The Difference With Which The Strata Of Air Flow Back From The Two Poles Towards The Equator Cannot Be The

Same in every degree of longitude, that is to say, on points of the globe where the continents are of

Very different breadths, and where they stretch away more or less towards the poles.

It is known, that in the passage from Santa Cruz to Cumana, as in that from Acapulco to the Philippine Islands, seamen are scarcely ever under the necessity of working their sails. We pass those latitudes as if we were descending a river, and we might deem it no hazardous undertaking if we made the voyage in an open boat. Farther west, on the coast of Santa Martha and in the Gulf of Mexico, the trade-wind blows impetuously, and renders the sea very stormy.* (* The Spanish sailors call the rough trade-winds at Carthagena in the West Indies los brisotes de Santa Martha; and in the Gulf of Mexico, las brizas pardas. These latter winds are accompanied with a grey and cloudy sky.)

The wind fell gradually the farther we receded from the African coast: it was sometimes smooth water for several hours, and these short calms were regularly interrupted by electrical phenomena. Black thick clouds, marked by strong outlines, rose on the east, and it seemed as if a squall would have forced us to hand our topsails; but the breeze freshened anew, there fell a few large drops of rain, and the storm dispersed without our hearing any thunder. Meanwhile it was curious to observe the effect of several black, isolated, and very low clouds, which passed the zenith. We felt the force of the wind augment or diminish progressively, according as small bodies of vesicular vapour approached or receded, while the electrometers, furnished with a long metallic rod and lighted match, showed no change of electric tension in the lower strata of the air. It is by help of these squalls, which alternate with dead calms, that the passage from the Canary Islands to the Antilles, or southern coast of America, is made in the months of June and July.

Some Spanish navigators have lately proposed going to the West Indies and the coasts of Terra Firma by a course different from that which was taken by Columbus. They advise, instead of steering directly to the south in search of the trade-winds, to change both latitude and longitude, in a diagonal line from Cape St. Vincent to America. This method, which shortens the way, cutting the tropic nearly twenty degrees west of the point where it is commonly cut by pilots, was several times successfully adopted by Admiral Gravina. That able commander, who fell at the battle of Trafalgar, arrived in 1802 at St. Domingo, by the oblique passage, several days before the French fleet, though orders of the court of Madrid would have forced him to enter Ferrol with his squadron, and stop there some time.

This new system of navigation shortens the passage from Cadiz to Cumana one-twentieth; but as the tropic is attained only at the longitude of forty degrees, the chance of meeting with contrary winds, which blow sometimes from the south, and at other times from the south-west, is more unfavourable.

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