THE SMITHSONIAN INSTITUTION. 

 TABLE XIV. 



MEAN DIURNAL VARIATION OF THE DEW-POINT AT PHILADELPniA. 



Computed from the observations made from the 1st July, 1843, to 1st July, 1845. 



221 



Minimum. 



Maximum. 



The variations of the figures, in table XIV and table Til, also follow 

 the same general law. 



TABLE XV. 



MEAN DIURNAL VARIATION OF DRYNESS, (APPROXIMATELY,) AT PHILADELPHIA. 



Computed from the observations made from July 1, 1843, to July I, 1845. 



Minimum, 



+ 



Maximum. 



From table XV, it does not appear that Mr. Russell's rule, for 

 ascertaining the dew point from the minimum temperature, holds true 

 in Philadelphia. Table No. IV, gives a much nearer approximation, 

 and, in moist seasons, the same will probably be the case in this 

 country, particularly at the south. By comparing the quantities given." 

 in table No. XV, with those in table No. IV, it will be seen that the 

 relative dryness of Philadelphia is much greater than that of London, 

 or Greenwich. 



