SWISS RANDOMIZED HAIL SUPPRESSION PROJECT 
if we restrict our record to the actual test period 
of the day, and does not permit any analysis in 
terms of intensity and location. The sparsity of 
the hailfalls compels us therefore to put aside 
any idea of an exact mathematical statistical 
treatment of the observational data, to wait at 
least for the results of the third test year, and 
for the time being to insist only that it is not 
now possible to make any statement having sta- 
tistical weight, as to the effects, either positive, 
negative, or neutral, of the AgI seeding which 
has been done to prevent hail. 
Two heavy hailstorms in the years 1957 and 
1958 which he outside the prescribed observa- 
tion period deserve to be mentioned. These 
therefore will not figure in a later statistical 
389 
evaluation of the test results. They are the hail- 
storm of August 13, 1957 and that of August 11, 
1958. The first occurred on a day for which the 
forecast had been that there would be no storms 
(and which was therefore not a test day). In 
the case of the second hailfall, the storm did not 
begin until 22h 55m, five minutes after the end 
of the test period, and cannot consequently, if 
we are to be correct in our methods, be taken 
into account in the evaluation, despite the fact 
that this was a test day when there had been no 
seeding! 
Particular interest attaches to the question 
whether the effect of Ag] seeding may not per- 
haps be registered in the volume of precipita- 
tion. Apart from the records of the pluviograph 
Fic. 1—Daily precipitation in the test region in millimeters, 1957; upper 
values, seeded test days; lower values, unseeded days 
