C H A P T E R I.
p r e l im in a r y s u r v e y o f t h e p h y s ic a l g e o g r a p h y o f
AFRICA, AND O p THE NATURAL SUBDIVISIONS OF THAT
S ection l.—General Observations.
E r a t o s t h e n e s is said, to have divided the whole ancient
world into twd parts, namely, Asia and Europe. He com-
jprised in one. department Africa and Europe, to which day
and night return at the same hotirs and which are only
separated from each other by a narrow sea. If we retain
this distribution of the countries anciently= known, and add
to the twh'departments thus marked out a third great region
in eluding the whole of America, we shall have a triple
division of the habitable world, each part of which will
comprise all latitudes and climates from the arctic countries
to the southern extremities of the three great continents, a
distribution better adapted than any other to the purpose
of affording an estimate,: by a comparison of phenomena,*
of the influence of local conditions on the nature
of organized beings. From Nova Zembla or Spitzbergen
we may trace an almost unbroken - line through Europe
and Africa to a country beyond the southern tropic, and
observe the gradations of temperature and their, effects on
the, figure, colour and organization of human races and
of various tribes of animals. A similar field of observation
will be afforded by Asia, jfWbfephsider that division of the
world as comprising all the countries which reach from the