The decimal dollar had already been agreed upon in principle in 1785, but would not be implemented until after passage of the Mint Act in 1792. After correspondence with William Waring and others, Jefferson proposed two systems of units in mid-1790. The first was evolutionary, and was based on refinement of the definitions of the units of the existing English system, as well as simplification of their relationship to each other. The second system was revolutionary, and was based on units linked by powers of ten, very similar to the decimal metric system which would be proposed in France. The base units for length, mass, and volume in Jefferson's revolutionary system (named the foot, the ounce, and the bushel, respectively) were relatively close in size to their pre-existing counterparts and bore identical names, although the manner in which they were defined was very different.