GENERAL FIELD OF WORK 49 



probably the correct one, is that it is wholly sedentary like 

 the clays and gravels. What would seem more reasonable 

 to an ungeological observer is the theory that this series of 

 great successive sand dunes is a relic oi' ancient seashores, 

 although close search yields no trace of seashell or coral. 

 And this we may note as the first of a host of deceptions 

 practiced upon us by the tropical elements and animals— 

 these dunes of the finest of white sand deep hidden within 

 these mighty forests, whose grains have never danced at 

 the roar of pounding breakers nor felt the slithering rush 

 of salt water. Here the white sand lies beneath the ebony 

 mold of the jungle, undisturbed except when flung into the 

 light by the wrenched-up roots of a falling tree, or when 

 scratched up by armadillos, or patiently borne to the sur- 

 face, grain after grain by indefatigable ants. 



So this particular region, although so near the Atlan- 

 tic coast and so distant from the Andes, in ages past began 

 as volcanic or igneous upthrusts of rock, and not by the 

 gradual accumulation of sediment brought down by rivers 

 and held in tenure by the clutching fingers of mangroves 

 and courida. But that time of mineral dominance is long 

 past, and today we find the underlying structure, whatever 

 it is, clothed with running water and with vegetation, in the 

 shelter of which animal life teems, while mankind has merely 

 begun to paddle painfully along the rivers, and to follow 

 narrow trails — molewise — through the jungle. 



