S70 M. Macaire Prinsep o« the Colouring of the 



ed after ignition. The remaining fluid was evaporated to dry- 

 ness, and the residue ignited and weighed. Re-dissolved, it 

 left a httle insoluble matter, which was a mixture of silica and 

 alumina. The solution, when concentrated, gave no precipitate 

 with muriate of platinum, and, by evaporation, gave cubical 

 crystals. They were, therefore, chloride of sodium, from which 

 the quantity of soda was calculated. 



The mean of two analyses gives the following result : 



Silica, 55.073 



Alumina, .... 22.225 



Soda, 13.711 



Water, . . . . 8.217 



99.226 



On the Colourmg of the Leaves in Autumn. By M. Macaire 



PrInsep *. 



JtiivKRY person has been struck with surprise, and often with 

 admiration, on viewing the varied and glowing colours with 

 which nature suddenly invests the vegetable creation in autumn. 

 It seems as if, after gratifying the eye of man, by a mild and 

 almost uniform tint, during the period when the sun displays 

 all his brightness, she took advantage of the last moments that 

 remain to her for unfolding all her power, by giving to the land- 

 scape the richest and most varied hues, and terminating by this 

 brilliant display the exhibition of the yearly phenomena of ve- 

 getation. This remarkable change has naturally attracted the 

 attention of physiologists ; but scarcely any have viewed it others 

 wise than in a cursory manner^ and as connected with another 

 fact, the fall of the leaves, the explanation of which has seemed 

 to them of much greater importance. Thus several, as M. de 

 Lamarck, have viewed this autumnal colouring of the leaves a& 

 a diseased state ; M. Senebier, as an alteration or diminution in: 

 their nutritious juices, which only prepares their fall by paralys- 

 ing the upper network of the leaves. It has appeared to me 

 that thesd two phenomena were so far independent of each other 



• Memoires de ki Societe de Physique et d'Histoire Naturelle de Geneve, 

 torn. iv. pr. I. 



