R. Meldola—Bright Lines in the Solar Spectrum. 293 
regions, but that somewhere in the higher regions, or above 
the chromosphere,* the temperature falls off sufficiently for 
some kinds of chemical combination to take place—say, in the 
d 
States that ‘gases in the solar atmosphere which are kept 
asunder by the temperature of its lower strata may be able to 
b ’ 
* 
im temperature for combustion to take place: 
€ region which is called the chromosphere is distinguish- 
able as such through what may be called an optical accident : 
it is that zone of incandescent hydrogen which is rendered 
visible by the telespectroscope; the true boundary of the hy- 
rogen atmosphere lies far above the visible chromosphere ; and 
from this latter zone outward the temperature falls off rapidly. 
* It is generally admitted that the true height of the chromosphere is consider- 
ably greater than that seen by means of the telespec since the amount of 
dispersion ni to weak red t 
Weaken and shorten the hydrogen lines by which the chromosphere is reveal 
+ It is well known that the oxyhydrogen flame does not show the lines of either 
burning gases, 
of the bu n the owever, the ons P ly very 
different. The comb es may be largely diluted with other inactive 
Furthermore the p as shown by the researches o Lockyer 
i to 
, in our 
False the point of ignition of the gases in question, so that a much higher temper- 
re would be necessary to bring about combination than if they were undiluted 
t Proc. Roy. Soe., xvii. § Loe. cit., p. 366. 
