386 FIRST YEAR SCIENCE 



176. Wind Work. The wind must be considered among 

 the forces affecting the earth in its relation to man. 

 Whenever the wind blows over dry land, particles of dust 

 and sand are blown away and deposited elsewhere. The in- 

 teriors of our houses often become covered with dust blown 

 from the dry streets. Even on ships at sea, thousands of 

 miles from land, dust has been collected. 



In volcanic eruptions great quantities of dust are thrown 

 into the air and spread broadcast over the earth. On the 

 highest and most remote snow fields particles of this dust 

 have been found. In the great eruption of Krakatoa, dust 

 particles made the complete circuit of the earth, remaining 

 in the air and causing a continuance of red sunsets for 

 months. 



Sand is not carried as far as dust, but at times of strong 

 wind it is often borne for long distances. Even houses, 

 trees and stones of considerable size may be lifted and 

 moved by a fierce wind storm. The wind-swept detritus 

 has been known even to obstruct and modify the course of 

 streams. Where the wind blows dust constantly in one 

 direction, deposits of great thickness are sometimes made. 



In Kansas and Nebraska there are beds of volcanic dust, 

 reaching in some places to a thickness of more than a 

 score of feet and yet there are no known volcanoes either 

 past or present within hundreds of miles. In China there 

 is a deposit of fine dustlike material, in some places a 

 thousand feet thick, which is thought by some to be wind 

 blown. This forms a very fertile and fine-textured soil 

 and supports a great population. Many of the inhabitants 

 of the region live in caves dug in the steep banks of the 

 streams, so firm and fine textured is the material. Wind 

 deposits of this kind are called loess beds, 



177. Wind Erosion. Not only does the wind take up 

 particles of dust and sand and carry them from one place 



