300 TJk- AlHi'l'lcan, Orologixf. Ncsemher, ISW 
the former :u\' pcKuliui'ly subject to sliding tiiid slushing out at 
base. The amount of erosion which has taken place since the 
occupation of the earlier glacial lakes may be more perfectly real- 
ized when we learn that the prominent high terrace found along 
the Missouri. AVhilc and Cheyenne rivers is more than 300 feet 
above their present water level. This terrace dati'S from the 
time of the second moraine, or possibly of the first of the '-sec- 
ond glacial epoch." And this terrace is much more recent than 
the lakes under consideration. Aw erosion, which has excavated 
these valleys to such a depth, must certainly have greatly changed 
the surface along the old lake borders. 
4. Yet another influence may have frequently done much to mask 
lacustrine features, viz.. orographic changes, (xilbert has recognized 
this as prominent in the cases of lakes Bonneville and Ontario. 
Chamberlin finds an elevation of Champlain deposits, of 330 
feet in eastern Wisconsin, and of 5-600 feet in northwestern part 
of the same state. And this has been in a much less time than 
has elapsed since lake Missouri was filled with loess. 
8o much on general principle. As may be remembered the 
writer has held that the extra-morainic drift of the Missouri val- 
ley is prol)ably of sub-aqueous origin, that lake Missouri which 
deposited the loess, at an earlier stage was partly filled with sand, 
gravel and boulder clay; that a similar lake occupied the Red 
Lake region, from the Bijou hills to the big bend. Also that a 
similar one covered a wide scope of country from near the mouth 
of the Moreau northward. Hitherto, I have found rather scanty 
evidence of an old water level in the distribution of boulders 
about the Bijou hills, 500 above the Missouri or 1,900 above 
the sea, and a patch of l»ouldery gravel and clay 510 feet above 
the Missouri, covering an acre or so, south of the mouth of 
White river. 
In 188S Prof. (1. F. Wright reported the finding of something 
like a moraine along the divide south of the Moreau river. (See 
]^roc. A. "A. A. S., 1888.) 
It has been my privilege the past season (1890) to traverse the 
course of Prof. Wright, with the same companion, Rev. T. L. 
Riggs, and to spend a few days in the examination of this feature. 
I found Fox ridge a high sandy plateau, forming the divide 
between the Moreau and Big Cheyenne rivers. Upon it, and on 
its south slope, T found no northern erratics. Its summit, twenty 
