848 
are of different rapidity, as is usually the 
case, the result will be different. A diagram 
was shown of a slightly modified light-curve 
of variable No. 7 of cluster M. 5. In order 
to represent the variable at a complete min- 
imum the exposure must close before the 
beginning of the maximum phase. The 
photograph, the middle of whose exposure 
is at the beginning of maximum, will have 
the first half of its exposure at minimum 
and will record the variable as of less than 
maximum brightness, and the maximum 
possible on such plates will be recorded on 
the exposure commencing at the beginning 
of maximum. With the usual exposure of 
one hour for this cluster, the photograph 
beginning an hour before maximum would 
record the minimum photographic magni- 
tude. This retardation will depend upon 
the light-curve and the exposure time. In 
general the difference in time between the 
photographed and the actual maximum or 
minimum varies, with zeroas a limit, as the 
exposure is reduced. Evidently a large 
telescope and very sensitive plates are de- 
sirable. 
Probably the shortest period yet found is 
that of No. 91 in w Centauri, 6° 117; as 
it is not improbable that much shorter pe- 
riods may be discovered, it is clear that the 
relation of the exposure to the period be- 
comes very important. (To be published 
in the Astrophysical Journal.) 
Neither the original papers nor abstracts 
have been obtained of the following : 
WILLIAM HARKNESS: On the Semi- Diameters 
of the Sun and Moon. 
F. R. Moutton: Problems in Modern Celestial 
Mechanics Treated by the use of Power 
Series. Laplace's Ring Nebular 
Hypothesis. 
The committee on the total solar eclipse 
of May 28, 1900, consisting of Professors 
Newcomb, Barnard, Campbell and Hale 
SCIENCE. 
[N.S. Vou. X. No. 258. 
(Secretary), presented this preliminary re- 
port: 
THE TOTAL SOLAR ECLIPSE OF MAY 28, 1900. 
The committee on the total solar eclipse 
of May 28, 1900, appointed at the Second 
Conference of Astronomers and Astrophys- 
icists, presents herewith a preliminary re- 
port. 
The aim of the committee has been: 
1. To ascertain the opinion of astrono- 
mers regarding the best means of securing 
cooperation, the most important classes of 
observations and the best means of making 
them, and the plans of the various eclipse 
parties. 
2. To collect other information likely to 
be useful to persons planning to observe the 
eclipse. 
For the purpose of securing information 
on the various points referred to in para- 
graph (1) a circular letter was addressed to 
American astronomers. From an examina- 
tion of these replies it appears: 
1. That there is a general willingness to 
codperate with the committee in securing 
thorough observations of the eclipse phe- 
nomena and effective distribution of sta- 
tions along the line of totality. 
2. That, in the opinion of those from 
whom the replies were received, the most 
important observations includes studies of 
the minute structure of the corona, both 
visually and by means of large scale photo- 
graphs ; photography of the flash spectrum 
and determination of the wave-length of 
the green coronal line ; measurement of the 
heat radiation of the corona ; photographic 
search for an intra-mercurial planet. 
3. That several institutions, including the 
Princeton, Lick, Naval, Goodsell, Chabot, 
Flower and Yerkes Observatories, will prob- 
ably be represesented by well-equipped 
parties, while a considerable number of as- 
tronomers with good instrumental equip- 
ment will take part as individuals. 
