OP ARTS AND SCIENCES. 545 



NOTE COXCERXIXG THE TABLE OF ATOMIC WEIGHTS. 



Three new elements are included in the table, namely, Neon, Krypton, 

 and Xenon, discovered by Ramsay in the atmosphere. Their molecular 

 weights cannot be considered as wholly settled, but approximate values are 

 given in the list. There is a possibility that each of these values, as well as 

 those given for Argon and Helium, should be halved in order to obtain the 

 atomic weights ; but for the present it seems safest to assume a monatomic 

 molecule in each case. 



Radium, the singular substance discovered by Madame Curie, is not 

 included on account of the great uncertainty concerning its atomic weight. 

 It is possible that some of the work upon thorium and uranium is vitiated 

 by radium, and that the presence of this impui-ity may account for the 

 inconsistencies of the data. The value given for uranium depends primarily 

 on recent work by Richards and Merigold, as yet unpublished; but the 

 matter cannot be considered as settled. 



Attention is called to the low atomic weight of iron,* which was included 

 without comment last year. Investigation upon this important constant 

 is still in progress. 



* Richards and Baxter, These Proceedings, 35, 253. (1900.) 



VOL. XX XVI. — 85 



