0.0307, and unit lengths for the curves y^ and y^ are 



tj =25 

 and 



t2 = 32.5, 



respectively. In Figure 3 the curves yj, y^ and y, + y^ are shown 

 for values of m and n equal to 1, 2, 3, etc. 



In practice, sometimes very little information is available upon 

 which to base the preceding computations. We may, therefore, be 

 required to adopt the following procedure in order to obtain a first 

 order approximation of the flushing time. 



The mean high tide volume is computed and divided into two parts, 

 giving A = B. Also, we can put r . = r^ = r*. When substituted into 

 (16) these give _ 



Cn = A(l-r)" + nrA(l-r)'" 



= A(l-r)"+^-^)(l-r)" (22) 



from which 



= A(l-r)"ri+_ilJ^"| 



Ql.,,= A(l-r)7ri+^— T 



= 2 A(l-r)T,, 

 approximately, or Ci = (A + B)(0.35) . 



r 



The only curve to be plotted in this situation is, therefore, 

 y = (A + B)(0.35)", n = l,2, 3, etc. 



The value r to be employed in order to determine the nunnber of tidal 

 cycles corresponding to ni = 1, n^ = 2, etc. still remains to be found. 

 (For an example see Figure 3.) Now the total volume of sea water 



* Also, the value r^^ can be retained in the first member on the right 

 of (20), and '' = ? ('' +''b) substituted in the second member on 



the right of (20). This procedure is probably to be preferred to the 

 above. 



**Here for simplicity (1-r) is assumed to be close to unity. For 



example, when 



r = -^ = J- , (1 - r) = 0.967. 

 A 30 



7 



