AMERICAN 



JOUENAL OF SCIENCE AND ARTS. 



[THIRD SERIES.] 



Art. LIV.— i\^ofe on the Duplicity of the "1474" line in the 

 Solar Spectnim ; bj Professor C. A. YouNG, 



The line " 1474 " is the one which is reversed in the spectrum 

 of the Solar Corona, and coincides with one of the short lines 

 in the spectnim of iron. In the iron spectrum it is brought 

 out, however, only by the Ley den jar spark, and not by the 

 electric arc between carbon points. As seen in the solar spec- 

 trum, with ordinarv, or even very powerful, spectroscopes, it 

 appears like a fine, "hard, black line. 



In examining this portion of the spectrum recently with a 

 diffraction spectroscope, armed with a silvered glass "gitter- 

 platte " of 8640 lines to the inch, for which I am indebted to 

 the kindness of Mr. Rutherfurd, I find this line to be unmistak- 

 ably double ; the two components are separated by a distance 

 of only about j of a division of Angstrom's scale, i. e. about 

 ?'» of the distance of the D lines. The more refrangible com- 

 ponent is heavier than the other and slightly winged or hazy at 

 the edges, while the other is narrower and better defined. The 



more refrangible line is undoubtedly the real 



the other belongs to the spectrum of iron, the close coincidence 



being merely accidental. 



As long ago as 1870 I suspected the bright 1474, as seen on 

 the limb of the sun, to be very slightly more refrangible than 

 its dark analogue (the position of which with insufificient dis- 

 persive power would apparently correspond to the mean of the 

 two components) ; and the suspicion has recurred from time to 

 time on many occasions since then, while there has not been 

 a single instance in which the bright line appeared to fall below 



Am- -Jopk. Scl-Thibd Sbribs, Vol. XI, No. 66.-Juini!, 187«. 



