418 



retained its red colour to the last ; but when quite dry, it became of 

 a dirty red colour. 



Sulphuric acid, diluted with eight or ten parts of water, being 

 poured upon the colouring matter, if no heat be applied, remains 

 perfectly colourless ; but, by the assistance of heat, it forms a lilac 

 solution, which remains unaltered for a great length of time, though 

 exposed to light ; but if heat be applied, so as to evaporate part of 

 the water, the colour is destroyed in proportion as the acid becomes 

 more concentrated. 



The effect of nitric acid is to destroy the colour in greater or less 

 time, in proportion to the quantity employed. 



Acetic acid dissolves the colouring matter, with appearances simi- 

 lar to those of the muriatic solution. 



The solution in oxalic acid is of a brighter red than any other 

 hitherto noticed. In tartaric acid the solution approached to scarlet. 



The alkalies also, or their subcarbonates, dissolve the colouring 

 matter ; and the solutions may be evaporated nearly to dryness with- 

 out losing their red colour. 



The next object of Mr. Brande was to find such combinations of 

 the colouring matter as would be insoluble, and might therefore 

 afford a permanent dye. When combined with alumina it is red 

 while moist, but becomes brown when dried. With oxide of tin it 

 may also be combined, but becomes of a dull red by drying ; neither 

 does supertartrate of potash give permanent brilliancy to the colour. 

 But when a piece of calico has been previously dipped into infusion 

 of oak-bark, and afterwards steeped in an alkaline solution of the 

 colouring matter, it acquires a redness nearly equal to that given by 

 madder, and tolerably permanent. But the most effectual mordants 

 appeared to be some of the solutions of quicksilver. Pieces of woollen 

 cloth, calico, or linen, steeped first in a solution of corrosive sub- 

 limate, and afterwards in a solution of the colouring matter, acquired 

 a permanent red tinge, which remained unaltered by washing with 

 soap. 



The author has, therefore, considerable hopes that this substance 

 may be of some utility in the art of dyeing ; and he remarks, that 

 blood has, in fact, been already employed by the Armenian dyers, 

 along with madder, to ensure the permanency of the colour. 



Observations of a Comet, with Remarks on the Construction of its dif- 

 ferent Parts. By William Herschel, LL.D. F.R.S. Read De- 

 cember 19, 1811. {Phil. Trans. 1812, p. 115.] 



The author first gives us, in detail, the succession of appearances 

 that he has observed respecting this comet and its various parts, con- 

 sisting of a planetary body, perceptible only by the best telescopes, 

 in the luminous spherical head, which to the naked eye appears as 

 a nucleus. The head is surrounded by an envelope that is hemisphe- 

 rical on the side towards the sun, but extends in an opposite direc- 



