THE PAGE OF NATURE. 179 



cause them to run ashore. Similar showers are not un- 

 frequent in China, and spread over several provinces at 

 once and far out to sea. They are raised from the Mon- 

 golian steppes regions of sand more than 2000 miles 

 long and 400 broad and falling into the waters of the 

 Yellow Sea, give it that peculiar tinge from which it 

 derives its name. During the dry season in the lifeless 

 plains of the Orinoco, and the great Amazonian basin, 

 when the soil is parched and triturated by the intense, 

 long-continued drought, dense clouds of diatomaceous 

 dust are raised by the winds and wafted to great dis- 

 tances. These showers happen most frequently in spring 

 and autumn after the equinoxes, but at intervals varying 

 from thirty to fifty days. From the nature of the spe- 

 cies wafted by these winds, the region which originally 

 produced them can be ascertained with tolerable accuracy ; 

 and hence they afford a clue to those mysteriously wayward 

 aerial currents, and cyclical relations in the upper and 

 lower atmosphere, which have hitherto perplexed meteoro- 

 logists. It has been observed that these storms, in cer- 

 tain districts, amply compensate for the annoyance they 

 occasion. The soil of the countries most subject to the 

 visitation, when of a compact character, is loosened and 

 lightened by the dust, and at the same time the lighter 

 fertilizing matters carried away by the great rivers are 

 replaced by organic remains, so that an abundant harvest 

 follows the devastations committed by these dust-showers. 

 Nearer home these curious meteoric phenomena have 

 occasionally been observed. Black rain, composed of 

 portions of decayed plants, mixed with the skeletons of 

 diatoms, fell in Ireland in April 1849, over a district of 



