^'ATER AXD THE ENGIXEER. 



663 



Let R equal the radius of the inner curve by ray formula. 

 Let X equal the half-width of the required channel. 



The above is a quadratic equation, and the formula may be 

 more simply stated as follows : — 



X ;= V (BA)"'^ + R^) — E, which contains no unknown <|uantities 



in the second part of the equation. The width of the channel is 

 twice X. 



For ships of 200 ft. in length passing each other in opposite 

 directions on the tabulated inner curve of 858 ft. radius, the width 

 of channel would be as follows : — 



Tangential Clearance = B. 



Ship's length x 2 = 400 ft. 



., X 21 ==420 ft. 



„ X 2i = 450 ft. 



„ X 2i = 500 ft. 



Width of Channel = 2X. 

 178 ft. 

 194 ft. 

 222 fr. 

 270 ft. 



Tliere are, of course, many other aspects of the question that I 

 have not even referred to, such as the development and use of steam 

 ■ — water supply and hydraulic power for cities, &c. : and, to 

 come nearer home, the vast natural reservoirs of excellent water 

 stored in the great sandy islands that fringe the Southern coast of 

 Queensland, but I have already exhausted the time at my disposal. 



