118 BULLETIN OF THE ESSEX INSTITUTE. 



built approximately at water-level, some of the cones 

 being built up above water-level. On the assumption 

 that delta fronts are indicative of water-level, the very 

 diverse altitudes of plains along the same line of retreat 

 and in the same limited area separated in construction by 

 the shortest possible space of time, makes it highly im- 

 probable that the water-level was also sea-level. It is 

 more reasonable to suppose that the limit of construction 

 of wash-plains was determined l)y the level of local bodies 

 of water on a land area as claimed by Crosby and Gra- 

 bau, or that, if the region was submerged, wash-plain 

 levels have, as apparently held by Professor Shaler, no 

 detinite relation to sea-level. 



5. As having a 1)earinir on the rival hypotheses just 

 named, an examination of the area shows that numerous 

 blocks of ice remained long in the field to embarrass aland 

 drainage and to produce temporary lakes. 



The accompanying map, on account of its small scale, 

 has not been made to show many wash-plains which sur- 

 round ice-block holes. The features which are new are 

 the morainal accumulations running northeastward from 

 Providence and the Hue of plains foHowiug the same direc- 

 tion from Woonsocket in the northeastern corner of Rhode 

 Island. 



