10 Tlie American Geologist. July, i899 
the surface of the lake would fall to a lower level and a new 
beach would begin to be formed. 
It is a necessary consequence of the general relations in- 
volved in the retreat of the glacier that whenever a new outlet 
was first opened the ice-front was always present just then 
at that place and not somewhere else miles away. The first 
outflow was always close along the edge of the ice, so that now, 
where an old outlet channel is found running close along the 
front of one of the moraines of recesion, it follows that the ice- 
front stood just there while the outlet stream was flowing at its 
base, and if that moraine be traced continuously across the lake 
basin it will show the precise position which the ice-dam occu- 
pied at that time. But even if the moraine be not traceable, the 
emerging place of the dam on the other side of the basin may 
be determined by a correlation of the moraines in the series as 
pointed out above. And where a lake was sustained by two 
ice-dams, their contemporary positions may be found in the 
same way. Where the outlet crossed a hill or ridge which sep- 
arated the lake basin from an adjacent valley with lower drain- 
age and where the ridge sloped downward in the direction of 
the ice retreat, there was a tendency for the outlet to hug the 
ice-front in the re-entrant angle. Good examples of this rela- 
tion are found in the area here considered. 
The close relationship between new outlets and moraines of 
recession furnishes a basis for the approximate determination 
of another important matter. It furnishes the data for deter- 
mining theoretically a definite limit beyond which the beach or 
shore line of the next preceding lake stage cannot extend. For 
at the opening of a new outlet, all or a part of the discharge 
through the old one must have ceased and the surface of the 
lake must have fallen to a lower level. The beach associated 
with the old outlet was then abandoned and the formation of a 
new one begim on a lower plane. It follows, therefore, that the 
moraine associated with the new outlet marks the extreme pos- 
sible limit of extension of the beach associated with the old 
outlet. This beach could not extend beyond the new outlet 
on the one side of the basin, nor beyond the emerging place of 
the same moraine on the other side. It would be expected, 
however, that the begch on both sides would grow fainter to- 
wards its points of termination, and this would result from two 
