464 W. MM. Harvingion—Brief Study of Vesta. , 
ter at mean distance from the Sun is 0°49, her diameter in 
miles must be not inconsiderable. In fact, a simple calculation — 
shows that with this angular diameter the diameter is about 
justified on general principles. The albedo of Saturn is peculiar 
and is approached only by that of Neptune. The asteroids are 
much more likely to be like their nearest neighbors, Jupiter or 
Mars. Considering their small size, however, and remembering 
how important a part the size plays in the process of cooling, 
causing presence or absence of clouds, water, etc., we may i 
sider it more probable that these bodies resemble those other 
small bodies, the Moon and Mercury. 
As a result of my observations and of the other considerations 
just mentioned, we may, I think, conclude that the present state 
of knowledge renders the following conclusions probable: — 
1. Vesta is a body upwards of 500 miles in diameter. 
2. She is like the moon in her albedo and therefore probably 
like her in lacking an appreciable atmosphere and water. 
8. To account for the irregularities of her light, we may pre 
sume that she has a very rough surface and rotates on oedowip 
The time of rotation can not be guessed at, but the rapidity 0 
the changes in her light indicates that it is short. : 
4, What is true of Vesta is likely to be true, mutatis mulan- 
dis, of the other asteroids. : 
Subsequent observation may modify these conclusions Oe 
rially, or may prove that the asteroids are even more dissimila 
Ann Arbor, Michigan, Oct. 10, 1883. 
