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other sources of information. This is straight clerical work and may be done with a pen on one card after another with great rapidity. Ordinary liquid drawing ink is the best for the figures, as the opaqueness of the drawing ink gives better blue prints than are obtainable from writing ink. This is often partly transparent and prints pale blue instead of clear white. After the figures have been entered on all the cards, the cards are taken rapidly one by one and a sharp leadpencil is used to mark on the proper vertical line a point which, according to the vertical scale, corresponds with the newly recorded figures in the upper margin. When all the curve points have been located by lead-pencil marks on the curve cards, a drawing pen is used to draw the line on each card to show the change that has occurred since the previous point was plotted. As the new point has already been indicated in each case by the lead-pencil

CURVES FOR THE EXECUTIVE 277

mark, all the ink lines can be drawn in rapidly with a draftsman's ruling pen. If the suggested procedure is used, the lines may be drawn so rapidly that there is no chance for the ink to dry on the pen and the ruling operation is almost continuous.

In Fig. 212 we have complete in black ink the same card which in Fig. 206 is given full scale, using two colors to make the contrast between the green-ink background and the black-ink curve. Though Fig. 212 shows the card in reduced size, it nevertheless gives a very good idea of the appearance of a card suitable for the plotting of records for one year by weeks, making it necessary to have fifty-two entries of figures in the upper part of the card.