r>76 



DR EDWIN H. BARTON ON THE TEMPERATURE VARIATION 



Results. — The kicks obtained with mixtures 2 and 3, and the deduced values of k 

 for tliem, are shown in the following table : — 



No. of Mixture. 



Scale Divisions for a. 



Scale Divisions for 0. 



K 



2 



+ 118-5 



-56-2 



0-86 



3 



+ 113 



-51-2 



0-78 



Hence the value of k for the specimen of magnetite used is 



0-82 nearly 



(7) 



24. Other Results. — Having k we can get T from either (4) or (5). Putting in (4) 

 k = 0"86 and a=118"5, we obtain 



r=(o-oooi2i) 7 



(8) 



From r we can determine k. Thus in the case where, with the secondaries balanced, 

 ;i kick of 202 was obtained with this specimen of magnetite, we have the equation 



|(HV4,r^)=r sin[ arctan 144Q N ) 



1440 being the distance in scale divisions of the needle from the scale. 

 And on substituting here the value of V already quoted, we obtain 



k' = 0-39 , (9) 



Again from equation (4), Art. 17, we have 



N= 



K — K 



(10) 



Thus for the piece of magnetite in question 



0-82- 0-39 

 0-82 x 0-39 



(11) 



This piece has a length equal to 3 "36 times its equivalent diameter (i.e., the diameter of 

 a cylinder of equal cross-sectional area). Now applying the formula * 



^-i)(^4±- : .-i) . . 



* Maxwell's Electricity and Magnetism, 3rd edition, vol. ii. p. 69. 



(12) 



