104 BULLETIN or THE ESSEX INSTITUTE. 



Pond. A well-defined esker divides the lake into two 

 lobes. On the eastern and western sides of the pond are 

 wash-plains. 



At North Pembroke, plains are developed in succession 

 on the south side of the North River. Long Hill, on the 

 east of the town, is a high plateau apparently of wash ori- 

 gin. A well-formed wash-plain rises above the village 

 immediately east of the principal street. It should be noted 

 that a well-defined esker comes down the hill on the north 

 of the river and passes beneath the swampy stream at a 

 point opposite the mouth of Robinson's Creek. 



The plains in the northern part of this atlas sheet have 

 been described by Crosby and Grabau in connection with 

 Lake Bouve. 



Numerous deposits on the Duxbury atlas sheet are 

 resolvable into high plains and cones of washed gravels. 

 Everywhere steep slopes marking ice-contacts appear. 



On the Plymouth sheet, there is a double alignment of 

 ice-block holes and lakelets. One line runs northwest 

 at a distance of two or three miles from the shore of the 

 Bay and includes the following ponds, beginning on the 

 north: Smelt, Triangle, Billington Sea, Cook, Great 

 South, Boot, Gunner's Exchange, Crooked, Long, Half- 

 way, Bloody, Little and Great Herring. Springing out 

 from this line and extending south westward are at least 

 six marked lines of ponds beginning with Buttermilk Bay 

 on the south. Next come White Island, Glen and Spec- 

 tacle ponds ; farther northwest is a line of lakelets run- 

 ning southwest from Crooked Pond of the main line series ; 

 another set intersects the main line in Great South Pond. 

 Billington sea has a spur in West Pond ; Triangle Pond 

 in the main trend is in line with Round Hole, Clear and 

 Darby ponds. The ponds in the main line have their 

 axes northwest and southeast; those in the spurs are 



