A man prepared to show his data in the form of curves, for example like Fig. 157 or Fig. 159, feels that he would have an almost hopeless task to convey the vital facts if only spoken words might be used. The writer ventures to predict that within ten years practically all corporation directors and executives will be able to interpret curves with satisfaction to themselves and with great benefit to their business. The executive who cannot read curves will in the near future be the exception rather than the rule.

If any general manager will take the trouble to train his department heads to read curves and will then supply to them curves showing the facts of his business, he will be tremendously repaid in the interest, enthusiasm, and real progress toward improvement which will be aroused in his men.

It is possible to use a reflecting lantern like that pictured in Fig. 218 to show on a screen the curves from the curve cards described in Chapter XIII. Lantern slides are not practicable when frequent meet-

RECORDS FOR THE EXECUTIVE

making

ings of department heads must be held. The expense of lantern sHdes each time a new point is plotted on each curve would be too great for even the largest corporations. Another disadvantage of using lantern slides is the impossibiUty of getting shdes made quickly enough to represent always the latest points plotted on the curves. By using the original curve cards directly in the reflecting lantern there is always a certainty that the picture shown on the screen represents the very latest data which are available in curve form. When these curve cards are used in a reflecting lantern a simple slide carriage is made