SOME STATISTICS OF THUNDER AND LIGHTNING AT 
KIMBERLEY. 
By J. R. Sutton. 
The annexed Tables I, II, III, give summaries of the results of eye and ear 
observations of thunder and lightning made at Kimberley during the twenty- 
three years 1897 to 1919. They show, month by month, the duration of all 
the lightning seen, and of thunder heard, in the period. Division by twenty- 
three would give monthly means, but, in order to save decimal places, this 
has not been thought necessary. The numbers given in the tables must err 
in defect somewhat, since it cannot be that all lightning occurring has been 
seen, and all thunder heard, particularly during the hours between midnight 
and sunrise. The error, so far as thunderstorms are concerned, cannot 
amount to many hours, however, and certainly not by enough to displace the 
times of maximum and minimum. 
Table I shows that thunder and lightning together, shortly thunder- 
storms, have a well-marked maximum a few hours before sunset in the warm 
months, and a few hours after sunset in the colder ones. The intermediate 
months show a tendency to a double maximum, one before and one after 
sunset. Moreover in July the diurnal variation tends to vanish altogether ; 
while there is some evidence of a winter maximum some time between sunrise 
and noon. 
The totals for the year show a maximum about 4 p.m. But this might 
be an illusory effect, seeing that the annual totals are made up for the most 
part of the large summer totals. For the purpose of eliminating the 
exaggerated effect of the summer numbers, the last column ("weighted year'') 
has been computed. This column postulates an equal duration, i. e. 266 
hours, of thunderstorm for each month, the hourly totals being reduced 
accordingly. The issue lessens the annual totals between noon and sunset, 
and enlarges the others, leaving the time of maximum unaltered. It also 
emphasises the influence of the winter maximum after sunrise. 
Table II gives statistics of the duration of lightning without thunder seen 
during the same period. The numbers between midnight and sunset cannot 
claim much for themselves : first, because there was no systematic watch set 
between midnight and sunrise ; and next because " sheet " lightning is not 
usually visible in daylight, only coming into view when the luminosity of the 
sky becomes less than that of the discharge. 
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