89 



and the quantities of vapor contained in a given 

 space, have not been appreciated with the same 

 degree of certainty. These considerations have 

 induced me to publish the indications of the 

 hair and whalebone hygrometers just as they 

 were observed, marking the degree shown by 

 the thermometers connected with these two in- 

 struments. To facilitate to a certain point the 

 comparison of the observations made in different 

 latitudes, I shall here insert a table, which was 

 calculated by Mr. d'Aubuisson, when he made 

 his valuable researches on the coefficients of 

 the barometric formulas. The whole of the re- 

 sults prove that as we advance toward the equa- 

 tor, the air approaches the point of saturation. 

 We have chosen the periods, when the tempera- 

 ture of the sea was nearly equal to that of the 

 air. Of eight columns, which compose this 

 table, the first contains the time of the observa- 

 tion : the second the latitude of the place ; the 

 third the state of the thermometer ; the fourth 

 the state of the hygrometer ; the fifth the weight 

 of vapor contained in a cubic metre of air, sup- 

 posing it saturated ; the sixth the weight of va- 

 por contained in a cubic metre of air, at the de- 

 gree of the hygrometer observed; the seventh 

 the thickness of the sheet of water which should 

 be evaporated in an hour s time, if the surround- 

 ing air was perfectly dry ; the eighth the same 



