The Columbia Encyclopedia, Sixth Edition. 2001-07.
horse latitudes
two belts of latitude where winds are light and the weather is hot and dry. They are located mostly over the oceans, at about 30° lat. in each hemisphere, and have a north-south range of about 5° as they follow the seasonal migration of the sun. The horse latitudes are associated with the subtropical anticyclone and the large-scale descent of air from high-altitude currents moving toward the poles. After reaching the earth’s surface, this air spreads toward the equator as part of the prevailing trade winds or toward the poles as part of the westerlies. The belt in the Northern Hemisphere is sometimes called the “calms of Cancer” and that in the Southern Hemisphere the “calms of Capricorn.” The term horse latitudes supposedly originates from the days when Spanish sailing vessels transported horses to the West Indies. Ships would often become becalmed in mid-ocean in this latitude, thus severely prolonging the voyage; the resulting water shortages would make it necessary for crews to throw their horses overboard.
