Double Suspension Mirror. 481 



Let S«// denote the sensitiveness as defined above, then 



c, 1 1 



r — r 



by (4), or say 





(5) 



where 



p=zr' + nk 2 , (6) 



and <f is a constant. This equation may be written 



\ v 1\ ^ v) P 2 



p / \ T p/ p' 

 and is represented by the rectangular hyperbola in fig. 4, its 



Fig. 4. 



/ 



k 2 









/ 

 / 



0' 1 



1 



/ 

 / 



(? 





/7 



// c 2 „2\ _ £2 <7 2 



centre 0' being at the point I — , — ) and its constant — .— . 



\p p/ p p 



As the fibres are separated the sensitiveness tends to the 



