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cated that the object was really made up of two bodies revolving round each other — perhaps actually joined into one. But it seems more likely that the variations of light were due to there being light and dark regions on the surface of the little planet, which therefore changed in brightness according as bright or dark regions predominated on the surface of the hemisphere turned toward us. The case was made perplexing by the gradual disappearance of the variations after they had been well established by months of observation. There seems to be some mystery in the constitution of this body.

From a scientific point of view Eros is most interesting because, coming so near the earth from time to time, its distance may be measured with great precision, and the distance of the sun as well as the dimensions of the whole solar system thus fixed with greater exactness than by any other method. Unfortunately, the nearest approaches occur only at very long intervals. What is most tantalising is that there was such an approach in 1892 before the object was recognised. At that time it was photographed a number of times at the Harvard Observatory, but was lost in the mass of stars by which it was surrounded. Its distance was, astronomically, only sixteen hundredths, or some fifteen millions of miles, while the nearest approaches of Mars are nearly forty millions. There will not be another approach so near for more than sixty, perhaps not for more than a hundred years.

In 1900 it approached the earth within about thirty