( 247 ) 



and tliis is tlie equation, from wliicli ,i' can he solved. Unfortnnatcly 

 liovvevc)' ii' cannot be solved fVom Uiis in an ('.I'/tUcif form. 

 Now llic minimum disappears, when (see [>. 1()8, I.e.): 



, ^'i — Ï'. 

 i^J'^-V- (2) 



That this lakes place exactly at the same inomoit as dial al w hich 

 the case of fig. 6 occurs, is expressed by the relalion : 



2 





= 2. (3). 



If \vc write for short noss : 

 72 





<fi 



^ = ^^^ 



^1 V ii ffi 



the equation (3) l)ecomes: 



+ e 





(1 + <fi.) 



2, (3«) 



where ;. will always be <^ 1 {7\ is assumed <^ 7\). 



It is now easy to see that there are always corresponding values 

 of ;., <r, and (f^ to be found, which satisfy (3), so that the minimum 

 may just as well disappear before as after the case of fig. 6. In 

 order to define the limits of 7\, 1\, q^ and ^j, "i which either tlie 

 one or the other will occur, we shall express e. g. <f^ in functioji 

 of <Pi and ).. We get then successively : 



'Pi 



V^. 



2 1 .^<P. ^ 



- — <r., — 2, 



«/)ji— A 



•.i e 



1 / 



/3 





- /o7 2 e 



so finally : 



^/2 = 



Zo,., \^2 6' ^' —e 



V. 



</^l 



V. 9^1 — :j r 



« 1 — ;. 



2 



(4) 



Vll— -^ 



73 



This will l)e equal to (lii-sl limiling-\alue, as— cannot become 



<^0), wheji 



17* 



