For ancient and medieval man, the Mediterranean had a deserved reputation for benevolence. Compared to the Atlantic and the North Sea, it offers favourable conditions for navigation for many more months of the year. Clear skies, moderate winds, and slight seas can be expected across most of the sea from late March through to late October. Because of the small size of the sea, in world geographical and meteorological terms, the huge rollers which make Atlantic navigation so dangerous in storms are not to be found in the Mediterranean; although it is true that the short, steep chop raised by strong winds in some parts of the Mediterranean can be equally as hazardous as the Atlantic's rollers. Similarly, the tides, which so governed navigation in the North Sea as to affect the evolution of ship design, are virtually absent from the Mediterranean except in certain narrows. The many islands scattered throughout the northern half of the sea reduced the need to make long voyages out of sight of land and thus promoted maritime traffic in an age of small ships. The clear skies of summer nights facilitated navigation by the stars. But if the Mediterranean was particularly favourable to men's endeavours upon the sea by comparison to other waters, nevertheless geographical and meteorological factors still influenced profoundly matters such as ship design, the rhythms of seasonal voyaging, and the choice of routes.