unded, it was as inconsistent with known
dynamic law as the variation of it now appears to be. Professor
Newcomb's own happy explanation has already set aside the first
difficulty, as it would appear, and advanced the theory by an
important step. Are we so sure yet of a complete knowledge of all the
forces at work as to exclude the chance of a _vera causa_ for the
second?"

[Sidenote: Faraday's words.]

There is a splendid ring of resolution about these words. Let us compare
them with a notable utterance of Faraday:--

"The philosopher should be a man willing to listen to every
suggestion, but determined to judge for himself. He should not be
biassed by appearances; have no favourite hypothesis; be of no
school; and in doctrine have no master. He should not be a respecter
of persons, but of things. Truth should be his primary object. If to
these qualities be added industry, he may indeed hope to walk within
the veil of the temple of Nature."

[Sidenote: Chandler's other work at this time.]

[Sidenote: His ultimate satisfactory solution.]

[Sidenote: Interference of two waves.]

Tested by this severe standard, Mr. Chandler fails in no particular, least
of all in that of industry. The amount of work he got through about this
time was enormous, for besides the main line of investigation, of which we
have only had after all a mere glimpse, he had been able to turn aside to
discuss a subsidiary question with Professor Comstock; he had examined
with great care some puzzling characteristics in the variability of stars;
he computed some comet ephemerides; and he was preparing a new catalogue
of variable stars--a piece of work involving the collection and
arrangement of great masses of miscellaneous material. Yet within a few
months after replying as above to Professor Newcomb's criticism, he was
able to announce that he had found the key to the new puzzle, and that
"theory and observation were again brought into complete accord." We will
as before listen to the account of this new step in his own words, but a
slight preliminary explanation may help those unaccustomed to the
terminology. The polar motion was found to be compounded of _two_
independent motions, both periodic, but having different periods. Now, the
general results of such a composition are well known in several different
branches of physics, especially in the theory of sound. If two notes of