* 
W. M. Harrington—Brief Study of Vesta. 468 
where mM, Mg, Ms, an 
of extinction of 2164, 2163 and Vesta respectively. The change 
the later hours as the stars approached the horizon—as it should 
do. The errors arising from this source would be large if we 
all) the record gives no evidence of its being less trustworthy 
than the others. On the contrary, Vesta was at that time in 
the best position for comparison, and I had already had some 
practice in comparing her with a single star. Her faintness at 
that time was so great as to strike my attention before putting 
the wedge on my instrument. But leaving that out, the 
observations show a maximum at about XV" on the 18th, one 
18th. In general, Vesta is brighter on the 17th than on the 
16th, while as she was leaving opposition she should have 
been slightly fainter if her light is not variable. 
The series of observations on the 16th and 17th were taken 
With the hopes of finding some periodicity which might lead 
to some determination of Vesta’s rotation on her axis, but 
Without entire success. _ : 
A few remarks as to Vesta’s albedo may not be out of place. 
Several attempts have been made to measure her diameter, and 
though the measures are inharmonious, they agree among 
themselves better than do the different measures of other aste- 
roids—as Ceres and Pallas. The mean of the measures of 
Schréter, Madler, Secchi, Tacchini and Millosevich, reduced to 
Vesta’s mean distance from the Sun, as given by Houzeau 
(Vade-mecum, p. 687), I find to be 0°49. Employing this, 
using Zdllner’s formula for computing albedo (Phot. Unter- 
suchungen, page 159), and giving Vesta a purely geometrical 
phase, I find her albedo to be about 0°1.or much like that of 
the Moon and Mercury. This suggests that she has somethin 
of the physical condition of the Moon, which is also a 
by her size. We may note, however, that if her angular diame- 
