Page:Physical Geography of the Sea and its Meteorology.djvu/388

362 declination, but appear to wait until the temperature of the sea water puts it in motion. If a ship which has come into the belt of calms between May and September could lie still in the place where it came into this belt—cast anchor, for example—then it would perceive a turning of the monsoon or of the trade-wind. It would see the belt of calms draw away to the north, and afterwards get the south-west monsoon, or, standing more westerly, perhaps the south-east trade. On the contrary, later than September, this ship lying at anchor will see the north-east gradually awake. The belt of calms then moves towards the south, and removes from the which remains there anchored on the north side."

676. The influence of the land upon the winds of the sea.—The investigations that have taken place at the Observatory show that the influence of the land upon the normal directions of the wind at sea is an immense influence. It is frequently traced for a thousand miles or more out upon the ocean. For instance, the action of the sun's rays upon the great deserts and arid plains of Africa, in the summer and autumnal months, is such as to be felt nearly across the Atlantic Ocean between the equator and the parallel of 13° north. Between this parallel and the equator, the north-east trade-winds, during these seasons, are arrested in their course by the rainy seasons and heated plains of Africa, as observation shows they are in India, and instead of "blowing home" to the equator, they stop and ascend over the desert sands of the continent. The south-east trade-winds, arriving at the equator during this period, and finding no north-east trades there to contest their crossing the line, continue their course, and blow home as a south-west monsoon, where they deposit their moisture and ascend. These southwardly monsoons bring the rains which divide the seasons in these parts of the African coast. The region of the ocean embraced by these monsoons is cuneiform in its shape, having its base resting upon Africa, and its apex stretching over till within 10° or 15° of the mouth of the Amazon. Indeed, when we come to study the effects of South America and Africa (as developed by the Wind and Current Charts) upon the winds at sea, we should be led to the conclusion—had the foot of civilized man never trod the interior of these two continents—