Monsoon (Arab, mausim, season, corrupted by the Portuguese into moncao), an intertropical wind which blows part of the year from one point of the compass, and the remainder of the year in a contrary direction. These winds are more particularly known in the seas adjoining the great Asiatic continent and archipelago, including Papua and the N. part of Australia, whence they extend to about Ion. 100° E. The causes which produce them are, in theory, the same as those generally supposed to cause the trade winds. When the sun is in X. latitude and comes over a large portion of Arabia, Hin-dostan, Burmah, and Cochin China, and these lands become heated to a much higher temperature than the surrounding equatorial sea and atmosphere, the cooler air Mows toward these regions; and as they have less rotary velocity than the latitudes bordering upon the equator whence the current comes, it acquires a rela-tive N. E. direction in passing to the north, and is called the S. W. monsoon. In the northern hemisphere, when the land is cooled by the sun being in S. latitude, the regular N. E. trade wind prevails throughout these seas, and what is called the N. E. monsoon is in reality the N. E. trade wind.
South of the equator the S. E. trad.- wind continues to blow over all that part of the wean which has not large tracts of land to the south; but where this is the case, as in the Java seas, and as far E. as New Ireland, we find the same causes operating again, and a N. W monsoon taking the place of the regu-lar S. E. trade wind when the sun has southern deehnation. These general laws, with trilling exceptions, apply to all monsoons: that to say. when the S. W. monsoon blows N. or the equator, the wind blows from S E in the region S. of the equator; and when the N". W. monsoon prevails in S. latitude, the wind blows from N. E. in N. latitude.