Scale of Maps.—Formerly map-makers contented themselves with placing upon their maps a linear scale of miles. They now usually add the proportion which the units have to nature.
The linear scale of maps can obviously be used only in the case of maps covering a small area, for in the case of maps of greater extension measurements would be vitiated owing to the distortion or exaggeration inherent in all projections.
Map Projections are dealt with separately below. It will suffice therefore to point out that the ordinary needs of the cartographer can be met by conical projections. The indiscrimi nate use of Mercator's projec tion, for maps of the world, is to be deprecated owing to the exag geration of areas in high lati tudes.
Delineation of the Ground. —The mole-hills and serrated ridges of mediaeval maps were still in almost general use at the close of the i8th century, and are occasionally met with at the pres ent day, being cheaply produced, readily understood by the un learned, and in reality preferable to the uncouth and misleading hatchings still to be seen on many maps. Far superior are those sce
nographic representations which enable a person consulting the map to identify prominent land marks.
Delineations such as these do not, however, satisfy scientific requirements. This was recog nized by J. Picard and other members of the Academy of Science whom Colbert, in 1668, directed to prepare a new map of France, for on David Vivier's map of the environs of Paris (1674, scale i :86,40o) very crude hachures bounding the rivers have been substituted for the sceno graphic hills of older maps. Towards the close of the 18th century horizontal contours and hachures regulated according to the angle of inclination of all slopes were adopted. These contours are the intersections of the surface and horizontal planes (see fig. I). Con tours of this kind were first utilized by M. S. Cruquius in his chart of the Merwede 728) ; Philip Buache (1737) introduced such contours or isobaths (Gr. Zoos, equal; gain, deep) upon his chart of the Channel, and intended to introduce smaller contours or isohypses (i5tkos, height) for a representation of the land.