The lines for different fuels now appear in their correct order, and the reader sees at a glance that Pocahontas coal has more fuel value than anthracite coal. Notice that a heavy line has been used for the curve line drawn for anthracite coal. As this line is the standard by which the values are compared, it seems best to give it prominence on the chart. The position of other curve lines above or below this line shows instantly whether the fuels are better or worse than anthracite in relative value.

In Fig. 85 an effort has been made to show detail time-studies by the use of curves. There is an error here, however, in that the curve has been arranged in such manner that the independent variable is drawn vertically and the information desired as "time in seconds" must be read off from the horizontal scale. The reader wishes to know how many seconds are required for any one step or any series of steps in the whole work. The chart can be interpreted in the accustomed way if the page is turned over, and the diagram read by holding the page in such manner that the zero on the scale of "time in seconds" appears at the lower left-hand corner of the chart when the

GRAPHIC METHODS

page is held up toward a light. The curve for operator No. 1 then appears below the curve for operator No. 2 and the chart shows correctly the relative merits of the two operators. Fig. 86 is a redrawing of the data shown in Fig. 85. Here the curves for the two operators appear in their correct relative position, and it is seen at once that operator No. 1 is the more rapid worker, since he uses less time. With the independent v a r i - able made the horizontal scale, a chart can be interpreted quickly.