On the Mural and Physical Condition of the Working Classes in 



Manchester. By Dr Kay— -From the Author. 

 Nouveaux Memoires de I'Acadeniio Royaie dos Sciences et Belles 



Lettres de Bruxelles. Tomes V. and VI.— From the Academy. 

 Memoires Couronnes en 1829 et 1830, par I'Academ.o Royaie 



des Sciences et Belles Lettres de Bruxelles. Tome VIII.— 



From the Academy. 

 Astronomische Beobachtungen auf der Koniglichen Univers.lats 



Sternwaite in Kbnigsberg. Von F. W. Bessel. Funfzehnte 



Abtheilung. — From the Author. 

 Two Specimens of the Draco Lineatus, from Ava.— From Mrs 



R. Cockburn. 

 Twenty-nine Specimens of British Fishes.— Presented by J. F. 



W. Johnston, Esq., F.R.S.E. 



The following communications were then read : — 

 1. On the Colours of Natural Bodies. By Sir David 

 Brewster, V.P.R.S. Ed. 



The only Theory of the Colours of Natural Bodies that has met 

 with reception in modern times, is that of Sir Isaac Newton, who 

 considers them as identical with those of thin plates, and as vary- 

 in(T with the size of the ultimate particles of the body. 



"Although this theory, ingenious as it is, be liable to many great 

 objectionsrand be not capable of explaining the phenomena, even 

 if its postulates be admitted; yet the author of the present paper 

 does not assail it with any arguments of this kind. He has, on 

 the contrary, attacked it in its stronghold, and has endeavoured to 

 bring it to the test of direct experiment. 



Sir Isaac Newton considers the green colour of plants (the most 

 general colour which nature presents to us) as a green of the third 

 order of periodical colours, and has also given us the exact com- 

 position of this particular colour. 



In order to determine the composition of the green colour of 

 plants, the author dissolved their colouring matter in alcohol; and 

 having analyzed it by a fine prism, he found it to have, in every 

 case, the same composition. The portions of the spectrum, how- 

 ever', which entered into its compound tint, were totally different 

 from its theoretical composition, as assigned by Sir Isaac Newton; 

 and had no relation whatever to the colour of their plates. The 



