etween its legs, is not known, but the belief
was current as early as the 16th century. The statue was thrown down by
an earthquake about the year 224 B.C.; then, after lying broken for
nearly 1000 years, the pieces were bought by a Jew from the Saracens,
and probably reconverted into instruments of war.

Other Greek colossi were the Apollo of Calamis; the Zeus and Heracles of
Lysippus; the Zeus at Olympia, the Athena in the Parthenon, and the
Athena Promachos on the Acropolis--all the work of Pheidias.

The best-known Roman colossi are: a statue of Jupiter on the Capitol; a
bronze statue of Apollo in the Palatine library; and the colossus of
Nero in the vestibule of his Golden House, afterwards removed by Hadrian
to the north of the Colosseum, where the basement upon which it stood is
still visible (Pliny, _Nat. Hist._ xxxiv. 18).

COLOUR (Lat. _color_, connected with _celare_, to hide, the root
meaning, therefore, being that of a covering). The visual apparatus of
the eye enables us to distinguish not only differences of form, size and
brilliancy in the objects looked upon, but also differences in the
character of the light received from them. These latter differences,
familiar to us as differences in _colour_, have their physical origin in
the variations in wave-length (or frequency) which may exist in light
which is capable of exciting the sensation of vision. From the physical
point of view, light of a _pure colour_, or homogeneous light, means
light whose undulations are mathematically of a simple character and
which cannot be resolved by a prism into component parts. All the
visible pure colours, as thus defined, are to be found in the spectrum,
and there is an infinite number of them, corresponding to all the
possible variations of wave-length within the limits of the visible
spectrum (see SPECTROSCOPY). On this view, there is a strict analogy
between variations of _colour_ in light and variations of _pitch_ in
sound, but the visible spectrum contains a range of frequency extending
over about one octave only, whereas the range of audibility embraces
about eleven octaves.

Of all the known colours it might naturally be thought that white is the
simplest and purest, and, till Sir Isaac Newton's time, this was the
prevailing opinion. Newton, however, showed that white light could be
decomposed by a prism into the spectral colours red, orange, yellow,
green, blue, indigo and violet; the colours appearing in