ON A CHARGED ELECTRIC CONDENSER MOVING THROUGH SPACE. 
171 
Since t] never exceeds 23|-°, it is always possible to choose 6 so as to satisfy this 
condition. When 9 is so chosen, we can rotate the condenser al)ont its axis of 
suspension until the angde /x is 45°. The couple then liecomes N {u/vy, which is the 
greatest possible. 
Tlie aziinuth of the drift, measured as })Ositive from the meridian easterly, is deduced 
from the following :— 
In triangle NPQ, gin NPC^) _ sin NQ _ 
sinPNQ sin PQ ' 
or, since NPQ = ^ - fi, sin - /x) = ^ cos - 9). 
sm A 
But sin \ has been cliosen as unity, therefore 
or 
sin (<^ — p,) = cos rj cos — 9), 
cos {(f) 
_ sin Yf 
cos 5lT 
(v.) 
The angle {(f) — /x) is tlie azimuth of the drift. 
The dotted curve, fig. 8, shov's the time of day when drift is entirely horizontal. 
N 
Fig. 6. 
The dotted curve, fig. 9, shows the azimuth of the drift. 
If the condenser Ije placed as in the diagram (tig. 6), then it should tend to move 
so as to Increase the angle NOC.^' That is, the motion should be in the direction 
E.S.W. We shall call this the positive direction. NOC = (/n QO(! = /x. 
* Accepting Larmor’s Theory, the angle NOC would diminish. 
z 2 
