to the tides and currents along that route, the average passage both from Europe and America to our north-west coast was not less than 180 days. It has been reduced so as to average only 135 days. This route is now so well established, and the winds of the various climates along it so well understood, that California bound vessels sailing about the same time from the various ports of Europe and America are, if they be at all of like prowess, almost sure to fall in with and speak each other by the way.
628. Obstructions to the navigator.—The calm belts at sea, like mountains on the land, stand mightily in the way of the voyager, but, like mountains, they have their passes and their gaps. In the legions of light airs, of baffling winds, and deceitful currents, the seaman finds also his marshes and his "mud-holes" on the water. But these, these researches have taught him how best to pass or entirely to avoid. Thus the forks to his road, its turnings, and the crossings by the way, have been so clearly marked by the winds that there is scarcely a chance for him who studies the lights before him, and pays attention to directions, to miss his way.
629. Plate VIII.—The arrows of Plate VIII. are supposed to fly with the wind; the half-bearded and half- feathered arrows denote monsoons or periodic winds; the dotted bands, the regions of calm and baffling winds. Monsoons, properly speaking, are winds which blow one half of the year from one direction, and the other half from an opposite, or nearly an opposite direction. The time of the changing of these winds, and their boundaries at the various seasons of the year, have been discussed in such numbers, and mapped down in such characters, that the navigator who wishes to take advantage of them or to avoid them altogether is no longer in any doubt as to when and where they may be found.
630. Deserts.—Let us commence the study of the calm belts as they are represented on Plates I. and VIII. The monsoons and trade-winds are also represented on the latter, they often occupy the same region. But, turning to the trade-winds for a moment, we see that the belt or zone of the south-east trade-winds is broader than the belt or zone of north-east trades. This phenomenon is explained by the fact that there is more land in the northern hemisphere, and that most of the deserts of the earth—as the great deserts of Asia and Africa—are situated in the rear, or behind the north-cast trades; so that, as these deserts become
