62 



as in the South Sea, that, when we change both 

 latitude and longitude at the same time, the 

 waters often do not change one degree of tem- 

 perature, in an extent of several thousand square 

 leagues ; and that in the space comprised be- 

 tween the twenty-seventh degree north and 

 the twenty-seventh south, this temperature of 

 the seas is almost entirely independant of the 

 variations of the atmosphere * A very long 

 calm, a momentary change in the duration of 

 the currents, a tempest mingling the inferior 

 strata of the water with the upper, may for 

 some time produce a difference of two or even 

 three degrees ; but as soon as these accidental 

 causes cease to act, the temperature of the ocean 

 resumes it's former stability. I shall have 

 occasion to return to this phenomenon, one of 

 the most invariable that nature offers. 



I have constructed a chart of the temperature 

 of the seas, as well from my own observations, 

 made from the forty-fourth degree of north to 

 the twelfth degree of south latitude, and from 

 the forty-third to the hundred and fifth of west 



* To show what little influence the air has on the tempera- 

 ture of the immense basin of the seas, I have added, in the 

 journals, the indication of the heat of the atmosphere to that 

 of the heat of the ocean. The latter ma y be changed by 

 very remote causes, such as the more or less rapid melting of 

 the polar ice, or winds blowing in other latitudes, and produc- 

 ing currents. 



