Great Ice- Dams. — Taylor. 33 
erett, some of the old channels are demonstrable products of 
river action, and were therefore connected with lake waters. 
He notes the fact that the Chicago outlet had rapids near 
Joliet, where a descent of 70 feet was made in only nine miles.* 
Several of the channels near Syracuse, N. Y., show the sites of 
abandoned waterfalls. It seems obvious that the shore lines 
which lead into the heads of such channels mark the bound- 
aries of lake waters standing at some considerable hight above 
sea level, and not of gulfs or bays of the ocean. The fact that 
the Ubly and other channels show no well marked sites of 
rapids or waterfalls has no weight against the supposition that 
they too are products of river action. This is a mere accident 
of topography. Most of them show more or less of a delta 
deposit at one end, and gravel bars and bowlders in their 
course indicate the direction of flow. The Chicago and Syra- 
cuse channels are in the same series and drained the same basin 
as the Ubly and Imlay and Fort Wayne channels; but the 
former are at lower levels and were active at later times. If 
the waters were fresh when they flowed past Syracuse 
and Chicago what reason is there to suppose that they were 
marine when they stood at higher levels? The Grand River 
channel is 50 miles long and one mile wide. If its evidences of 
current action are due to ocean tides then the waters that 
connected with it must have had considerable tidal oscillation ; 
but the beaches which enter it are plainly the product of waters 
that had very little if any tidal oscillation. These are some of 
the general reasons against a marine origin for the beaches and 
channels. For the Ubly channel in particular, the significant 
fact may be noted that the Belmore beach which connects 
with its head has no representative on the inner or north side 
of the Port Huron-Saginaw moraine, although that side at the 
level of the beach would have been openly exposed to heavy 
surf from over the basin of lake Huron if the ocean had stood 
at that level. Thus, the tidal or marine theory of the channels, 
including the Ubly, and of the beaches connected with them, 
must be discarded as untenable for both general and specific 
reasons. 
For some of the channels of the lake region the idea of tem- 
porary lakes due to elevated land barriers is quite plausible. 
^Letter referred to above, p. 196. 
