216 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



ments in question are made with the object of ascertaining 

 the practical value of the discovery of Mr. Lockyer, upon 

 which this observer founded a theory of possible quantitative 

 analysis; namely, that when a powerful induction coil is em- 

 ployed, and the distance between the metallic electrodes is 

 gradually increased, certain of the lines in the spectrum 

 break in the middle ; and that, upon further increasing the 

 distance between the electrodes, the hiatuses in the spectrum 

 lines increase proportionally, until the lines themselves finally 

 disappear. Without entering into the details of the experi- 

 ments of Mr. Outerbridge, it will suffice to state the results 

 which lie announces concerning the value of Mr. Lockyer's 

 proposed method on a working scale. lie found that the 

 visible differences in the spectra of two alloys of considerable 

 difference in constitution were but slightly appreciable, and 

 that when the constitution of the two alloys whose spectra 

 were composed was more nearly identical, the spectral differ- 

 ences were quite inappreciable. A variation, for example, 

 of yoVo required an effort of the imagination to detect any 

 difference. Again, the quantity of metal vaporized in the 

 process, the author claims, is too infinitesimal to give safe 

 results for a large melt, since this would be affected by the 

 least want of homogeneity of the alloy. He found, for in- 

 stance, that the loss of metal for each spark was not more 

 than one millionth of a grain. Another difficulty detected by 

 the author is in the fact that while the spectroscope is very 

 sensitive to pure metals, a comparatively large quantity of 

 gold may be present in an alloy and the spectroscope not in- 

 dicate its presence. He states that in an alloy of gold and 

 copper containing from 200 to 250 parts of gold, the gold 

 spectrum is barely visible, and the same want of sensitive- 

 ness holds good with other metallic alloys. His conclusions 

 are announced in the following words : 



"It is not impossible that future discovery may succeed in 

 explaining this anomaly, in harmonizing apparent inconsist- 

 encies, in eliminating the sources of error, and in reducing 

 the operation toVnore practical certainty; but in the present 

 state of spectroscopic science, so far as I have been able to 

 perceive, I have arrived at the opinion, not without regret, 

 that assaying by means of spectrum analysis is impracticable 

 for the purpose of mint operations." 



