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Fig. 74. Prices of Cement, per Barrel, in Bulk, at the Mill, from 1880 to 1910

Columns of printed figures or a series of vertical bars could not portray this information as vividly as it is brought out by the curve shown above

GRAPHIC METHODS

hour, or even more frequently. The curve, therefore, was plotted on much more numerous points than are indicated by the vertical lines of the horizontal scale. Frequent observations of the gauge height and the numerous points plotted on the curve in Fig. 76 explain those fluctuations in the line of the curve which occur in the spaces between the vertical lines. Ordinarily a chart is sufficiently accurate if straight lines are drawn from point to point of the plotted data for a curve, without attempting to make a smooth, flowing line.

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