iOO THE PHYSICAL GEOGRAPHY OF THE SEA. 



162. May not, therefore, the whirlwinds which accompany the 

 vernal equinox, and sweep over the lifeless plains of the Lower 

 Oronoco, take up the "rain dust" which descends in the northern 

 hemisphere in April and May ? and may it not be the atmospher- 

 ical disturbances which accompany the autumnal equinox that take 

 up the microscopic organisms from the Upper Oronoco and the 

 great Amazonian basin for the showers of October ? 



163. The Baron von Humboldt, in his Aspects of Nature, thus 

 contrasts the wet and the dry seasons there : 



" When, under the vertical rays of the never-clouded sun, the 

 carbonized turfy covering falls into dust, the indurated soil cracks 

 asunder as if from the shock of an earthquake. If at such times 

 two opposing currents of air, whose conflict produces a rotary 

 motion, come in contact with the soil, the plain assumes a strange 

 and singular aspect. Like conical-shaped clouds, the points of 

 which descend to the earth, the sand rises through the rarefied air 

 on the electrically-charged centre of the whirling current, resem- 

 bling the loud water-spout, dreaded \ij the experienced mariner. 

 The lowering sky sheds a dim, almost straw-colored light on the 

 desolate plain. The horizon draws suddp.nly nearer, the steppe 

 seems to contract, and with it the heart of the wanderer. The 

 hot, dusty particles which fill the air increase its suffocating heat, 

 and the east wind, blowing over the long-heated soil, brings with it 

 no refreshment, but rather a still more burning glow. The pools 

 which the yellow, fading branches of the fan-palm had protected 

 from evaporation, now gradually disappear. As in the icy north 

 the animals become torpid with cold, so here, under the influence 

 of the parching drought, the crocodile and the boa become mo- 

 tionless and fall asleep, deeply buried in the dry mud 



" The distant palm-bush, apparently raised by the influence of 

 the contact of unequally heated and therefore unequally dense 

 strata of air, hovers above the ground, from which it is separated 

 by a narrow intervening margin. Half concealed by the dense 

 clouds of dust, restless with the pain of thirst and hunger, the 

 horses and cattle roam around, the cattle lowing dismally, and 

 the horses stretching out their long necks and snufhng the wind, 

 if haply a moister current may betray the neighborhood of a not 



wholly dried-up pool 



" At length, after the long drought, the welcome season of the 

 rain arrives ; and then how suddenly is the scene changed ! 



