706 
lines of hydrogen and three of helium were all that 
could be measured. The H line of calcium is con- 
cealed by the broad H of hydrogen. On some of 
the plates the presence of the fainter component 
of the binary is made evident by the doubling of 
the lines of hydrogen and helium, so that on these 
plates three different velocities are indicated—that 
of each component of the binary and that of the 
K line. 
The orbital elements derived are as follows: 
Bright Com. Faint Com. 
Period, P ....... 6.8292 
Eecentricity, e .. 0.25 
Time of  perias- 
tO, JE sosocKs 1908 July 2.98 
Dist. node to peri- 
astron, w ..... 20° 200° 
Semi-amplitude of 
vel. curve, K .. 126 km./sec. 166 km./sec. 
Maximum velocity -+150km./seec. +120 km./sec. 
Minimum velocity —102km./sec. —211km./see. 
Projected semi-axis 
major,asint?.. 11,457,000 km. 15,094,000 km. 
Ratio of masses . 1:0.91 
Velocity of system —6.0 km./sec. 
Velocity of calcium —16.40.6 km./sec. 
The velocity of the calcium differs by ten kilo- 
meters per second from that of the center of 
gravity of the binary system—a difference that 
seems too great to be explained by errors of meas- 
urement or of the assumed wave-lengths. Since a 
uniformly moving mass accompanying the system 
would be expected to have a velocity equal to that 
of the common center of gravity of the revolving 
stars, this investigation may be regarded as tend- 
ing to support the hypothesis, favored by Slipher 
and others, of a detached calcium cloud in the line 
of sight. 
There is some indication that the period is 
slowly lengthening. It is hoped that data derived 
from some older plates by Dr. Slipher may decide 
this point. This will also have a bearing on the 
question of the location of the calcium since, if the 
star is involved in a cloud of calcium or other sub- 
stance, the friction should cause the period to 
shorten. 
The Dissolution of Solar Prominences: FREDERICK 
SLOCUM. 
Among the photographs of solar prominences at 
the Yerkes Observatory there are several series 
which show prominences in the act of dissolving. 
In general the prominences dissolve in one of the 
four following ways: 
SCIENCE 
[N.S. Vou. XXXV. No. 905 
1. By floating up and dissipating like smoke 
from a fire. 
2. By ascending and contracting into a long, 
fine filament. 
3. By being torn into fragments and borne 
away as if by a strong wind. 
4. By dissolving in situ like the trail of a 
meteor. 
These processes were illustrated by lantern slides 
giving series of views of the prominences of June 
19-20, 1911; September 19, 1911; July 25-29, 
1908; March 25, 1910, and single views of other 
prominences. 
All of the photographs were taken in the light 
of the H line of calcium with the Rumford spec- 
troheliograph attached to the 40-inch telescope. 
The Parallax of Nova Lacerte 1910: FREDERICK 
SLOCUM. 
Nova Lacerte was discovered by Espin Decem- 
ber 30, 1910. During the year 1911 ten photo- 
graphs of the region around the Nova were made 
with the 40-inch telescope for the purpose of deter- 
mining the parallax of the star. Cramer instan- 
taneous isoplates were used in connection with a 
yellow color filter. In general two exposures were 
made on each plate. The exposure time was in- 
creased from 5 to 15 minutes as the star dimin- 
ished from somewhat brighter than the 8th down 
to the 12th magnitude. Six comparison stars were 
selected as symmetrically situated as possible, and 
as near as possible to the mean brightness of the 
Nova. The parallactic displacement parallel to the 
ecliptic was measured. The value of the parallax 
came out + 0”.013 with a probable error of 
= 0”.014. This would mean that the outburst 
observed in 1910 really occurred 250 years ago. 
A Simple Pyrheliometer: W. J. HUMPHREYS. 
This instrument consists essentially of a spher- 
ical Dewar bulb filled with mercury and provided 
with means for absorbing solar energy and meas- 
uring its effect. 
A hollow platinum cone, polished on the inside, 
about seven centimeters long and with an opening 
one centimeter in diameter is symmetrically im- 
mersed in the mercury and set so that it will re- 
ceive sunshine through a suitable system of dia- 
phragms. Such a cone is well nigh a perfect 
absorber of radiation parallel to its axis, and as 
constructed the heat absorbed is rapidly trans- 
mitted to the mereury, the expansion of which is 
measured in a thermometer stem. 
The readings consist in taking the time interval 
during the expansion of the mercury up the ther- 
