§ S79. THE ACTINOxMETRY OF THE SEA. 4(J9 



CHAPTER XXII. 



§ 879-893. — THE ACTINOMETRY OF THE SEA. 



879. One of the columns in the man-of-war log of the Briis- 

 A new field. sels Conference calls for the temperature of the 

 water below as well as at the surface of the sea. Only a few 

 entries have been made in this column ; but these, as far as they 

 go, seem to indicate that the warmest water, especially in tropical 

 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 sub- 

 ject opens a new field of inquiry ; it is one from which much use- 

 ful and instructive information is doubtless to be obtained by any 

 one of our co-operators who patiently and with diligence will en- 

 ter upon the investigation.*" 



* On the 26th of March, 1852, the late Passed Midshipman A. C. Jackson, 

 tl. S. N., being in the Gulf Stream, lat. 31° 55' N., long. 7-i° 8' W., found the tem- 

 perature of the water 71.5° 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 care- 

 fully conducted set of observations, and found it 78° at the surface, and 79.5° at the 

 depth of 161^ 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 ./. Berminghaj/i, 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 (June 5) to this port, we experienced the 

 most remarkably fine weather and smooth sea that I have ever witnessed on the Pa- 

 cific, or any where 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 

 surftice, 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 often 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 mad'j 



