The current, which at the equator averages a rate of more than twenty miles daily, carried us so far to the westward as to make us cross the line, at 8 p.m. of the 10th, in longitude 25° 54′ W.; and, in accordance with our observations on our outward voyage, the rate of the current in latitude 2° N. exceeded fifty miles per diem.
July 15.On the 15th we entered the variables and experienced the usual unpleasant weather; between 5h 30m and 6 a.m. an inch and a half of rain fell, and an inch and a quarter in the two following hours; its temperature was 72°, that of the air, 76°; and again, between noon and 2 p.m. on the 16th, 2½ inches of rain fell.
July 22.On the 22nd, when in latitude 12° 36′ N., and longitude 25° 35′ W., we had no soundings with 1850 fathoms, the temperature at that depth 39°.6; at 1350 fathoms, 39°.5; at 300 fathoms, 47°.6; at 150 fathoms, 52°; and at the surface, 79°.5. We were at this time only 140 miles from the Cape de Verd Islands.
Our barometrical experiments appear to prove that the atmospheric pressure is considerably less at the equator than near the tropics; and to the south of the tropic of Capricorn, where it is greatest, a gradual diminution occurs as the latitude is increased, as will be seen from the following table, derived from hourly observations of the height of the column of mercury, between the 20th of November, 1839, and the 31st of July, 1843.
