384 Dr. C. Chree. Collimator Magnets and the 



The probable errors in the mean values found in these three cases 

 are certainly sensible, but still they form only a comparatively small 

 percentage of the value of P. Certain drawbacks attending large values 

 in P are dealt with later. 



§ 14. A general survey of Tables I and II shows merits and demerits 

 in most of the groups of magnets. Thus in group B the temperature 

 coefficients are exceptionally small, but on the other hand the magnets 

 are somewhat weak. Again, in group E the magnets are exceptionally 

 uniform in quality, but they possess exceptionally large permeability 

 for temporary magnetism. 



Relationships between Magnetic Constants. 



§ 15. In attempting to determine the existence or non-existence of 

 relationships between the magnitudes of the several magnetic constants, 

 one naturally turns first to the large group C. To determine whether 

 the size of the permanent magnetic moment influenced the other quan- 

 tities, I arranged the eighty-two magnets of the group in sub-groups as 

 below, and found the mean values of the several constants for each. 



Table IY. — Analysis of Magnets of Group C according to Magnetic 



Moment. 



Value of m. 



Number in sub- 

 group. 



Mean 

 m. 



Mean 



7T 2 K. 



Mean Mean 

 10 6 g. ,10V. 



Mean 

 M- 



Mean m % 

 Mean \l 



Mean 1 

 When +. 



5 xP/r*. 

 When - . 



>1000 



11 



1044 



2812 



346 



140 



5-96 



175 



1399 



481 



1000 to 950 



10 



973 



2745 



313 



143 



5-53 



176 



884 



304 



950 „ 900 



11 



921 



2702 



331 



135 



5-72 



161 



849 



188 



900 „ 875 



9 



888 



2759 



359 



149 



5-61 



158 



628 



286 



875 „ 850 



12 



. 862 



2809 



352 



144 



5-65 



153 



859 



680 



850 „ 800 



10 



827 



2720 



300 



147 



5-42 



152 



613 



350 



800 „ 750 



10 



779 



2791 



365 



156 



5-57 



140 



757 



257 



<750 



9 



653 



1 2684 



433 



137 



5-58 



117 



472 



298 



It is only natural to expect a sensible departure between the means 

 of any single property in a sub-group of ten magnets and in a whole 

 group of eighty-two magnets, supposing the sub-group selected by pure 

 chance. Bearing this in mind, we must, I think, conclude that no clear 

 relationship exists between the value of m and that of K, q, q', or fx. 

 The absence of apparent connection between m and 7r 2 K seems strong 

 evidence of the comparatively small variability in the actual size of the 

 magnets. The fact that /x is nearly, if not quite, independent of m is 

 important, because it is expedient ceteris paribus that m/fi should be as 

 large as possible. If q, q', or /x had shown an appreciable tendency to 

 vary with m we should have been led to suspect, as a priori probable, a 

 tendency to alteration in these constants as the magnet grew weaker 

 with age. The absence of any apparent connection of the kind is not, 

 however, proof positive that no such tendency exists (see § 37 later). 



