1170 



cf. J. Clay, Jahrb. Rad. u. Elektr. XII, p. 263, 1915. 

 (drawn on lialf as small a scale compared to the others). 

 (h) . Aii = (w)p,i' ~(to)ptm 



H.KamerlinghOnnes and J.Clay Leiden Comm. N'. 996; cf. J. Clay I.e. 

 c) ...... . Am ={io)pt^i — (ir)^^ 



obtained bv computing from the tables for Pt\ ^) the values of 70 

 corresponding to the temperatures at which Pf — 21 was measured. 



(^ -^ IV = («'),! — ('"),. 



(from table III). 



(«).-. Av = («')» -i^v),, 



(The platinum wire Pt — 28 was measured at the same time as 

 Pt — 21 and others at the temperatures of liquid methyl chloride, 

 ethylene, oxygen and hydrogen, but not in the range between 20° K. 

 and 56° K.) 



Some of these curves show striking points of resemblanoe, others 

 equally striking differences. Three of them, viz- Aj, An, Am may 

 be represented with a sufficient approximation by a linear function 

 of éJ: 



A/ = — 3-03 <9. 10-5 . . . . . . . (3) 



(down to — 180° C. v e. as far as the measurements extend) 



A// = — 0-748. <9. 10-5 ^ (4) 



(down to — 216° C. again as far as the measurements reach) 



A/iy = — 0-748. <9. 10-5 (5) 



(down to the hydrogen region) ') 



This last result is very noteworthy: A,,, does not show any sign 

 of the bend which occurs in Aiy and Ay. It follows that this line 

 is better represented as a linear function of ^ than as a linear 

 function of lu (Nernst's formula). Compare for this: table IV which 

 gives besides the observed value of Am 

 in column A . 



A,4 =1 — 0-748 .<9. 10-5 (5) 



and in column B: 



Ab = \S9 .10-^ .{l -icptr) . ..... (6) 



It is also interesting to note that Aj, and A,,, coincide completely 

 (down to —216° C); the resistance of Pt 777 (Comm. N». 99b, 1907) 

 and that of Pt 21 (1915 16) thus display a similar course in this 

 region. 



^) H. Kamerlingh Onnes and G. Holst, Leiden Coram. N'^. 141a; these Proceedings 



XVII (1) p. 501. G. Holst, Leiden Gomm. N". 148a ; these Proceedings XVIII (1) p. 829. 



2) In fig. 2 these differences are represented by the straight lines I, II and III. 



