ded him to the end, and he died in 1822 without seeing
it even in prospect of solution. His estimate of the minimum distance of
the nearest star, based though it was on the fallacious test of apparent
brilliancy, was a singularly sagacious one, but it was at best a
scientific guess, not a scientific measurement.

The Distance of the Stars

Just about this time, however, a great optician came to the aid of the
astronomers. Joseph Fraunhofer perfected the refracting telescope,
as Herschel had perfected the reflector, and invented a wonderfully
accurate "heliometer," or sun-measurer. With the aid of these
instruments the old and almost infinitely difficult problem of star
distance was solved. In 1838 Bessel announced from the Konigsberg
observatory that he had succeeded, after months of effort, in detecting
and measuring the parallax of a star. Similar claims had been made often
enough before, always to prove fallacious when put to further test; but
this time the announcement carried the authority of one of the greatest
astronomers of the age, and scepticism was silenced.

Nor did Bessel's achievement long await corroboration. Indeed, as so
often happens in fields of discovery, two other workers had almost
simultaneously solved the same problem--Struve at Pulkowa, where the
great Russian observatory, which so long held the palm over all others,
had now been established; and Thomas Henderson, then working at the
Cape of Good Hope, but afterwards the Astronomer Royal of Scotland.
Henderson's observations had actual precedence in point of time, but
Bessel's measurements were so much more numerous and authoritative that
he has been uniformly considered as deserving the chief credit of the
discovery, which priority of publication secured him.

By an odd chance, the star on which Henderson's observations were made,
and consequently the first star the parallax of which was ever measured,
is our nearest neighbor in sidereal space, being, indeed, some ten
billions of miles nearer than the one next beyond. Yet even this nearest
star is more than two hundred thousand times as remote from us as the
sun. The sun's light flashes to the earth in eight minutes, and to
Neptune in about three and a half hours, but it requires three and a
half years to signal Alpha Centauri. And as for the great majority of
the stars, had they been blotted out of existence before the Christian
era, we of to-day should still receive their light and seem