ADVERTISEMENT. 



The present publication is one of a series devoted to the discussion 

 and more precise determination of various " Constants of Nature ; " and 

 forms the Fifth contribution to that subject published by this Institution. 



The First number of the series, embracing tables of " Specific Gravi- 

 ties " and of Melting and Boiling Points of Bodies, prepared by the saVne 

 author, Prof. F. W. Clarke, was published in 1873. The Fourth part of 

 the series, comprising a complete digest of the various "Atomic Weight " 

 determinations of the chemical elements published since 1814, com- 

 mencing with the well-known "Table of Equivalents" by Wollaston 

 (given in the Philosophical Transactions for that year), compiled by 

 Mr. George F. Becker, was published by the Institution in 1880. The 

 present work comprises a ver}^ full discussion and recalculation of the 

 " Atomic Weights " from all the existing data, and the assignment of 

 the most probable value to each of the elements. 



The first edition of this work was published in 1882, and this new 

 edition, revised and enlarged by Professor Clarke, contains new informa- 

 tion accumulated during the past fifteen years. 



£. P. L ANGLE Y, 



Secretary of the Smithsonian Institution. 

 Washington, January^ 1897. 



(iii) 



