perpetual change, acting always in one direction. Unless
fully counteracted by some opposing reaction,
therefore (as it seems not to be), the effect must be
cumulative, the ultimate consequences disastrous.
The exact character of these consequences was first
estimated by Professor G. H. Darwin in 1879. He
showed that tidal friction, in retarding the earth, must
also push the moon out from the parent planet on a
spiral orbit. Plainly, then, the moon must formerly
have been nearer the earth than at present. At some
very remote period it must have actually touched the
earth; must, in other words, have been thrown off from
the then plastic mass of the earth, as a polyp buds out
from its parent polyp. At that time the earth was spinning
about in a day of from two to four hours.

Now the day has been lengthened to twenty-four
hours, and the moon has been thrust out to a distance
of a quarter-million miles; but the end is not yet. The
same progress of events must continue, till, at some remote
period in the future, the day has come to equal
the month, lunar tidal action has ceased, and one face of
the earth looks out always at the moon with that same
fixed stare which even now the moon has been brought
to assume towards her parent orb. Should we choose to
take even greater liberties with the future, it may be
made to appear (though some astronomers dissent
from this prediction) that, as solar tidal action still
continues, the day must finally exceed the month,
and lengthen out little by little towards coincidence