2i5 porter's journal. 



panied by a little increase of wind, but more frequently 

 calms. But little change was perceived in the temperature 

 of the air ; and the clouds continued to hover over and ob- 

 scure the sun. We have not seen, since we left the Cape 

 de Verds, any specimens of that weed, commonly known in 

 America by the name of the gulf-weed nor any other kind 

 of weed floating on the surface of the sea, or any birds that 

 could lead us to suppose we were in the neighbourhood of 

 such places as they generally resort to. The only lish that 

 came near the vessel were a few porpoises, and of them we 

 did not succeed in striking any. 



On the 8th, in latitude 3' north, we began to experience 

 the S. E. trade winds ; and a considerable change took place 

 in the temperature of the air, as the thermometer fell to 82°. 

 In the afternoon we saw several of those birds called sheer- 

 waters ; but as they are to be met with, at times, in every 

 part of the Atlantic, I did not consider their appearance as a 

 certain indication of the vicinity of land, although by our 

 calculation we suppose ourselves to be only about {oriy 

 leagues from Penedro de St. Pedro. I this day caused the 

 crew to be paid in cash the amount due them for the stop- 

 pages of provisions. 



It has excited much astonishment among seamen why the 

 temperature of the air should be so much warmer to the 

 northward of the line, at all seasons of the year, than at the 

 southward, and that the N. E. trades should always be met 

 in a northern latitude, particularly when the sun is in his 

 highest southern declination, as he happens to be at present ; 

 but by running the eye over the chart the mystery is solved. 



It is well known that the trade winds blow from the east- 

 ward to the westward throughout the year, but undergoing 

 some slight variations from local causes, or the change of the 

 sun's place in the ecliptic. Those winds, it is generally ad- 

 mitted, are caused by the highly rarefied state of the air be- 

 tween the tropics, and the passage of the sun from east to 

 west, or rather the earth's rotary motion from west to east ; 

 it follows thence that a current of cold air must rush to those 

 points where the air is most rarefied, to restore the equili- 

 brium. And as the coast of Africa to the north of the equa- 

 tor, and between Cape Verd and Sierra Leone, projects 

 west, to within ten or twelve degrees of the usual track of 

 vessels crossing the line bound to the southward, and as the 



