In this chart a normal was first decided upon and marked as zero. The departures from this normal, or average, were then plotted above and below the zero line. The deviations below normal are distinguished from those above normal by color.

2^2 GRAPHIC PRESENTATION

Abstracts from Time Series Charts. A Manual of Design and Construction, 1938, prepared by Committee on Standards for Graphic Presentation, under procedure of American Standards Association, with The American Society of Mechanical Engineers as sponsor body.

FUNDAMENTAL CONVENTIONS OF FORM

1. A TimoS«ne$ Chort is one of severol types of bi-numericol scole cherts. A binumericol scole chort is based on the conception of twodimensionol movement in o single plane.

2. The field or coordinate surfoce on which the voloes ore located is formed by intersecting verticol ond horizontal rulings located ot measured intervols from the two principal axes.

3. It is the convention that positive values are measured upword from the horizontal oxis and to the right of the verticol axis and negative values ore measured downward from the horizonlol axis and to the left of the vertical axis.

4. In o time-series chart the vertical or Y axis measures amount, ond the horizontal or X oxis meosures time.

5. Time values In o time-series chart ore usuoily represented as positive and move from left to right on the horizontal or time scale.

6. Every plotted point in o time-series chart has two values: An amount volue meosured on the verticol oxis ond o time value measured on the horizontal axis.