74 ABSOLUTE ATOMIC WEIGHT. 



Actual determinations of Half Eagles the legal weight 



being taken as standard. 



Ratio. Excess. 



20 Half Eagles, of 1881, mean, 0.99 689 311 low. 



20 Half Eagles, of 1897, mean, 0.99 976 24 low. 



Estimated Weight at mint i.oo 024 24 high. 



Legal Weight shall be i.oo ooo o high. 



Rejected coin of 1897, 0.99 593 407 low. 



Amount of Abrasion, 16 years, 287 



hence per year, 18 



These ratios and the corresponding excesses are very 

 instructive. They show 7torv very rigid the comparison of 

 ratios to the fifth place is. Our carefully made estimate of 

 the new coin at the mint, differing only by 2 milligrammes 

 from the legal standard, here shows up with an excess of 24! 



We see also that the "rejected" coin of 1897 fell almost 

 a hundred below the analytical excess of the mean for 1881. 



Again, it appears strikingly, that the mean weight of the 

 gold coin gradually approaches the legal weight, as the year 

 of coinage is less and less distant from the present. The 

 mean of 1881 was 311 low, that of 1897 only 24 low. 



It will be well to keep these cases before our eyes through- 

 out the study of this work. 



II. THE ATOMIC WEIGHT OF LEAD. BERZELIUS. 



The atomic weight of lead we find to be fully established 

 by the splendid determinations made by Berzelius more than 

 seventy years ago. The many later determinations have 

 only clouded the work of Berzelius for a time. We there- 

 fore put his name at the head of this section, hoping that 

 hereafter due credit will be given this our great master for 

 the experimental determinations which have definitely and 

 permanently established the true atomic weight of lead, 

 the metal of Saturn. 



A. Lead Carbonate Ignited. 



The earliest work of Berzelius I can find recorded on the 

 ignition of the carbonate, yielded 83.5 per cent of lead 



