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by the double reflection of light between the two inner lenses of the object-glass, provided their curvatures were nearly, but not exactly the same. It was suggested that he point the telescope at Sirius and see if a similar appearance did not surround the star. He probably found that such was the case.

The transits of Venus across the sun's disk are among the rarest phenomena of astronomy, as they occur, on the average, only once in sixty years. For many centuries past and to come there will be a regular cycle, bringing about four transits in two hundred and forty-three years. The intervals between the transits are one hundred and five and a half years, eight years, one hundred and twenty-one and a half years, eight years; then one hundred and five and a half years again, and so on. The dates of the last six transits and the two next to come are as follows:

It will be seen that no person now living is likely to see this phenomenon, as the next transit does not occur until 2004. Yet, the time when Venus will appear upon the disk on June 8 of that year can now be predicted for any point on the earth's surface, within a minute or two.