established. If we could determine our motion with reference to the
ether, we should have a fixed line of reference to which all other
motions could be referred. This would give us a line of ever-increasing
length from which to measure stellar distances.

Still another method depends on the motion of the sun in space. There is
some evidence that this motion is not straight, but along a curved line.
We see the stars, not as they are now, but as they were when the light
left them. In the case of the distant stars this may have occurred
centuries ago. Accordingly, if we measure the motion of the sun from
them, and from near stars, a comparison with its actual motion will
give us a clue to their distances. Unfortunately, all the stars appear
to have large motions whose law we do not know, and therefore we have no
definite starting point unless we can refer all to the ether which may
be assumed to be at rest.

If the views expressed to you this morning are correct, we may expect
that the future of astronomy will take the following form: There will be
at least one very large observatory employing one or two hundred
assistants, and maintaining three stations. Two of these will be
observing stations, one in the western part of the United States, not
far from latitude +30°, the other similarly situated in the southern
hemisphere, probably in South Africa, in latitude -30°. The locations
will be selected wholly from their climatic conditions. They will be
moderately high, from five to ten thousand feet, and in desert regions.
The altitude will prevent extreme heat, and clouds or rain will be rare.
The range of temperature and unsteadiness of the air will be diminished
by placing them on hills a few hundred feet above the surrounding
country. The equipment and work of the two stations will be
substantially the same. Each will have telescopes and other instruments