00 BULLETIN OF THE ESSEX INSTITUTE. 



nant tongues of the ice-sheet rather than along its main 

 front. In the broad lowlands of eastern Rhode Island and 

 the southeastern part of Massachusetts, embracing all of 

 "The Old Colony," wash-plains abound. 



The age of the plains in this field is, in general terms, 

 successively newer from south to north. The outermost 

 plains fronting the terminal moraine pertain to the height 

 of the last or third glacial epoch. The more northern 

 plains belong to the retreat of the ice-sheet and fall with- 

 in the time commonly known as Champlain. But there 

 is reason for believing that till- and drumlin-making may 

 have been going on, about Boston, while the plains in the 

 latitude of Providence were being deposited, so shadowy 

 is the demarcation between the Glacial Period so-called 

 and the Champlain Period as originally defined. It would 

 be more consistent to speak of the superficial glacial drift 

 of this field as pertaining to the last or third glacial epoch, 

 allowing the term Champlain, as seems to be the tendenc}^ 

 to become obsolete. 



The distribution of plains in this lowland district of New 

 England is at first sight without order ; but amid the laby- 

 rinth of passages in the decaying ice, channels which are 

 now marked by accumulations of gravel and sand, there 

 are certain well marked and massive accumulations which 

 upon examination on the ground arrange themselves in 

 lines comparable to moraines. To a certain extent, mo- 

 rainal accumulations attend the wash-plains which are thus 

 distinofuished from the irregular accumulations of this 

 nature. In the following pages, the most prominent of 

 these retreatal lines will be indicated, and under the head 

 of sporadic plains, are placed a few notes concerning 

 deposits which may yet be arranged in a coherent system, 

 but which are not at present distinguishable from the 

 irregular disposition of gravels and sands about chance 

 blocks of ice left in the general retreat of the glacier. 



