Here we perceive the variation of the temperature of tlie air, 

 following the course of the sun, pretty considerable whilst it is 

 above the horizon, and very insignificant during the night; and 

 this, I mav remark, is a general fact at sea, and one of the prin- 

 cipal features of difference l)etvveen the temperature of the at- 

 mosphere over the land, and over the ocean. 



The law of the regular variation of temperature is frequently 

 interrupted. Even in fine weather, when the air is not in mo- 

 tion, it is subject to interruption. During a calm, the variation 

 of temperature is nearly the same as on land, the maximum de- 

 gree of heat not being at noon precisely, but some time after, 

 and for the same reason ; because there is an accumulation of 

 heat, and not only in the ship, but actually in the water itself, 

 as I may show by noticing the temperature of the air and of the 

 sea, during even a short calm, hardly of twenty-four hours du- 

 ration. 



E- long. 76° ?>!". 



Of the Sea. 



;/ 



SO 



81 



81,5 



82,5 



83,5 



83,5 



But the law is more remarkably interrupted during storms and 



unsettled 



