496 



FINAL EESULTS. 



App. it. 



By my own calculation of the boiling-point of water observation, the altitude is 2432 feet. 



KoTE. — The apparent discrepancy in the relative height of 

 places near the sea-level arises principally from the fact tliat the 

 method of observation usually adopted is not sufficiently acciii'ate 

 for the determination of low elevations. The variation in the 

 pressure of the atmosphere during the interval between the 

 observations made on different days at two or more stations, may 

 cause a discordance of several hundred feet, unless a correction 

 be applied for the amount of the variation. The only wRy to 

 obtain this correction is to have corresponding barometric obser- 

 vations statedly made near the sea, or at a station of knoAvn alti- 

 tude. By this "means we obtain materials for correcting the 

 observed barometric readings, or of those deduced from the 

 boiling point thermometer. In practice, however, it has been 



