The Rhombus or Lozenge figure ſo viſible in this order, vvas alſo a remarkable form of battle in the Grecian Cavalry, […] As being moſt ready to turn every vvay, and beſt to be commanded, as having its ductors, or Commanders at each Angle.
Source: wiktionary
1883, Andrew Overend, "Inking apparatus for printing-machines", US patent US363760, filed 9 November 1883, issued 24 May 1887.
The combination, with a fountain-roller and an ink-cylinder, of a ductor movable between said roller and cylinder for delivering ink from one to the other...
Source: wiktionary
Ink is transferred to the ink distribution rollers by a ductor roller.
Source: wiktionary