used heliometers. Dr. Elkin had charge of the fine instrument then
recently erected in Yale College Observatory; Sir David Gill employed
one of seven inches, just constructed under his directions, in
first-rate style, by the Repsolds of Hamburg. Dr. Elkin completed in
1888 his share of the more immediate joint programme, which consisted in
the determination, by direct measurement, of the average parallax of
stars of the first magnitude. It came out, for the ten northern
luminaries, after several revisions, 0.098", equivalent to a
light-journey of thirty-three years. The deviations from this average
were, indeed, exceedingly wide. Two of the stars, Betelgeux and
Alpha Cygni, gave no certain sign of any perspective shifting; of the rest,
Procyon, with a parallax of 0.334", proved the nearest to our system. At
the mean distance concluded for these ten brilliant stars, the sun would
show as of only fifth magnitude; hence it claims a very subordinate rank
among the suns of space. Sir David Gill's definitive results were
published in 1900.[1582] As the average parallax of the eleven brightest
stars in the southern hemisphere, they gave 0.13", a value enhanced by
the exceptional proximity of Alpha Centauri. Yet four of these
conspicuous objects--Canopus, Rigel, Spica, and Beta Crucis--gave
no sign of perspective response to the annual change in our point of
view. The list included eleven fainter stars with notable proper
motions, and most of these proved to have fairly large parallaxes. Among
other valuable contributions to this difficult branch may be instanced
Bruno Peter's measurements of eleven stars with the Leipzig heliometer,
1887-92;[1583] Kapteyn's application of the method by differences in
right ascension to fifteen stars observed on the meridian 1885-89;[1584]
and Flint's more recent similar determinations at Madison,
Wisconsin.[1585]

The great merit of having rendered photography available for the
sounding of the celestial depths belongs to Professor Pritchard. The
subject of his initial experiment was 61 Cygni. From measurements of 200
negatives taken in 1886, he derived for that classic star a parallax of
0.438", in satisfactory agreement with Ball's of 0.468". A detailed
examination convinced the Astronomer-Royal of its superior accuracy to
Bessel's result with the heliometer. The Savilian Professor carried out
his project of determining all second magnitude stars to the number of
about thirty,[1586] convenie