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values of meteorological elements, at least in high latitudes. The 

 application of this formula is justified by the consideration that 

 monthly means for a given month may, as far as our actual knowledge 

 goes, be regarded as independent of each other, whereas e.g. daily 

 means are certainl}^ not so. 



If the deviations are distributed according to the normal, exponential 

 law : 



-^e-^'^'dx (1) 



the quantity h' must be equal to h. Another criterion to ascertain 



whether the distribution of deviations is regulated by the normal 



law, as advocated by Cornu ^), is obtained by calculating rr by means 



of the formula : 



2J\P 



(2) 



jr 



^^ 



it is equivalent to the criterion previously mentioned as it holds 

 only when h = h' . 



The quantities M and h may be regarded as a measure of the 



TABLE I. Monthly means of barometric height, Helder. 



1) Ann. de I'Observ. de Paris. XIII, 1876. 



