[96]

With but two symbols, one for the units, the other for the tens, every
number could be expressed by attending to a rule of position like that
governing our written numeration; at each step to the left, a single sign,
the vertical _wedge_, increased sixty-fold in value; the tens were placed
beside it, and a blank in this or that column answered to our zero.

Founded upon a sexagesimal numeration, the metrical system of Babylon and
Nineveh was "the most scientific of all those known and practised by the
ancients: until the elaboration of the French metrical system, it was the
only one whose every part was scientifically co-ordinated, and of which the
fundamental conception was the natural development of all measures of
superficies, of capacity, or of weight, from one single unit of length, a
conception which was adopted as a starting point by the French commission
of weights and measures."

The cubit of 525 millimetres was the base of the whole system.[97] We shall
not here attempt to explain how the other measures--itinerary, agrarian, of
capacity, of weight--were derived from the cubit; to call attention to the
traces left in our nomenclature by the duodecimal or sexagesimal system of
the Babylonians, even after the complete triumph of the decimal system, is
sufficient for our purposes. It is used for instance in the division of the
circle into degrees, minutes, and seconds, in the division of the year into
months, and of the day into hours and their fractions.

This convenient, exact, and highly developed system of arithmetic and
metrology enabled the Chaldaeans to make good use of their observations, and
to extract from them a connected astronomical doctrine. They began by
registering the phenomena. They laid out a map of the heavens and
recognized the difference between fixed stars and those movable bodies the
Greeks called planets--among the latter they naturally included the sun and
the moon, the most conspicuous of them all both in size and motion, whose
courses were the first to be studied and described. The apparent march of
the sun through the crowded ranks of the celestial army was defined, and
its successive stages marked by those twelve constellations which are still
called the _Signs of the Zodiac_. In time even these observations were
excelled, and it now appears certain that the Chaldaeans recognized the
annual displacement of the equinoctial point upon the ecliptic, a discovery
that is generally