496 



PINAL EESULTS. 



App. ir. 



Note. — Tlie apparent discrepancy in the relative height of 

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

 method of observation usually adopted is not sufficiently accurate 

 for the determination of lovf elevations. The variation in the 

 pressure of the atmosphere during the interval between the 

 observations made on different daj's 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 way to 

 obtain this correction is to have corresponding barometric obser- 

 vations statedly made near the sea, or at a station of known 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 



