154 LIVING LIGHTS. 



mulated an inch deep ; and it has been estimated that, sup- 

 posing it to average two lines in depth, there would be for 

 each square mile an amount equal to nearly three thousand 

 cubic feet. A similar panic was caused some years ago by 

 a swarm of butterflies. Everywhere they left a drop of 

 blood-colored fluid, so that the fences, houses, and cattle 

 were covered with it. The insects were so numerous that 

 they obstructed the vision. 



In the "blood-rains" of Italy, and generally in such in- 

 stances, the red hue comes from red oxide of iron. At a 

 single shower in Lyons in 1846, Ehrenberg estimated that 

 seven hundred and twenty thousand pounds of material fell, 

 ninety thousand pounds of which were microscopic organisms, 

 including thirty-nine species of siliceous diatoms, and many 

 others of great beauty of form and shape. 



Ehrenberg enumerates a very large number of these show- 

 ers, referring to Homer's "Iliad" for one of the earliest 

 known ; and asks, with such facts before us, how many thou- 

 sand millions of hundred-weight of microscopic organism have 

 reached the earth since Homer's time ? The whole number 

 of species made out is over three hundred. The species, 

 as far as ascertained, are not African; fifteen are North 

 American. But the origin of the dust is yet unknown. The 

 zone in which these showers occur covers Southern Europe 

 and Northern Africa, with the adjoining portion of the 

 Atlantic, and the corresponding latitudes in Western and 

 middle Asia. 



When blown along by the wind, these showers perform 

 another office besides affecting, perhaps, the color or tint of 

 the atmosphere ; they wear away rock, and polish and 

 furrow it. Such work can be seen in the granite rocks 



