Page:An account of a voyage to establish a colony at Port Philip in Bass's Strait.djvu/60

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tion of oil. The copious vapours exhaled from the earth and sea, in tropical climates, may produce this effect, which is found to decrease as we recede from the equator, either north or south.

In latitude 6° North, we lost the N. E. trade-wind, and for a few days experienced the usual equinoctial calms, and squalls, with heavy rains, and strong easterly currents. The line was crossed in the longitude of 25° W.[1], with the


  1. Navigators differ in their opinions respecting the most eligible meridian to cross the line on; but agree, that it ought to be between the longitudes of 20° and 25° W.; but by crossing it so far to the eastward as 20°, calms of long continuance, and strong easterly currents, setting into the gulph of Guinea, will commonly be met with; by crossing it to the westward of 25°, strong westerly currents are found setting into the immense bight between Cape St. Augustine and Florida; the meridian of 23° W. on the line, seems to be the boundary of these different currents. In the various opinions upon this subject, sufficient regard has not been paid to the season of the year. When the sun is far in the northern tropic, the winds to the southward of the line, incline more southerly, and, during the contrary season, they incline more northerly than the regular course of the trade-wind. Intending to touch at Rio Janeiro, between the months of March and September, I would prefer crossing the line in 26° W.; and between September and March again in 28°. But if it is not intended to touch at Rio, I would, during the first season, cross the line in 23; and during the latter, in 25°: crossing the line from the southward, I look upon 27° to be the best meridian, as being not only less liable to calms, but also for the probability of meeting the trade well to the eastward, and perhaps, even to the southward of east. When the sun is in the northern tropic, I would recommend keeping on the last meridian till to the northward of the Cape Verd Isles for, by coming nearer to these islands at this season, you will most probably meet with calms, and baffling winds.