197 



Dividing by B, the values of tan (equation 288) are entered in column 

 (15) and the corresponding values of </> in column (16). The com- 

 puted value of at station 100 should check with that derived in 

 paragraph 378. 



The value of lalg, column (17), for all subsections, is (par. 373): 



/a/gr=0.000,004,37X40,000 = 0.175. 



The values of Blajg are entered in column (18) and those of 

 H= (Bla/g) /sin 4>, from equation (289), in column (19). Tne values of 

 H°, derived from the computed values of ^ and 0, are entered in 

 column (20), and the corresponding computed coordinate amplitudes 

 H sin H° and H cos H° in columns (21) and (22). The computed 

 values at station 100 should check with those found in paragraph 

 378. The initially computed values at this station should be entered 

 in these columns, even if minor inaccuracies have produced slight 

 differences in this check computation. A material difference would 

 indicate the need for reviewing the entire work. 



381. Adjustment of coordinate heads. — As is to be expected, the sums 

 of the computed coordinate amplitudes of the surface heads in the 

 subsections, in columns (21) and (22) differ by small residuals from 

 the total coordinate amplitudes of the heads between the entrances 

 showm in columns (2) and (3). The computed values are adjusted 

 in columns (23) and (24), by dividing the residuals as equally as may 

 be between them, so that the sums agree with the actual coordinate 

 amplitudes of the head between the entrances. 



382. Recom.putation of tides, currents, and heads. — The corrected 

 coordmate amplitudes of the tides at the storage stations, which in 

 this case are at the ends of the subsections, are next recomputed in 

 columns (2) and (3) of figure 62, by successively adding the adjusted 

 values of H sin H° and H cos H°, found from the first computation, 

 to the coordinate amplitudes of the tide at the initial entrance. The 

 coordinate amplitudes of the tide at the further entrance, station 200, 

 afford a check on the results. It will be seen that the corrected coor- 

 dinate amplitudes of the tides at the storage stations differ materially 

 from those used in the first computation. The currents and the 

 resultant heads are therefore recomputed as shown in figure 62 from 

 the corrected data. In the present example, the adjusted coordinate 

 amplitudes of the head in the middle subsection, station 100, in col- 

 umns (23) and (24) of the initial computation, differ so little from, 

 their original values, in columns (21) and (22) that a recomputation 

 of the coordinate amplitudes of the currents in the middle subsection 

 is unnecessary. 



