THE BRIMFIBLD LAKE. 565 



As the ice melted back across Worcester County the water ran off 

 across it iuto more eastern (b'ainage systems and lias left its esker ridges 

 behind it to mark the place of the ice sti-eams, hut as the ground began to 

 slope toward the Connecticut and became grooved by deep valleys, at once 

 the retreat of the ice became more irregular and the escape of the water 

 more inteiTupted. 



ICE BARRIERS. 



Upon the ma}) tlie position <>f the ice barriers which (-(implctcd the 

 shore line of glacial lakes and watercourses is markeil 1)\' a series of red 

 circles. This position is, in the nature of the case, only an approxim.ate one, 

 often an average of many shifting positions. At times a later erosion has 

 removed the beds left at the line of contact, and a series of later teiTaces 

 occupies its place. In this case it seemed in several instances nece-ssary for 

 the clearness of the map to represent as closely as possible the fact and the 

 approximate position of the ice boundary, and since to represent it in its 

 true position would confuse the expression of these later tei'races with which 

 it had no relation, it was found necessary to draw this boundary ujxm the 

 color representing the lake area and along that edge of the area nearest to 

 its true position. Whenever possible it is di'awn just outside this area 

 across the till. On the map these ice ban-iers are numbered from southeast 

 across the State to uorth\vest No. 1 is applied to the oldest series of bar- 

 riers, approximately contemporaneous and representing portions of a single 

 ice front which retained the Brimfield lakes and turned their drainage awav 

 east of the Monson Valley and across Brimfield and Wales; No. 2 is applied 

 to the next clearly recognizable series, which diverted the waters into the 

 Monson Valley, and so with the others. The evidence upon which these 

 barriers have been located is given in detail in the description of the 

 separate basins. Arrows are also used on the map to indicate the direction 

 of flow of the waters, and especially the passes by which the lakes were 

 drained. 



THE BRIMFIELD LAKE. 



This, the oldest and highest of the lakes, occurs on the ea.stern Ix.rder of 

 Hampden County, in the northwest corner of Brimfield, at a height of 830 

 feet above sea (PI. XXXV, D, 1 b). It is a square basin, the north and 

 south sides of which are rock; on the east the waters l)athed an enormous 

 "felsenmeer" of great bowlders of gneiss, a rock which always furnishes the 



