278 THE CHEMISTRY OF CREATION. 



it is most necessary. In hot climates the dews 

 are most profuse; and the morning sun rises 

 in its strength upon a landscape which the 

 gentle hand of night has cooled, refreshed, and 

 invigorated with a sea of dew-drops. Thus, 

 though no rain-carrying cloud may cross the 

 blue air during the day, to shed its supplies 

 of refreshing waters upon a parched earth, 

 the clear and brilliant evenings witness, in 

 the phenomenon we have been considering, 

 a grateful and efficient compensation ; and the 

 thirsty vegetation, satisfied with its evening 

 portions, is enabled without injury to endure 

 the rays of the burning luminary all the day 

 long. 



Dew, in common with all water shed upon 

 the ground, has important duties to fulfil. Be- 

 sides quenching the thirst of plants, dew is 

 largely instrumental in facilitating the evapo- 

 ration of some important bodies. Thus, when 

 it is evaporated by the heat of the sun, it is the 

 vehicle by means of which ammonia escapes 

 into the air, and becomes subservient to the 

 wants, not only of the isolated spots in which 

 it was probably first produced, but to those of 

 vegetation at large. Hence, as has been before 

 observed, the farmer's carefully-stored heap of 

 manure becomes robbed of half its ammonia, 

 which escapes with the evaporating water, and 



