ON THE MEAN RESULTS OF OBSERVATIONS. 245 



Mean Daily Error. 



Magnetic declination, . . Daily error = 0'-95. 

 Atmospheric pressure, . . =0 '301. 



Atmospheric temperature, . = 4'25. 



Now, the mean value of n in each month (Sundays being 

 omitted) is 26. Hence the mean correction, in the case of a single 

 deficient observation, is, for the magnetic declination, 0' - 04 ; for 

 the atmospheric pressure, 0'012 ; and for the temperature, 0-17. 

 In the case of the two meteorological elements, and especially in 

 that of the atmospheric pressure, the correction is too considerable 

 to be overlooked ; in the case of the magnetic declination, and 

 probably also in that of the other magnetic elements, it may be 

 disregarded. 



