Geneology Chart. -- A chart used as a method of showing ancestry and heredity traits.

Genetics Chart. -- See geneology chart.

Graphic Narrative. -- A story told by means of pictures.

Grid. -- The surface or field composed of coordinate rulings on which data are plotted or graphed.

__^^^^^__^-- ^-^-- 503 GLOSSARY

Guide Map. -- A detailed map on which highways, railroad routes, or other methods of transportation are indicated together with cities, etc. Sec route map. Gun-Shot Chart. -- See scatter chart.

Halftone. -- A method of reproducing on a printing plate the details of a photograph, drawing, painting, etc.. including all the gradations of color. High- Low Chart. -- A chart in which the difference between two curves is the center of interest.

Independent Variable. -- The data presented in a chart or table which does not vary because of some influence within the data. The time scale on a curve chart is the independent variable.

Index Numbers Chart. -- A chart in which all items are expressed as percentages relative to a base figure.

Interpolation. -- Process of locating data between two known points.

Key. -- See legend.

Lag. -- The condition that exists when two curves are not concurrent, but one "lags" behind the other to some extent.

Legend. -- An explanation or identification of symbols, etc., used in a chart.

Logarithmic Chart. -- See ratio chart.

Logarithmic Scale -- A scale of numbers on a grid so arranged that the spacial intervals are proportional to the differences between the logarithms of the numbers.