* 
Winslow —The Mapping of Missouri. 93 
cadastral division lines in black. They constitute the first 
series of maps which even attempts to display, in a compre- 
hensive and systematic way, the topography of the State, or 
of any large part of it. They are much in advance of any- 
thing previously published. The principal objections which 
can be urged against them are that the scale is too small and 
the contour interval too great for the characteristics of much 
of the topography of the State to be well brought out or for 
many valuable details to be closely located or even included. 
Further the method of work employed furnished a weak 
vertical control and the altitudes represented are, hence, very 
inaccurate in places. A fifty foot contour and a scale of two 
miles to the inch though calculated to well display the general 
features of a mountainous country of large and bold features, 
fails to be adequate in a prairie country where differences of 
elevation of twenty feet are significant and conspicuous. 
The method of construction of these maps is described in 
the following words by Mr. Henry Gannett, Chief Topog- 
rapher of the United States Geological Survey, in a letter to 
the writer: — 
‘* The primary horizontal control consists of the triangula- 
tion of the Coast and Geodetic Survey and of the Missouri 
River Commission, supplemented where these surveys have 
not.extended, by astronomic determination.* The secondary 
horizontal control consists in part of the location made by the 
U. S. Land Surveys (their township and section corners) this 
system having been connected with the primary locations for 
the purpose of eliminating their accumulated errors; and in 
part of traverses of roads and other routes of travel. In these 
traverses the directions were measured by compass and dis- 
tances by the wheel. The primary measurements of height 
were obtained from levels along the Missouri river and the 
profiles of railroads, secondary height measurements were 
made by the cistern and aneroid barometers, the latter being 
corrected by comparison with cistern barometer and by com- 
parison with the known heights of points upon railroads. 
* Points were established at Springfield and Bolivar, Mo., and at points 
adjacent to the State line in Kansas. A 
