22 



into the machine for preparing the paper, is compounded of galls, 

 anhydrous ferro-prussiate of potassium, and carbonate of lime, so 

 diluted with rice flour, that enough, and no more of the powder than 

 enough, remains among the fibres of the paper. The paper is sized 

 before being passed through the machine, and is afterwards finished 

 in the usual manner. Specimens of different qualities of paper 

 were laid on the table, and written on with the colourless ink by the 

 membei's present. 



3. On the Use of Metallic Reflectors for Sextants, and on 

 the Determination of the Errors arising from Non- 

 Parallelism in the Mirrors and Sun-Shades of Reflect- 

 ing Instruments. By John Adie, Esq. 



The object of this communication was to shew that, by the use of 

 metallic reflectors for sextants, greater accuracy was obtained in 

 the observed angles, and also that larger angles could be observed. 

 Objects were seen reflected by metallic mirrors, which could not 

 be seen when glass was used ; and that when the alloy was formed 

 of pure metals, it was not subject to rust or tarnish, even when 

 exposed to action of the sea air. 



The author then exhibited a sextant fitted with these mirrors, 

 which had been employed for a season in the survey of the north 

 coast of Scotland, under Mr Mossman, and read extracts of letters 

 from that gentleman. 



In the second part, he describes methods by which the non- 

 parallelism in mirrors and shades may be determined with great 

 accuracy, before they are applied to reflecting instruments. 



A Ballot then took place for the following Candidates, 

 recommended by the Council at last Meeting for filling 

 places in the Foreign Honorary list : — 



MM. Cauchy, Paris, 



Charpentier, Bex, 



Ehrenberg, Berlin, 



Elie de Beaumont, — Paris, 



Guizot, Paris, 



Hansteen, Christiania, 



Jacobi, Konigsberg, 



Lamont Munich, 



