Page:Graphic methods for presenting facts (1914).djvu/51

 would be well to have a broad line for the zero line, so that the eye may at once perceive that zero is not at the left-hand edge of the chart. It would have been better if the zero line in Fig. 31 were somewhat broader. Another help to the reader could be given by placing an arrow pointing to the right with the word "increase" and an arrow pointing to the left with the word "decrease."

''Journal Amer. Soc. Mechanical Engineers''

Fig. 32. Comparative Losses Between the Power House and Locomotives with Different Systems of Electric Traction

The comparison of the losses in the different power systems is very clearly shown in this illustration, which was taken from a paper by George Westinghouse

Broad bars can be used either vertically or horizontally. The horizontal arrangement is usually the more convenient, as it lends itself more readily to the use of type and horizontal lettering for the titles, data, etc., of each bar, without forcing the reader to turn the book at right angles. In Fig. 32, however, the lettering can perhaps be more conveniently grasped by the reader with the bars placed vertically instead of horizontally.

Note the lines connecting different bars to show how the components compare in size therein. These lines assist greatly in giving a clear and rapid interpretation of the chart.

Fig. 33 is an admirable example of what the graphic method can do to boil down complex facts for quick interpretation by the reader. In this case the schools of each of the forty-eight United States were