Scientific Intelligence — Arts. 401 



may be saved without any detriment to the profession ; 2dly, That 

 the interior and exterior of houses may be painted without the least 

 risk of the colours changing or blackening by sulphurous emanations ; 

 3dly, That pictures will be no longer liable to change their appear- 

 ance and harmony with the lapse of time, as has happened with so 

 many pictures of the old masters. 



M. Leclaire constantly employs about two hundred workmen in 

 Paris. From the time that he substituted zinc-white for white-lead, 

 not only has he never had a case of lead-colic, but he affirms that 

 no indisposition has at any time appeared among his workmen which 

 can be attributed to their profession. The work has been entrusted 

 to the examination of a commission .-^i^ro?7i L'Institut, No. 734, 

 January 1848, p. 30. 



19. Preparation of a Substitute for Horn. By M. Rockon. 

 (Voigt. Mag. de Naturk. und Revue Scient,, Feb. 1846, p. 25(5.) — In 

 many of the arts, more especially where steel instruments are manu- 

 factured, glass windows are of great inconvenience, owing to frequent 

 breakage by fragments of steel. The substitution of horn is at- 

 tended with some inconvenience, principally on account of its want 

 of transparency. A substitute is proposed to be made by very light 

 cloth or wire-gauze, composed of fine brass wire, which is to be im- 

 mersed repeatedly into a solution of isinglass until all the meshes 

 are filled, and a sufficient thickness acquired, after which it is 

 covered with a coat of copal or other varnish to protect it from the 

 weather. 



20. 0?j the Colouring Principles of some of the Lichens. By Dr J. 

 Stenhouse. — The lichens, it is well known, yield no colour to water ; 

 and it is difficult to imagine how the Celtic inhabitants of the High- 

 lands of Scotland were led to look to so unpromising a source for 

 some of the brightest colours which they have long imparted to their 

 national tartans. The father of the late C. Mackintosh and his 

 partner, Mr Cuthbert Gordon, first added them to the chemical arts, 

 about the middle of the last century, probably availing themselves of 

 the indigenous processes ; and the article known by the name of 

 Cudbear (a corruption of the Christian name of Mr Gordon) is still 

 manufactured by their representatives in Glasgow. The researches 

 of Heeren, Dumas, Kane, Schunck of Manchester, and other chemists, 

 led to the discovery of several organic principles in these lichens, 

 chiefly of a neutral or acid character, themselves colourless, but con- 

 verted by ammonia into the delicate reds and purples of archilo, lit- 

 mus, and Cudbear. Dr Stenhouse has been enabled to add largely 

 to the number of these principles, and to illustrate their singular re- 

 lations, chiefly from having discovered the proper mode of extracting 

 them from the lichens ; which is by means of hot-water and lime, 

 and not by means of boiling water, as hitherto practised. Plants, 

 botanically the same, but from different localities, are here found to 



VOL. XLIV. NO. IvXXXVIII. — APRIL 1848. 2c 



