50 BRUSH— KINETIC THEORY OF GRAVITATION. 



TABLE I. 



Aluminum 130 



Zinc 100 



Tin 100 



Lead 93 



Silver 80 



Bismuth ^2, 



Each of the above values is the nearest whole number to the 

 mean of many observations except in the case of silver, which is 

 based on one set only. 



Occasionally, though not often, deflections were observed which 

 were considerably less than usual for the metal used, and sometimes 

 unequally less for the two metals being compared, thus showing less 

 or more contrast between them — usually less. But in no case was 

 the contrast even nearly obliterated, nor its sign changed. The 

 cause or causes of these occasional irregularities have not yet been 

 ascertained, but are diligently sought. In view of them, however, 

 the values given in the table must be regarded as fairly good first 

 approximation only. 



Pure iron was tried because, magnetically, it is the antithesis of 

 bismuth. But while it caused deflections neither very large nor very 

 small, they were quite irregular, doubtless due to local disturbance 

 of the earth's magnetic field. The slight residual magnetism after 

 the iron cylinder was subsequently magnetized horizontally caused 

 it to give widely different deflections when differently oriented. But 

 from certain pendulum experiments next to be described it is thought 

 that iron should have a place in Table I, somewhat nearer zinc than 

 bismuth, say about 87. 



The zinc and tin used in these experiments are of commercial 

 purity only ; the bismuth, silver and lead are almost chemically pure, 

 and the aluminum contains traces of silicon and iron. 



It is interesting to note that bismuth exhibits much the smallest 

 attraction per unit of weight, as was hopefully predicted ; and al- 

 though this may not be due to its exceptional diamagnetic qualities, 

 the possibility that it is so due promises a fruitful field for future 

 exploration. If further experimentation seems to warrant it, I 

 shall, in a future paper, endeavor to expand the idea that diamag- 



