^8 Russegger's Benutrks on the Cliinate of Egypt. 



shade in the month of April was 20° R. (^T F.), and in tJie 

 sun 28°.2 R. (95°.4 F.) ; the lowest in the shade 14°.3 R. 

 (ahout 64° F.), and in the sun 23° R. (83°.7 F.) ; and therefore 

 the differences = 5°.7 R. (about 13° F.), aud 5°.2 R. (about 

 11°.7 F.) ; therefore much smaller than at Cairo, which acci- 

 dentally hai'monizes with the law according to which these 

 differences increase as we approach the equator, while the dif- 

 ferences of the extremes of the pressure of the atmosphere 

 diminish. 



If we take the mean of all the observations in the shade, 

 about three hours after the minimum, we have, 



For Cairo, For Alexandria, 



16°.7 R. (69°.6 F.) 16°.9 R. (70° F.) ; 



and in the same way the mean of all the observations at 2 

 F. M., at the time of the maximum, we have, 



For Cairo, For Alexandria, 



23°.l R. (about 84° F.) 18°.5 R (73°.6 F.) 



therefore the differences are 



For Cairo. For Alexandiia, 



6°.4 R. (14°.4 F.) 1°.6 R (3°.6 F.) 



The mean of the means of the two series of observations 

 made at the same hour for April are thus : 



For Cairo, For Alexandria, 



19°.9 R. (76°.7 F.) ..... 17°.7 R. 7r.8 F.) 

 If we consider the observations made on temperature in Lower 

 Egypt during a whole year, we find that the months of July 

 and August are those which present the highest elevation of 

 the thermometer, and the month of February that which is 

 characterized by the lowest temperature. This is an arrange- 

 ment of temperature which reminds us completely of Europe. 

 Niebuhr observed the lowest temperature in Cairo in Feb- 

 ruary in the morning, and it was 42° F. ; and the highest in 

 June and July, when it was 101° F. ; the first having been 

 during a south wind, and the second during a north wind. 

 The difference of these extremes is 59° F., being the range of 

 temperature in a period of eight or ten months ; the mean of 

 these extremes is 71°.5 F., which approaches nearly the mean 

 temperature assigned to Lower Egypt, 



