BRUSH— KINETIC THEORY OF GRAVITATION. 61 



It is seen that the bismuth pendulum had the shorter period by 

 one part in 1333. This is a very gratifying confirmation in kind of 

 the earher gravity pendulum findings. 



It is also extremely interesting to note that the wcigJit-viass dif- 

 ference between bismuth and zinc appears to be many times 

 greater (''^''^^/isss) when the mass is measured by the accelerating 

 force of a steel spring than when it is measured by the accelerating 

 force of gravity as in the former pendulum experiments. This is 

 very suggestive and will be discussed in a future paper. Of course, 

 these relative values are only rough first approximations ; but their 

 difference is very much too large to be attributed to experimental 

 errors. 



More torsion-pendulum experiments are in progress, and all, thus 

 far, confirm the above findings. A pair of pure silver cylinders are 

 being prepared to compare both with the zinc and with the bismuth 

 ones. 



Although the three distinctly different lines of experiment de- 

 tailed herein loyally support each other, I hesitate to draw general 

 conclusions from their (to me) astonishing results until after much 

 further experimentation for additional data, and much more time 

 for reflection. 



I am greatly indebted to Charles F. Brush, Jr., for efficient aid 

 in preparing the apparatus described, in reducing observation data 

 and in making computations. 



Cleveland, April, 1921. 



