EXPERIMENTAL METEOROLOGY 311 
movies are being obtained through the cooperation of the Air 
Weather Service of the USAF in such scattered places as Sweden, 
England, Germany, Italy, Japan, Hong Kong, and Bermuda. 
From the more than 30,000 feet of film now on hand, a series 
of movies will be prepared to illustrate the variations and similari- 
ties which occur in clouds that form under a wide variety of geo- 
graphic, topographic, and climatologic situations. Such films wil! 
be made available for educational purposes by the Foundation. 
Future Prospects of Increased Water Supplies from the Atmos- 
phere 
Although it must be admitted that there is no currently avail- 
able easy solution to the tapping of unlimited water from the sky 
rivers which flow over arid lands, there are still many research 
angles to probe. Under certain physical conditions such as have 
been described in this paper, it is fairly certain that some addi- 
tional water may be secured above that subject to the variations 
of natural conditions. 
The future possibilities of securing additional water supplies in 
arid regions from atmospheric sources depend on several factors. 
The most immediate may be expected from improvements in 
current techniques of cloud-seeding activities. The most remote 1s 
the natural variation in the general world circulation, which in 
the past produced so much rain and snow as to cause the great 
alluvial deposits that cover the Rio Grande Valley hundreds of 
feetaeep) 
The most important in the foreseeable future is the promise 
indicated by the studies and hypotheses of Langmuir (18) and 
Bowen (6), which suggest that optimum concentrations of effec- 
tive ice nuclei may play a dominant role in controlling hemispheric 
weather. Although their findings are still the subject of consider- 
able controversy, it seems reasonable to expect that a proper 
understanding of trigger effects in the atmosphere, which may 
cause singularities, abnormal weather patterns, extensive storms, 
and the persistencies, which lead to drought or flood, will eventu- 
ally lead to a certain degree of weather control. 
The time which will be required to reach this goal will depend 
to a major degree on basic research and the vision, enthusiasm, 
