EGYPTIAN AGRICULTURE 



CHAPTER I. 



ATMOSPHERE AND CLIMATE IN RELATION 

 TO AGRICULTURE. 



TN its relation to agriculture the atmosphere may best 

 1 be considered from two points of view : the chemical 

 and the physical. The composition of dry air is very 

 constant and for practical purposes may be taken at : 



Oxygen 20*90 per cent, by volume. 



Nitrogen 79'06 .. .. ,. 



Carbon Dioxide ... 0*04 



The atmosphere, however, contains other substances 

 of which the most important is water vapour, present 

 in varying quantities 1*40 per cent, on the average 

 dependent largely upon the temperature. The water 

 vapour will be best considered under the physical condi- 

 tions of the atmosphere. 



The nitrogen gas is not directly of any use but indi- 

 rectly, by diluting the oxygen gas, it renders possible the 

 existence of the present forms of life. The oxygen and 

 carbon dioxide are the two components of the air which 

 are of vital importance : without either of them all life 

 would be impossible. Plants and animals must constantly 

 breathe or death quickly ensues. Breathing consists in 



