Russegger's Remarks on the CUmate of Egypt. 07 



but even, though more rarely, in the deserts of the interior of 

 Africa. 



As the temperature is lowered by the north wind on the 

 one hand, so, on the other, it is raised by the south wind, to 

 which latter also, in respect of its direction, the Chamsin be- 

 longs. This elevation of temperature is not inconsiderable, 

 and amounts to several degrees of Reaumur, so that the ther- 

 mometer rises at Cairo to considerably above 30° R. (99°.5 

 F.) ; but it is not so great as some have asserted, at least in 

 southern latitudes, where I observed the Chamsin wind long 

 and carefully, and where the phenomenon is more powerfully 

 displayed than in Egypt. Sometimes the south winds of 

 Egypt lower the temperature just like the north winds, and 

 this takes place when early and very violent periodical rains 

 occur in the tropical regions. 



In reference to the observations on the temperature of the 

 air in the shade and in the sun, which I made at Cairo and 

 Alexandria in the month of April, I have drawn up tables* in 

 which are also introduced the direction of the wind, the na- 

 ture of the clouds, and the state of the weather. These tables 

 do not give us the laws of the daily range of temperature, as 

 they want observations at the time of the minimum, and afford 

 too few terms for accurate calculation. Observations free from 

 these deficiencies were made by me during a subsequent resi- 

 dence in Egypt, and will afterwards enable us to determine 

 these laws. The tables, however, of which I now speak, shew 

 us pretty nearly the maximum of the daily temperature, and 

 its fall on both sides towards the period of minimum. 



The highest temperature observed in the shade at Cairo in 

 the month of April was 27°.3 R. (93°.4 F.), and in the sun 

 31^8 R. (103.6 F.) ; the lowest in the shade 14°.l R. (about 

 64° F.), and in the sun 19° R. (74°.7 F.) ; the differences ob- 

 served, therefore, = 13'.2 R. (about 29°.4 F.), and 12'.8 R. 

 (about 28°.9 F.) These differences, however, are not those of 

 the extremes, as we want the observations on the minimum. 



In Alexandria the highest temperature observed in the 



* Page 211 of the first part of the " Behou** 

 YOL. XXXIII. NO, LXV. — JULY 1842. O 



