Graphic Methods for Presenting Facts
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fully watched tliere are certain to be in every herd cows whose milk production is far below the average. Individual records of each cow are now being kept regularly by up-to-date dairies, and any cow that fails to give a definite minimum of milk with a definite per cent of butter-fat is sent to the butcher. Curve cards are a convenient means of recording the output of each cow in such form that instant comparison between cows is possible.
In Fig. 214 a record for one cow for a period of five years is shown on a 4-by-12- inch card. As the card 12 inches long is necessary for weekly records, a card of the same size can be used conveniently to show five years by months instead of using five separate 4-by-6-inch cards, one for each year. In Fig. 214, the figures at the top of the card show the
CURVES FOR THE EXECUTIVE 281
milk production each month and the total milk production for each calendar year. The notes in the left-hand margin show the dates on which calves were born.