ESKERS IN THE VICINITY OF ROCHESTER, NEW YORK. 165 



by the ice, they never occur beyond the terminal moraine in the mar- 

 ginal zone of outwash. They occur at all elevations above sea level. 



Eskers find their best development in Sweden, where they were 

 first recognized as being a distinct phase of the glacial drift. How- 

 ever in south Sweden, Germany, and Denmark, they are almost 

 entirely absent. They are wanting or rare in many regions where 

 other glacial phenomena are strongly developed, as in Switzerland, 

 Norway, and southern Greenland. They are especially numerous in 

 central Ireland, and occur also in Scotland, Finland, and north- 

 west Russia. 



In the United States they are best developed in ]\Iaine (99). 

 They are common in New England, but rare over the interior states 

 (61,62,63). 



Occurrence in fJie Nezv York area. In New York they are 

 infrequent in occurrence, widely distributed, and are low short 

 ridges. They occur in much the same way as over the whole 

 glaciated area to the west. 



General Description. 



DUnensions. Eskers vary greatly in dimensions. In height 

 they may be from 3 feet to 150 or even 200 feet. One in the Con- 

 necticut river valley has been described as being 250 feet high (117). 

 In most cases they are less than 50 feet in height. 



Eskers vary in length from a fraction of a mile to 100 miles or 

 more. Several of the esker systems of Maine attain a length of 130 

 to 140 miles (99). 



In breadth at the base they are in most cases only a score or a 

 few SQore of feet, less than 75 or 100 feet, but locally they may 

 broaden to 500 feet, and a basal width of over a mile has been 

 recorded. The height exceeds one-eighth, and may reach one- 

 fourth or one-third the width of the base. Width may increase as 

 height diminishes or vice versa. They are neither constant in width 

 nor uniform in height. One esker has been described as one-eighth 

 of a mile wide throughout its whole length (63, p. 203). Eskers 

 tend to be small near their point of origin, becoming larger toward 

 their termination. 



