REDUCTION OF CURRENT RECORDS U7 
a velocity ratio of unity and an epoch difference of 90° or 270°, the ellipse becomes a 
circle, indicating that the current constituent flows with a uniform velocity throughout 
its entire cycle as its direction swings around the circle. The direction of rotation of 
the constituent current may be determined from the epochs of the north and east 
components, A, and K, respectively, by the following rule: 
When the difference between K, and K, is less than 180°: 
If K, is less than K, the rotation is clockwise. 
If K,, is greater than K, the rotation is counterclockwise. 
When the difference between AK, and K, is greater than 180°, the above 
directions of rotation are reversed. 
186. Table 8 for the time and direction of current constituent at maximum veloc- 
ity and Table 9 for maximum and minimum velocities are based upon formulas (8), 
(9), and (10). Assuming that R is the ratio H./H, and D the difference (K,—K,), 
the tabular values in Table 8 give directly, with due regard to proper sign as indicated 
in footnote, the time of occurrence of one of the two maximum velocities of the current 
cycle, expressed by the angle (7—K,,), and the corresponding azimuth of the current 
as reckoned clockwise from the north. If this direction is taken as corresponding to a 
flood current, the value obtained for T will be the epoch (kappa) of the constituent as 
referred to the major axis of the ellipse. When RF is unity and D is equal to 90° or 270°, 
T is indeterminable since in this case the constituent ellipse becomes a circle, the velocity 
of the current being uniform without any maxima or minima. The table provides 
TaB_E 9.—Mazimum and minimum velocities of rotary current constituent 
R 
-D D 
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 
0 | 180 |1. 000/1. 005) 1. 020) 1. 044} 1. 077] 1. 118] 1. 166] 1. 221] 1.281] 1. 345] 1. 414] 180 | 360 
0. 000\0. 000} 0. 000} 0. 000} 0. 000} 0. 000) 0. 000} 0. 000} 0. 000} 0. 000) 0. 000 
10 | 170 }1. 000)1. 005} 1. 019} 1. 043) 1. 075} 1. 115} 1. 163] 1. 217] 1. 276) 1. 340) 1. 409] 190 | 350 
0. 000\0. 017} 0. 034) 0. 050} 0. 065} 0. 078) 0. 090) 0. 100) 0. 109} 0. 117) 0. 123 
20 | 160 j1. 000)1. 004) 1.018) 1.039) 1. 069] 1.107) 1. 152) 1. 204) 1. 262) 1. 325) 1. 393} 200 | 340 
(0. 000\0. 034| 0. 067) 0. 099) 0. 128] 0. 154) 0. 178) 0. 199] 0. 217) 0. 232) 0. 246 
30 | 150 |1. 000)1. 004) 1.015) 1. 034) 1. 060) 1. 094) 1. 136] 1. 184) 1. 240) 1. 300) 1. 366] 210 | 330 
0. 000|0. 050) 0. 099) 0. 145) 0. 189} 0. 228) 0. 264) 0. 296) 0. 322) 0. 346) 0. 366 
40 | 140 }1. 000/1. 003) 1.012) 1. 027) 1.049) 1. 078) 1. 114} 1. 157) 1. 208) 1. 265} 1. 329} 220 | 320 
0. 000/0. 064) 0. 127) 0. 188} 0. 245) 0. 298) 0. 346) 0. 389) 0. 426) 0. 457) 0. 484 
50 | 130 j1. 000)1. 002) 1. 008) 1. 019) 1. 036) 1. 058) 1. 087) 1. 123) 1. 168) 1. 221) 1. 282] 230 | 310 
0. 000/0. 076) 0. 152) 0. 225) 0. 296) 0. 362) 0. 423) 0. 477) 0. 525) 0. 565) 0. 598 
60 | 120 |1. 000)1. 001) 1. 005) 1. 012) 1. 022) 1. 037) 1. 058) 1. 085) 1. 122) 1. 168) 1. 225) 240 | 300 
0. 000\0. 086) 0. 172) 0. 257| 0. 339) 0. 418) 0. 491) 0. 559] 0. 618) 0. 667) 0. 707 
70 | 110 }1. 000)1. 001) 1. 002} 1. 006) 1.011) 1. 018} 1.030) 1. 046) 1. 071) 1. 108] 1. 158] 250 | 290 
0. 000)0. 094) 0. 187) 0. 280) 0. 372) 0. 461) 0. 548) 0. 629) 0. 702) 0. 763) 0. 811 
80 | 100 |1. 000/1. 000) 1. 001) 1. 001} 1. 003) 1. 005) 1. 008} 1. 014) 1. 023) 1. 043) 1. 083} 260 | 280 
0. 000)0. 098) 0. 197| 0. 295) 0. 393) 0. 490] 0. 586] 0. 680] 0. 770} 0. 850) 0. 909 
90 90 }1. 000)1. 000) 1. 000} 1. 000) 1. 000) 1. 000} 1. 000} 1. 000) 1. 000) 1. 000} 1. 000} 270 | 270 
0. 0000. 100} 0. 200) 0. 300) 0. 400) 0. 500} 0. 600} 0. 700) 0. 800} 0. 900} 1. 000 
Upper values for each double line refer to maximum velocities and lower values to minimum velocities, All values are positive. 
For further explanation see paragraph 186. 
