The general Characteristics of the frequencyfunction of stellar movements 15 



Regard, for instance, only the variâtes x and y, letting z have any value. 

 Their frequency function will he obtained by integrating the function F(x, y, s) for 

 all z between -f x and — oo. 



Calling the resultant frequency function F t (x, y) we have 



(27) F,(x, y) = ?1 (.r, y) + £ By i +j > 3 

 where 



¥>i(«, 2/) = tl i«~ 1/2/1 



(28) f x ^A^ + B^A r 2F 1 xy, 

 and similarly as by three variables writing 



3=1 A v F x 

 F„ B, 



'20' 'it 

 'lV V 02 



we have 



1 



'.-(Si 



_ _8§_ JL _ j)m 1 



V ° 2_ 85, S ; 1_ 8v 02 w- 



Now the parameters of F^x, y) are obtained expressed in the parameters of 

 F(x, y, e) through the equation 



fF(x t y, e) de = Ffa y\ 



or more conveniently, by observing that 

 (29*) 



through the equations 



Ö 110 



(30) 



88 1 _ aA 1 

 dA l § ~ dA A 

 / do\ 1 /8A i 1 



UfJ S ^fJ A 



8§ 1 _ 8A 1 

 dB] 8~ dB A ' 



and 



