ny of these units of measure
are contained in the period to be measured--is to ascertain the distance
between two points in time by means of a _scale of days_, just as we
ascertain the distance between two points in space by a scale of feet or
inches: and in each case the scale coincides with the thing
measured--mentally in the one; visibly in the other. So that in this
simplest, and perhaps earliest case of quantitative prevision, the
phenomena are not only thrust daily upon men's notice, but Nature is, as
it were, perpetually repeating that process of measurement by observing
which the prevision is effected. And thus there may be significance in
the remark which some have made, that alike in Hebrew, Greek, and Latin,
there is an affinity between the word meaning moon, and that meaning
measure.

This fact, that in very early stages of social progress it is known that
the moon goes through her changes in about thirty days, and that in
about twelve moons the seasons return--this fact that chronological
astronomy assumes a certain scientific character even before geometry
does; while it is partly due to the circumstance that the astronomical
divisions, day, month, and year, are ready made for us, is partly due to
the further circumstances that agricultural and other operations were at
first regulated astronomically, and that from the supposed divine
nature of the heavenly bodies their motions determined the periodical
religious festivals. As instances of the one we have the observation of
the Egyptians, that the rising of the Nile corresponded with the
heliacal rising of Sirius; the directions given by Hesiod for reaping
and ploughing, according to the positions of the Pleiades; and his maxim
that "fifty days after the turning of the sun is a seasonable time for
beginning a voyage." As instances of the other, we have the naming of
the days after the sun, moon, and planets; the early attempts among
Eastern nations to regulate the calendar so that the gods might not be
offended by the displacement of their sacrifices; and the fixing of the
great annual festival of the Peruvians by the position of the sun. In
all which facts we see that, at first, science was simply an appliance
of religion and industry.

After the discoveries that a lunation occupies nearly thirty days, and
that some twelve lunations occupy a year--discoveries of which there is
no historical account, but which may be inferred as the earliest, from
the fac