[Footnote 80:  On board his majesty’s ship Elizabeth, from 1758 to 1764; by William Nichelson, master of the said ship.—­London, 1773.]

While we were amongst these islands, we had light breezes of wind, varying from the S.E. to E., and some calms.  This shews that the Cape de Verde islands are either extensive enough to break the current of the trade wind, or that they are situated just beyond its verge, in that space where the variable winds, found on getting near the Line, begin.  The first supposition, however, is the most probable, as Dampier found the wind westerly here in the month of February; at which time the trade wind is supposed to extend farthest toward the equinoctial.[81] The weather was hot and sultry, with some rain; and, for the most part, a dull whiteness prevailed in the sky, that seems a medium between fog and clouds.  In general, the tropical regions seldom enjoy that clear atmosphere observable where variable winds blow; nor does the sun shine with such brightness.  This circumtance, however, seems an advantage; for otherwise, perhaps, the rays of the sun, being uninterrupted, would render the heat quite unsupportable.  The nights are, nevertheless, often clear and serene.

[Footnote 81:  Dampier’s Voyages, vol. iii. p.10.—­Captain Krusenstern appears to be of the same opinion, as to the Cape de Verde islands being of sufficient magnitude to alter the direction of the trade winds, remarking that S.W. winds are frequently met with there, and that if they are not, the wind is always very moderate in their vicinity.  He recommends vessels, on their passage to the equator, to take their course to the westward of these islands, so as to cross the parallel of 17 deg., or that of the island of Antonio in 26-1/2 deg., or even that of 27 deg., and then to steer S.E. by S. directly to the equator.  He further advises, that, if possible, the passage of the Line be effected in 20 deg. or 21 deg., as then there is the advantage of a directly free wind as soon as the S.E. trade sets in, and of course the ship gets quicker to the southward.  But this can rarely be done.  He himself crossed the equator in 24 deg. 20’ W., after a passage of thirty days from Santa Cruz.  Ships, he informs us, when crossing in a more westerly direction than 25 deg. and 26 deg., have been driven by strong currents, and a too southerly trade wind, so near the coast of Brazil, as not to be able to clear Cape St Augustin.  The present opportunity is taken of mentioning, that this very cautious and intelligent navigator agrees, in general, with Cook, as to Nichelson’s rule.  “His instructions for crossing the Line, on the voyage to India, with 6 deg. 30’ and 7 deg. 00’ west variation, but in returning to Europe, with eight degrees, might have been of use forty years ago, when the method of finding the longitude at sea by distances of the sun and moon was known to very few navigators, and for a time no great error was committed by pursuing them; but at present a variation of seven degrees would hardly be found on the coast of Africa.”—­The reason is, as the scientific reader must know, that the variation has been on the western increase since the period alluded to.  Thus Nichelson found it at St Helena, in 1764, to be 11 deg. 38’, and Captain Krusenstern, in 1806, a space of forty-two years, 17 deg. 18’ 10".—­E.]