74 



Prom the thirtieth degree of north latitude, 

 the results which I attained agree very well with 

 the observations of Perrins and Quevedo. It is 

 not probably to the local influence of the sea- 

 sons, as we have just proved, but to the motion 

 of the waters, and to remote causes, that we 

 must attribute the extent of the variations of 

 temperature observed between the tropics in the 

 voyage from London to Bombay. These varia- 

 tions have risen to five degrees, while in the 

 South Sea I found them only 2*7°o Quevedo, in 

 traversing from south to north a space of six 

 hundred and forty leagues, saw the heat of the 

 Atlantic ocean from the tropic of Capricorn to 

 the ninth degree of north latitude, change only 



naturalists, who inhabit the coasts of the ocean, in Spain, in 

 France, and in England, to ascertain, for each month in the 

 year, the mean temperature of the sea at it's surface, com- 

 pared with the mean temperature oftheairon the neighbour- 

 ing coasts. What has been published on this subject is founded 

 either on theoretical considerations, or on a small number of 

 experiments, which have not been made in the open sea, but 

 in harbours, and sheltered roads. What is the maximum of 

 cold which the ocean attains in the forty-fifth degree of 

 latitude, taking the mean average of several days ? to what 

 month does this maximum correspond? It is asserted, 

 that, near Marseilles, the sea is never colder than 6'5°, or 

 warmer than 25° ; though the extremes of the temperature 

 of the air are often —4° and -f 35° (Mem. de la Soc. Royal 

 de Med. 1778, p. 70). Can it be admitted, that, in the open 

 sea, the heat of the Atlantic rises to 20° in latitude 45q. 



