in trying to get a condensed visualization of the chart. There are relatively few curve charts which cannot be presented for report purposes on paper 8j^ by 11 inches, the commonest size used for a typewriter. Though the placing of a chart on paper of typewriter size requires more care than is necessary if a very large sheet of paper is used, the resulting chart is frequently more easy to interpret than it would be if made to a larger scale.

A warning seems justifiable that the background of a chart should not be made any more prominent than actually necessary. Many charts have such heavy co-ordinate ruling and such relatively narrow lines for curves or other data that the real facts the chart is intended to portray do not stand out clearly from the background. No more coordinate lines should be used than are absolutely necessary to guide the eye of the reader and to permit an easy reading of the curves. Too

A FEW CAUTIONS

many magazine articles and transactions of scientific societies contain charts which are reproduced direct from finely ruled co-ordinate paper and show all of the lines of the co-ordinate paper in the finished illustration. Co-ordinate ruling does not appear prominently on most original charts because the ruling is usually printed in some color of ink distinct from the curve itself. When, however, a chart is reproduced in a line engraving the co-ordinate lines come out the same color as the curve or other important data, and there may be too little contrast to assist the reader.