1117 



thai those metals, which show the greatest resistance change also 

 give the most difTerenl resistance curves in a Iran verse and a 

 longitudinal field. I hope to return to this point later. Fig 2 shows 

 the orientation curve. 



The full line represents the formula: 



—^ = [0,519—0,510 .sh> 1 ,125 (81— 1.0 sin yi)] ^ 



+ [0,167—0,1696 .sm 2,665 (30— [Xp ros f/.|)]l 



where q is the angle between the direction of the field and the 

 principal axis of the crystal. 



To represent the resistance change in the field in one of the two 

 principal directions, different types of formulae were tried. Finally 

 certain considerations, which may be omitted here, led to the form 



^' . , 



~ = a -\- h sine (d — p;^|) (3). Because of the connexion between the 



constants for the field Sp =z 0, this formula has three constants. The 

 above formula (2) is derived from (3) by resolving the Jp under the 

 sin. into its components. As R' — R is very small compared with 

 R and as there were no special precautions taken with regard to the 

 orientation, we may regard the agreement of the observed points 

 with the calculated ones as fairly satisfying. 



§ 4. Isothermal curves-. Fig 3. 



As to these we may remark, tiiat the quasi-linear part of the field 



curves is already reached at 30 KG. Of earlier investigations must 



be mentioned those of Lf,nard ^), who used pressed antimony wire, 



0.2 mm. thick. This highest field was 6.6 KG. where he found 



R' 



— ^1.012 for a constant current; and also those ot v. Ettings- 



R 



nAUSEN "), Lebret ") and Bariow ^). 



Fig. 3 shows the field curves for 18° and — 188° in two principal 



directions. The formulae used are: 



Table 2. —^"=1.519 — 0.510 .s/« 1.125 (81 - |.r-)// |) 



•) In this and in the other formula 'c is expressed in dogrees. 



2) Ph. Lenard, Wied. Ann. 39, p. G37, 1890. 



S) A. V. Ettingshausen, Wien. Akad. Ber. 59, p. 714, 1887. 



*) A. Lebret, Diss. Leiden, 1895. 



5) G. Barlow. Ann. d. Phys.. 12, p. 916, 1903. 



