428 C. Barns — Certain generic Electrical 



The expression for electrical conductivity is here 1 //*(#, t), to 

 be abbreviated X. If s=s (l + at-hftt 2 -\- . . . .), it follows that 

 ^=^ (1 — etf-f (a 2 — ($)t — . . . .) ; and hence the temperature coeffi- 

 cients, taken in the sense just defined, are numerically identical, 

 no matter whether reference is made to s or to X. 



The alloys of which the present paper treats are all character- 

 ized by high melting points, and by non-crystalline structure. 

 Alloys fusing below red heat have not been systematically 

 investigated, or lead to involved results. The case of amal- 

 gams* is complicated by changes of the physical state of aggre- 

 gation. Strictly speaking investigations like the present hold 

 only for those alloys for which data are in hand. Cf. § 3. 



2. The advantages of selecting platinum- alloys for the in- 

 vestigation in question are manifold. Melted platinum appears 

 to be a universal solvent of metals, and hence the variety of 

 bimetallic platinum alloys, easily producible, is very great. 

 Again one of the remarkable electrical properties of platinum 

 is the tendency to form alloys of phenomenally high specific 

 resistance ; and quite within the limits stated in §1, an elec- 

 trical effect of alloying amounting to as much as 500 per cent 

 of the specific resistance of platinum, is no unusual occurrence. 

 Finally platinum alloys have not yet been systematically studied. 

 The present contribution is therefore new. 



In the case of steel to which I shall allude in passing, varia- 

 tions of resistance allied in character to those here discussed 

 may be produced by changes of temper. The range of elec- 

 trical variation here is also very large, amounting to more than 

 300 per cent of the resistance of soft steel. 



Phenomena extending over such an enormous range, and 

 which admit of exact measurement throughout the whole in- 

 ternal of variation, deserve most careful scrutiny and compari- 

 son even in their approximate relations. But there is further 

 evidence in hand of the importance of which, when my work 

 was in progress, 1 was quite unaware. I shall endeavor to 

 digest it in the next paragraph. 



3, A research into the relations of electrical conductivity 

 and temperature makes up a part of the labors of Matthiessen. 

 In addition to his well-known results for pure metals, Mat- 

 thiessenf and his friends investigate the electrics of alloys of 

 PbAg, Sn Au, SnCu, SnAg, ZnCu, AuCu, AuAg, PtAg, PdAg, 

 CuAg, FeAu, FeCu, PCu, AsCu, and some other metals. Un- 

 fortunately not all of these alloys are available for the present 

 discussion, as Matthiessen's purpose seems rather to have been 

 the exploitation of a great number of series of groups of 

 alloys. On the other hand it is my purpose to examine the 



*Cf. 0. L. Weber: Wied. Ann., xxiii, p. 447, 1884; ibid., xxxi, p. 243, 1887. 

 Battelli: Beiblatter, xii, p. 587, 1888. 



f Matthiessen and Vogt: Pogg. Ann., cxxii, p. 19, 1864. 



