erature of 18 deg. F. at an altitude of 2000 ft.
has been recorded in January.

The atmospheric pressure varies between a maximum in January and a
minimum in July, the mean difference being about 0.29 in. In a series
of records extending over 14 years the mean pressure varied between
29.84 and 29.90 in.

The most striking meteorological factor in Egypt is the persistence of
the north wind throughout the year, without which the climate would be
very trying. It is this "Etesian" wind which enables sailing boats
constantly to ascend the Nile, against its strong and rapid current.
In December, January and February, at Cairo, the north wind slightly
predominates, though those from the south and west often nearly equal
it, but after this the north blows almost continuously for the rest of
the year. In May and June the prevailing direction is north and
north-north-east, and for July, August, September and October north
and north-west. From the few observations that exist, it seems that
farther south the southern winter winds decrease rapidly, becoming
westerly, until at Assuan and Wadi Haifa the northerly winds are
almost invariable throughout the year. The _khamsin_, hot sand-laden
winds of the spring months, come invariably from the south. They are
preceded by a rapid fall of the barometer for about a day, until a
gradient from south to north is formed, then the wind commences to
blow, at first gently, from the south-east; rapidly increasing in
violence, it shifts through south to south-west, finally dropping
about sunset. The same thing is repeated on the second and sometimes
the third day, by which time the wind has worked round to the north
again. During a khamsin the temperature is high and the air extremely
dry, while the dust and sand carried by the wind form a thick yellow
fog obscuring the sun. Another remarkable phenomenon is the _zobaa_, a
lofty whirlwind of sand resembling a pillar, which moves with great
velocity. The southern winds of the summer months which occur in the
low latitudes north of the equator are not felt much north of Khartum.

One of the most interesting phenomena of Egypt is the mirage, which is
frequently seen both in the desert and in the waste tracts of
uncultivated land near the Mediterranean; and it is often so truthful
in its appearance that one finds it difficult to admit the illusion.

_Flora._--Egypt possesses nei