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A FUETHEE NOTE ON THE DIUENAL VARIATION OF 
LEVEL AT KIMBEELEY. 
By J. E. Sutton, ScD., F.E.S.S.Af. 
(Eead July 20, 1910.) 
I have made a number of experiments during the past few months 
with the object of determining whether the diurnal oscillation of level is 
by any chance wholly or in part of photo-electrical origin ; since, for 
reasons already stated, neither the distortion of the crust by heat and 
cold, nor the movements of subsoil water, nor the variation of load set up 
by the diurnal march of barometric pressure, seem to be competent to 
produce more than a small portion of the oscillation." The results 
obtained so far are conflicting ; while some have appeared to support the 
idea, others do not. The investigation, which is being continued as 
occasion offers, will be described later on, provided it yields anything 
definite and succeeds in reconciling the discrepancies. 
My meteorological observations are not in disagreement with some 
kind of photo-electric theory of the diurnal oscillation of level. Seeing, 
nevertheless, that the earth's surface at Kimberley is scarcely ever at rest 
— the level being depressed north, south, east, and west almost unceasingly 
— no great amount of success is to be anticipated in disentangling the 
elements that really matter from those that do not. A heavy shower of 
rain, for example, will set up very large disturbances of level lasting many 
days, and interfering considerably with the diurnal oscillation. The 
passage of a barometric depression also has its own disturbing influence, 
which may be added on occasion to that of the rain. The following 
numbers show the daily averages of the hourly values of the deviation, to 
the west of the datum line, of the stylus of the horizontal pendulum, 
* "Preliminary Note on the Diurnal Variation of Level at Kimberley," Trans. 
R.S.S.A., July, 1909. 
