Chandler winds up his second paper thus:--

"We thus find that the comparison of the simultaneous series at
Pulkowa and Washington, 1863-1867, leads to the same conclusion as
that already drawn from the simultaneous series at Berlin and
Cambridge, 1884-1885. The direction of the polar motion may therefore
be looked upon as established with a large degree of probability.

"In the next paper I will present the results derived from PETERS,
STRUVE, BRADLEY, and various other series of observations, after
which the results of all will be brought to bear upon the
determination of the best numerical values of the constants
involved."

[Sidenote: Bradley's observations.]

[Sidenote: Latitude varied in twelve months then.]

The results were not, however, presented in this order. In the next paper,
which appeared on December 23, 1891, Mr. Chandler begins, with the work of
Bradley, the very series of observations at Kew and Wansted which led to
the discoveries of aberration and nutation, and which we considered in the
third chapter. He first shows that, notwithstanding the obvious accuracy
of the observations, there is some unexplained discordance. The very
constant of aberration which Bradley discovered from them differs by
half-a-second of arc from our best modern determinations. Attempts have
been made to ascribe the discordance to changes in the instrument, but Mr.
Chandler shows that such changes, setting aside the fact that Bradley
would almost certainly have discovered them, will not fit in with the
facts. The facts, when analysed with the skill to which we have become
accustomed, are that there is a periodic swing in the results _with a
period of about a year_, and not fourteen months, as before, "a result so
curious," as he admits, that "if we found no further support, it might
lead us to distrust the above reasoning, and throw us back to the
possibility that, after all, BRADLEY'S observations may have been vitiated
by some kind of annual instrumental error. But it will abundantly appear,
when I have had the opportunity to print the deductions from all the other
series of observations down to the present time, that the inference of an
increase in the period of polar revolution is firmly established by their
concurrent testimony." We shall presently return to this curious result,
which might well have dismayed a less determined researcher than Mr.
Chandler, but which on