Construction for Steering Course of a Ship. 561 



between them. The one touching the upper half of the 

 circle is used when v acts up, that touching the lower half 

 when v acts down. The time of doing AB is the same as 

 that taken to do AC with velocity v, or CB with velocity u y 



AC CB 



t = 



or 



u 



Fig. 5. 



3. For two belts, velocities v x and v 2 , and breadths*a r and 

 a 2 , fig. 5, to find minimum time path from A x in first belt to 

 Co in second belt. 



Describe circle centre A-. and radius -^ai 



and 



7/ 



circle centre C 2 and radius -a 2 . 



u 



Then for any path A 1 C 1 C 2 the steering directions are B x Ci 

 Phil. Mag. S. 6. Vol. 25. No. 148. April 1913. 2 Q 



