On Perusing What Spanish And Portuguese Authors Relate Respecting The Existence Of The Fabulous Isle Of San Borondon, Or Antilia, We Find That It Is Particularly The Humid Wind From West-South-West, Which Produces In These Latitudes The Phenomena Of The Mirage.

We shall not however admit with M. Vieyra, "that the play of the terrestrial refractions may render visible to

The inhabitants of the Canaries the islands of Cape Verd, and even the Apalachian mountains of America."* (* The American fruits, frequently thrown by the sea on the coasts of the islands of Ferro and Gomera, were formerly supposed to emanate from the plants of the island of San Borondon. This island, said to be governed by an archbishop and six bishops, and which Father Feijoa believed to be the image of the island of Ferro, reflected on a fog-bank, was ceded in the 16th century, by the King of Portugal, to Lewis Perdigon, at the time the latter was preparing to take possession of it by conquest.)

The cold we felt on the top of the Peak, was very considerable for the season. The centigrade thermometer, at a distance from the ground, and from the apertures that emitted the hot vapours, fell in the shade to 2.7 degrees. The wind was west, and consequently opposite to that which brings to Teneriffe, during a great part of the year, the warm air that floats above the burning desert of Africa. As the temperature of the atmosphere, observed at the port of Orotava by M. Savagi, was 22.8 degrees, the decrement of caloric was one degree every 94 toises. This result perfectly corresponds with those obtained by Lamanon and Saussure on the summits of the Peak and Etna, though in very different seasons. The tall slender form of these mountains facilitates the means of comparing the temperature of two strata of the atmosphere, which are nearly in the same perpendicular plane; and in this point of view the observations made in an excursion to the volcano of Teneriffe resemble those of an ascent in a balloon. We must nevertheless remark, that the ocean, on account of its transparency and evaporation, reflects less caloric than the plains, into the upper regions of the air; and also that summits which are surrounded by the sea are colder in summer, than mountains which rise from a continent; but this circumstance has very little influence on the decrement of atmospherical heat; the temperature of the low regions being equally diminished by the proximity of the ocean.

It is not the same with respect to the influence exercised by the direction of the wind, and the rapidity of the ascending current; the latter sometimes increases in an astonishing manner the temperature of the loftiest mountains. I have seen the thermometer rise, on the slope of the volcano of Antisana, in the kingdom of Quito, to 19 degrees, when we were 2837 toises high. M. Labillardiere has seen it, on the edge of the crater of the peak of Teneriffe, at 18.7 degrees, though he had used every possible precaution to avoid the effect of accidental causes.

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