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" he iargest delta of this class observed in the region, at Bristol Springs 
on the west side of the Canandaigua lake valley, was built in the Naples- 
Middlesex glaeial lake at one nearly static or slowly subsiding level. The 
top, about one-half by ene-quarter of a mile in area, is smooth and gently 
sloping forward from the 1,200 to the 1,100-foot level. The surface ma- 
terial is very coarse, containing rounded cobbles up to six inches in diam- 
eter, often with little admixture of finer sediment. This delta was built 
by a stream from the Bristol valley, which during the process must have 
drained a loaded ice lobe and not a lake. 
Such simple, flat-topped. steep-sided deltas, resembling the bastion of 
a fort or an abutment prepared by a daring engineer from which to spring 
Fig, 3. Naples Delta. Two Upper Levels. A kettlehole in the woods. 
the arch of a bridge, are formed rapidly by strong or torrential streams 
and are composed of relatively coarse materials. From their striking and 
characteristic form and position they may be called bracket deltas. 
Garlinghouse delta, a few miles south of Naples, does not project like 
a bastion from the face of the valley wall but fills a niche a mile deep 
and half a mile wide, the walls of which rise sharply 500 feet above its 
surface. The niche now receives two or three insignificant brooks, but one 
of them comes from a gap in the wall which opens northward to the upper 
Honeoye valley. This gap probably once transmitted a strong stream from 
the ice front but a few miles distant. This delta may be the only one of 
its kind, and if so, belongs in a class by itself—that of niche deltas, 
