This is equivalent to an average speed of between 11 and 12 miles per hour. [Illustration: FIG. 16.--Roman galley. About 110 A.D.] [Illustration: FIG. 17.--Liburnian galley. Conjectural restoration.] The timber used by the ancient races on the shores of the Mediterranean in the construction of their ships appears to have been chiefly fir and oak; but, in addition to these, many other varieties, such as pitch pine, elm, cedar, chestnut, ilex, or evergreen oak, ash, and alder, and even orange wood, appear to have been tried from time to time. They do not seem to have understood the virtue of using seasoned timber, for we read in ancient history of fleets having been completed ready for sea in incredibly short periods after the felling of the trees. Thus, the Romans are said to have built and equipped a fleet of 220 vessels in 45 days for the purpose of resisting the attacks of Hiero, King of Syracuse. In the second Punic War Scipio put to sea with a fleet which was stated to have been completed in forty days from the time the timber was felled. On the other hand, the ancients believed in all sorts of absurd rules as to the proper day of the moon on which to fell trees for shipbuilding purposes, and also as to the quarter from which the wind should blow, and so forth. Thus, Hesiod states that timber should only be cut on the seventeenth day of the moon's age, because the sap, which is the great cause of early decay, would then be sunk, the moon being on the wane. Others extend the time from the fifteenth to the twenty-third day of the moon, and appeal with confidence to the experience of all artificers to prove that timber cut at any other period becomes rapidly worm-eaten and rotten. Some, again, asserted that if felled on the day of the new moon the timber would be incorruptible, while others prescribed a different quarter from which the wind should blow for every season of the year. Probably on account of the ease with which it was worked, fir stood in high repute as a material for shipbuilding.