A General History & Collection of Voyages and Travels ... - Nauticus

| Air. |of the |certain |Fathoms. |Deep. |up. |Date |Latitude | |Sea. |Depth. | || |--------------------------------------------------------------------------1772Sept. 5 00°52'N. 75° 74° 66° 85 F. 30'27-1/2'Sept.27. 24°44'S. 72-1/2 70° 68° 80 F.15' 7'Oct. 12. 34°48'S. 60° 59° 58° 100 F.2O' 6'Dec. 15. 55°00'S. 30-1/2° 30° 34° 100 F.17' 5-1/2'Dec. 23. 55°26'S 33° 32° 34-1/2° 100 F.16' 6-1/2'1773Jan. 13. 61°00'S. 37° 33-1/2° 32° 100 F.20' 7'--------------------------------------------------------------------------From this table it appears, that under the Line and near the tropics, the water is cooler at a greatdepth than at its surface. In high latitudes, the air is cooler sometimes, sometimes very near upon apar, and sometimes warmer than the sea-water at the depth of about 100 fathoms, according as thepreceding changes of the temperature of the air, or the direction and violence of the wind happen tofall out. For it is to be observed, that these experiments were always made when we had a calm, or atleast very little wind; because in a gale of wind, we could not have been able to make them in a boat.Another probable cause of the difference in the temperature of the sea-water in the same highlatitude, undoubtedly must be sought in the ice; in a sea covered with high and extensive ice islands,the water should be colder than in a sea which is at a great distance from any ice."--F.This table is evidently too confined, and made up of too few elements, to justify almost any generalinferences. The subject is certainly a curious one, and merits full investigation, but presents veryconsiderable difficulties, as many circumstances, which are likely to modify the result, may escapenotice during the experiments. It has been said, that as water is most dense at from 37 to 39Fahrenheit, this may be presumed to be the mean temperature at the bottom of the sea; but suchhypothetical deductions are, perhaps, entitled to little confidence. It may however be safely enoughpresumed, that the temperature of the sea is kept tolerably uniform on the well-known principle ofstatics, that the heavier columns of any fluid displace those that are lighter. The waters of the ocean,perhaps, are the great agent by which the average temperature of our globe is preserved almostentirely invariable. We shall have an opportunity, in the account of another voyage, to make someremarks on this subject, and to notice more exact experiments than those just now mentioned.--E.The calm was succeeded by a light breeze at S.W., which kept veering by little and little to the south, andat last to the eastward of south, attended with clear serene weather. At length, on the 8th of September, wecrossed the Line in the longitude of 8° W.; after which, the ceremony of ducking, &c., generally practised