re is the great period of the precession
of the equinoxes, amounting to twenty-six thousand years; and then
there is the stupendous Annus Magnus of hundreds of thousands of
years, during which the earth's orbit itself breathes in and out in
response to the attraction of the planets. But these periodic
phenomena, however important they may be to us mere creatures of a
day, are insignificant in their effects on the grand evolution through
which the celestial bodies are passing. The really potent agents in
fashioning the universe are those which, however slow or feeble they
may seem to be, are still incessant in their action. The effect which
a cause shall be competent to produce depends not alone upon the
intensity of that cause, but also upon the time during which it has
been in operation. From the phenomena of geology, as well as from
those of astronomy, we know that this earth and the system to which it
belongs has endured for ages, not to be counted by scores of thousands
of years, or, as Prof. Tyndall has so well remarked, "Not for six
thousand years, nor for sixty thousand years, nor six hundred thousand
years, but for aeons of untold millions." Those slender agents which
have devoted themselves unceasingly to the accomplishment of a single
task may in this long lapse of time have accomplished results of
stupendous magnitude. In famed stalactite caverns we are shown a
colossal figure of crystal extending from floor to roof, and the
formation of that column is accounted for when we see a tiny drop
falling from the roof above to the floor beneath. A lifetime may not
suffice for that falling drop to add an appreciable increase to the
stalactite down which it trickles, or to the growing stalagmite on
which it falls; but when the operation has been in progress for
immense ages, it is capable of the formation of the stately column.
Here we have an illustration of an influence which, though apparently
trivial, acquires colossal significance when adequate time is
afforded. It is phenomena of this kind which the student of nature
should most narrowly watch, for they are the real architects of the
universe.

The tidal consequences which we have already demonstrated are
emphatically of this non-periodic class--the day is always
lengthening, the moon is always retreating. To-day is longer than
yesterday; to-morrow will be longer than to-day. It cannot be said
that the change is a great one; it is indeed too small to be
apprec