Fourth Partial Report: In further pursuit of information concerning the artificial production of precipitation from cumulus clouds, tests were carried out during May and June 1949 in the Gulf States area near Mobile, Ala. These tests are a continuation of those conducted by the Cloud Physics Project in Ohio in 1948. The experiments in the Gulf area seemed necessary to show if the results of the Ohio tests were in any way influenced by the particular type of cloud encountered there.

The second phase of the Cloud Physics Project was carried on in the vicinity of Wilmington, Ohio, during the spring and summer of 1948. The organization, facilities, and general mode of attack were the same as those used in the first phase of the project. In this second phase of the study, the basic objective was to determine in definite quantitative terms the practical limits and economic importance of cloud modification processes in producing precipitation from cumuliform clouds.