202 
SIR NORMAN LOCKYER AND OTHERS ON THE 
A very noticeable feature of the chromospheric spectra, which the photographs 
enable us to investigate at different elevations, is the difference in the behaviour of 
the gaseous and metallic lines. In the spectrum taken very near the moment 
of second contact, representing that of the lower strata with the spectra of higher 
ones superposed, the metallic arcs are relatively short and very bright, while in 
later photographs representing the spectra of successively higher strata free from 
admixture with lower ones, the metallic arcs aie relatively feeble. This is also 
indicated in another way by the varying effects seen over the tops of lunar mountains 
and through indentations in the moon’s limb. 
Some of the lines are seen to be relatively much brighter in the upper strata than 
in the lower, such 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 the series of comparison spectra 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.* 
• Fig 7. Comparison of Chromosphere and Carbon Fluting at A 3883. 
‘ Astio-l'hys. Jour.,’ vol. G, ]). 237. , 
