390 
in the Osservatorio Ticinese and of two other 
pluviographs which were put up during the 
course of the project, the only available figures 
for the daily amount of precipitation are those 
of the usual rainfall recording stations of the 
official Meteorological Service. If one considers, 
however, that seeding lasts for 14 hrs, that is, for 
more than half the day, then it is reasonable to 
expect that, if loading the atmosphere with 
silver iodide really has a strong influence on the 
amount of rain that falls, this must show up in 
the daily amount of precipitation. 
The values obtained for mean daily rainfall 
in the years 1957 and 1958, are entered respec- 
tively on Figures 1 and 2. The upper figure 
Reckingen 
76% 
mS 
RAYMUND SANGER 
written beside the recording stations gives the 
mean quantity of precipitation for the seeded 
days, and the lower figure the mean for the un- 
seeded days. 
The astonishing result for 1957 (Fig. 1), 
namely that the increase in precipitation ap- 
parently caused by seeding is in the order of 
100% (though there is some falling off towards 
the Alpine Divide), led to the enquiry being 
extended to find out how much rain had fallen 
in the nearby Italian districts and in the zone 
south of the Po. The necessary data was most 
obligingly put at our disposal by the Servizio 
Meteorologico della Aeronautica Nazionale 
through the good offices of Ezio Rosini. Since 
Fre. 2—Daily precipitation in the test region in millimeters, 1958; 
upper values, seeded test days; lower values, unseeded days 
