188 Loomis — Effects of Changes of Temperature on 



less than 2°, making the angular throw of the needle less than 

 one degree. The deflections in scale divisions were therefore 



taken as proportional to sin — . The error in case of the larg- 



est reading would not exceed one part in 3,500 ; and as the 

 results are obtained by subtraction of two throws, the error in 

 the result may be neglected. 



/Specimen Calculation. 

 Magnet A.— Middle to North End. 













Difference 













in distribu- 





Average 



Average 





Difference 



tion in 





observed 



observed 



Corrected 



in distribu- 



C.G.S. 





throw at 



throw at 



throw at 



tion in scale 



lines of 



Steps. 



14° C. 



99°5 C. 



99- °C. 



divisions. 



inductions. 



I 



18-0 



17-5 



18 3 



— 0-3 



— 0-4 



II 



18-4 



18-1 



18-9 



— 0-5 



- 0-7 



III 



11-8 



12-6 



13*2 



— 1*4 



— 2-0 



IV 



- 7-2 



- 4-2 



— 4-4 



— 2-8 



- 3'9 



V 



— 34-3 



-27-2 



— 28-4 



— 5-9 



— 8-3 



VI 



— 42-0 



-27-7 



— 28-9 



— 13-1 



— 18-3 



YII 



— 49-0 



— 19-4 



— 20-3 



— 28-7 



— 40*2 



End 



— 5-4 



— 2-2 



— 2-3 



— 3-1 



— 4-3 



In getting the sum of the distributions it was found necessary 

 to make use of the formula on p. 187, because the angles were too 



large to take sin — proportional to tan 20. The corrected read- 

 ings were reduced to absolute measure in the way just de- 

 scribed. Thus we have the sum and difference of the linear 

 distribution of the two magnets in absolute measure. One half 

 the sum plus one half the difference gives the distribution of 

 one magnet ; and one half the sum minus one half the differ- 

 ence gives that of the other. The distribution at the higher 

 temperature was obtained by subtracting* the change in distri- 

 bution due to the heating from the distribution at the lower 

 temperature. The induction at each point of the magnet was 

 obtained by adding up the number of lines of induction pass- 

 ing out of the magnet beyond that point. 



Tables of the results for magnets A and B are given on pages 

 192 and 193. The first column gives the distance of the exploring 

 coils from the centers of the magnets at the end of each step. 

 The second and fourth columns give the number of C.G.S. 

 lines of induction passing out from the magnet at 14° C. and 

 99°*5 C. respectively in the step of the coil shown in the first 

 column. The third column gives the change in distribution. 

 The fifth and sixth columns give the magnetizations at the two 

 temperatures, i. e., the number of C.G.S. lines of induction 

 per square centimeter of cross-section passing through the mag- 



