1874.J loo [Outerbridge. 



sitions, he has omitted any explanation of the anomalous results in the 

 final part of his report. And yet it seems evident that where two metals 

 are present, the spark will to some extent elect for its vehicle the one 

 which is roost rapidly vaporized. This is notably shown in alloys of 

 gold with copper. It is also very striking in the alloy of nickel and cop- 

 per, of which our five-cent piece is made. The nickel, which constitutes 

 one-fourth, controls the color of the alloy entirely ; and yet, being far 

 more difficult of fusion than the copper, scarcely shows a trace in spec- 

 trum analysis. This resvilt is pai'ticularly regretted, because a shorter 

 way of assaying this mixture for coinage is very desirable. 



These experiments, it is believed, will be of use to show what may, and 

 what may not, be expected from the spectroscope in the way of analysis 

 where several metals are components. They may also be of use in other 

 departments of investigation. D. 



Philadelphia, October 30, 1873. 

 Wm. E. Du Bois, Esq., 



Assayer U. S. Mint. 



Sir : — In pvirsuance of instructions received from you, to examine the 

 subject of the " Electrical Spectra of Metals" with a view to its possible 

 application to assaying, I beg respectfully to report, as follows : 



"With a small induction coil, and with a two-prism Browning Spectro- 

 scope, I tried some experiments to obtain the effects recently discovered 

 by Mr. J. Norman Lockyer, of England, viz., the discernment of differ- 

 ences in the lines of the Spectra of different Alloys of Gold and Silver. 

 In other words, to utilize the Spectroscope as a means of quantitative, as 

 well as of qualitative analysis. 



I had several interviews with Professor Barker, of the University of 

 Pennsylvania, (a recognized authority on the Spectroscope), who had re- 

 cently met Mr. Lockyer in England, and to whom I am indebted for 

 valuable information pertaining to the subject. 



I soon found that although I was able to distinguish clearly between 

 the spectra of pure gold, 1000 fine, and of an alloy of gold and copper 

 900 fine, inasmuch as the copper lines appeared in the one case, and not 

 in the other, the induction coil was quite inadequate in its length of spark 

 to exhibit any appreciable differences between two alloys of gold and 

 copper. I then applied for, and was accorded by my friend President 

 Morton, of the Stevens Institute of Technology at Hoboken, the privi- 

 lege of conducting my experiments at that Institution. 



Professor Morton most kindly placed at my service the elaborate 

 apparatus in his collection ; and I visited New York on Monday last, the 

 27th inst., returning this evening. 



During these four days, I experimented very critically with known 

 alloys of gold, silver and copper, previously prepared for this purpose, 

 and I obtained some very interesting results. Many practical difficulties 



