■S94-] 269 [Dodge. 
be left tom]Mii-nrily while tlie river was euttinii" down to its 
base-level immediately after the inauguration of a new cycle. 
Terrace-making due to a stream of constant volume cutting 
down into a rising land is well illustrated l)y TTugh Miller^ who 
gives an interesting account of such a process, l)ase<l on liis 
investigations of a sniall strenni in Kngland that w;is forming 
terraces ra})i<lly. 
The explanation given above seems to account for the forma- 
tion of the grenter number of existing terraces, namely, those 
formed in the river valleys influenced l)y the action of the last 
ice age. Of such terraced valleys that of the Connecticut is the 
best knoAvn though it shows us no finer terraces than those 
found in many of the v:illeys of Cannda and of New Brunswick. 
Such terraces, according to the classification given above, are 
best described as complex. "^Fhe upper terrace plain was formed 
during glacial times and the rest of the work has lieen subsequent, 
and is due to a different cause from glaciation. The process of 
formation was j>robably something as follows. Streams that under 
the pressure of the confining ice sheet were capable of carrying- 
great loads dropped them on issuing from under the ice sheet, and 
have built deposits in front of their mouths, of the flood jilain 
type, such as are descriV)ed by Mr. Kussell- in the valleys of the 
Alnskan rivers. The rivers, overcharged with detritus and flowing 
out upon a land that had a sIo]ie too slight to allow all the detritus 
to be transported by the existing volume, would at once begin 
to aggrade their valleys to a slope adjusted to the load and to 
the carrying power. As the level of the valley deposits grad- 
unlly rose to the re(]uired grade, the aliility of the stream to 
carry mateiial at th:it )>oint would increase, and the waste 
deposited, would naturally grow coarser l)ecause the size of the 
transported j)articles would vary directly with the carrying 
jtower. Consequently many of the alluvial terraces formed 
during the last ice time shonld present materials gradually 
increasing in coarseness from the }>ottom upwards. An exam- 
ination of the materials in cert:iin of the terraces in glaciated 
'River terracirifj, its niethnds .ind their results. Proc. roy. phj^s. soc. Edinb., 
session 112, 1882-3, 1883, p. 2G3-305. 
5 Second expedition to Mt. St. Eliiis. Thirteenth Annual report U. S. geol. survey, 
p. 57. 
