Applying the isopiestic m ethod to the mass determination of hygroscopic nuclei in cloud droplets, we found that the isopiestic method can produce a satisfactory result when a 10% NaCl solution is used as a vapor-pressure controlling solution. We sampled the nuclei from layer-ty p e warm clouds at the 7.8 Gome (3,400 m) of Mt. Fuji during June 20th to 28th in 1967. We determined the nucleus mass by the isopiestic method for 1318 cloud droplets. The nucleus masses of the cloud droplets were almost the order of 10-14-10-12 gm, and the number of nuclei with weight over 8 × 10-14 gm (dtection limit)' was 27% of all the droplets. The relation between the size of the cloud droplet and the nucleus mass was not found in the early stage of droplet growth, but a high correlation was found in the later stage; that is, the larger droplets contain lamer hvzroscopic nuclei.
Aerosol observations on cloud nuclei together with Aitken nuclei and giant sea-salt nuclei were made in order to clarify the relation of aerosol distribution to the nature of air-mass at Irozaki, Izu Peninsula, and Mt. Fuji (650 m,1,300 m,2,100 m levels). An inverse correlation was noticed between Aitken nuclei concentration and giant sea-salt nuclei (chloride nuclei) concentration. There are two types of supersaturation spectra of cloud nuclei: one under the influence of inland air-mass and another under that of maritime air-mass. From the sepoints of view the interrelation of air-mass and aerosol distribution are discussed. Also Aitken nuclei concentrations had a fairly close relation to the stabilities of the atmospheric layer. High stabilities corresponded to small concentrations of Aitken nuclei. The mode radius of cloud nuclei usually appeared at 0.01 to 0.02 micron in the case of soluble materials. In the inland the size distributi o ns were of a rather flat type which was inferred from the fact that various sorts of cloud nuclei were found mixed.