396 
xME. J. EVERSHED OX WAVE-LEXC4TH DETERMIXATIOXS, ETC., 
Group IV. 
(Lines weak in flash and in solar spectrum.) 
Zr . . . atomic weight 90‘6 
. . . „ „ 12-0 
The elements of which the identifications are somewhat doubtful are— 
Si . . . atomic weight 2§'4 One line only X 3905‘660 
Co . . . ,, ,, 59’0 Many Co lines seem unaccountably absent 
in the flash 
La . . . ,, ,, 138‘5 Two lines only X 4123'384 and X 3649'654 
It is jDrobable that the elements of Grouj) I. are diffused throughout the entire 
depth of the flash-spectrum layer, but become denser near the photosphere. Those of 
Group II. are possibly absent from the very lowest strata, but are widely diffused in 
the higher regions; whilst the elements Fe and Ni (Group III.) would appear to he 
mostly concentrated in the lowest strata where the density is great enough to 
produce the winged absorption lines. 
Group TV. probably represents low-lying elements of small density. 
The bright lines of the flash spectrum corresponding to Grouj) 11. may he considered 
to he true reversals of the dark solar lines of these elements ; that is to say, the whole 
of the matter concerned in the absorption contributes to the emission spectra, and the 
bright and dark lines are jDractically of equal width. 
But in the emission lines of Groups I. and III. the radiation from the very lowest 
region, where the density of each element is considerable, contributes very little 
indeed to the total light, most of which comes from the higher more extensive regions 
of low density ; consequently the lines appear narrow and without aj^preciable shading. 
These lines, therefore, can only be considered as partial reversals of the corresjDonding 
absorption lines. 
The metallic elements found in the lower chromosphere (including those doubtfully 
identified) include all the known metals having atomic weights between 20 and 60, 
with the single exception of potassium. Arranged according to their atomic weights, 
they are :— 
Na . . 
approximate atomic 
weight 
23 
Mg . . 
• It tt 
3 
24 
A1 . . 
• tt 5 ? 
5 
27 
Ca . 
• 5 * 5 ? 
5 5 
40 
Sc . . 
• 35 
3 
44 
Ti . . 
• 3 3 3 } 
3 
48 
V . . 
• 15 11 
3 
51 
* Pi'obiiljly the compound cyanogen. 
