370 =W. W. Jacques—Diamagnetie Constants of Bismuth. 
Bismuth and cale-spar were the two crystals experimented 
upon; quite a number of other substances were tried but failed 
to give good results because of the iron contained in them as 
an impurity. e bars were each about 15™™ long and about 
2™™" in cross section. The force to be measured being only 
about ‘00000001 of that exerted in the case of iron it was 
necessary to carry out the experiments with the very greatest 
_ In order to reduce to a minimum the causes that might 
interfere with the accurate determination of the times of vibra- 
and suspended by this, Outside the glass case was a micro- 
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