76 MANUAL OF CURRENT OBSERVATIONS 
184. By substituting values of T corresponding to maximum and minimum veloci- 
ties in formulas (1) and (2) the corresponding component velocities V, and V, may be 
obtained. The azimuths and velocities of the resultant current may then be readily 
obtained by means of the following formulas: 
Tan A=WV_/V, 
BESS VV aot ln aly MR See EGS CS Sate eR OR eC a (10) 
185. The two maximum velocities will be of the same strength but in opposite direc- 
tions and the two minimum velocities will also be equal and opposite. After the azi- 
muth of one of the maximum velocities has been calculated, the other may be taken as 
180° different, and the azimuths of the minimum velocities will differ from the maxi- 
mum velocities by 90°. When the maximum and minimum velocities are plotted they 
form the major and minor axes of the current constituent ellipse. The eccentricity of the 
ellipse depends not only upon the velocity ratio of the component amplitudes (H,/H,,) 
but also upon the epoch difference (K,—K,). When this difference is 0° or 180° the 
minimum current becomes zero regardless of the velocity ratio, and the ellipse becomes 
a straight line indicating a reversing current. For any given velocity ratio, the eccen- 
tricity of the ellipse becomes a minimum when the epoch difference equals 90° or 270°, 
in which case the axes of the ellipse extend north-and-south and east-and-west. With 
Tasty 8.—Time and direction of rotary current constituent at maximum velocity 
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 | 0.0 | 0.0 0. 0 0.0) 0.0) 0.0 0. 0 0. 0 0.0} 0.0 0.0 | 180 | 360 
0.0 | 5.7 | 11.3 | 16.7 | 21.8 | 26.6 | 31.0 | 35.0 | 38.7 | 42.0 | 45.0 
10 | 170 | 0.0 | 0.1 0.4) 08 1.4 2.0 2. 6 3.3 3.9 | 4.5 5.0 | 190 | 350 
0.0 | 5.6 | 11.2 | 16.5 | 21.6 | 26.4 | 30.8 | 34.8 | 38.6 | 41.9 | 45.0 
20 | 160/0.0)/02) 07 1.5 2. 6 3.8 &, il 6. 4 7.7 8.9 | 10.0 | 200 | 340 
0.0 | 5.4 | 10.7 | 15.9 | 20.9 | 25.7 | 30.2 | 34.4 | 38.3 | 41.8 | 45.0 
30 | 150 | 0.0 | 0.2 1.0 2.1 3. 7 5. 4 7.4 9.4 | 11.4 | 13.3 | 15.0 | 210 | 330 
0.0 | 5.0 9.9 | 14.9 | 19.8 | 24.6 | 29.2 | 33.6 | 37.7 | 41.5 | 45.0 
40 | 140 | 0.0 | 0.3 ils il 2.5 4.4 6. 6 9.2 | 12.0 | 14.8 | 17.5 | 20.0 | 220 | 320 
0.0 | 4.4 8.9 | 13.4 | 18.1 | 22.8 | 27.6 | 32.3 | 36.8 |] 41.1 | 45.0 
50 | 130 | 0.0 | 0.3 il, il 2.6 4. 6 7.2 | 10.4 | 13.9 | 17.7 | 21.4 | 25.0 | 230 | 310 
0.0 | 3.7 7.5 | 11.5 | 15.7 | 20.3 | 25.2 | 30.2 | 35.4 | 40.3 | 45.0 
60 | 120 | 0.0 | 0.2 1.0 2.3 | 4.3 6.9 | 10.4 | 14.7 | 19.6 | 24.8 | 30.0 | 240 | 300 
0.0 | 2.9 5. 9 9.1 | 12.7 | 16.8 | 21.6 | 27.0 | 32.9 | 39.0 | 45.0 
70 | 110 | 0.0 | 0.2 0.8 18] 3.3 5. 6 8.9 | 138.4 | 19.5 | 27.0 | 35.0 | 250 | 290 
0.0 | 2.0 4.1 6. 4 9.0 | 12.3 | 16.3 | 21.6 | 28.3 | 36.4 | 45.0 
80 | 100 | 0.0 | O.1 0. 4 1.0 1.8 3. 2 5. 3 8.6 | 14.4 | 24.6 | 40.0 | 260 | 280 
0.0} 1.0 2. 1 3. 3 4.7 6. 5 9.0 | 12.7 | 18.8 | 29.4 | 45.0 
90 90 | 0.0 | 0.0 0. 0 0.0 0. 0 0.0); 0.0 0. 0 0. 0 OOM Sse a 270 | 270 
0.0 | 0.0 0. 0 0. 0 0. 0 0.0 | 0.0} 0.0 0. 0 @;@ jensan- 
Upper values for each double line refer to times of maximum velocities and are positive when JD is in the Ist or 3d quadrants, 
negative when D is in the 2d or 4th quadrants. 
Lower values refer to corresponding azimuths of the current and are positive when D is in the 1st or 4th quadrants and negative 
when D is in the 2d or 3d quadrants. 
For further explanations see paragraph 186. 
