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 for a curve are available, it can be seen that even if there were only three points instead of four in Fig. 242, the curve would still be valuable to convey the desired information. In Fig. 53 and Fig. 54 methods are shown by which charts which are essentially curve charts may be drawn even though there are available only two points for each curve. When curves become as widely understood as the bar method of presentation, it will be found that curves can be used advantageously in almost every case where it is now common to use either vertical or horizontal bars.

American Railway Association

Fig. 243. Freight-Car Shortage and Surplus in the United States for Four Years, 1907 to 1911, Inclusive

The horizontal bars here are so numerous and are placed so close together that the charts have practically the general form of curves drawn vertically instead of horizontally. It would seem just as well to represent the data by real curves drawn with the standard horizontal arrangement

In Fig. 243 the horizontal-bar method has been elaborated so that the resulting chart has practically the general effect which would be obtained by a curve chart. The reader who wishes to read Fig. 243 in the form of curves is, however, forced to turn the book so that he may see the chart from the left with the curves running in a generally horizontal direction. The data would likely be just as well understood by railroad men if shown by real curves drawn in the standard manner.