Page:Graphic methods for presenting facts (1914).djvu/154

 W. J. Cunningham, in the Railway Age Gazette

Fig. 122. 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

Compare this chart with Fig. 123. The data plotted here by the ordinary natural scale of co-ordinates are replotted in Fig. 123, using logarithmic co-ordinates. Note the peak in 1904 in Curve D. The number of passengers injured was approximately doubled in a short period of time. In the same period of time the number of passengers killed increased to seven times what it had been, yet the peak on Curve F does not attract great attention. Notice these same peaks in Fig. 123 with the logarithmic scale

It is unfortunate that there is so much difficulty in obtaining paper having the logarithmic ruling in one direction and the arithmetical ruling in the other direction. The arithmetical ruling in one direction is essential for statistical work, since we must ordinarily plot as one scale data representing years or other subdivisions of time. In statistical work we cannot well use a paper having logarithmic ruling in both directions, yet that is the only kind of logarithmic paper which can be obtained from most stores selling drawing materials