228 
THE MEDITERRANEAN NATUI A LIST 
The Sahara. 
The Sahara is an immense zone of desert which 
commences on the shores of the Atlantic Ocean, 
between the Canaries and Cape de Verde, and 
traverses the whole of North Africa, Arabia, and 
Persia, as far as Central Asia. The Mediterranean 
portion of it may be said roughly to extend bet- 
ween the loth and 30th degrees of north latitude. 
This was popularly supposed to have been a 
vast inland sea in very recent times, but the theory 
was supported by geographical facts wrongly in- 
terpreted. It has been abundantly proved by the 
researches of travellers and geologists that such a 
sea was neither the cause nor the origin of the 
Libyan Desert. 
Rainless and sterile regions of this nature are 
not peculiar to North Africa, but occur in two 
belts which go round the world in either hemis- 
phere, at about similar distances north and south 
of the equator. These correspond in locality to 
the great inland drainage areas from which no 
water can be discharged into the ocean, and which 
occupy about one-fifth of the total land surface of 
the globe 
The African Sahara is by no means a uniform 
plain, but forms several distinct basins containing 
a considerable extent of what may almost be cal- 
led mountain land. The Hoggar Mountains, in 
the centre of the Sahara, are 7,000 feet high, and 
are covered during three months with snow. The 
genera] average may be taken at 1,500. The phy- 
sical character of the region is very varied. In 
some places, such as Tiout, Touat, and other oases 
in or bordering on Morocco, there are well-watered 
valleys, with fine scenery and almost European 
vegetation, where the fruits of the north flourish 
side by side with the palm tree. In others there 
are rivers like the Uied Guir, an affluent of the 
Niger, which the French soldiers, who saw it in 
1870, compared to the Loire. Again, as in the bed 
of the Uied Eir, there is a subterranean river,, 
which gives a sufficient supply of water to make a 
chain of rich and well-peopled oases equal in ferti- 
lity to some of the finest portions of Algeria. The 
greater part of Sahara, however, is hard and undu- 
lating, cut up by dry watercourses, such as the 
Igharghar which descends to the Chott Melghigh, 
and almost entirely without animal or vegetable 
life. 
About one-sixth of its extent consists of dunes 
of moving sand, a vast accumulation of detritus 
washed down from more northern and southern 
regions — perhaps during the glacial epoch — but 
with no indication of marine formation. These 
are difficult and even dangerous to traverse, but 
they are not entirely destitute of vegetation. Wa- 
ter is found at rare but well-known intervals, and 
there is an abundance of salsolaceous plants which 
serves as food for the camel. This sand is largely 
produced by wind action on the underhung rocks, 
and is not sterile in itself — it is only the want of 
water which makes it so. Wherever water does 
exist, or artesian wells are sunk, oases of great 
fertility never faii to follow. 
Some parts of the Sahara are below the level of 
the sea, and here are formed what are called eh ■ 'is 
or sebkhass, open depressions without any outlets, 
inundated by torrents from the southern slopes of 
the Atlas in winter and covered with a saline efflo- 
rescence in summer. This sal by no means proves 
the former existence of an inland sea. It is pro- 
duced by the concentration of the natural salts, 
which exist in every variety of soil, washed down 
by winter rains, with which the unevaporated 
residue of water becomes saturated. 
A year’s insect-hunting at Gibraltar. 
BY JAMES J. WALKER, R.X., F.E.S. 
II. 
A fairly good road (for Spain) leads from the 
beach through the Village of Campamento to the 
small and clean town of San Roque, rather pret- 
tily situated on the top of a low hill about six 
miles from Gibraltar. Beyond this the country, 
hitherto bare and treeless, except fora few gardens 
and a grove of blue gun, trees at Campamento, 
improves very much. Two large plantations of 
the stone pine ( Pinus cembra) may be mentioned 
as especially good collecting ground, and in the 
early spring the country is one sheet of beautiful 
wild flowers, species of I/e/ianthemum and Cistus 
predominating. Just beyond the “second Pine 
Wood,' at about nine miles from the Rock, com- 
cences the “Cork Woods, ’ the great hunting ground 
