ADMINISTRATIVE REPORT. I 5 



elev^atiun above sea, based uii exact le\els, are also shown by 

 means of tigures printed on tlie contour lines. Each contour 

 passes through points which ha\e the same altitude. One who 

 follows the contour on the ground will go neither up hill nor down 

 hill but on a level. By the use of contours the maps of the plains, 

 hills and valleys as well as their elevations are shown. The line 

 of the sea coast itself is a contour line, the datum or zero of 

 elevation being mean sea level. The contour line at, say, 20 feet 

 above sea level is a line that would be the sea coast if the sea 

 were to rise or the land to sink 20 feet. Such a line runs back 

 up the valleys and forward around the points of hills and spurs, - 

 On a gentle slope this contour line is far from the present coast 

 line, while on a steep slope it is near it. Thus a succession of 

 these contour lines far apart on the map indicates a gentle slope; 

 if close together a steep slope; and if the contours run together 

 in one line, as if each were vertically under the one above it, they 

 indicate a cliff. The heights of many definite points such as road 

 corners, railroad crossings, railroad stations, summits, water sur- 

 face, triangulation stations and bench marks are also given on 

 the map. The figures in each case express the elevation to the 

 nearest foot. 



In addition to indicating relief and actual elevation above sea, 

 these maps show all the natural features, such as lakes, ponds, 

 rivers, streams, canals, swamps, and all cultural features including 

 public roads, railroads, towns, cities, county and state boundaries. 



The topographic maps thus prepared find many uses. They 

 are above all essential to the proper planning of drainage opera- 

 tions throughout all the interior of the state. It is a well known 

 fact that we have in Florida, particularly in the iiatwoods sections, 

 large areas of land that, although not actually flooded, yet would 

 be much improved by the more rapid removal of the heavy summer 

 rains. The state contains also valuable muck lands in addition 

 to those already being drained. The topographic maps such as 

 are here contemplated are essential to a proper planning of drain- 

 age operations. 



The topographic maps are of verv great assistance in the 

 preparation of detailed soil maps. They afford first of all an 

 exact base map of the area to be surveyed, thereby reducing the 

 cost of the average soil map in Florida about one-half; They 



