842 
sible, the photographic magnitude. This 
would also furnish a quantitative measure 
of the color. 
As it is believed that this catalogue will 
be found convenient for general reference, 
the value would be greatly increased if the 
precise position, the precession, the secular 
variation, and the proper motion were 
added. ‘This does not seem advisable, how- 
ever, since owing to the uncertainties of 
proper motion, and systematic errors in 
various catalogues, the labor involved in 
this work would be very great, and prob- 
ably many astronomers would be dissatis- 
fied with the results, however obtained. 
A simple plan would be, for the northern 
stars, to take the positions for 1875 given 
in the catalogues of the Astronomische Gesell- 
schaft, and for the southern stars those given 
in the Argentine General Catalogue. Re- 
siduals for a few other catalogues could be 
given and thus permit other places to be 
used if desired. These positions would be 
sufficiently accurate for stars of the eighth 
and ninth magnitudes, but they would be far 
from representing the accuracy with which 
the places of the brighter stars are known. 
Any suggestions and criticism relating to 
the above plan will be gratefully accepted, 
as it is not yet too late to make use of 
them. 
Some Researches in Stellar 
Color. 
By placing a coarse grating in front of 
the objective of a telescope the image of a 
star is broken up into a series of spectra 
symmetrically placed on opposite sides of a 
central image, and, as is well known, the 
distance of the several spectra from the cen- 
tralimage depends upon the grating interval 
and the wave-length of the light in question. 
When the grating interval is large, e. q., 
10 mm. to 50 mm., the first order spectra 
of stars are almost indistinguishable from 
stellar points, and if their angular separation 
G. C. Comsrock : 
SCIENCE. 
[N.S. Vou. X. No. 258. 
is measured with a filar micrometer an ex- 
cellent determination of the mean wave- 
length of the light in question is easily ob- 
tained. Observations. of this kind are in 
progress with the 40 cm. equatorial telescope 
of the Washburn Observatory, special atten- 
tion being given to colored stars and to the 
planet Mars for the purpose of determining 
any possible effect of the stellar and plane- 
tary color upon observations for the deter- 
mination of the solar parallax. While 
definite results are not yet obtainable, it 
may be stated in general that the mean re- 
frangibility of the ight of Mars is markedly 
less than that of any red stars yet examined. 
Attention has also been given to the color 
of Jupiter’s satellites on account of the ap- 
plication of interference methods to the de- 
termination of their diameters made by 
Michelson and Hamy. Both of these in- 
vestigators appear to have assumed too 
small values of the mean wave-length, that 
of Hamy requiring to be reduced about 
twelve per cent. 
F. L. Coase: Refraction of Red Stars. 
Gill in 1877 and Newcomb in 1895 have 
spoken of the importance of the effect that 
a difference in the refraction of Mars and 
minor planets from that of the comparison 
stars might have on the apparent parallaxes 
of the planets. Although feeling that in 
case of Victoria and Sappho this color effect 
was inappreciable, as stated in his recent 
work on the solar parallax, Dr. Gill re- 
quested the several observatories engaged in 
the solar parallax work to make a short 
series of heliometer observations on several 
highly colored stars. Not having time to 
carry out the program suggested by Dr. 
Gill, the author selected five other suitable 
stars and carried out the work as follows: 
The plan was to observe the distances 
between the red star and each of two nearly 
equally distant comparison stars, one pre- 
ceding in right ascension and the other fol- 
