Page:Graphic methods for presenting facts (1914).djvu/134

 Data of J. J. Hinman, Jr., Indianapolis Department of Public Health

Fig. 103. Monthly Averages of Butterfat Contained in Milk on the Indianapolis Market, 1906 to 1913. The Curves Represent Averages from Several Hundred Samples each Month

In order to find what fluctuations are typical for various months of the year, it is convenient to chart the data as seen here with curves for different years one above the other. Definite peaks in April and in October or November are seen at once. This chart is drawn on the same universal co-ordinate paper shown also in Fig. 57, Fig. 130, Fig. 134 and Fig. 156