Page:Graphic methods for presenting facts (1914).djvu/155

 W. J. Cunningham in Railway Age Gazette

Fig. 123. Passengers and Employees Killed and Injured in Train Accidents for All Railroads in the United States. (From Quarterly Reports of the Interstate Commerce Commission)

Curve A. Passenger miles (2000 on scale equals 20 billion passenger miles)

Curve B. Ton miles (2000 on scale equals 20 billion ton miles)

Curve C. Number of employees injured

Curve D. Number of passengers injured

Curve E. Number of employees killed

Curve F. Number of passengers killed

This illustration is a replot of Fig. 122 by using the logarithmic scale in the vertical direction. In reading a chart in which a logarithmic vertical scale is used, attention may be given to the slope of the curve lines. Curves having the same slope upwards or downwards have the same percentage change. Note that curves with a logarithmic scale do not have zero for the bottom line of the chart. It is, however, desirable to have the bottom line either at ten or some power of ten on the vertical scale

and engineering supplies. A person doing statistical work for which paper with the logarithmic ruling is desirable may occasionally have to rule his own paper. This, however, is not an impossible task especially if one has a slide rule. The spacing of the lines can be copied from either scale of the slide rule, or it may be worked out easily to fit any