MOVEMENTS OE SAND DUNES 51 



waters of Pamlico Sound, afford another excclicnt example 

 of such dunes. 



In this country the greatest dune districts are found about 

 the southern end of Lake Michigan, where an abundance of 

 sand of glacial origin is swept upon the shores in times of 

 storm, and is borne away by the w^inds. Ikit if the student 

 of these features would find them at their best he should visit 

 the dunes of eastern England or those about the head of the 

 Bay of Biscay, where these masses of sand not only grow to 

 a great height, but frequently separate themselves from the 

 shore and slowly march as moving hills to great distances 

 inland. Thus in Britain one of these dunes in the last cen- 

 tury invaded the village of Eccles, and buried the dw^ellings 

 and the parish church so that even the top of the spire was 

 hidden. After a number of years the summit of the church 

 began to reappear on the leeward side of the hill, and in time 

 the remote descendants of the dispossessed people ma)- be 

 restored to their heritage. In the Biscayan lands the incur- 

 sions of the sand have proved so menacing to the fertile 

 fields of that country that the government has expended large 

 sums of money in order to root the invading dunes to their 

 places. The spectacle of these wandering masses of the fri- 

 able portions of the earth's crust shows us how^ great is the 

 effect of the plants in restraining the action of the winds. 

 Where, as in the great deserts, the soil is too arid to main- 

 tain vegetation, the finely divided portions of the rock, which 

 the plants convert into soil, are at the mercy of the air, and 

 are set upon endless marches, which often alter the neigh- 

 boring fertile districts to the state of the Sahara. 



The way in which these hills of sand march is ver\- simple. 

 On the windward side the hill is scoured away by the blasts. 



