158 Proceedings, <&a, for 1884. 



March 13th, 1884. 



Present, the President (in the chair) and 40 members and associates . 



Professor Andrew read a note on "The Red Sunsets," in which 

 he explained the principle according to which the fine dust, sup- 

 posed by some to be the cause of these phenomena, might float in 

 the upper regions of the atmosphere without showing any tendency 

 to descend. He said that Mr. Ellery had raised a difficulty in 

 connection with one of the theories that had been propounded to 

 account for the remarkable afterglows which created so much 

 public interest, to the effect that if they had been due to the 

 suspension of fine particles of volcanic or meteoric dust, they 

 would have ceased long ago, as the particles would be quickly 

 precipitated. The theory that the red sunsets were due to the 

 presence of particles in the air would naturally lead any thinking 

 person to ask how it was possible that particles specifically heavier 

 than the air could remain for a long time in the atmosphere? 

 Three theories had been propounded to account for the remarkable 

 afterglows, and from those three were two offshoots. The theory 

 which Mr. Ellery announced was, that the red glow after sundown 

 was due to the accumulation of an unusual quantity of aqueous 

 vapour in the upper regions of the atmosphere. That theory had 

 received the support of the President's colleague, Mr. Pussell, 

 Government Astronomer, Sydney, and of Professor Michie Smith, of 

 Madras College, who attributed the peculiar green colour of the sun 

 and moon, which had been observed in India, to the presence of 

 aqueous vapour in the atmosphere. The second theory was that 

 the earth at present is, and had for some time past been passing 

 through a band or zone of meteoric dust ; and the third theory 

 attributed the afterglow to the distribution in the atmosphere of 

 volcanic dust, consequent on the explosion at Krakatoa. The two 

 offshoot theories were — (1) a combination of the first and third, 

 and (2) a combination of the second and third. The only modes 

 of testing the truth of these theories was the use of the spectro- 

 scope and the actual production of dust precipitated from the 

 atmosphere. His own observations, made with an inferior instru- 

 ment, and without actual measurements, led him to agree with 

 those made much more carefully by Mr. Ellery ; but the fact that 

 in Holland there had been falls of rain impregnated with black 

 dust, and in Spain falls of sno*w similarly impregnated, and that 

 this dust was found on careful analysis to be identical with that 

 brought from the scene of disaster, rendered the evidence from the 

 two sources antagonistic. The volcanic-dust theory was most 

 generally adopted at home, though with very great diffidence; but 

 no scientific man of any eminence had ventured to say that the 

 problem had been solved with any certainty ; indeed, Professor 



