Page:The National geographic magazine, volume 1.djvu/123

 tically the same thing, 1:62,500. The relief of the surface is represented by the contour lines, or lines of equal elevation above sea, traced at vertical intervals of 20 feet. These contour lines, which are becoming a common feature of modern maps, add an additional element. They expresssexpress [sic] quantitatively the third dimension of the country, viz: the elevation. An inspection of such a map not only shows the horizontal location of points, but their vertical location as well. It gives the elevations of all parts of the country represented, above the sea.

The map represents all streams of magnitude sufficient to find place on the scale, and all bodies of water, as lakes, swamps, marshes, etc. In the matter of culture, in which definition is included all the works of man, it seemed desirable to represent only such as are of a relatively permanent nature, and to exclude temporary works, for the very apparent reason that if temporary works were included, the map would be not only a constant subject for revision, but even in the interval between the survey and the publication, the culture might change to a large extent, and the published map be correspondingly incorrect from the outset. In searching for a criterion which could be consistently followed in distinguishing between culture which should and should not be represented, it was found that by limiting the representation to that which may be denominated public culture, that is, that which has relation to communities, as distinguished from individuals, a consistent line could be drawn. Adopting this criterion, the map contains all towns, cities, villages, post offices,—in short, all settlements of any magnitude, all railroads and all roads, with the exception of such as are merely private ways, all public canals, tunnels, bridges, ferries and dams. There were excluded under this ruling isolated houses, private roads, fences and the various kinds of crops, etc. Forest areas are shown. Subsequently, however, in response to the urgent wish of the commissioners, the survey consented to locate the houses upon the maps, although in the engraving these have been omitted. The omission of all private culture leaves the maps very simple and easy to interpret. For convenience the field work was done upon a larger scale than that upon which the maps were to be published, viz a scale of 1:30,000, or a little more than double the publication scale. The map of the state as planned is comprised in 52 atlas sheets, each of which comprises 15 minutes of latitude by 15 minutes of longitude and an area of about 225