Page:Physical Geography of the Sea and its Meteorology.djvu/495

Rh seas, is not to be found at the top, but in a stratum a little way down. What is the depth of this stratum, and what may be the thermal difference between its waters and those of the surface, are questions for future observations to settle. Indeed, this subject opens a new field of inquiry; it is one from which much useful and instructive information is doubtless to be obtained by any one of our co-operators who will enter upon the investigation patiently and with diligence. On the 26th of March, 1852, the late Passed Midshipman A. C. Jackson, U. S. N., being in the Gulf Stream, lat. 34° 55' N., long. 74° 8' W., found the temperature of the water 74.5° at the surface, 79° at the depth of six feet, and 86.5° at the depth of 16½ feet. Again, on the 30th, in lat. 24° 10' N., long. 80° 11' W. (near the edge of the Gulf Stream), he tried the temperature of the water by another carefully conducted set of observations, and found it 78° at the surface, and 79.5° at the depth of 16 feet. The sea was rough, and he did not, for that reason, observe the temperature at six feet. The temperature of the air in the shade was 69.5° on the 26th, and 79° on the 30th. (Vide p. 59, 5th ed., Maury's Sailing Directions, 1853.) Extract of a Letter from J. Bermingham, Chief Engineer of the American Steamer "Golden Age," dated Bay of Panama, June 29, 1860, and addressed to Lieut. John M. Brooke, U. S. N.

"On our late trip from San Francisco (5th June) to this port we experienced the most remarkably fine weather and smooth sea that I have ever witnessed on the Pacific, or anywhere else.

"On the 14th, while crossing the Gulf of Tehuantepec, we found the temperature of the sea water on the surface (where it had not been disturbed by the progress of the vessel) 88°, and upon taking the temperature at the same time ten feet below the surface the mean of three thermometers gave 90°. Temperature of atmosphere 93°.

"I do not exactly understand why the temperature of the sea water should be so much greater at a distance of ten feet from the surface than it was immediately upon the surface.

"Mr. Agassiz (a son of Professor Agassiz) was on board, and he and myself made repeated tests of the temperature of the water during the four hours we were running through it—the warm belt.

"Ninety degrees is the highest temperature that I have ever known the water of the ocean to attain."

882. ''The warmest waters in the sea—where are they? at or below the surface?''—The observations that we possess do not prove that the warmest water of inter-tropical seas is not at the surface: they go no farther than to show that it is sometimes not at the surface, and to suggest that, in all probability, it is generally below, especially in "blue water." Reason suggests it also. Supposing that, as a rule, the hottest water is below the surface, we may, in order to stimulate research, encourage investigation, and insure true progress, propound a theory in explanation of the phenomenon, looking to future observations to show how far it may hold good.