Hutchins and Holden — Elements in the Sun. 455 



metals may be classed together. Lockyer finds four coinci- 

 dences each for molybdenum and vanadium, three for urani- 

 um, and two for cerium. The arc spectrum of each is charac- 

 terized by great complexity and vast numbers of lines. So 

 numerous are the lines in fact, that often on the photographs 

 the total space occupied by them is greater than the space not 

 so occupied. A plate ten inches long may contain a thousand 

 or so. Evidently coincidences between these and solar lines 

 cannot fail to occur as matters of chance, and therefore prove 

 nothing. One can easily count a hundred or so such coin- 

 cidences without the slightest conviction that the connec- 

 tion is other than fortuitous. Of course all this is nothing 

 against the probability of these metals being in the sun ; but 

 at the same time those peculiarities of grouping, strength of 

 lines, and other characteristics which occur in the case of iron 

 and other spectra, and which alone can serve as evidence in 

 such cases, are conspicuously absent. 



Among the metals whose existence in the solar atmosphere 

 has seemed probable, we have examined the following: 



Bismuth. — The line of the above metal at 4722*9, the only 

 line of bismuth in the arc in that whole region, coincides per- 

 fectly with the more refrangible of a very faint pair of solar 

 lines. 



Tin. — The solitary tin line at 4525, thought by Lockyer to 

 coincide, falls directly between two fine lines in the solar 

 spectrum. 



Silver. — Lockyer mentions a certain possibility of silver in 

 the solar atmosphere from the apparent agreement of two of 

 its nebulous lines with solar lines. One of these we have never 

 been able to find in the course of many photographs of the re- 

 gion in which it is given by him. 



We find seven lines of silver between 4000 and 4900. Of 

 these seven, three are what Thalen calls nebulous ; so broad 

 and hazy that their true positions cannot be determined with 

 much accuracy. These lie at about 4055'5, 40636, and 4212. 

 A fourth line at 4023 is of the same general character, but has 

 a sharp reversal which agrees with a solar line. The remain- 

 ing three lines are represented in the sun, and are given by 

 Thalen in the spark spectrum of the metal. 



4476"2. Very strong line; nebulous on lower edge. Sun 

 line strong. (Thalen, 4475.) 



4668-8. Strong, solitary line. (Thalen, 4666"5.) 



4874-3. Fairly strong. (Thalen, 4874.) 



Thus, between the limits given above, every line of silver, 

 as far as can be determined, coincides with a solar line. 



Potassium. — We could find but two lines of potassium, the 

 same that were examined by Lockyer, 4044*5 and 4048"35. 



