He can, however, and, I believe, now often does, use the Jevonian method to work out definite results in half-pennies and tons from the intersection of plotted curves recording actual statistics of rates and traffic.
Since Jevons's time the method which he initiated has been steadily extended; economic and statistical processes have become more nearly assimilated, and problems of fatigue or acquired skill, of family affection and personal thrift, of management by the _entrepreneur_ or the paid official, have been stated and argued in quantitative form.

As Professor Marshall said the other day, _qualitative_ reasoning in economics is passing away and _quantitative_ reasoning is beginning to take its place.[43] [43] _Journal of Economics_, March 1907, pp.

7 and 8.

'What by chemical analogy may be called qualitative analysis has done the greater part of its work....

Much less progress has indeed been made towards the quantitative determination of the relative strength of different economic forces.