86 The Spectroscope in Mint Assaying. (January, 
A very curious fa¢t is apparent in all these spectra, viz., 
the unequal lengths of the spectral lines. Some of the lines 
of bismuth, for example, are seen to extend nearly across 
the field of vision, while others appear as mere points upon 
the edge. Mr. Lockyer has published some most interesting 
investigations upon the subject of these ‘‘long and short 
lines?” 
Proceeding to the examination of gold alloys, and starting 
with base poles,—making the lower poie 250 fine and the 
upper pole 500 fine, —the gold lines from the upper half were 
both longer and brighter. Now substituting in place of the 
250 pole one 700 fine, the lower half showed the brighter 
gold lines. Then, changing the 500 pole for one 800, the 
brightness of the gold line was again reversed. ‘This alter- 
nating effect may be continued, decreasing in degree as the 
fineness of the poles approach more nearly together, until 
both poles are of the same fineness, when the lines will be 
equal in length and intensity, 
These experiments proved satisfactorily that comparatively 
wide variations in the composition of gold alloys were dis- 
cernible. A series of graduated alloys, of more approximate 
fineness, was now prepared at the Mint, viz.— 
Gold and Copper. Gold, Silver, and Copper. 
g38°0 g40°1 
917°0 g18°7 
go6'o 860°8 
888°3 | 888°0 
883°5 884°1 
876°5 883°0 
These alloys were carefully prepared, and assayed closely. 
With one electrode pure gold and the other 938 fine, the 
difference between the respective spectra was of course very 
marked, the copper lines appearing in the one and not in the 
other. Substituting for the pure gold the alloy 876'5, the 
difference was still very marked, for, although both gold and 
copper appeared in each, the copper lines were much 
brighter and somewhat longer in the baser alloy, while the 
gold lines were brighter and longer in the finer. But on 
comparing the alloys 876°5 and 883°5 (reducing the variation 
to seven-thousandths), it was both a surprise and disap- 
pointment to find the visible difference of result but slightly 
appreciable. And the same with regard to the alloys of 
883'5 and 8883, and the same with other alloys with equal 
or less comparative variation of fineness. A variation. of 
one-thousandth required an effort of the imagination, as well 
