We sailed from Nueva Barcelona on the 24th of November at nine o'clock in the evening; and we doubled the small rocky island of Borachita. The night was marked by coolness which characterizes the nights of the tropics, and the agreeable effect of which can only be conceived by comparing the nocturnal temperature, from 23 to 24 degrees centigrade, with the mean temperature of the day, which in those latitudes is generally, even on the coast, from 28 to 29 degrees. Next day, soon after the observation of noon, we reached the meridian of the island of Tortugas. It is destitute of vegetation; and like the little islands of Coche and Cabagua is remarkable for its small elevation above the level of the sea. In the forenoon of the 26th we began to lose sight of the island of Marguerita and I endeavoured to verify the height of the rocky group of Macanao. It appeared under an angle of 0 degrees 16 minutes 35 seconds; which in a distance estimated at sixty miles would give the mica-slate group of Macanao the elevation of about 660 toises, a result which, in a zone where the terrestrial refractions are so unchanging, leads me to think that the island was less distant than we supposed. The dome of the Silla of Caracas, lying 62 degrees to the south-west, long fixed our attention. At those times when the coast is not loaded with vapours the Silla must be visible at sea, without reckoning the effects of refraction, at thirty-three leagues distance. During the 26th, and the three following days, the sea was covered with a bluish film which, when examined by a compound microscope, appeared formed of an innumerable quantity of filaments. We frequently find these filaments in the Gulf-stream, and the Channel of Bahama, as well as near the coast of Buenos Ayres. Some naturalists are of opinion that they are vestiges of the eggs of mollusca: but they appear to be more like fragments of fuci. The phosphorescence of sea-water seems however to be augmented by their presence, especially between 28 and 30 degrees of north latitude, which indicates an origin of some sort of animal nature.