PORTER’S JOURNAL. 
43 
where it spends itself, under the name of the land breeze, at the 
distance of a few leagues. On the rising of the sun a new eleva¬ 
tion takes place, and a fresh current of air, called the sea breeze, 
rushes towards the land to supply the vacuum. Every where 
throughout the world, where the sun’s rays are felt, this elevation 
of atmosphere, in a more or less degree, takes place, but not so 
much as to produce land winds, except within the tropics, and 
this elevation is always greatly increased by the opposition of 
land to the sun’s rays. The change in the temperature of the 
earth cannot, as has been falsely supposed, produce this extra¬ 
ordinary elevation of the atmosphere ; was the heat of the sun 
absorbed by the earth, the effect, instead of being heightened, 
would be lessened. The elevating effects produced by the earth 
on the atmosphere may be attributed to reflection alone, and the 
current of air, called the land breeze, is owing entirely to the earth’s 
form. An extensive flat country without mountains, would pro¬ 
duce, by reflection, a great elevation of atmosphere; but when the 
sun, the cause of this elevation was removed, little or no land 
breeze would ensue, for the want of mountains to change the 
course of the atmosphere from its vertical direction. A great rise 
and fall of the atmosphere in the like manner takes place at sea* 
at a great distance from coasts, but owing to the smooth surface of 
the ocean and the absence of mountains, we are rendered insensi¬ 
ble of it. 
On the 18th discovered a sail; and this being the first we had 
discovered since the capture of the Nocton, it excited great in¬ 
terest among the ship’s company; but on approaching her, dis¬ 
covered her to be a brig under Portuguese colours, standing to¬ 
wards St. Salvadore; but as I did not wish to make ourselves 
known to her, hoisted English colours, and stood on our course. 
On the 20th, spoke a Portuguese vessel from St. Salvadore 
bound to Laguira, out 18 days; we boarded her under English 
colours, and on the captain’s coming on board, he informed me, 
that an English sloop of war had put into St. Salvadore in distress 
a short time before he sailed, laden with specie, from Rio de la 
Plata, last from Rio Janeiro, and bound to Europe. From the 
description he gave me of this vessel, there can be no doubt of her 
