Ui?. 



the influence of fliu'liialions in ihe ma,ü:net ciirrenl. Tlie enrrent was 

 taken from tiie central Berlin ligliting circuit net. The chief errors 

 in tlie measurements were due to the temperature and to a less 

 extent (o the field measurement. An unfavourable circumstance is, 

 that the effect is roughly proportional to the square of the field, so 

 that an error in the field gets a double weight. When an accuracy 

 of Vs 7o is desired, the magnetic field must be known to Vsoo ^^'^^ 

 this accurac}' is not so easily attained as is often supposed. 



The purpose of this research was not to make very accurate 

 measurements, but to see, whether in this case also the orientation 

 of the crystal axis has a great influence. For graphite this has 

 already been proved by D. E. Robeuts (loc. cit.), for bismuth by 



VAN EVERDINGEN^) and LOWNDS'^). 



^ 2. Temperatare carve without field. First the cliange of the 

 resistance of antimony in the basic plane was investigated. The 

 specific resistance was not determined because of the undefiniteness 

 of the soldering places, which much diminishes the accuracy of the 

 measurements. The different temperatures were reached on the principle 

 of the Henning") cryostate. In a vacuum vessel with petroleum ether 

 was put a tube, which was closed at the lower end. With a vacuum 

 siphon this tube was filled with liquid air. This filling was not 

 regulated automatically, but with the hand. The temperature was 

 read on a pentane thermometer. 



After some practice it was found that by good stirring the tempe- 

 rature could be kept sufficiently constant. Below — 140° the petro- 

 leum ether became thick, which made good stirring difficult and 

 for this reason the lowest points were measured in the liquid air 

 itself. At —190° the curve R/R, = {^) (fig. 1) does not yet show a 

 point of inflexion. The greater the j)urity of the bismuUi the lower 

 the temperature at which the point of inflexion occurs and the 

 weaker this point of inflexion. From this we may also conclude, 

 that the antimony from Merck was very pure''). From the obsei'ved 

 values a formula A* = R^ (1 -\- ad -f- ^6) was calculated by the 

 method of least squares. 



Such a formula holds within this range of temperature. The 

 formulae of Neknst, K.amert-ingh Onnes and Wien have not been 



1) E. VAN EvERDiNGEN, Cümiii. Leiden iN". !2ü. 37. 40. 41. 4!2. 48. 53. 58, 61 

 63, 72. Suppl. 2. 



^) L. LowNDs, Ann. der Phys. 6 p. U6, 19Ü1 ; 9 p. 677, 1902. 

 3) F. Henning, Zeitschr. f. Instrk. 33 p. 33, p. 1913. 

 ^) F C. Blake, loc. cit. Table 1. 



