THE FLORA OF ADEN. 56 



has been greatly altered by the action of the sea and rain since the 

 time when the volcano was active. " To passing travellers," says 

 Mallet, " it may appear strange to speak of pluvial denudation at Aden, 

 but residents of the place are well acquainted with its force and extent. 

 Rain seldom falls, it is true, but when it does it generally comes down in 

 torrents. Of Aden it may be said with some degree of truth that there 

 ' it never rains but it pours'. During the last fall which has occurred 

 there (1870) seven inches fell in a couple of hours. The water swept 

 along the torrents, filling all the drains with stones, many of them 

 bigger than a man's head, and doing considerable damage to the station. 

 Such very heavy falls only occur once in ten years or so, but other 

 smaller but still heavy ones occur at shorter intervals." 1 The varieties 

 of rock met with are very numerous. There are perfectly compact lavas 

 of brown, grey, and dark green tints ; besides, rocks exhibiting every 

 degree of vesicularity until we arrive at lavas resembling a coarse 

 sponge and passing into scoriae. In some places the lava is quite schis- 

 tose, and might if seen per se be easily mistaken for a metamorphic 

 rock. Also volcanic breccias are met with, as near the Main Pass where 

 fragments of dark green lava are imbedded in a reddish matrix. 2 



The climate of Aden during the north-east monsoon (October to 

 April) is cool, and in the months of November, December, and Januarv 

 pleasant and agreeable. During the rest of the year hot sandy winds 

 known as u 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. Vanden Broeck, who visited Aden 

 in 1614, was witness of the " Shamal " and described it thus: "About 

 noonday there came upon the earth a surprising darkness, followed by 

 very 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 

 thickness of a finger's breadth. Some intelligent inhabitants informed 

 us that these winds were formed of the sea-sand, and often buried 

 whole caravans." 3 Playfair calls this a tolerably accurate description 

 of the 'Shamal", but he adds that usually it is not accompanied by 



1 F. H. Mallet, Memoirs of the Geol. Mirv. of India, Vol. VII, Part 3 ; p. 4. 



3 Cf. F. K. Mallet, I.e. 



3 Hiat. Gen. dea Voyages, XXXI, 426. 



