407 



This acid contains no nitrogen ; it does not reduce oxide of copper 

 in Trommer's test ; it dissolves in concentrated sulphuric acid with- 

 out forming any conjugate combination. When boiled with a mix- 

 ture of hydrochloric acid and chlorate of potash it is decomposed, 

 but without giving rise to chloranile ; it gives no coloration when 

 boiled with solution of hypochlorite of lime. Nitric acid, especially 

 when aided by heat, attacks larixinic acid, leaving oxalic acid as the 

 only fixed product. When heated with bromine it is destroyed, hy- 

 drobromic acid vapours are given off, and an uncrystallizable resin 

 remains. Salts of copper give to solutions of larixinic acid an 

 emerald-green colour, but cause no precipitate ; chloride of manga- 

 nese produces neither coloration nor precipitation. Characteristic 

 effects are produced by salts of iron : perchloride and persulphate 

 give a beautiful purple colour which stands dilution well ; and 

 larixinic acid becomes in this way an excellent reagent for detecting 

 the presence of iron, even in minute quantity. It does not affect 

 neutral proto-nitrate of mercury in the cold, and on the application 

 of heat no mercury is reduced. 



This acid appears to be peculiar to the larch tree ; at least the 

 author has not been able to find any trace of it in the spruce fir 

 (Abies excelsa), or in the Scotch fir (Pinus sylvestris). It evidently 

 belongs to that small group of substances, of which pyrogallic acid 

 and pyrochatechin, the oxyphenic acid of Gerhardt, are the only 

 other members yet known. It is much less easily oxidizable than 

 oxyphenic acid, which again is less easily oxidated than pyrogallic 

 acid. Larixinic acid volatilizes at a much lower temperature than 

 either of these two substances, from which it also differs in being 

 a ready-formed proximate principle, and not an educt. 



III. "On the Great Magnetic Disturbance of August 28 to 

 September 7, 1859, as recorded by Photography at the 

 Kew Observatory." By BALFOUR STEWART, Esq., A.M. 

 Communicated by General SABINE, R.A., Treas., V.P.R.S. 

 Received June 28, 1861. 



(Abstract.) 



During the latter part of August, and the beginning of September, 

 1859, auroral displays of almost unprecedented magnificence were 



