IN CONNEXION WITH THE SPECTKUM OE THE SUN. 
483 
The opposite pole was composed of some supposed pure lead, and it was observed 
that its lines were longer than those of the lead in the alloy. A very faint line was 
observed in its spectrum opposite to the silver line 5290 ; but this was most probably 
the faint lead line 5206, as the longer silver lines did not exhibit themselves in its 
spectrum. 
The opposite pole was now replaced by one of common sheet lead (it had at first 
been pure assayers’ sheet), and the line in question was not stronger than in the pure 
lead ; hence it was almost certainly the line 5206 of lead. 
In order to see how much silver was required to render its spectrum visible, and as the 
common sheet lead was suspected to contain traces of silver, an alloy was made which 
contained 0-01 per cent, of silver. In this no silver lines were visible ; and the same 
result appeared when ’05 per cent, silver was alloyed with the lead. The same was the 
case when 0T1 per cent, was added; and even the use of a large jar failed to cause the 
silver lines to appear. 
Finally, an alloy containing TO per cent, was made, and in this the silver lines 
appeared very distinctly, and three in number; 5464 was the longest, 5209 next, and 
5470 the shortest. 
Another alloy with 0 - 5 per cent, was now made, and in this the two lines of 
silver at w. 1. 5464, 5209 were at last discovered, but they were very short and faint. 
Continued work showed that the line 5464 dies out between -05 per cent, and 0-2 
per cent, of silver (for it was at last discovered in the ’05 per cent, alloy), and also 
convinced me of the extreme irregularity of the various portions of the alloy, though 
they had been made with the greatest accuracy which the means at my command 
permitted. 
Experiments were also made with alloys of tin and cadmium, the latter forming 0-154 
per cent, of the alloy. The longest cadmium line at w. 1. 5085 alone remained perma- 
nently visible, exceedingly faint, but unchanged in length ; it had a short bright stump. 
When the line at w. 1. 4799 was observed it appeared as a stump only, and neither 
4677 nor any other cadmium lines could be found. Another alloy of tin with 1-0 
per cent, cadmium showed 5085 distinct and bright, as was 4799; 4677 was likewise 
distinctly visible, and the tip of the least refrangible winged line 5377 commenced to 
appear. The other winged cadmium line, 5338, could not be identified, as it is nearly 
coincident with a tin line. After this, with the increased percentages of 5 per cent, 
and 10 per cent, of cadmium, the effect was mainly to lengthen and brighten the longest 
lines. 
In order to determine whether these results would be affected by the presence of other 
metals in the alloy, one was made of 89-11 per cent, lead, 9-90 per cent, zinc, -09 per 
cent, cadmium, and 0‘85 per cent, tin; and the cadmium line showed no appreciable 
difference from its appearance in an alloy containing 0T per cent, cadmium with 
99-9 per cent, of a single other metal. 
In the Mint specimens with their small variations I found the same phenomena en 
