observer. When the glass was simply turned over
so as to have the right face outward, the defect disappeared.

[1] In justice to Mr. Blank, I must say that there seems to have been
some misunderstanding as to his observations. What he had really
seen and observed was a star long well known, much more distant from
Procyon than the companion in question.

[2] Otto Struve was a brother of the very popular Russian minister to
Washington during the years 1882-92. He retired from the direction
of the Pulkowa Observatory about 1894. The official history of
his negotiations and other proceedings for the construction of the
telescope will be found in a work published in 1889 in honor of the
jubilee of the observatory.

VI

THE TRANSITS OF VENUS

It was long supposed that transits of Venus over the sun's disk
afforded the only accurate method of determining the distance of the
sun, one of the fundamental data of astronomy. Unfortunately, these
phenomena are of the rarest. They come in pairs, with an interval
of eight years between the transits of a pair. A pair occurred
in 1761 and 1769, and again in 1874 and 1882. Now the whole of
the twentieth century will pass without another recurrence of the
phenomenon. Not until the years 2004 and 2012 will our posterity
have the opportunity of witnessing it.

Much interesting history is associated with the adventures of the
astronomers who took part in the expeditions to observe the transits
of 1761 and 1769. In the almost chronic warfare which used to rage
between France and England during that period, neither side was
willing to regard as neutral even a scientific expedition sent out
by the other. The French sent one of their astronomers, Le Gentil,
to observe the transit at Pondicherry in the East Indies. As he
was nearing his station, the presence of the enemy prevented him
from making port, and he was still at sea on the day of the transit.
When he at length landed, he determined to remain until the transit
of 1769, and observe that. We must not suppose, however, that he
was guilty of the eccentricity of doing this with no other object in
view than that of making the observation. He found the field open
for profitable mercantile enterprise, as well as interesting for
scientific observations and inquiries. The eight long years passed
away, and the morning of June 4, 1769, found him in readiness for
his work. The season had been exceptionally fine. On th