In That Direction Are Situated Portland Rock, Pedro Keys And South Key, All Surrounded By Dangerous Breakers. The Depth Is

Six or eight fathoms; but, in advancing to the middle of the bank, along the line of the summit, first

Towards the west and then towards the north-west, the depth becomes successively ten, twelve, sixteen and nineteen fathoms. When we survey on the map the proximity of the high lands of San Domingo, Cuba and Jamaica, in the neighbourhood of the Windward Channel, the position of the island of Navaza and the bank of Hormigas, between Capes Tiburon and Morant; when we trace that chain of successive breakers, from the Vibora, by Baxo Nuevo, Serranilla, and Quita Sueno, as far as the Mosquito Sound, we cannot but recognize in this system of islands and shoals the almost-continued line of a heaved-up ridge running from north-east to south-west. This ridge, and the old dyke, which link, by the rock of Sancho Pardo, Cape San Antonio to the peninsula of Yucatan, divide the great sea of the West Indies into three partial basins, similar to those observed in the Mediterranean.

The colour of the troubled waters on the shoal of La Vibora has not a milky appearance like the waters in the Jardinillos and on the bank of Bahama; but it is of a dirty grey colour. The striking differences of tint on the bank of Newfoundland, in the archipelago of the Bahama Islands and on La Vibora, the variable quantities of earthy matter suspended in the more or less troubled waters of the soundings, may all be the effects of the variable absorption of the rays of light, contributing to modify to a certain point the temperature of the sea. Where the shoals are 8 to 10 degrees colder at their surface than the surrounding sea, it cannot be surprising that they should produce a local change of climate. A great mass of very cold water, as on the bank of Newfoundland, in the current of the Peruvian shore (between the port of Callao and Punta Parina* (* I found the surface of the Pacific ocean, in the month of October 1802 on the coast of Truxillo, 15.8 degrees centigrade; in the port of Callao, in November, 15.5; between the parallel of Callao and Punta Parina, in December, 19 degrees; and progressively, when the current advanced towards the equator and receded towards the west-north-west, 20.5 and 22.3 degrees)), or in the African current near Cape Verd, have necessarily an influence on the atmosphere that covers the sea, and on the climate of the neighbouring land; but it is less easy to conceive that those slight changes of temperature (for instance, a centesimal degree on the bank of La Vibora) can impart a peculiar character to the atmosphere of the shoals. May not these submarine islands act upon the formation and accumulation of the vesicular vapours in some other way than by cooling the waters of the surface?

Quitting the bank of La Vibora, we passed between the Baxo Nuevo and the light-house of Camboy; and on the 22nd March we passed more than thirty leagues to westward of El Roncador (The Snorer), a name which this shoal has received from the pilots who assert, on the authority of ancient traditions, that a sound like snoring is heard from afar. If such a sound be really heard, it arises, no doubt, from a periodical issuing of air compressed by the waters in a rocky cavern. I have observed the same phenomenon on several coasts, for instance, on the promontories of Teneriffe, in the limestones of the Havannah,* (* Called by the Spanish sailors El Cordonazo de San Francisco.) and in the granite of Lower Peru between Truxillo and Lima. A project was formed at the Canary Islands for placing a machine at the issue of the compressed air and allowing the sea to act as an impelling force. While the autumnal equinox is everywhere dreaded in the sea of the West Indies (except on the coast of Cumana and Caracas), the spring equinox produces no effect on the tranquillity of those tropical regions: a phenomenon almost the inverse of that observable in high latitudes. Since we had quitted La Vibora the weather had been remarkably fine; the colour of the sea was indigo-blue and sometimes violet, owing to the quantity of medusae and eggs of fish (purga de mar) which covered it. Its surface was gently agitated. The thermometer kept up, in the shade, from 26 to 27 degrees; not a cloud arose on the horizon although the wind was constantly north, or north-north-west. I know not whether to attribute to this wind, which cools the higher layers of the atmosphere, and there produces icy crystals, the halos which were formed round the moon two nights successively. The halos were of small dimensions, 45 degrees diameter. I never had an opportunity of seeing and measuring any* of which the diameter had attained 90 degrees. (* In Captain Parry's first voyage halos were measured round the sun and moon, of which the rays were 22 1/2 degrees; 22 degrees 52 minutes; 38 degrees; 46 degrees. North-west Passage, 1821.) The disappearance of one of those lunar halos was followed by the formation of a great black cloud, from which fell some drops of rain; but the sky soon resumed its fixed serenity, and we saw a long series of falling-stars and bolides which moved in one direction and contrary to that of the wind of the lower strata.

On the 23rd March, a comparison of the reckoning with the chronometric longitude, indicated the force of a current bearing towards west-south-west. Its swiftness, in the parallel of 17 degrees, was twenty to twenty-two miles in twenty-four hours. I found the temperature of the sea somewhat diminished; in latitude 12 degrees 35 minutes it was only 25.9 degrees (air 27.0 degrees). During the whole day the firmament exhibited a spectacle which was thought remarkable even by the sailors and which I had observed on a previous occasion (June 13th, 1799). There was a total absence of clouds, even of those light vapours called dry; yet the sun coloured, with a fine rosy tint, the air and the horizon of the sea.

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