114 ON THE GEOLOGY AND NATURAL HISTORY 
are located upon the third terrace, which is far above high water mark. Near Bellevue 
and Omaha city we have very fine examples of terraces, and these villages are located 
upon the third. In a forthcoming official report I hope to treat this subject in detail, 
illustrating it with numerous outline sketches. We regard this subject as one of great 
interest, and most intimately connected with the history of the elevation of the western 
portion of the continent, for we can hardly doubt that the terraces result from the gradual 
elevation of the Rocky mountain range. 
CHAPTER XITI. 
RESUME OF THE GEOLOGY OF THE MIssourrl RIVER AND ITS TRIBUTARIES. 
In the following chapter I desire to present a résumé of the geology of that portion of 
the Northwest under consideration, with the additional information obtained since the 
preceding report was written. ‘The foregoing chapters, with very slight alterations, re- 
main as they were prepared over two years since, inasmuch as I have not felt authorized to 
make any important changes on account of my relations to a subsequent expedition to the 
Northwest, under the command of Captain Wm. F. Reynolds, 'T. E., a report of which 
exploration is now in a state of preparation. By permission of Captain Reynolds, a sum- 
mary of the principal geological results was published, which is now before the world, and 
from it and from other sources I hope to make a condensed statement of the leading 
geological discoveries up to the present time, and to harmonize some of the conflicting 
opinions which may have been advanced in regard to the age of the different deposits in 
the West. Opinions differing widely from those which Mr. Meek and the writer have 
advanced, derived from the personal observations of the latter, and our joint investigations 
of extensive collections of organic remains, have been put forth by a writer who never 
visited the country explored by me, which may have had a tendency in some minds to 
weaken the force of our statements. Without entering into any discussions I would simply 
say, that all of my statements have been made with a conscientious regard for the truth, 
and such conclusions have been derived as seemed legitimate, leaving to the future to 
correct that which is wrong and approve that which is right. I cannot feel satisfied, how- 
ever, to have any geologist, after a brief exploration and even without any personal know- 
ledge of the country, pronounce my observations, which have been made with great care 
and patience, through the toil of many years, as entirely at variance with the truth. 
We may very properly separate the western portion of our continent into two divisions, 
mountain and prairie, and a combination of the two will form the Rocky mountain district. 
