The present writer has made an extensive and laborious study on the transformation of the equatorial air-mass moving from the Southern Hemisphere in the Far East. He has plotted dry and pseudo-wet-bulb temperatures for the individual Batavia flights.(1) In table I, he gives a brief resumé of 57 soundings used in this paper and the frequencies of the stability up to 30_??_mm Hg Level. It conforms well with the usual expectations of equatorial maritime air, being quite wet and unstable. For example, 78% cases are latent unstable, 4% cases psudo-unstable, and only 19% cases stable in the dry season (May-Oct.); 87% cases are latent unstable, 10% cases pseudo-unstable and only 3% cases stable in the rainy season (Nov.-April). Thus the instability is more pronounced in rainy season than in dry season.The mean values of greatest realisable energy up to 300mm Hg level for rainy and dry season are as follows:- rein_??_ season: 0.352 joule/g dry season: 0.205 joule/g (Nov.-april) (May-Oct.) From the same data the present writer has worked out for rainy season and dry season separately, as seasonal variations may affect the values of characteristic properties of air masses to a considerable extent. In table II, only readings taken during ascent at intervals of every 1km above M. S. L. have been included.When the Northern Hami sphere is summer, during the passage of the equatorial air from Batavia to Manila(1), Hong-Kong(2) or Nanking(3), there are definite increases in temperature and humidity at a_??_l heights above the surface. These results cited in table III indicate that while over China Sea or southern sea of Japan(4) the equatorial air is warmed at the surface, resulting in strong convection and through mixing.