RED FOGS AND SEA DUST. 119 



the equinoxes. Do not these conditions appear sufficient to afford 

 the "rain dust" for the spring showers? 



280. At the period of the autumnal equinox, another portion of 

 the Amazonian basin is parched with drought, and liable to winds 

 that fill the air with dust, and with the remains of dead animal 

 and vegetable matter ; these impalpable organisms, which each 

 rainy season calls into being, to perish the succeeding season of 

 drought, are perhaps distended and made even lighter by the gas- 

 es of decomposition which has been going on in the period of 

 drought. 



281. 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 ? 



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

 contrasts the wet and the dry seasons there : 



"When, tinder 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 mo- 

 tion, 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 by the experienced mariner. 

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

 desolate plain. The horizon draws suddenly 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 



