20 Scientific Proceedings, Royal Dublin Soviety. 
F. W. Very, however, claims that “ the chief absorbent of the 
Earth’s atmosphere is water-vapour, but its action is complicated 
by the relation between vapour and mist. Even considerable 
changes in atmospheric aqueous vapour in warm weather, if unat- 
tended by misty condensation, produce only slight variation in 
the direct rays of the midday sun—not, however, because water- 
vapour does not exercise a great absorption, even on solar rays, but 
because so much moisture is always present in warm weather that 
nearly all of the rays absorbable by aqueous vapour have been 
eliminated, and the remaining radiation is comparatively trans- 
missible.: Haze, however, of whatever description, . . . acts at 
all seasons, and independently of the amount of the vapour of 
water dissolved in the air. Mist and haze have little effect on the 
emission of radiations of long wave-length from air by virtue of 
its own temperature, or on the transmission of long ether-waves 
by the atmosphere ; but they have great influence in stopping and 
scattering those short ether-waves which are especially prominent 
in sunlight.’” 
Moreover, “the gradual formation of closed chains as the 
aqueous vapour approaches saturation must take place most readily 
if the molecules of vapour are not widely separated by diluting 
air. Meteorologists have often commented on the peculiarities of 
nearly saturated air; and some have conjectured that gaseous water 
exercises no appreciable absorption, and that the absorbent effects 
attributed to it are really due to a mist of liquid water, relative 
humidity being more important than vapour-tension as an index 
of absorptive power. We have seen that gaseous water does pro- 
duce a very potent influence of its own; but it seems to me to be 
demonstrated by what precedes that there is a remarkable increase 
in absorption by water at the critical point of incipient condensa- 
tion, and as this point is somewhat closely approached. The suffo- 
cating sensations experienced in a very hot, muggy atmosphere 
1 My own observations do not at all support this statement. It is an undoubted 
fact that at Kimberley, under a perfectly clear sky, an increase of aqueous vapour 
indicates an increase of air-temperature, and a corresponding decrease of the heating 
effect of the Sun’s rays. Such also appears to be the plain interpretation of some 
recent volumetric work in America.—J. R. 8. 
2 F. W. Very, ‘* Atmospheric Radiation,” 1900, p. 79. 
