ICE AND SNOW IN THE DUNES 99 



bordered by zones of small crater-like pits with 

 as ragged edges as the craters on the moon. The 

 cause and method of formation, at first obscure, 

 was solved by digging in the soft sand of this 

 zone. Then it was found that bubbles of gas 

 from imprisoned and decaying vegetation formed, 

 on bursting at the surface of the soft and watery 

 sand, these miniature craters. 



In the spring one may find in hollows in the 

 dunes circular depressions about a foot across 

 and three or four inches deep, marked with con- 

 centric and radial cracks in the sand. These 

 are to be found singly or grouped in such numbers 

 that they also suggest the craters on the moon. 

 It is probable they are formed in the same man- 

 ner as glacial kettle-holes and I have therefore 

 called them miniature glacial kettles. 



Glacial kettle-holes occur commonly in the 

 glacial drift or gravel throughout New Eng- 

 land as well as in other parts of the glacier- 

 visited world. They are pits a few feet to a 

 hundred feet deep, and as many yards across 

 and more or less circular in form. Their sur- 

 rounding banks are as steep as the gravel will 



