10 Ss. yYoKOTA: A METHOD OF DETERMINING THE CROSS-SECTION 
(15) Oman, or. 
Hence öx has always the same sign as dr and vanishes when m—1. 
For m>1, it increases with m from zero until it takes the value «adr 
at m= oo For m < 1, it inereases as m diminishes from zero to 
oo when m=—r. 
In our cases, the values of g are: 
a = 4:23 for 0307 
el i a eee 
4 = 1°50 Be Won Se OOo 
„=1:00 rl: 
while dr is less than 0°03. 
Hence we may safely leave out the correction dx for m>l in all 
eases. The correction is sensible when the channel becomes very shallow, 
so that the hyperbolas (12) are drawn for two values of d= ft. and 8 
or 10 ft; in" Plates I tov lV. 
x : Ei, 1 ? 
For intermediate values of d, the ratios + and | may be assigned by 
. ( 
taking a point between the two hyperbolas. 
