The standard color scheme should be used if no conditions preclude its use, but if other colors can be used with greater economy without sacrificing clearness the use of the standard colors should be waived.
BLACK-LINE CONVENTIONS.
A complete set of the black-line patterns used to distinguish areas on a map is given in [Plate VIII] ([p. 60]), and their application to a finished drawing is shown in [figure 9] ([p. 62]). These patterns, however, should preferably not be used by the author in his preliminary work on an illustration. For this purpose water colors or colored crayons are preferable, and the distinctions between areas may be emphasized by letter symbols.
MATERIALS USED IN PREPARING MAPS.
PAPER.
For large and important maps which may at some time be extended to cover a greater area or which may be made to fit maps already prepared or published the paper used should be mounted on muslin to reduce to a minimum the shrinking or stretching caused by atmospheric changes. Pure white paper produces a better negative than a cream or yellowish paper and will retain its color longer, but all papers become more yellow with age and exposure to light.
The following brands of paper are used in the Survey in the preparation of maps:
"Normal" K. & E., unmounted. Has an excellent surface and comes in flat sheets, 19 by 24, 22 by 30, and 27 by 40 inches.
"Paragon" K. & E., mounted on muslin. In 10-yard rolls 72 inches wide. Used in the Survey for large office drawings and maps of large scale.