th no additional expense except the moderate one of their salaries. A
single observatory could thus easily do double the work that could be
accomplished if its resources were divided between two of half the
size.

A third, and perhaps the best, method of making a real advance in
astronomy is by securing the united work of the leading astronomers of
the world. The best example of this is the work undertaken in 1870 by
the Astronomische Gesellschaft, the great astronomical society of the
world. The sky was divided into zones, and astronomers were invited to
measure the positions of all the stars in these zones. The observation
of two of the northern and two of the southern zones were undertaken by
American observatories. The zone from +1 deg. to +5 deg. was undertaken by the
Chicago Observatory, but was abandoned owing to the great fire of 1871,
and the work was assumed and carried to completion by the Dudley
Observatory at Albany. The zone from +50 deg. to +55 deg. was undertaken by
Harvard. An observer and corps of assistants worked on this problem for
a quarter of a century. The completed results now fill seven quarto
volumes of our annals. Of the southern zones, that from -14 deg. to -18 deg. was
undertaken by the Naval Observatory at Washington, and is now finished.
The zone from -10 deg. to -14 deg. was undertaken at Harvard, and a second
observer and corps of assistants have been working on it for twenty
years. It is now nearly completed, and we hope to begin its publication
this year. The other zones were taken by European astronomers. As a
result of the whole, we have the precise positions of nearly a hundred
and fifty thousand stars, which serve as a basis for the places of all
the objects in the sky.

Another example of cooperative work is a plan proposed by the writer in
1906, at the celebration of the two-hundredth anniversary of the birth
of Franklin. It was proposed, first to find the best place in the world
for an astronomical observatory, which would probably be in South
Africa, to erect there a telescope of the largest size, a reflector of
seven feet aperture. This instrument should be kept at work throughout
every clear night, taking photographs according to a plan recommended by
an international committee of astronomers. The resulting plates should
not be regarded as belonging to a single institution, but should be at
the service of whoever could make the best use of them. Copies of any,
or all, would