VI - CUMULUS STUDIES 



The most spectacular, fruitful, and controversial results produced 

 by the activities of the project were those produced as a result of the work 

 on cumulus clouds. This work, which started in the earliest days of the 

 project, continued throughout its duration and let into some very inter- 

 esting other activities. 



Flight tests on November 23 and 29, 1946, were made on isolated 

 cumulus -type clouds. The whole of each cloud was changed into ice 

 within five minutes after seeding, and snow began falling from the base 

 of the cloud. '^5) But it was realized that experiments with small cum- 

 ulus clouds were of little interest, for the effects lasted but a few minutes. 

 Other experiments were conducted with cumulus clouds in the early days 

 of the project and, although many of them were changed to snow, the re- 

 sults were of comparatively little interest. 



By the summer of 1947, however, some spectacular results were 

 obtained with cumulus clouds, especially with thunderstorms. These were 

 so impressive that it was decided to make some studies of cumulus clouds 

 and thunderstorms in New York State's Sacandaga Reservoir territory, not 

 far from Schenectady. 



This reservoir is situated just south of the southeast corner of the 

 Adirondack Mountains. Evidence pointed to the probability that this large 

 body of shallow water provides the moisture which feeds thunderstorms in 

 eastern New York State. It was believed that the unusual conditions there 

 could be used to observe the effect of seeding the intense thunderstorms 

 developed. Actually, however, no seeding was performed there, although 

 many photographs were taken and considerable time was spent in a study 

 of conditions in that area. 



HONDURAS 



In 1948 and 1949, Langmuir visited Honduras, Guatemala, and Costa 

 Rica to study tropical cloud formations, and particularly to learn what was 

 being done by Joe Silverthorne, a commercial cloud seeder, in seeding 

 clouds for the United Fruit Company. The work was being conducted for 

 the purpose of testing out the possibility of controlling rainfall, and partic- 

 ularly in the hope of stopping blow -downs that result from winds associated 

 with thunderstorms, which occasionally destroy large stands of fruit trees. 



At Langmuir J s suggestion, Silverthorne tried out a number of ex- 

 periments early in 1949 and made many worthwhile observations. It was 

 sometimes desired to produce rain, and sometimes it was desired to pre- 

 vent rain. On the one hand, by overseeding the top of a high cumulus 

 cloud, rain would be prevented. The top of the cloud would float off into 

 _a higher altitude, where it would be blown away by the counter trade wind. 



