exchange of wealth to centre her attention on any species of ship other than those which would carry freights. But so many defeats had she endured at the hands of the Saracens and pirates that ships specially suitable for combat had, from the year 841, to be built. The Saracens hailed from Arabia, and it is notable that at that time the Arabian sailors who used to sail across the Indian Ocean were far and away the most scientific navigators in the whole world, many of their Arabic terms still surviving in nautical terminology to this day. Indeed, the modern mariner who relies so much on nautical instruments scarcely realises how much he owes to these early seamen. Just as the Cilicians and others had in olden times harassed the shores of the Mediterranean, so now the Saracens made frequent incursions into Sardinia, Corsica, Sicily, as well as intercepting the ships of the Adriatic.
Let us remember that both in the north and south of Europe the sailing seasons for century after century were limited to that period which is roughly indicated between the months of April and the end of September. Therefore the pirate knew that if he confined his attentions to that period and within certain sea-areas, he would be able to encompass practically the whole of the world's sea-borne trade. These sailing periods were no arbitrary arrangement: they were part of the maritime legislation, and only the most daring and, at the same time, most lawless merchant skippers ventured forth in the off-season.
Realising that the mariner had in any lengthy voyage to contend not merely with bad weather but probably with pirates, the merchant pilots were instructed to know how to avoid them. For instance, their main object should be to make the merchant ship as little conspicuous on the horizon as possible. Thus, after getting clear of the land, the white sail should be lowered and a black one hoisted instead.
