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A POSSIBLE LUNAE INFLUENCE UPON THE VELOCITY 
OF THE WIND AT KIMBERLEY. 
By J. E. Sutton, M.A., Sc.D., F.E.S.S.A., Hon. Memb. E. Met. S., Hon. 
Memb. S.A.S.C.E. 
The object of the present discussion is to determine whether there is a 
lunar term in the velocity of the wind at Kimberley. A test investigation 
made on a small scale some years ago established the possiblity of such a 
term ; but it is obvious that definite proof of the same could only be 
furnished from the results of a long series of observations. Because, for 
one thing, any share of the movement of the air which can depend upon 
any conceivable lunar influence must be a very small fraction of the share 
depending upon recognised meteorological factors ; and hence our discussion 
must be on such a scale as will afford a reasonable guarantee that the 
effects of ordinary meteorological irregularities are lost in the mass. 
Seasoning a priori, a lunar term in the velocity of the wind should be 
expected. If the moon can generate and maintain a tide in the atmosphere, 
as we know it does, it must also be able, directly or indirectly, to raise the 
wind. The only question would seem to be whether it can raise it to a 
measurable amount, and how. The lunar atmospheric tide at Kimberley is 
of the order "003 inch in amplitude with very little establishment. Hence, 
since the diurnal, thermal, variation of barometic pressure at Kimberley 
has a range of about *09 inch (i. e. thirty times the lunar tide), corresponding 
to a range of wind velocity of about 3*4 miles an hour, we should expect, 
for the sake of argument, a lunar variation in the velocity of the wind 
of about 3*4/30 (= O'll) miles an hour. We shall see presently that, if 
the observations are accounted adequate to prove the case, this estimate is 
too low. 
The Kimberley register contains hourly values of the velocity of the 
wind since 1897, with only an occasional break. The site of the anemo- 
meter is none of the best, though perhaps good enough to give a negative 
or affirmative answer to the simple question whether the moon is of any 
account at all in the matter of the wind. The automatic records of velocity 
are easily read to one-tenth of a mile an hour. The average velocity of the 
wind at Kimberley is in the neighbourhood of five miles an hour, rising 
occasionally to more than thirty. 
For the purposes of this discussion the hourly velocities in the Kimberley 
register have had to be rearranged in terms of the lunar day. This has been 
done by arranging the hourly velocities in twenty-five columns, the middle 
column, containing the velocity for the hour in which the moon made its 
upper meridian passage (U.M.P.), being accounted lunar noon, the mean 
of the first and twenty-fifth columns being accounted lunar midnight (L.M.P.). 
