'I'hc fce-Sheef in X((rrti<i<(iis(;tf lidij. — Wooihrorlh. 167 
the saiid-plaiii construction went on during summer rather 
tiian winter conditions, that is, during times of most rapifl 
melting. We cannot, therefore, assume that successive sand- 
plains one mile apart represent annual halts of the ice-sheet; 
for this would postulate that during the intervening winter 
the ice-front receded one mile, a result, to sa_y the least, incom- 
patible with the rate of melting during the construction of a 
single sand-plain. It seems most likely that the interval in 
this region is dependent upon some cause 'tending to repro- 
duce the same conditions of drainage at regular space inter- 
vals on the border of the ice-sheet, without definite control by 
the passage of time. 
The occurrence of kame-like mounds in the intraglacial field 
back of tiie sand-plains suggests the overlapping of the delta 
deposits upon the attenuated if not baseleveled margin of 
the ice so as to protect the ice beneath from the sun's rays. 
The identity in the materials of the sand-plains and these 
kames corroborates this view. The ice back of the overlapped 
zone would melt away in time, and the streams would tend to 
flow in the depression at the inner side of the overlap and so 
would be diverted for a time to one side. In the open space 
thus formed sand-plain building may be renewed after a time. 
In this view, the interval between successive sand-plains de- 
pends upon the width of the overlapping frontal drift plus the 
width of the depression pi-oduced interior to tliis overlap by 
the melting of the uncovered ice. 
That something analogous to this supposed course of events 
took place in Barrington, R. I., is indicated by the occurrence 
of the ice-pit in the margin of the Harrington plain, by the 
kames along the contact slope of the Nayatt Point plains, and 
by the wide-winged form of the liarriiigton ])]ain. All tiiese 
indications are explained if we su pjjose that the marginal 
portion of the ice-sheet at its contact with the head of the 
Nayatt Point plains had not yet melted out when the Har- 
rington plain was nearly if not (juite completed. 
Relation of tiik Saxd-tlains to Ska Levki,. 
There can be no doubt that the Nayatt Point eastcu-n sand- 
plain was deposited in a body of water whose surface was aj)- 
proximately fifty feet higher against the land than the i)resent 
sea level, if it was not still higher. A more important pre- 
