The great wind and pressure belts of the globe are much more constant and sharply defined over the oceans than over the land, and it was upon the high seas that mankind first distinguished them and gave them their names. The northeast trade winds of the Atlantic wafted Columbus to the New World and aroused the misgivings of his sailors, who wondered how they should ever sail homeward against them. The high-pressure belt north of these trade winds is a region of calms, which Maury called the “calms of Cancer.” This region, or a part of it, is likewise known as the “horse latitudes,” the story being that, in the old sailing days, vessels laden with horses were often becalmed here so long that the cargoes had to be thrown overboard. As a matter of course, the prosaic modern etymologist declines to accept this origin of the name and has proposed others less picturesque. The so-called equatorial calms, which lie mostly a little north of the equator, are often nicknamed the “doldrums,” or sometimes the “equatorial doldrums,” to distinguish them from other regions of dolorous, baffling calms. The doldrums vary a great deal in width and the masters of sailing ships try to cross them where they are narrowest. The name of the trade winds implies that, according to the old nautical phrase, they “blow trade,” or constantly in one direction. Strictly speaking, they vary considerably in direction, at any one spot, though they are nearly always from an easterly quadrant, and they are even more variable in force. The average speed of the Atlantic trades is about eleven miles an hour. In view of the prospective requirements of aeronauts, it is a fact of much interest that the trades are rather shallow winds. Their vertical thickness has been found, by observations with pilot balloons and otherwise, to range from less than a mile to two or three miles. Some distance above the trades there are winds blowing more or less in the opposite direction, known as the _counter-trades_. Aircraft will probably use the trade winds in flying from southern Europe to the Caribbean, and the countertrades on the return voyage to Europe. In contrast to the permanent or quasi-permanent winds just described, there are certain important winds of the “periodic” type, which reverse their directions in the course of the year or from day to night. Some of these, also, first became generally known through the reports of mariners. The ancient Greek navigators utilized the monsoons in trading with India; while we owe to the voyages of William Dampier, in the seventeenth century, one of the earliest and best descriptions of land and sea breezes.