88 The Great World's Farm 



great abundance in many parts of this desert; and the 

 fruit, which remains good for a year in dry seasons, 

 affords the natives almost their only supply of water when 

 they are journeying across this rainless region. Evidently, 

 therefore, the sama is able to make the most of its limited 

 opportunities, and cannot only appropriate, but also keep, 

 moisture, where most plants would simply perish of thirst. 



Trying as are the droughts of the South African desert, 

 they are less severe than those of Australia, for at all 

 events such rain as does fall is kept, and sinks into the 

 sub-soil, there being no rivers to drain it away; whereas 

 in Australia the rivers quickly carry it off again. Even 

 here, however, some trees, and among them the eucalypti, 

 manage to store water in their roots; and from this supply 

 the natives were in the habit of helping themselves in time 

 of need. The long side roots were laid bare, as much as 

 twenty or thirty feet, and divided into short lengths, from 

 which water dripped at once, clear, cool, and free from 

 any unpleasant taste or smell. 



How the water remains so cool, buried only from six 

 to twelve inches beneath the burning surface, is one of the 

 many mysteries connected with the great mystery of life. 



Water in a pipe, from which there was little or no 

 evaporation, and water in a dead root, would speedily 

 grow warm under similar circumstances. Water in a 

 porous vessel keeps cool, indeed, in the hottest sun, 

 because the vessel is porous, and water is constantly pass- 

 ing through it and being turned into vapor; with the result 

 that the air immediately surrounding the vessel is being 

 constantly cooled. The water is turned into vapor by 

 means of the heat abstracted from the air. 



But the water in the roots of the eucalyptus is not kept 



