Rotareme
Rotareme ( Latin rotaremis , rotating rudder, from rota , turning 'and remus , rudder, belt ') is the modern name for an antique paddle wheel ship with paddle wheels on the sides. In a late antique source, De Rebus Bellicis, we can read about a paddle wheel ship that was intended as a warship.
De Rebus Bellicis , the work by an anonymous author that cannot be dated precisely, contains not only reform proposals for administration and taxation but also a description of or ideas for new types of weapons and vehicles. The late antique text refers to the ship as a liburna , the general term for a warship at that time. However, that particular Liburna was not driven with belts as standard, but with paddle wheels. Today there is only one copy of the De Rebus Bellicis from the Middle Ages, and the illustration of that special ship contained therein shows a number of inaccuracies. It could be that the version of the Roman Rotaremis planned or actually built in late antiquity also had three paddle wheels on each side of the ship. This seems sensible, because it would make full use of the space that would otherwise have been available to the many rowers. And more paddle wheels also means more driving force, especially since in the late antique Rotaremis it was not people but heavy working oxen (possibly two animals per pair of paddle wheels) that were used as pulling forces for the mechanics of the paddle wheels. Otherwise, according to the medieval illustration, the ship was probably quite similar to a normal late Roman liburna . It is quite certain that the design of the Rotaremis is based on the construction of a perfectly normal Liburna, so that an expensive redesign could be avoided. Modifications to existing ships appear to have been cheaper, and it is known that the late Roman Empire had an interest in saving costs.
The late antique text mentions the extraordinary speed of the ship, and also that it could deliver a very powerful ram.