Similar deflections from the ordinary course of the trade winds occur also on the coast of Guinea (5° N. Lat.), in the Mexican Gulf, and in that part of the Pacific which borders on Central America, through the influence of the heated plains of Africa, Utah, Texas, and New Mexico, and have a similar influence on the distribution of moisture. Thus the sea monsoon, which prevails during the summer months on the coast of northern Guinea, carries a rainy season over the land as far as the eighteenth or nineteenth degree of northern latitude, and fertilises a vast extent of country which, from its position on the western side of an immense continent, would otherwise have been as naked and barren as the Sahara. As the tropical rains, though generally confined only to part of the year, and then only to a few hours of the day, fall in so much greater abundance than under our constantly drooping skies, it may naturally be supposed that the single showers must be proportionally violent. Descending in streams so close and so dense that the level ground, unable to absorb it sufficiently fast, is covered with a sheet of water, the rain rushes down the hill-sides in a volume that wears channels in the surface. For hours together the noise of the torrent, as it beats upon the trees and bursts upon the roofs, occasions an uproar that drowns the ordinary voice and renders sleep impossible. In Bombay nearly nine inches of rain have been known to fall in one day, and twelve inches in Calcutta, or nearly half the mean annual quantity of rain on the east coast of England. During one single storm which Castelnau witnessed at Pebas, on the Amazon, there fell not less than thirty inches of rain--nearly as much as the annual supply of our west coast. The hollow trunk of an enormous tree in an exposed situation gave the French traveller the means of accurate measurement.