Page:Graphic methods for presenting facts (1914).djvu/183

 gallons per square mile." The scale could just as well have been made to show the total gallons of rainfall in the whole watershed, but it was more convenient to put the scale on a square-mile basis, dividing the total rainfall by the number of square miles in the water-*shed.

Cumulative or mass curves are very frequently used for the study of quantities in earth work, especially in railroad construction. Cumulative curves showing the total quantities of earth removed from cuts and the total amount used in fills can be kept to give the whole information in the most convenient form for quick reference and accurate study.