190 Scientific Intelligence^'-^Cheniistry. 



fresh made is transparent, and exhibits no particular structure ; 

 but if kept for some time it loses its transparency, and, by a 

 diange of the arrangement of its particles, its structure gradu- 

 ally changes from compact into stellular radiated. This case is 

 analogous to changes we have observed in minerals, which, al- 

 though solid, and without any particular structure, in the course 

 of time acquire a particular structure, such as the fibrous, radia- 

 ted, or foliated. 



17. Constituent parts" of Magnesian Limestones from the vi- 

 dmty of Jedburgh^ as ascertained by Mr William Copland. 



Carbonate of Lime, - 45 50 53 



Carbonate of Magnesia, - 33 35 15 



Carbonate of Iron, - 16 8 27 



Alumina, - - 6 7 5 



100 100 100 



18. Analysis of a Powder wliich is sold in Paris under the 

 nam£ of Colour^ and used in giving trinket gold the colour of 



fine gold. — Cupidity and ignorance have often issued in com- 

 merce, under different names, a multitude of more or less noxi- 

 ous substances, to which extraordinary properties have been at- 

 tributed ; and the credulous public, having no suspicion of the 

 dangerous qualities which these substances often possess in a 

 very high degree, and according to which they exert a specific 

 agency, are frequently exposed to the most serious accidents. 

 Secret preparations of this kind cannot be too well made known, 

 nor can too much publicity be given to their composition, and 

 the analysis that may be made of them, the knowledge of the re- 

 sults of which maybe so eminently useful to society. The powder 

 which the trinket-manufacturers used to apply for the purpose of 

 colouring gold, was composed of marine salt, nitrate of potash, 

 and alum ; but, for some time back, another substance has been 

 vended, the composition of which is different. This powder is 

 of a dirty white colour, having a tinge of red, its taste is salt, 

 and like that of common sea-salt, but it leaves a disagreeable 

 metalKc taste in the mouth; and it sensibly attracts moisture 

 from the air. Its analysis has furnished the following results. 

 Twenty grammes of it have yielded, 



