. 
The next alloy tested was Sn 3 Pb. In this case the change of 
resistance was effected by a single fall, as in the case of a simple 
metal ; repeated experiments failed to show any break in the 
sudden alteration of conductivity. 
The authors were led to employ these two alloys in consequence 
of some observations made by Rudberg,f who states that the alloy 
Sn 3 Pb has one solidifying point, but that the others exhibit a 
higher one also, which in the case of SnPb 3 is very far above the 
lower one. The temperatures given by him do not exactly corre- 
spond with those at which the dips appear in the conductivity curves, 
but these temperatures do not profess to any great accuracy, for the 
object was in this case rather to determine the change of tempera- 
ture from observation to observation, than to give the absolute 
temperature of the alloy at any observation. 
One alloy of zinc and lead (ZnPb) has also been tried. It 
gives evidence of a break in the alteration of conductivity, but 
a sufficient number of observations has not been made upon it to 
justify any great dependence on this result. 
The conclusion which these facts would seem to indicate, 
although it is premature as yet to adopt it as established, is that 
there is a definite alloy, corresponding to Professor Guthrie’s 
“ Eutectic Alloy,” from which the other constituents separate out 
and solidify, giving rise to the first fall in resistance as the metal 
cools, and that afterwards, when the eutectic alloy itself solidifies, 
the second fall occurs. A point of great importance in this connec- 
tion is brought out by a comparison of figs. 4 and 5. In the 
alloy SnPb 3 the second fall in resistance occurs at the same 
temperature as the whole fall in the (eutectic) alloy Sn 3 Pb. The 
* “ On Eutexia,” Phil. Mag., vol. xvii. 5th series, 1884. 
t Quoted in Gmelin’s Handbook of Chemistry, vol. v. p. 180, Engl, transl. 
by Henry Watts, in the Cavendish Soc. Works. 
2 z 
VOL. XIII. 
