92 Trans. Acad. Sci. of St. Louis. 
levels was continued to St. Louis. In 1880 a line of care- 
fully checked levels was run from Sioux city, Iowa, to the 
mouth. During the succeeding years, up to October 1884, no 
further surveying was done, but, during the fall of that year, 
the Commission determined upon a secondary triangulation 
of the river from bluff to bluff and also determined to establish 
lines of permanent bench marks, the whole to be connected 
with the former survey. This work was commenced October 
12th at Glasgow and reached Boonville December 15th; the 
work was continued all of the winter and was closed with the 
Coast Survey triangulation station at Tavern Rock the follow- 
ing May. In 1889 triangulation was extended above Fort 
Leavenworth. In the autumn of 1890 a new shore line sur- 
vey was made of the whole of that portion of the river, 
within the State. One series of maps is published containing 
the results of this work, on a scale of one mile to the inch. 
The area covered by these sheets is also indicated on the 
diagram on page 90. They contain less detail than do the 
larger sheets of the Mississippi river survey. 
The United States Geological Survey has undertaken, as 
part of its work, the preparation of a topographical atlas of 
the country. For this purpose, along with work prosecuted 
elsewhere, maps have been constructed of about one-third of 
the area of this State. The distribution of this mapping is 
clearly shown in the diagram on page 90. The survey 
was begun in the year 1884 and was continued uninterrupt- 
edly up to July of 1889. Since that time no further work 
has been done. The product up to the present date is 25 
sheets in Missouri und five sheets including portions of 
Missouri and Kansas, all on a scale of zss555, or about 2 
miles to the inch, with a contour interval of 50 ft. ; also two 
sheets, including St. Louis and parts of St. Louis county, and 
Illinois, on a scale of ¢z455, or about one mile to the inch, 
with a contour interval of 20 ft. All of these sheets are of 
uniform size, 164 by 20 inches, and the area represented on 
each is a geographic one and is a fraction of a square degree of 
latitude and longitude. These maps have represented upon 
them the drainage in blue; the hypsometry in brown; the 
cultural features, such as towns, railroads, roads, political and 
