Noi*^ Proctlcet rec6mm«nd*d In Ihli tecllon apply primarily to lolld lin* curvai.

Principlet

1. Corves should be sufficiently heavy to attract immediate attention and to impress a visual image on the mind of the reader.

2. In general, time-series curves should be heavier than is the practice in the case of engineering and scientific charts.

Procedures

1. RELATION TO WEIGHT OF RULINGS. Curves should be sufficiently heavy to be distinguished readily from the co-ordinate rulings.

2. RELATION TO WEIGHT OF REFERENCE LINES. Single curves should normally be heavier than the zero line or other principal line of reference. Multiple curves should normolly be no lighter than reference lines.

3. RELATION TO NUMBER OF CURVES. Curves usually should be heovier when shown singly than when several are shown together Iperhaps decreasing % for each additional curvel.

4. RELATION TO CHARACTER OF CURVES. Irregular curves should normally be lighter than relotively smooth ones (the greater the irregularity the lighter the curvel.

5. RELATION TO OTHER COMPONENTS. Curves should not be so heovy as to appear crude or to overpower the other elements of the chort.

6. GENERAL PICTURE vs. CLOSE READING. The weight of curves should vary according to the use -- from relatively heavy lines in charts for popular appeal to very light lines in charts used for close reading of values.

7. VARIATION OF WEIGHTS on the same chart: la) To distinguish one curve from another.

(b) To indicate the relotive importance of curves.

8. OVERLAPPING CURVES. The more curves intersect or overlap on the same grid, the greater should be the contrast in weight las well os pattern).