PHYSICAL ASPECTS OF ADEN. 
35 
As humidity is considerably influenced by temperature and wind, high 
temperature lowering the percent of relative humidity and low tempera- 
tures raising it, we shall, as far as reliable records go, briefly discuss 
those climatic factors. 
The climate of Aden during the north-east monsoon (October to April) 
is cool, and in the months of November, December, and January pleasant 
and agreeable. During the rest of the year hot sandy winds known as 
“ Shamal ” or north, prevail within the crater. On the western side, 
however, or Steamer Point, the breezes coming directly off the sea, are 
cool and refreshing. Van den Broeck, who visited Aden in 1614, was 
witness of the Shamal and described it thus : 
“About Monday there came upon the earth a surprising darkness, 
followed by heavy rain, and in the further extremity of that terrible 
cloud a very bright red, that might almost be mistaken for a fiery oven. 
The cloud continued to roll away towards Ethiopia, the rain ceased, and 
we were surprised to find our vessel covered with red sand, to the thick- 
ness of a finger's breadth. Some intelligent inhabitants informed us that 
these winds were formed of the sea-sand, and often buried whole 
caravans . }>1 
Playfair calls this a tolerably accurate description of the Shamal, but 
he adds that usually it is not accompanied by rain, nor even so serious 
in its results. 
Anderson gives us a vivid description of the climate of Aden in his 
Florula Adenensis : 
“ In so low a latitude/* he says, “ the sun shines with intense force 
nearly throughout the year, and at Aden the solar power is increased 
by every peculiarity of physical conformation and climate. The 
undisturbed atmosphere stagnates in the walled-in valleys, where a death- 
like stillness always reigns. The black and naked rocks absorb by day 
the scorching rays transmitted through an ever cloudless sky, only to 
radiate the pent-up heat by night, thus confining to the shore the cool 
but feeble breezes that occasionally spring up from the Indian Ocean. 
Accordingly, even in December, when the sun's power is at its lowest, 
Dr. Hooker found the temperature of the soil at 107° Fahr. a few feet 
below the surface. In the hotter seasons of the year, the sun, even in 
the early morning, is overpowering, and above the rocks the air flickers 
from the intense heat, while all distant objects are disturbed by an 
imperfect mirage." 1 2 
t> 2 
1 Hi.st. Gen. "es Voyages, XXXI, 420. 
2 Anderson, Floiula Adenensis, p. vi-yih 
