268 The American Geologist. ^^y- ^^os. 
ascends, i. e. about twenty feet above the upper surface of the 
limestone forming the floor of the tunnel. The Alissouri was 
diverted to the other side of its .channel. There was a wash 
from the adjacent hills, the little tributary contributed its own 
flood wash, the limestone and the shale were mingled with the 
debris, a little drift (Kansas age) came from the region, and 
the human remains were buried either in the latest part of the 
erosive stage or earlier part of the flood-plain-building stage. 
This all took place since Wisconsin glaciation. "The antiquity 
of the burial is measured by the time occupied by the Missouri 
river in lowering its bottoms, two miles more or less in width, 
somewhere from fifteen to twenty-five feet, a very respectable 
antiquity, but much short of the close of the glacial invasion." 
Professor Chauiherlin's points separately considered. 
It may be conducive to the proper appreciation of these con- 
clusions to consider them, by number, somewhat seriatim, and 
to make sundry references and comparisons. 
No. I, we have no reason to call in question. We will 
simply remark that it necessitates the extension of the same 
lowan loess into all pre-existing valleys and gorges except 
where it can be shown that it has been replaced by some later 
deposit, or has been excavated without replacement. The pre- 
sumption is that it subsists in the old valleys. It is therefore 
the first general fact that confronts the unbiased investigator. 
The writer would refer here to the discussion of the upland 
lowan loess and its methods of accumulation and its composi- 
tion and variation by Mr. W. J. McGee in the eleventh annual 
Report of the United States Geological Survey,* and to the 
epitome recently presented in the writer's retiring address to 
the Geological Society of America. If one t)e seeking for 
agencies "closest at hand in time" he may ignore this great 
fact, but in so doing he might ignore the agencies closest at 
hand and most obtrusive in nature. 
No. 2. There is no reason to question the present approxi- 
mate adjustment of the flood-plain debris of the tributary with 
the flood-plain debris of the Missouri. It could hardly be 
otherwise with any stream that has a little flood-plain of its 
own at the point of debouchure upon a larger stream, what- 
* Op. cit., Pleistocene History of Northeastern Iowa. 
