6 " 0.21 "
" " 5 " 0.23 "

[Sidenote: Main object of the work.]

This may serve as an illustration of various incidental results which are
already flowing from the enormous and laborious piece of work which, as
far as the University Observatory at Oxford is concerned, we have just
completed, though some of the other colleagues are not so far advanced.
But the main results will not appear just yet. The work must be repeated,
and the positions of the stars just obtained must be compared with those
which they will be found to occupy at some future date, in order to see
what kind of changes are going on in the heavens. Whether this future date
shall be one hundred years hence, or fifty, or ten, or whether we should
begin immediately to repeat what has been done, is a matter not yet
decided, and one which requires some little consideration.

[Sidenote: The concluding year.]

I have said perhaps enough to give you a general idea of the work on which
we have been engaged at Oxford for the last ten years. Ten years ago it
seemed to stretch out in front of us rather hopelessly; the pace we were
able to make seemed so slow in view of the distance to be covered. We felt
rather like the schoolboy who has just returned to school and sees the
next holidays as a very remote prospect, and we solaced ourselves much in
the same way as he does, by making a diagram representing the total number
of plates to be dealt with and crossing off each one as it was finished,
just as he sometimes crosses off the days still remaining between him and
the prospective holidays. It was pleasant to watch the growth of the
number of crosses on this diagram, and by the end of the year 1902 we had
the satisfaction of seeing very little blank space remaining. Now, up to
this point it had not much mattered whether any particular plate was
secured in any particular year, or in a subsequent year, so long as there
were always sufficient plates to keep us occupied in measuring them. But
it then became a matter of importance to secure each plate at the proper
time of year; for the sun, as we know, travels round the Zodiac among the
stars, obliterating by his radiance a large section of the sky for a
period of some months, and in this way a particular region of the heavens
is apt to "run into daylight," as the observatory phrase goes, and ceases
to be available for photography during several months, u