THE GROWTH OF THE DUNES. 221 



material composing them is carried out to be 

 again returned and built up in a new place. 

 Thus much of the sand is in constant circula- 

 tion, and the necessary new supply is not so 

 great as it appears to be. 



The dunes constitute the most striking and 

 characteristic feature of the shore line. They 

 are great sand ridges, sometimes continuous for 

 a mile or more, but more often broken or cut by 

 "blow-outs" into isolated rounded hills which in 

 places reach one hundred and ninety feet above 

 the level of the lake. In some places the ridges 

 are for long distances wholly destitute of vege- 

 tation. Their bared surface, fifty to a hundred 

 feet in height, with the sand piled just as 

 steeply as it will lie, gleams and glistens in the 

 sunlight, and reflects the summer's heat with 

 unwonted force. Other ridges and rounded 

 hills, especially those a mile or more from the 

 lake, are often covered with black oak, northern 

 scrub pine, stunted white pine and many shrubs 

 and herbs peculiar to a soil of sand. Notable 

 among these is a thick-leaved species of the 

 prickly cactus, the only Indiana example of that 



