PACE (passus, from pando, I extend), the unit of itinerary measure among the Romans, consisting of 5 Roman feet. The passus, or double step, was distinguished from the gradus, or single step, in not being the distance from heel to heel when the feet are at their ordinary extension in walking, but the distance from the point which the heel leaves to that in which it is again set down. A thousand of such paces formed the mille passus, or Roman mile. The word passus was sometimes applied to the distance formed by the extension of the arms in the same straight line (the Greek ὁρύξα), which accounts for Pauson's derivation of the word a passis manibus, instead of a passis pedibus. The Roman "pace" was equal to about 58.1 English inches, or 48416 feet.