( 211 ) 



W, = T^e j 1 + 0,39097 (^^^ - 0,009862 (^^ 



For instance cat —139° it gives W—E: +0,084. A straight line 

 may be drawn through — 182°, — 195°, — 204' and — 212° and 

 then — 217° deviates from it by 0°,25 towards the side opposite to 

 — 158''. Hence the existence of a point of inflection is certain 

 (comp. sub d). Therefore it is evident that a quadratic formula will 

 not be sufficient for lower temperatures. 



h. But also a cubic formula, even when we leave out of account 

 the hydrogen temperatures, appears to be of no use. 



For the cubic formula through the points — 88°,14, — 158°,83, 

 — 204°,69, we obtain : 



''( -^ +0,0,583861 -* 



Wt= W, j 1+0,393008 — _0,0J3677(^— J +0,0368386^^^^ 



It gives for instance at —182° a deviation of —0,110, at — 217° 

 a deviation of +0,322^). 



c. In consequence of difficulties experienced with formulae in 

 ascending powers of t, we have used formulae with reciprocal powers 

 of the absolute temperatures (comp. the supposition mentioned in ^ 1 

 that the resistance becomes infinite at the absolute zero). 



Three of these have been investigated : 



lF: = ^+^ïöó + 'tï^J+\ïööJ+lT--273;Ö9j- • (^) 



Wt _ t f ^ Y / t y no^ lo^ \ 



1f7~ "^""ÏÖÖ"^ [JÖö) ^yïööj "^ '\"7^"~ 273,09 J "^ 



"10^ 10^ 



+ « 



T» (273,09) 



Wt . t /" t y / t Y /lo» 10 



.]■ 



(^) 



l + a \-b{ +c ] +d{ + 



,Ö9J 



W^ ' 100 ' \100J ' \100J ' \T 273 



/10« 10 



"^ ' V T^ ~ (273,09)7 ' ^^^ 

 We shall also try a formula with a term — instead of — . 



For the first we have sought a preliminary set of constants which 

 was subsequently corrected after the approximate method indicated 

 by Dr. E. F. van de Sande Bakhcyzen (comp. Comm. N°. 95a) in 

 two different ways. First we have obtained a set of constants Ai 

 with which a satisfactory accurate agreement was reached down to 

 — 217°, a rather large deviation at — 252° and a moderate deviation 

 at — 259°. Column W—Rai of table II contains the deviations. 

 Secondly we have obtained a set of constants which yielded a fairly 



These values deviate slightly from those comraunicated in the original. 



