Hekshev.] 



The River Terraces of the Orleans Basin* 



467 



with the period of deposition of the [owan loess in the Missis- 

 sippi Basin. This suggests the idea thai the loess may have 

 been due to more abnormal conditions than simply a subsidence 

 of the region. 



Relative Age of Different Terraces. — In comparing the 

 canons excavated between the different terrace levels. I will 

 ignore the alluvial deposits. The time occupied by their removal 

 is a very small fraction of the entire period of canon cutting, 

 and consequently they introduce a needless complication into 

 what will at best be a very rough computation. 



By inquiring among the Indian fishermen and others who 

 are acquainted with the river, I have derived the estimate that 

 the average depth of the bed-rock below present low-water mark 

 is about ten feet, and as the bed-rock floor of the forty-five- 

 foot terrace averages ten feet above the river, twenty feet may 

 be assumed as the average depth of the Modern rock-canon. 



The most delicate part of this discussion is the determination 

 of the probable age of the Modern canon. We have no natural 

 chronometers, such as art' constituted by Niagara and St. 

 Anthony Falls. Extensive inquiry among the old settlers has 

 not yielded very definite results. However, it is certain that 

 the canon has not been eroded within a period of several hundred 

 years. By reason of the placer miners' tailings, the river has 

 been aggrading its channel for some years, but that does not 

 prevent it from eroding the banks. In 1860, and again in 1890. 

 severe winters caused many landslides along the river, but. con- 

 sidered as a whole, there has been no appreciable widening of 

 the channel in the past fifty years. 



Less than one-half mile downstream from the Orleans post- 

 office, and on the same side of the river there is an old Indian 

 village site. The edge of the bank is about twenty-five feet 

 above the river, and a gentle slope leads back from it to a flat 

 plain which is about 250 feet wide and has a height of about 

 thirty-five feet above the river. Back of it, another gentle slope 

 leads up to the flat plain of the forty-five-foot terrace. The lower 

 terrace is composed mainly of a deep bed of dark brown sand. 

 Similar sand beds occur at this level at various places along the 

 river, and they -are usually essentially non-pebbly. But at this 



