January 4, 1901.] 
| THE 6-INCH STEEL TRANSIT CIRCLE. 
[Professor Milton Updegraff, U. S. N., in charge. ] 
This instrument is made entirely of steel 
and mounted very solidly, so that the con- 
stants might reasonably be expected to be 
unusually steady. In the case of the level 
and collimation this expectation has been 
realized, but not in the case of the azimuth. 
Both the collimation and the level are re- 
markably uniform, excepting that on one 
or two occasions the latter has shown 
slight though anomalous changes. A se- 
ries of experiments made in November, 
1899, showed that the variation of the azi- 
muth keeps pace regularly with the varia- 
tion of the temperature of the steel in the 
microscope bearers on which the pivots 
rest. This variation is not, however, a 
linear function of the temperature, but is 
less per degree at low than at high temper- 
atures. The change of azimuth per degree 
of temperature (Fahrenheit) during the 
earlier part of its use seems to have been 
0°.032. Since the instrument is provided 
with a meridian mark to the north, this 
variation of the azimuth has been product- 
ive principally of inconvenience rather than 
inaccurate work; but the change is too 
great to make the instrument a suitable 
one for fundamental work. The instru- 
ment will in the near future be entirely 
dismounted and a careful investigation 
made in the hope of finding the source 
of this variation. 
THE PRIME VERTICAL TRANSIT INSTRUMENT. 
[Assistant Astronomer George A. Hill, in charge. ] 
The work on this instrument has been 
devoted to observations of « Lyre and a 
small list of suitable stars for the purpose 
of investigating the variation of latitude 
and the constants of nutation and aberra- 
tion. The number of observations is as 
follows: 
@) LEN VE2p 0 soonconsnasocadaneseTendse20050000006 89 
QOEWEL SEATS)... ccensceneceercnecesareeneceecse 75 
SCIENCE. 13 
A careful investigation of the level-con- 
stant, with a special reference to the coinci- 
dence and parallelism of the axis of the 
pivots, isin progress, but the material is not 
yet sufficient to determine whether any de- 
fect exists in regard to this which is of suffi- 
cient magnitude to affect the observations. 
THE 5-INCH STEEL ALT-AZIMUTH INSTRU- 
MENT. 
[Assistant Astronomer George A. Hill, in charge. ] 
This instrument is used principally as a 
zenith telescope for observations of latitude 
by Talcott’s method and the declinations of 
the stars of the American Ephemeris. Of the 
former there have been made 86 observa- 
tions of « Lyre and three of miscellaneous 
stars, which are reduced up to date, and 
the results in January, 1900, together with 
the material from the prime vertical instru- 
ment, sent to Professor Albrecht. Of the 
declinations of Ephemeris stars 330 obser- 
vations have been made, and the reductions 
are completed up to the end of the calendar 
year. 
The results have not yet been subjected 
to sufficient study to determine the quality 
of the instrument for obtaining absolute 
declinations, for which purpose the general 
form of the mounting is admirably adapted. 
When its usefulness in this field is estab- 
lished I propose to separate the work of the 
two instruments and employ more observers 
in this important ‘line of observation. I 
have not thought it expedient to attempt 
this until the arrears of publication are © 
brought up—a task on which all the avail- 
able force of the Observatory is now con- 
centrated. 
THE 40-FOOT PHOTOHELIOGRAPH. 
[Photographer George H. Peters, in charge. ] 
The series of daily photographs of the 
sun has been continued, weather permitting, 
except after April 2d, when they were in- 
terrupted by the preparations for the obser- 
vations of the total eclipsein May. Nega- 
