DESEliT SANDS 345 



sufficiently demonstrated. The rock wlicn it first emerges 

 from the water rises bare and rugged like a sea-clifl" ; no 

 living thing, annnal or vegetable, is harboured anywhere 

 on its naked surface. In time, however, as rain falls upon 

 its jutting peaks and barren pinnacles, disintegration sets 

 in, or, to speak plainer English, the rock crumbles ; and 

 soon streams wash down tiny deposits of sand and mud 

 thus produced into the valleys and hollows of the upheaved 

 area. At the same time lichens begin to spring in yellow 

 patches upon the bare face of the rock, and feathery ferns, 

 whose spores have been wafted by the wind, or carried by 

 the waves, or borne on the feet of unconscious birds, sprout 

 here and there from the clefts and crannies. These, as 

 they die and decay, in turn form a thin layer of vegetable 

 mould, the first beginning of a local soil, in which the 

 trusty earthworm (imported in the egg on driftwood or 

 floating weeds) straightway sets to work to burrow, and 

 which he rapidly increases by his constant labour. On the 

 soil thus deposited, flowering plants and trees can soon 

 root themselves, as fast as seeds, nuts or fruits are wafted 

 to the island by various accidents from surrounding 

 countries. The new land thrown up by the great eruption 

 of Krakatoa has in this way already clothed itself from 

 head to foot with a luxuriant sheet of ferns, mi sses, and 

 other vegetation. 



First soil, then plant and animal life, are thus in the 

 last resort wholly dependent for their existence on the 

 amount of rainfall. But in deserts, where rain seldom or 

 never falls (except by accident) the first term in this series 

 is altogether wanting. There can be no rivers, brooks or 

 streams to wash down beds of alluvif.1 depcjsit from the 

 mountains to the valleys. Denudation (the term, though 

 rather awful, is not an improper one) must therefore take 

 a difterent turn. Practically speaking, there is no water 



