I 



Russegger's Bemarks on the Clvnate of Egypt. 99 



From Niebuhr's whole observations we find that the arith^ 

 metical mean of the yearly averages of the two extremes =: 

 17°.82 R. (about 72° F.), which corresponds nearly with the 

 arithmetical mean of the whole observations, viz., \T.2b R. 

 (70°.7 F.) We have, then, these two numbers, but especially 

 the first, viz., 72° F., which maybe regarded as the mean tem- 

 perature of Cairo. 



Winds. — In Lower Egypt, during the whole year, the wind 

 blows from the N. N.E. and NW., with a little interruption of 

 E. and W. winds ; and it is only in the months of April and 

 May that south winds occur. In the tropical regions, again, 

 in 15° lat., the north winds blow nearly six months, viz., dur« 

 ing a portion of November, and in December, January, Feb- 

 ruary, and March ; whereas, diu-ing the rest of the year, south 

 winds blow almost uninterruptedly, which advance towards the 

 north from the equator along with the southern tropical rains. 



Chamsin and Shmwi winds. — The Chamsin* occurs during 

 the period of the south winds, that is, in the months of April 

 and May. This wind has its name from Chamsin, which means 

 fifty, from the Arabians asserting that it blows repeatedly, ex- 

 clusively during a period of fifty days. It is frequently con- 

 founded with the Samumy from which, however, it is essentially 

 distinct. The Chamsin is a periodical, yearly recurring wind, 

 which always comes from the south and south-east, more rarely 

 from the south-west ; and its cause and its whole phenomena 

 appear to be of electrical origin. The Samum, on the other hand, 

 is an ordinary storm from the desert, which has no fixed period 

 of occurrence, and has no particular direction, but comes from 

 entirely opposite quarters. It is rendered formidable by its 

 heat, by its violence as a storm, and by the quantity of sand 

 and dust it brings along with it. The danger which is 

 combined with the Chamsin is quite of a difi'erent descrip- 

 tion from that of a hot storm carrying sand with it ; frequently 

 it is not at all a storm. Its alarming feature is an action pe- 

 culiar to itself, which operates in a positively hurtful way on the 

 body, and which probably depends on an extraordinary accumu- 



* The Ch is pronounced sharply like the x in Spanish, in the words Mexico^ 

 Quixoto, &c. 



