BELTS, in astronomy, zones or girdles surrounding the planet Jupiter, brighter than the rest of his body, and terminated by parallel lines. They are observed, however, to be sometimes broader and sometimes narrower, and not always oc cupying exactly the same part of the disc. Jupiter's belts were first observed and described by Huygens. Dark spots have often been observed on the belts of Jupiter ; and M. Cassini observed a per manent one on the northern side of the most southern belt, by which he deter mined the length of Jupiter's days, or the time in which the planet revolves upon its axis, which is 9h 56m. Some astrono mers suppose that these belts are seas, which alternately cover and leave bare large tracts of the planet's surface : and that the spots are gulphs in those seas, which are sometimes dry, and sometimes full. But Azout conceived that the spots are protuberances of the belts ; and others again are of opinion that the trans parent and moveable spots are the sha dows of Jupiter's satellites.
Cassini also speaks of the belts of Sa turn being three dark, straight, parallel bands, or fascia., on the disc of that pla net,. But it does not appear that Saturn's bells adhere to his body, as those of Ju .piter do; but rather that they are large dark rings surrounding the planet at a distance. Some imagine that they are clouds in the atmosphere of Saturn, though it would seem that the middle most is the shadow of his ring.
Baas, in geography, certain straits between the German ocean and the Bal tic. The belts belong to the King of Denmark, who exacts a toll from all ships which pass through them, excepting those of Sweden, which are exempted.