Ii2 PIirSICAL GEOGRAPHY OF THE SEA, AND ITS IIETEOEOLOGY. 



organisms, whicli each rainy season calls into being, to perisli tlie 

 succeeding season of drought, are perhaps distended and made 

 even lighter by the gases of decomposition which has been going 

 on in the period of drought. May not, therefore, the whirl- 

 winds which accompany the vernal equinox, and sweep over the 

 lifeless plains of the Lower Orinoco, take up the "rain dust" 

 which descends in the northern hemisphere in April and May ? 

 and may it not be the atmospherical disturbances which accompany 

 the autumnal equinox that take up the microscopic organisms from 

 the Upper Orinoco and the great Amazonian basin for the showers 

 of October ? 



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

 Humboldt's descrip- coutrasts the wot and the dry seasons there : 



tion of the dust- whirl- ,, txti t ji i- i r> n 



wmds of the Orinoco. "When, uudcr tno vertical rays oi the never- 

 clouded sun, the carbonized turfy covering falls into dust, the in- 

 dm-ated soil cracks asunder as if from the shock of an earthquake. 

 If at such times two opposing currents of air, whose conflict pro- 

 duces a rotary motion, come in contact with the soil, the plain as- 

 sumes 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 

 cmTent, resembling the loud water-spout, dreaded by the expe- 

 rienced mariner. The lowering sky sheds a dim, almost straw- 

 coloured light on the desolate plain. The horizon di'aws suddenly 

 nearer, the steppe seems to contract, and mth it the heart of the 

 wanderer. The hot, dusty particles Avhich fill the air increase its 

 suffocating heat, and the east wind, blo\\dng over the long-heated 

 soil, brings with it no refreshment, but rather a still more bm-ning 

 glow. The pools which the yellow, fading branches of the fan- 

 palm had protected fi'om evaporation, now gradually disappear, 

 xis in the icy north the animals become torpid with cold, so here, 

 imder the influence of the parchmg drought, the crocodile and the 

 boa become motionless and fall asleep, deeply bmied in the dry 

 mud. . . . The distant palm-bush, apparently raised by the 

 influence of the contact of unequally heated and therefore im- 

 equally dense strata of air, hovers above the ground, from which 

 it is separated by a narrow mtervening margin. Half-concealed 

 by the dense clouds of dust, restless with the pain of thhst and 

 hunger, the horses and cattle roam around, the cattle lovang dis- 

 mally, and the horses stretching out their long necks and snuffing 

 the wind, if . haply a moist current may betray the neighbour- 



