386 Dr. C. Chree. Collimator Magnets and the 



Table VII. 



2- 



Number 

 in sub- 

 group. 



Mean 

 loy 



Mean 



ioy. 



Mean fx. 



Mean m. 



Mean 1C 

 When + . 



¥ x P/r 2 . 

 When^. 



Above mean . . . 

 Below mean . . . 



33 

 49 



457 

 276 



160 

 133 



5*94 

 5-43 



873 

 873 



854 

 836 



303 

 387 



Table VII, like the two previous tables, points to soriie connection 

 between large values of /x and q. Out of the first twenty magnets, the 

 arrangement being in descending order of q, only two had a value of /x 

 below the mean for group C. 



The association of large values of /x and q in group C is not, how- 

 ever, without some conspicuous exceptions ; for instance, the magnet 

 coming eighteenth in the list just referred to had a /x of only 4*71. 



§ 17. There are several other interesting features in Table VII; e.g., 

 only about two-fifths of the magnets had a q above the mean. Again 

 the fact, partly accidental of course, that the two sub-groups should 

 have precisely the same mean m is strong evidence that in the magnets 

 of group C the size of the principal temperature coefficient is inde- 

 pendent of the capacity of the steel to retain a large magnetic moment. 



The mean q' of the first sub-group of Table VII is distinctly larger 

 than that of the second sub-group, but the evidence of a tendency in 

 large values of q and q' to go together is not wholly conclusive. Thus 

 out of the thirty-three magnets whose q exceeded the mean, fourteen 

 had a q' below the mean ; and two of these fourteen had the largest q's 

 t)f the group. The force of such notable exceptions is weakened, how- 

 ever, by the consideration that an experiment which makes q slightly 

 too big is more likely than not to make q' considerably too small. 



§ 18. Groups B and E are the only ones beside C which are suffi- 

 ciently numerous and homogeneous to merit analysis. In the two fol- 

 lowing tables I give the results obtained by subdividing each of these 

 groups into two numerically equal sub-groups, according to the size, 

 first of m, second of /x. 



Table VIII. — Mean Values of Constants in Sub-groups. 



Group. 



Sub-group 

 in order 

 of m. 



m. 



7T"K. 



lO 6 ?. 



ioy. 





Mean m. 

 Mean fx. 



10 5 x P/r 2 . 



B { 



First 6.. . 

 Second 6 . 



759 

 584 



2850 

 2685 



273 

 241 



135 

 102 



6-10 

 5-96 



124 

 98 



-475 

 -395 



E { 



First 5. . . 

 Second 5 . 



883 

 791 



2529 

 2511 



336 

 362 



162 

 150 



7'56 

 7'56 



117 

 105 



+ 737 

 + 572 



