The speed of the galley was calculated by the French engineer Forfait to be in the most favourable circumstances, that is to say in a flat calm, but four and a half knots for the first hour, and two and a quarter to one and a half miles per hour for subsequent hours; the exhaustion of the rowers consequent on their arduous toil would not admit of a greater speed than this.  The studies of Forfait were made when the invasion of England by rowing boats was a topic of burning interest.  It is evident from this that long voyages, trusting to the oar alone, could not be undertaken; but as we have seen, the galley was also provided with motive power in the shape of two masts carrying the lateen sail, which may be still seen in so many Mediterranean craft.

That the galley was no vessel in which to embark in bad weather is instanced for us by the disasters which befell a Spanish fleet of these craft in 1567 under the Grand Commander of Castile, Don Luiz de Requesens.  A revolt of the Moors in Granada had caused Philip the Second to wish to withdraw a certain number of Spanish troops from Italy.  Requesens was sent to Genoa with twenty-four galleys to embark a detachment of an army corps then stationed in Piedmont.  Each galley embarked one hundred and fifty soldiers; they then got under way and reached the island of Hyeres, where they anchored, the weather being too bad to proceed.  At the end of their eighth day in port a number of vessels were seen flying to the eastward before the wind; it was a squadron of Genoese.

Requesens, who was no seaman, was furious.  Here were the Genoese at sea, and he wasting his time in harbour; if they could keep the sea why could not he, he demanded?  He instantly ordered the anchors to be weighed.  The commander of the Tuscan galleys, of which there were ten in the fleet, immediately went on board the galley in which Requesens was embarked and represented that the wind was foul and that should they leave their anchorage they could make no headway once they got clear of the land.  But Requesens was obstinate:  “if others can go on their way it is shameful that I should not proceed on mine,” he protested.  Alfonso d’Aragona argued with him in vain, representing that his master, the Duke of Tuscany, would hold the Grand Commander responsible for damage to his galleys.  It was all in vain, as the Grand Commander was too arrogant and stupid to listen to advice from anybody.  The fleet put to sea and struggled out a mile from the land; when they got thus far Requesens discovered his mistake and regretted that he had not taken the advice of the mariners; but it was now too late, they had drifted to leeward of their anchorage and could not get back again.