of light in the ratio of 2.5 to 1, and an increase of two magnitudes an
accession of 6.25 to 1, the significance of such variations as Eros
exhibited becomes immediately apparent. The shortness of the period
within which the cycle of changes occurred, about two hours and a half,
made the variation more noticeable, and at the same time suggested a
ready explanation, viz., that the asteroid was rapidly turning on its
axis, a thing, in itself, quite in accordance with the behavior of other
celestial bodies and naturally to be expected.

But careful observation showed that there were marked irregularities in
the light fluctuations, indicating that Eros either had a very strange
distribution of light and dark areas covering its surface, or that
instead of being a globular body it was of some extremely irregular
shape, so that as it rotated it presented successively larger and
smaller reflecting surfaces toward the sun and the earth. One
interesting suggestion was that the little planet is in reality double,
the two components revolving around their common center of gravity, like
a close binary star, and mutually eclipsing one another. But this theory
seems hardly competent to explain the very great fluctuation in light,
and a better one, probably, is that suggested by Prof. E.C. Pickering,
that Eros is shaped something like a dumb-bell.

We can picture such a mass, in imagination, tumbling end over end in its
orbit so as to present at one moment the broad sides of both bells,
together with their connecting neck, toward the sun, and, at the same
time, toward the observer on the earth, and, at another moment, only the
end of one of the bells, the other bell and the neck being concealed in
shadow. In this way the successive gain and loss of sixfold in the
amount of light might be accounted for. Owing to the great distance the
real form of the asteroid is imperceptible even with powerful