B44 W. T. Sampson—=Spectrum of the Corona. 
and upon it seemed to depend the simple or compound nature 
of the gas emitting the green light. I therefore determined to 
commence my work by adjusting the slit tangent to the disap- 
pearing limb of the sun at the beginning of totality in order to 
witness the reversal of the Fraunhofer lines, so admirably seen 
Prof. Young in 1870, but not visible to some observers who 
looked for them in 1871. I proposed to look particularly for 
the 1474 line with the slit in this position and then to place it 
radially to see if the line thickened as it approached the sun’s 
surface. The remainder of the time was to be devoted to the 
dark lines of the coronal spectrum and to the polariscope. I 
was fortunate in securing the services of Dr. Dewitt, M.D., 
U.S.A., to direct my telescope. During two days we practiced 
upon the changes and adjustments I had decided upon making 
during totality. By practice upon bright clouds, the sky and 
the moon, I decided that I could open the slit to “1 mm. while 
searching for the dark lines. All previous observers had 
described the continuous spectrum as faint. It was therefore 
necessary to use a slit as wide as possible and at the same time 
e certain of seeing the lines. As totality approached we 
adjusted the slit carefully tangent to the narrow crescent of the 
sun. The slit plates had previously been covered with white 
paper to secure a distinct image of the corona at the focus of 
the objective. The telescope of the spectroscope was clamped so 
as to have the spectrum from about C to F in the field. Placing 
my eye at the telescope in time to get the last glimmer of the 
solar spectrum, I was greatly surprised an instant after at the 
briliancy with which the bright lines appeared, flashing out at 
once to their maximum brightness. The time during which 
this beautiful sight lasted was not sufficient for me to posl- 
tively identify the lines; yet their familiar grouping left no 
doubt in my mind that they occupied the places which a mo- 
ment before had been occupied by the dark lines of the solar 
spectrum. The continuous spectrum of the sun entirely disap- 
peared before the bright lines made their appearance. I coul 
not estimate the number of bright lines that were in the field 
during the probable two seconds they were visible, but they 
this brilhant line spectrum vanished, no lines either or 
right were visible, but a continuous spectrum held its place. 
I did not notice any continuous spectrum while the lines were 
visible. 
As previously arranged the slit was placed radially, still 
nothing was visible but a continuous spectrum, not bright. 
