The monetary system of Charlemagne was the precursor and source of the chief currency systems of mediæval and modern Europe, with the exception of Spain. It was itself an imitation of the system of the Eastern Empire.
Its basis was the libra or pound, which occurs in two forms—(1) the gold pound, (2) the silver pound. Under the first race of the French kings the monetary divisions of the former were—
1. The gold solidus, a name which gave birth to the Spanish and Italian soldo and the French sol. (sou).
2. The third of the gold solidus (Triens or Tremissis).
Of the latter the aliquot parts were—
1. The silver solidus.
2. 1⁄3 silver solidus (Tremissis).
3. The denarius.
1 gold solidus = 3 1⁄3 silver solidi = 40 denarii.
1 silver solidus = 12 denarii
Under the system of the Eastern Empire the gold solidus had weighed 85 1⁄3 grs. and under the Merovingian Kings 70 1⁄2 grs. Under the rule of the Second House a considerable alteration took place. Charlemagne adopted for the basis of his system the East Frank or Rhenish libra, which was one-fourth heavier than the Roman libra adopted by the Merovings. His denarius accordingly weighed 32 grs. If ideally constructed the system, as far as silver is concerned, would be this—
12 denarii = 1 solidus.
20 solidi = 1 libra.
32 × 20 × 12 = 7680 grs. = 1 libra.
As far as the more precious metal is concerned, the gold solidus was, as a matter of fact, hardly to be met with under the second race. But, theoretically, it was still considered equal to 40 denarii.