gS The America?i Geologist. August, i889 
brought forward to show that submarine channel-like depres- 
sions exist adjacent to the mouths of many rivers.* It is 
argued that these channels are the result of erosion, which 
erosion could not have occurred unless the land stood at a 
greater level than at present; and that, as these channels are 
now submerged, the land must have sunk since the erosion. 
This argument is plausible, and has been presented with such 
force by high authorities that these "submarine channels" are 
frequently accepted as absolute proofs of an upheaval ot the 
adjacent land areas, of a period of glacial and other erosion, 
and of a subsidence to the present conditions. 
But the existence of submarine valleys is not always proper 
evidence that they are the result of erosion during a previous 
era of upheaval. Channel building by bank elevation is a 
process of sedimentation which goes on under water as well as, 
or better than, under air,t so that the existence of nearly parallel 
banks on either side of the lines of discharge of the St. Law- 
rence, Congo, or other rivers, is not proper evidence that the 
adjacent lands were at one time elevated to a hight equal to, or 
greater, than their present submergence. 
Before a submarine valley shall be decided to be one of 
erosion, its form should be shown to correspond to proper 
lines, and the eroded material should be accounted for as a bar 
at the submarine mouth. 
The sediment which these rivers have borne to the ocean 
during their entire existence must have been deposited more 
upon the flanks of the outflowing fresh water, than in the direct 
lines of swiftest flow. If one will take the pains to plat to nat- 
ural scale the sections of some of these submarine channels 
and banks, he will find that the banks correspond more nearly 
to those of sedimentation. 
These submarine banks may therefore be evidence of the 
permanence of the existing levels of land and water, rather 
than evidences of fluctuations in these levels. 
*The Epeirogenic Theory of the Causes of the Ice Age. Prof. 
Warren Upham, F. G. S. A. The GlaciaHsts' Magazine, Vol. I.. No. 
10, pp. 211-217. Also Am. Geologist, Vol. VI. Dec. 1890, No. 6. 
tSee pp, 2,521-2,522, Appendix M. M., Report of Chief of Engi- 
neers, U.S. A. 1882, or Ex. Doc. No. 93, 46 Congress, 3rd Session, p. 
718. In these rej)orts the actual building up of the banks of such 
channels is shown to have been accomplished in less than one-half a 
century. 
