ntly observable at Oxford, obtaining as the
general outcome of the research an average parallax of 0.056", for
objects of that rank. But this value, though in itself probable, cannot
be accepted as authoritative, in view of certain inaccuracies in the
work adverted to by Jacoby,[1587] Hermann Davis, and Gill. The method
has, nevertheless, very large capabilities. Professor Kapteyn showed, in
1889,[1588] the practicability of deriving parallaxes wholesale from
plates exposed at due intervals, and applied his system, in 1900, with
encouraging success, to a group of 248 stars.[1589] The apparent absence
of spurious shiftings justified the proposal to follow up the completion
of the Astrographic Chart with the initiation of a photographic
"Parallax Durchmusterung."

Observers of double stars are among the most meritorious, and need to be
among the most patient and painstaking workers in sidereal astronomy.
They are scarcely as numerous as could be wished. Dr. Doberck,
distinguished as a computer of stellar orbits, complained in 1882[1590]
that data sufficient for the purpose had not been collected for above 30
or 40 binaries out of between five and six hundred certainly or probably
within reach. The progress since made is illustrated by Mr. Gore's
useful Catalogue of Computed Binaries, including fifty-nine entries,
presented to the Royal Irish Academy, June 9, 1890.[1591] Few have done
more towards supplying the deficiency of materials than the late Baron
Ercole Dembowski of Milan. He devoted the last thirty years of his life,
which came to an end January 19, 1881, to the revision of the Dorpat
Catalogue, and left behind him a store of micrometrical measures as
numerous as they are precise.

Of living observers in this branch, Mr. S. W. Burnham is beyond question
the foremost. While pursuing legal avocations at Chicago, he diverted
his scanty leisure by exploring the skies with a 6-inch telescope
mounted in his back-yard; and had discovered, in May, 1882, one thousand
close and mostly very difficult double stars.[1592] Summoned as chief
assistant to the new Lick Observatory in 1888, he resumed the work of
his predilection with the 36-inch and 12-inch refractors of that
establishment. But although devoting most of his attention to
much-needed remeasurements of known pairs, he incidentally divided no
less than 274 stars, the majority of which lay beyond the resolving
power of less keen and effectually aided eyesight. One of