8 Library. [Jan., 



sand or two miles from the centre of eruption is at least improbable, and we 

 may well require some specific confirmation of such a theory. I observed 

 with particular care that during the continuance of the phenomenon in 

 these parts there was not a breath of wind stirring. So soon as wind 

 came, the exceptional appearance vanished, and gave place to the ordinary 

 well known after-glow where the deeper tints were nearest to the horizon ; 

 this appearance is common always in the cold weather, and it is seen best 

 at times when the atmosphere is most free from dust, i. e., shortly after 

 the cessation of the rains. Naturally any agitation of the atmosphere 

 would tend to disturb such a state of distribution as would result from 

 complete quiescence under the influence of steady upward diffusion of 

 vapour and uniform radiation through a uniformly unclouded atmosphere. 

 A reference to the Meteorological Reports of the time will, 1 believe, show 

 that there was a complete absence of cloud and wind over very extensive 

 areas, and the laws of radiation, selective absorption, diffusion and conden- 

 sation of vapour tell us that, under such conditions, progressive condensa- 

 tion of vapour, beginning in the higher layers of the atmosphere and extend- 

 ing gradually downwards, should happen. Our knowledge also of the eif ects 

 of diffused cloud composed of particles whose diameters are comparable 

 to the amplitudes of light vibrations tells us that if the distribution of 

 water- particles was in fact what well-established theory showed it should be» 

 then the light effects observed were those which experience and equally 

 sound theory would dictate. 



J- 



IBRARY, 



The following additions have been made to the Library since the 

 Meeting held in December last. 



Transactions, Proceedings and journals, 

 presented by the respective Societies and Editors. 

 Allahabad. Punjab Notes and Queries, — Vol. I, No. 3. 

 Baltimore. American Chemical Journal, — Vol. V, No. 5. 

 Berlin. Entomologische Zeitschrift,— Vol. XXVII, No. 2. 

 Bordeaux. Societe de Geographie Commerciale, — Bulletin, No. 22. 

 Calcutta. Indian Meteorological Memoirs,— Vol. II, Part 2. 



. United Service Institution of India, — Journal, Vol. XII, 



No. 57. 



