245 



by the prism resembles that produced by absorption, the question 

 U, To what medium are we to refer that absorptive action? Evi- 

 dently not to pure air, since a distant light is red in a fog, and in 

 clear weather white, or nearly so. The author is disposed to at- 

 tribute the effect to the presence of vapour iu the very act of con- 

 densation. This intermediate or colorific stage occurs between 

 the colourless and transparent form of steam wholly uncondensed, 

 and that which may be termed the state oi proximate condensation 

 in which it is seen to issue from the spout of a tea-kettle, when it 

 is likewise colourless, but semiopake. During the transition, it 

 was shewn in the former paper that steam becomes intensely red, 

 and remains transparent. The absorptive action resembles then, 

 so far, that of the atmosphere observed under certain meteorologi- 

 cal conditions; the dark Hues and bauds noticed by Sir David 

 Brewster in the atmospheric spectra have not been discovered, and 

 Bo far the analogy is as yet imperfect.* 



In applying this theory to the colours of sunset in particular, the 

 author quotes many acknowledged facts to prove that the redness 

 of the sky is developed precisely in proportion to the probable 

 existence of vapour in that critical stage of condensation which 

 «hould render it colorific. And he applies the same reasoning to 

 account for the prognostics of weather, drawn from the redness of 

 the evening and morning sky. 



• Monday, \Sth Ftbruarij. 

 Dr ABEllCROMBIE, V. P., in the Chair. 

 The following Donations were presented :— 



Journal of the Asiatic Society of Bengal, No. 49. for January 1836. 



— By the Society. 

 Researches in Embryology. First Series. By Martin Barry, M. D. 



F. R. S. E — By the Author. 

 Elements of Chemistry. By the late Edward Turner, M. D. 6th 



edition. Revised by Justus Liebig, M. D., and W. G. Turner, 



Ph. D. Part ^.—By the Editors. 



' Some plausible reasons are assigned why these bands should not have 

 appeared in the experiment as it was made, when steam in every stage of 

 condensation must necessarily have been present : nor does it seem easy to 

 devise a form of experiment free from this objection. A very important 

 observation would be to examine the spectrum produced by a disUnt arti- 

 ficial light seen tlirough a red fog. 



