372 SECTIONAL TRANSACTIONS.—A. 
40. Mr. A. THomson.—Upper Wind Observations at Samoa, 1923-24. 
Pilot balloon observations were initiated at Apia Observatory in June, 1923, 
and have been continued to the present time. The Observatory is situated in 
the western part of the South Pacific Ocean in a region so remote from the 
continental areas of South America and Australia and the island groups of 
Tonga and Fiji that land masses must necessarily exert only a slight influence 
on the air currents. 
Observations were made by the single theodolite method on balloons inflated 
to rise at the rate of 180 metres per minute. 
The fifty-five balloon flights which reached heights greater than 5 km. 
were grouped in two periods: the dry or trade wind season from June to 
October, and the wet season from November to April. The results from the 
two periods were similar. From 1 to 4 km. there was a slight decrease of 
velocity, and from 4 to 12 km. a steady increase. At 12 km. the velocity 
had a maximum value, and if the region of maximum velocity corresponded 
to the tropopause, as in temperate latitudes, then the stratosphere was con- 
siderably lower than might have been expected. 
The easterly or trade wind component decreased from 5.8 m.p.s. at the 
surface to zero at 2.5 km., above which westerly winds persisted to the limit 
of observation. The north or south component was always small. 
41. Dr. W. Beit Dawson.—Effect of Wind on the Tide. 
The estuary of the St. Lawrence and the Bay of Fundy lie parallel to the 
storm tracks along the eastern coast of North America. The Tidal Survey 
has now observations of the tide during many years in these regions, and 
simultaneous meteorological record. There is thus an exceptional opportunity 
for the investigation of the effect of the wind in raising the tide, if this material 
could be worked up. 
Wednesday, August 13. 
42. Joint Discussion with Section B (g.v.) on Colloids. (Page 378.) 
CosmicaL Puysics SuB-SECTION. 
43. Prof. A. S. Epprneton, F.R.S.—Theory of the Outflow of 
Radiation from a Star. 
The outward flow of radiation through a star depends on the temperature- 
gradient (strictly the gradient of T‘) urging the flow, and on the absorption- 
coefficient or opacity resisting the flow. The temperature distribution is deter- 
mined by the conditions (1) that it must be such as to maintain itself auto- 
matically, (2) that the resulting pressure must support the material against 
gravity. Very general considerations as to the processes involved in absorption — 
indicate that the opacity will be approximately proportional to ef 3. In this 
way formule are obtained giving the total outflow of radiation from a star of 
given mass and density, provided that it is constituted of perfect gas; the total 
radiation depends mainly on the mass, the density making comparatively little 
difference. ‘whe observational data fit these formule very closely. The sur- 
prising thing is that a great part of the data refer to stars of density greater 
than water; it is suggested that these stars agree with the theoretical results 
for a perfect gas because the atoms, being broken up by intense ionisation, 
approximate closely to the ideal point-molecules of a perfect gas. The con- 
clusions conflict with the giant and dwarf theory of stellar evolution. 
44, Mr. E. A. Mine.—Radiation Pressure and the Equilibrium of the 
Solar Chromosphere. 
The variation of density with height in the solar chromosphere must depend 
intimately on the relative extents to which the atoms are supported against 
gravity by radiation-pressure and by the gradient of the gas-pressure. Let 
