G. F. Wright—G@lacial Era in Eastern North America. 121 
be no question that they were formed about the close of the 
Glacial period. 
' It occurred to the writer, some years ago, that these holes 
might be made to do service in estimating the date of the 
Glacial era. The results are not so definite as could be wished 
” 
t 
which appear in the kames I Srenend facts concerning one near 
Pomp’s Pond in Andover, Mass. 
Pomp’s Pond is one of the moraine basins to which we have 
referred, and is about a quarter of a mile in diameter and but 
slightly above the level of the Shawshin River into which it 
empties. Upon its north side is an accumulation of gravel 
and sand with pebbles intermingled, in which there are several 
of the smaller characteristic bowl-shaped depressions of which 
we have spoken. Their appearance is much like that of vol- 
canic craters. You mca a sharp declivity from every side 
to a rim of gravel and then descend as rapidly into the bowl- 
a or crater-like, depression. A section carried across 
will present the idea. 
. 
escend from its top to the valley, repeating almost exactly 
the first ascent and descent from the pond. The distance from 
rim to rim, or the diameter, is 380 feet. 
hus it is evident that since the first formation of this 
crater-like depression no material can have reached the bottom 
