\ 
s 
126 J. D. Dana—Phenomena of the Champlain Period. 
The other explanation, also—that the holes are places un- 
filled by depositions because of their depth and for the other 
reasons mentioned—has apparently its difficulties Itis a mat- 
ter for surprise that where so great depositions were in progress 
so many holes of the kind should have been left in the plain; 
and also that the terrace-formation should have been so gen- 
gins. 
Such results lose some of their seeming improbability when 
e flood, th 
e 
- isolated ice-masses could not have lasted long enough, or 4 
