m) 



V10 



T 



2500 



50Ji) 



7W 



and transverse effects are combined. At 4°,25 K the tiji is still in a 

 state of ordinary conductivity, the curve, which represents the 



resistance as a function of 

 the field decreases in steep- 

 ness (see fig. 2) with a dimin- 

 ishing field and meets the 

 axis of ordinates pretty nearly 

 parallel to the axis of abcis- 

 sae. The only thing, there- 

 fore, that is remarkable here 

 as compared to what is obser- 

 ved at higher temperatures, is 

 the decrease of the slope to 

 zero. There is no indication 

 of a sudden chansje. 



With the supra-conducting 

 «jw^Co^ tin at 2° A' we find, as with 

 Eig 2. lead a sudden change, in 



this case at the threshold value of 200 gauss. In fact with tin at 

 2° K we are much nearer to the temperature of sudden change for 

 the resistance (3^,8 K) than in the case of lead (sudden change for 

 the resistance 6° K (?) (comp. Comm. W. 133). 



§ 3. Separate observations of the longitudinal and of the trans- 

 verse ejfect loith lead. 



Pressed lead wire was wound on a plate, so as to cover it with a 

 few fiat layers of insulated windings. The windings could be so directed 

 that the effect was entirely transverse, or almost entirely longitudinal. 

 The results for the tempera- i5o' 



tures of 2° A' and 4°.25 A' 

 are given in the four curves 

 in fig. 3. 



The sudden change in 

 both effects takes place 

 almost at the same threshold 

 value of the field. The long- 

 itudinal effect is weaker than 

 the transverse effect. The 

 value of the effect at hydro- 

 gen temperatures was exam- 

 ined by Dr. K. Hof and 



myself, and I take this ^ isoo sooo 



opportunity to thank him Eig. 3. 



zoo 



■150 



^oo 



.50 



wii?-' 



Wo 



7500 



1000 comi 



O^i 



