green colouring matter exercised an arbitrary specific action upon 

 different parts of the spectrum, and its green colour was owing to 

 its having absorbed a certain number of rays, which, when sub- 

 tracted from the white light, left the colour under consideration. 

 In order to render this result more general, the author examined 

 an immense number of coloured solutions, obtained from plants and 

 artificial salts, and a great variety of coloured solids, either formed 

 by art, or obtained in nature ; and in all these cases, he found no 

 indication whatever of periodical colours. The colours were inva- 

 riably produced by the absorption of certain definite rays taken 

 arbitrarily and unequally from different parts of the spectrum ; 

 and, excepting in the case of certain imperfectly transparent and 

 opalescent fluids, there never was the slightest trace of a reflected 

 tint similar to that which might have been expected had the New- 

 tonian theory been true. 



2. Notice respecting the Determination of the Geogra- 

 phical Positions of the Village of Cliamouni, and of 

 the Convent of the Grand St Bernard. By James D. 

 Forbes, Esq., F.R.SS.L. &Ed. 



The author undertook the determinations of these positions at 

 the suggestion of Professor Gautier of Geneva, who informed him 

 that they had not been fixed by any direct observations. The 

 great discrepancies of the best maps of the Alps in laying them 

 down confirm this opinion ; and the author has quoted the lati- 

 tudes and longitudes, given by the best authorities, at the end of 

 his paper. 



The new determinations give for the position.s — 



Latitude. Long. E. of Geneva. 



Chamouni, 45° 55' 51" . . . 27°> 25» 



St Bernard, .... 4.5° 50' 16" . . . 28" 19» 



The latitudes were determined by successive altitudes of the 

 pole star, taken with an altitude and azimuth circle, upon Captain 

 Kater's construction, the circles being 4-1 inches in diameter, and 

 divided to 15". The position of St Bernard is the best deter- 

 mined, eight altitudes of the pole star having been taken, the re- 

 sults of seven of which agree closely. 



The longitudes were determined chronometrically, in the first 

 place, by comparisons with the Geneva Observatory clock, and in 



