38 Sir J. Norman Lockyer. 



upper strata than in the lower, snch lines showing no notable increase 

 of brightness at the points where lower strata are revealed through 

 lunar valleys. Chief among these lines are those of hydrogen, helium, 

 and calcium (H and K), but there is an additional line at wave- 

 length 4686*2 or thereabouts, which behaves in the same way. 



This line does not appear in Young's list of chromospheric lines, 

 and all attempts to trace it in known spectra have failed. A line 

 apparently coincident with it, however, has been found in the 

 photographed spectrum of a tube containing helium, which is one of 

 a series of comparison spectra being taken with the 6-inch prismatic 

 camera to facilitate the reduction of the eclipse photographs. 



The only recognised impurity in the vacuum tube used is oxygen, 

 but besides the line to which reference has been made, there are a 

 few faint lines for which no origins can at present be assigned. 



It is worthy of remark that this line falls very near to the first line 

 of the principal series in the spectrum of hydrogen, recently calculated 

 by Rydberg to have a wave-length of 4687*88.* 



As in the case of the photographs taken with the prismatic cameras 

 in 1893 and 1896, the spectrum of the chromosphere in 1898 is very 

 different from the Fraunhofer spectrum, so that we have not to deal 

 with a mere reversal of the dark lines of ordinary sunlight into bright 

 ones. (See fig. 1, next page.) 



Many very strong chromospheric lines, as the helium lines for 

 example, are not represented among the Fraunhofer lines, while 

 many Fraunhofer lines are absent from the chromospheric spectrum. 



2. The Spectrum of the Corona. 



The heights of the chief coronal rings as photographed are 

 roughly as follows : 



1474 K 60,000 miles (in lower parts of inner corona). 



3987*4 20,000 miles. 



4231 '3 More than 10,000 miles. 



The coronal rings not only differ from the chromospheric ones in 

 regard to the heights to which they extend above the photosphere, 

 but also in appearance. 



The outlines of these rings are distinctly not connected with the 

 configuration of the chromosphere and prominences. In photographs 

 taken near the beginning and end of totality, the 1474 ring is 

 brightest on the same side of the moon, although the chromosphere 

 and prominences are first visible on one side and then on the other. 

 None of the rings give any indications of increased brightness at the 

 places occupied by prominences. The green ring, corresponding to 



* Astro. Pliys. Jour.,' vol. 6. p. 237. 





