OF AIITS AND SCIENCES. 



241 



dence against it. Accordingly, another method of determination was 

 devised, and the two distinct but concordant series of results obtained 

 by this method fully confirmed the higher value. The aspect of the 

 case was now wholly changed, — it presented two series of coinci- 

 dences, of which one must necessarily be due to chance alone ; and 

 in such a case certainty can be reached only through a complete 

 and intelligent reconciliation of the conflicting evidence. A careful 

 examination of the possible sources of inaccuracy involved in all 

 recent analyses failed to reveal the probability of a constant error 

 greater than two or three units in the second decimal place. There- 

 fore a complete examination of the older work seemed imperative, 

 and the object of the present paper is to describe such a revision. 



A brief review of earlier determinations is given in the first paper 

 of the present series, but for the sake of convenient reference a com- 

 plete summary is repeated below. On account of the present uncer- 

 tainty with regard to the ratio of oxygen to hydrogen, the standard 

 to which the figures in the following table are referred is the arbitrary 

 one, 0= 16; and this standard has been adopted throughout the 

 present paper. 



Atomic Weight of Copper. 



0= 16.000. 

 Berzelius, 1828, from CuO 



(Pogg. Ann., VIII. 182.) 



Erdmaun and Marchand, 1844, from CuO 



(J. pr. Chem., XXXI. 391.) 



Dumas, 1859, from CuO and CugS (?) 



(Ann. de China, et de Phys., [3J, LV. 129, 198.) 



Millon and Comaille, 1863, from CuO 



(Compt. Rend., LVn. 147; Fres. Zeitschr., II. 474.) 



Hampe, 1874, from CuO 

 " " from CUSO4 



(Fres. Zeitschr., XIH. 352 ; XVI. 458 ) 



Baubigny, 1883, from CUSO4 



(Compt. Rend., XCVII. 854, 906.) 



Shaw, 1886, through electrolytic equivalent 



" " " " " corrected 



(Phil. Mag., [5], XXIII. 138.) 



Richards, 1887, 1888, by relation to Silver 



(These Proceedings, XXII. 342; XXIII. 177.) 



" 1890, from Cupric Bromide (two series) 



(These Proceedings, XXV. 195) 

 VOL. XXVI. (n. s. xviii.) 16 



Cu = 



63.29 



63.47 



63.50 



63.12 



63.34 

 63.32 



63.47 



63.48 

 63.51 



63.60 



63.61 



