ATMOSPHERE AKD CLIMATE, ETC. 



13 



ature, humidity and winds affecting p^nts and animals 

 will be briefly considered. It will be advisable, in the first 

 place, to say a word as to the effect vegetation has on the 

 climate. A covering of vegetation protects the soil from 

 the direct rays of the sun and tends to decrease surface 

 evaporation : it lowers the temperature while at the same 

 time it increases the moisture in the air. It must be 

 noticed that the total water removed from a cultivated soil 

 by surface evaporation and plant transpiration is much 

 greater than that removed from bare land. The effect 

 which forest would have on the climate of Egypt is a 

 subject admitting of much speculation. The air of a wood 

 is slightly moister and colder than in the open plain ; but 

 there is no proof that woods increase the total rainfall. 

 In any case it is highly improbable that, in such a rich 

 agricultural country as Egypt, the planting of trees will 

 ever be so extensive as to make any appreciable difference 

 in the climate. 



SHADE TEMPERATURE RECORDS 1884-1905. 



(Near Cairo). 



