THE ACTINOMETRY OP THE SEA. 469 



seas, is not to be found at tlie top, but in a stratum a little way- 

 down. AVliat 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 sub- 

 ject 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 investiga- 

 tion patiently and with diligence.* 



882. The loarmest imters in the sea — loliere are they ? at or helow the 

 •surface ? — The observations that we possess do not prove that the 

 warmest water of intertropical 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." Keason 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 phe- 

 nomenon, looking to future obsei-vations to show how far it may 

 hold good. 



» 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 16^ 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, 

 ^th 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. I^. 

 -" 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 tempe- 

 ratuie 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°. Tempera- 

 ture of atmosphere 93°. 



" I do not exactly understand why the temperature of the sea water should 

 foe so much greater at a distance of ten feet from the surface than it was im- 

 mediately upon the surface. 



" Mr. Agassi z (a son of Professor Agassiz) was on board, and he and myself 

 made repeated tests of the temperature of the water dmring the four hours we 

 were running through it — the warm belt. 



" Ninety degrees is the liighest temperature that I have ever known the 

 water of the ocean to attain." 



