A RECALCULATION" OF THE ATOMIC WEIGHTS. 



BY FRANK WIGGLESWORTH CLARKE. 



INTRODUCTION. 



In the autumn of 1877 the writer began collecting data relative to 

 determinations of atomic weight, with the purpose of preparing a com- 

 plete resume of the entire subject, and of recalculating all the estima- 

 tions. The work was fairly under way, the material was collected and 

 partly discussed, when I received from the Smithsonian Institution a 

 manuscript by Professor George F. Becker, entitled " Atomic Weight 

 Determinations: a Digest of the Investigations Published since 1814." 

 This manuscript, which has since been issued as Part IV of the " Con- 

 stants of Nature," covered much of the ground contemplated in my own 

 undertaking. It brought together all the evidence, presenting it clearly 

 and thoroughly in compact form ; in short, that portion of the task could 

 not well be improved upon. Accordingly, I decided to limit my own 

 labors to a critical recalculation of the data ; to combine all the figures 

 upon a common mathematical basis, and to omit everything which could 

 as well be found in Professor Becker's " Digest." 



In due time my work was completed, and early in 1882 it was pub- 

 lished. About a year later Meyer and Seubert's recalculation appeared, 

 to be followed later still by the less elaborate discussions of Sebelien and 

 of Ostwald. All of these works differed from one another in various 

 essential particulars, presenting the subject from different points of view, 

 and with different methods of calculation. Each one, therefore, has its 

 own special points of merit, and, in a sense, reinforces the others. At 

 the same time, the scientific activity which they represent shows how 

 widespread was the interest in the subject of atomic weights, and how 

 fundamentally important these constants undoubtedly are. 



The immediate effect of all these publications was to render manifest 

 the imperfections of many of the data, and to point out most emphatic- 

 ally in what directions new work needed to be done. Consequently, there 

 has been since 1884 an extraordinary activity in the determination of 

 atomic weights, and a great mass of new material has accumulated. The 

 assimilation of this material, and its combination with the old data, is 

 the object of the present volume. 



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