388 
MR. J. EYERSHED OX Y/AYE-LEXGTH DETERMIXATIOXS, ETC., 
For further faciiitating references to the bright lines a plate is given of the ultra¬ 
violet region of the spectrum of the lower chromosphere. In this a wave-length scale 
is given above and the designation of some of the principal lines below. The plate 
has been prepared by purely automatic methods from the original negative taken at 
second contact. By photographing a longitudinal section of this negative with a 
cylindrical lens interposed, the short sections of the chromosphere arcs are spread out 
into straight lines. 
Great care was taken to exclude spurious lines due to defects in the film or to dust 
on the slit. By using a rather wide slit these imperfections have been reduced to a 
minimum, although this involved a slight sacrifice of definition and loss of detail.—■ 
March 9, 1901.] 
Sijectrum No. 4 (Plate 11, fig. 2).—The exposure in this photograph was probably 
less than half a second duration, and was made several seconds after closing No. 3 
exposure. 
The continuous spectrum of the corona is faintly impressed^ and the green line is 
just traceable at the points where it is strongest in No. 3 spectrum. The chromo¬ 
sphere arcs H and K and the hydrogen series are narrow and well defined, the latter 
both in the visible spectrum and the idtra-violet. The three titanium lines at 
X\37G1‘5, 3759'3, and 3685'3 are shown as exceedingly fine threads, extending over 
an arc of about 60 degrees; they are distinctly stronger than the line Hp but fainter 
than H^. The hydrogen lines y, 8 and the calcium lines H and K can be traced 
Dver nearly the same extent of the limb as in No. 3 spectrum. 
The prominences are well defined in this negative and their spectra exhibit some 
interesting features. There are seven prominences clearly shown, which I have 
designated by the letters of the alphabet in the order of their position angles, as 
follows :— 
Prominence. 
Position angle. 
Solar latitude. 
A . . 
. . . 28° 
+ 54° 
B . . 
. . . 59 
+ 23 
C . . 
. . . 99 
-17 
L) . . 
. . . 126 
-44 
E . . 
. . . 306 
+ 44 
F . . 
. . . 315 
+ 53 
G . . 
. . . 322 
+ 60 
All these prominences are about equallv intense in the calcium lines H and K ; 
D is the largest and B and C are the smallest images. 
* In preparing a plate suitable for reproduction it was found necessary to intensify the image with 
uranium. This has made the continuous spectrum of the corona appear very much stronger than it is in 
the original negative. 
