380 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



Hence, 



From ratio 10 U = 237.244, ± .2665 



" 1 237.705, ± .1951 



" 8 238.397, ± .0285 



" 7 238.424, ± .0203 



" 6 238.902, ± .0235 



" 4 239.582, ± .0207 



" 5 239.663, ± .0279 



" 3 239.768, ± .1651 



" 2 240.228, ± .2975 



" 9 241.094, ± .6900 



General mean, U = 238.977, ± .0104 



Eatios 1, 2, 3, 9 and 10 are evidently worthless; but their omission 

 would only change the general mean by about 0.001, a negligible quantity. 

 The final result is higher than the values obtained by Eichards and 

 Merigold, which are probably the best of all the separate determinations. 

 It would hardly be safe, however, to reject the work of Zimmermanu, at 

 least until more evidence is available. The radio-active properties of 

 uranium may possibly affect its atomic weight, but that possibility re- 

 mains to be tested. 



