394 



Fly-rods and Fly-tackle. 



boundary line was part of a circle having a diameter of 

 twenty inches. The diameter of this circle for any 

 depth of water may readily be computed by the follow- 

 ing proportion: Assuming five feet to be the required 

 depth, for the purpose of illustration ; then 13 : 20 : : 60 

 (five feet reduced to inches) : to answer, 92-^ inches, or 

 nearly eight feet. These measurements, though not sci- 

 entifically accurate, are within a fraction of an inch of 

 the truth, and therefore sufficiently near for practical 

 purposes. 



The following diagram, in which the relative propor- 

 tions are carefully preserved, embodies the foregoing. 



E 



Fig. 86. 



A represents the tank ; B the glass ; C the water-level 

 at the time ; and D the position of the division between 

 the transparent and the opaque portions of the surface. 



The effort was next made to determine how far above 



