1919] ATMOSPHERIC BEFEACTION 599 At this point it is convenient to re-introduce 6, where cc = /3 cot 9, and dec = — /3 sin~2 Od6. We have d £sin-20d0 The upper limit oo for x corresponds to 0=0; the lower limit a corresponds to what after the integration we may still denote by 6, where a = /3 cot 0. Thus Also ' and . 1* xzdx *= 8^0^0=(10-8^20 s 5 w .(6) cos2 0 sin2 v2dx 1 (0 _ £ sin 40), 0 now referring, as above, to the point for which x = a. Using (6) and (7) in (5), we have (t * - si sn sn = ™ (sin 2 sin 20 + £ sin 40), ...... (8) in which, if we please, we may substitute r sin 0 for /3, so that r, 0 are the polar coordinates of the point of observation. Thus c2 sin 20- A sin 40 c4|0 - sin 20 + A sin 40 fv\ -—. ____ r_ _._____________&__ ______.__... ^ __ ____ ^ ^ _ ________ O ________ «9 01 n2V? r4 Qin4 (9 / Cull U I olll I/ .......................................(9) as we write it for brevity. It now remains1, to discuss (9) as a function of r and 0, under the limitation, however, that r > c. When 0 is small, /(0) = 40, F(6) = so that (9) becomes .(10) vanishing when 0 = 0, as was to be expected, since this is a line of symmetry. Inasmuch as .r > c, (10) takes its sign from 0, The table gives values of/ and F for certain angles of 0. In the fourth column are entered the values of (9) when r — c, that is on the surface of the cylinder. So far as 0 = 50° these are the highest admissible. For example at 50° = -8173 {(1-2049)2 - (1-2049 - c'/r8)3}. So long as r > c, the value of (9) increases as r diminishes, and the greatest admissible value occurs at the limit r — c. This state of things continues so-velocity U, is well known*. The problem may conveniently be reduced to one of "steady motion" by supposing the cylinder to be at rest while the fluid flows past it—a change which can make no