Page:Graphic methods for presenting facts (1914).djvu/160

 paper was used for a background. The upper half of the chart shows the 24 hours of the day divided between hours of darkness, hours of twilight and cloudiness, and hours of sunshine, totaling 100 per cent for each month in the year. The hours of darkness are definitely known from almanac figures and can be plotted as a smooth curve. The hours of cloudy weather, however, vary in different years. The area showing cloudiness and twilight was drawn from actual weather observations made in New York City during the year 1910. The percentage of sunshine in different months fluctuates considerably, as will be noticed in the chart.

New York Edison Company

Fig. 127. Industrial Accidents in Different Months of the Year Compared with the Hours of Sunlight Each Day in Different Months According to Weather Records for New York City in 1910

Twenty-four hours in a day are shown as 100 per cent divided between darkness, semi-darkness, and sunshine. Curves showing accidents for three different years have the same general shape as the upper curve representing hours of darkness. The scale for the accident curves should have been started so as to show zero at the bottom of the curve field