ADVERTISEMENT, 



The present publicatiou is one of a series devoted to the discus- 

 sion and more precise determination of various "Constants of 

 Nature ; " and forms the Fifth contribution to that subject pub- 

 lished by this Institution. 



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

 Gravities" and of Melting and Boiling Points of Bodies, prepared 

 by the same author. Prof. F. W. Clarke, was published in 1873. 

 The Fovrth part of the series, comprising a complete digest of the 

 various "Atomic Weight" determinations of the chemical elements 

 published since 1814, commencing with the well-known " Table of 

 Equivalents" by Wollaston, (given in the Philosophical Trans- 

 actions for that year,) compiled by Mr. George F. Becker, was 

 published by the Institution in 1880. The present work which may 

 be regarded as practically supplementary to that digest, (or perhaps 

 rather as the memoir to which that digest is introductory,) com- 

 prises a very full discussion and re-calculation of the "Atomic 

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

 most probable value to each of the elements. 



The manuscript of the work was presented to the Institution 

 in its completed form by Prof. F. W. Clarke, the cost of publica- 

 tion only being at the expense of the Smithsonian fund. 



Spencer F. Baird, 



Secrttary of Smithsoniati Institidion. 



Washington, January, 1882. 



