Observations in the North Atlantic. 353 



Sept. 



A large field of sea- weed is found over nearly the same space 

 occupied by these currents, but I unfortunately omitted to note 

 its position, and have not since been able to procure observa- 

 tions on it, sufficiently close to the localities of the above ob- 

 servations, to be of any use in connecting them. Humboldt 

 supposes that the weed composing these fields is detached from 

 the bottom by the equatorial currents, a view certainly favoui'ed 

 by the disposition of the currents noticed above. 



The ship seems to have left the current last mentioned a 

 little before noon on the 18th, for the specific gravity of the 

 water was then 1-02786 only, and the drift during the follow- 

 ing twenty-four hours, N. 29^ E., thirteen mdes. At noon on 

 the 19th, however, the specific gravity of the water had again 

 risen to 1-02794, and the ship was drifted N. 68° W., forty- 

 nine miles up the next noon, the specific gravity of the water 

 remaining much the same. The drift, up to mid-day on the 

 21st was, at 68° E., forty-three miles, and by that hour the 

 specific gravity had again fallen to 1-02782, the ship having 

 passed from a westerly to an easterly current soon after noon 

 the preceding day. The changes of temperature on these days, 

 too, display certain irregularities, which, though slight, and if 

 taken alone, of no great weight, still, when associated with 

 the observed differences in the saltness of the water, and the 

 set of the currents, assume much more importance. Thus the 

 fall of temperature from the NW. current on the 1 7th, to the 

 NE. one on the 18th, was l°-0 ; the fall from tliis to the NW. 

 one on the 19th, l°-3, and, on the 20th, while in this current, 

 only 0'-7 ; the following day, however, with a strong KE. cur- 

 rent, and diminished specific gravity, the temperature of the 



VOL. XXXIX. NO. LXXVIII. — OCTOBER 1845. Z 



