then, never changed. In other words, the planet turned always the same face to the Sun. The fact lay beyond a doubt, though of course not beyond a doubter.^[1]

The years that have passed since these observations were made have brought corroboration of them. Several

observers at Flagstaff have seen and drawn them and added discoveries of their own, among whom are especially to be mentioned, of the observatory staff: Miss Leonard, Dr. Slipher, and Mr. E. C. Slipher.^[2]

In character these markings were peculiar and distinctive. In addition to some of more ordinary char-