572 METEOROLOGICAL CORRECTIONS. 



of hourly observations taken at some station in a similar climatic situation, it is evident 

 that, whatever be the hours at which observations are taken, the means derived from 

 them can always be reduced to the true means by correcting them for that dif- 

 ference. 



The following tables furnish such corrections, both for periodic and non-periodic 

 variations of temperature, and for stations situated in various latitudes. They give 

 the quantities which must be added to, or subtracted from, the hourly means, in order 

 to obtain the true means of the day, of the month, and of the year. 



Two tables of the same description, for moisture, which may be considered as 

 specimens of the kind, close the set. 



Two other tables, for correcting the mean barometric pressures, are found at the 

 end of the Hypsometrical Tables, pp. 92, 93. 



