Saturday, November 19, 2011

The Mystery of the Ancient Oarsmen

Any study of ancient sea battles generates related discussions that go beyond numbers of ships, men, and battles. For this post I have selected one of those -- the oarsmen who acted as the means of propulsion for the ancient warship.

This subject is interesting because no one knows how the warships of antiquity were propelled. We know the ships had oarsmen, but where were the oarsmen placed and how were they organized to maximize the ship’s power and speed? The number of oars had to be chosen to avoid collisions between them, which when they occurred, would destroy the rhythm of the stroke and cause a loss of the ship’s propulsive force.

The trireme, original warship of the ancient world, was developed from the pentekontor, an open hulled craft which commonly used 25 rowers on each side. This is Homer’s craft and the craft of the Vikings. Extant examples of the pentekontor can be seen in the Oslo History Museum.

The trireme was developed during the early fifth century B.C. in Greece probably from designs the Phoenicians were using. The “tri” in trireme refers to the three types of oarsmen in the ship - thalamites, zygites, and thranites. Why these types existed and how they functioned is a mystery.

There are four principle ways to configure oarsmen in a trireme: in a single line on each side of the boat; vertically, one group above another; assigning multiple rowers per oar; or placing rowers next to each other on a common bench. The following discussion will attempt to determine which of these options was in use.

Greek triremes had a length of approximately 120 feet, as verified from available dry-dock ruins. One hundred twenty feet is also the engineering maximum because, even with internal support cabling, it can be shown that wave action will break a longer wooden ship in half. Because of the limit on the number of oarsmen who could be placed on each side of the ship, designers had to come up with other ways to arrange them.

The absence of historical writing on the configuration of the rowers leaves us in the dark – but we have other sources. The poets, philosophers, and playwrights of Athens have come to the rescue with tidbits of information.

From the standpoint of pictorial evidence (pottery and the like), we come up empty. The most widely analyzed artifact showing a trireme is called the Lenomant of the Acropolis believed to have been carved in 400 B.C.

The arguments over what this image tells us about the rower positioning are on-going.

Many historians assert the three types were placed along each side of the ship at three levels bottom to top and superimposed over each other, but this configuration is problematic. Collisions between the oars were likely and the requirement for longer oars for oarsmen farther from the water sacrificed mechanical advantage because of the inefficient angle of attack.

Regarding multiple rowers per oar we take Thucydides word (Book 2, 93.2) that each rower during the Peloponnesian War used one oar.

That leaves us with the rowers seated next to each other as the remaining option. Let us look at some quotes from those who have made a contribution to solving the mystery.

*In Aeschylus’ Agamemmon the statement is made that the thalamites sit below the zygites.

*Polybius describing a collision during the battle if Chios in 201 B.C. states that one ship penetrated the middle of the hull of the other under the thranites thole (fulcrum pin).

*Polyaenus notes that in a storm additional thranite oars were put out to aid in steering indicating that the thranites sat in the rear of the ship. Some historians believe that the Thranites were in the aft position, the zygites in the center, and the thalamites in the bow. This suggests a bow to stern division of rowers as opposed to a vertical division which doesn’t make sense given the need to layer the rowers and equip them with different length oars.

*A trireme oar inventory has been uncovered which lists 62 thranite oars, 54 zygite oars, and 54 thalamite oars.

*There is an Athenian dockyard record that indicates that thranite oars no longer serviceable could be made into zygite oars, i.e. be shortened by cutting off the worn parts.

*Aristotle in his Mechanics says that the mesoneoi (young rowers) sat in the “middle” and had the longest oars. One assumes he uses middle to mean the center line or farthest from the side of the ship.

In the crude drawings below I show how the rowers could have been positioned to satisfy all the historical statements. The rowers sat on benches angled to the back of the ship, with the thranites, zygites, and thalamites seated next to each other. The bench was stepped to allow the rowers to swing their oar without hitting the men sitting next to them.

A demonstration of this configuration was made using oar lengths of 10,12 and 13.5 feet and showed good results.

During the Golden Age of Athens, the trireme was the warship of choice. A dockyard record from 325 B.C, however, lists 360 triremes, 50 quadriremes, and 7 quinqueremes indicating an evolution in craft types.

By the First Punic War the Romans were using mainly quinqueremes as discussed in the previous article. With incomplete knowledge of how triremes were manned, we must throw up our hands as we contemplate how a quinquereme could be rowed using five groups of rowers. Most likely there was a group who moved their oars from a standing position, but this is a guess.

A few more relevant points are interesting. The trireme was said to be capable of 8 knots, which is good compared to sailing ships of the time. Pliny cites some Roman sailing records the fastest of which is a run from Ostia to Africa of 270 nautical miles at an average speed of 6 knots. How long the rowers could maintain their speed is unknown. One would imagine exhaustion setting in after 10-20 minutes, but we don’t know whether all rowers were pulling in order to make an 8 knot speed.

And one more thing. Rowers were not slaves as portrayed in popular culture – at least the Greek oarsmen weren’t. There are pay slips extant showing that the thalamite rowers were paid less because their oars were shorter.
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1 comment:

Mark D said...

The existence of Hexaremes, Septiremes, Octeres and higher polyremes shows that the number did not refer to banks of oars, at least in the higher numbers. the number probably referred to the number of oarsmen in each 'rank', with mutiple orasmen to each oar.

Ptolemy II's navy fielded 14 "elevens", 2 "twelves", 4 "thirteens", one "twenty" and two "thirties". Ptolemy IV even built a "forty".