212 ANNUAL OF SCIENTIFIC DISCOVERY. 



erty. The ribbons or zones in the different varieties of chalcedony, 

 which, in the kidney-formed masses of that substance, lie superim- 

 posed, differ in their texture and compactness; but owing to their 

 similarity of color in the natural state, they can only be distinguished 

 from each other with difficulty. The stone is, however, capable of 

 absorbing fluids in the direction of the strata ; this property the strata 

 possess in different degrees ; therefore, if a colored fluid be absorbed, 

 and the quantity taken up by the pores of the stone is different for every 

 stratum or zone, it is clear that a number of tints will be produced cor- 

 responding to the number of zones, each of which will be rendered dis- 

 tinct and colored in proportion to the quantity of fluid it may have 

 absorbed. Thus, a specimen of stone naturally but slightly colored may, 

 by this treatment, be rendered equal to fine stratified chalcedony or 

 onyx, and may be employed equally well in the engraving of cameos, 

 or for any other purpose where the variety of color can be rendered 

 available. The signs of value in these stones, when in their rough 

 state, are recognized by the merchants by an empirical test, which 

 rests upon the property of the absorption of liquids. In the trial, a 

 small piece is broken off that part of the rough stone which is expect- 

 ed to be of marketable value. When polished, this fragment is mois- 

 tened by the tongue ; the buyer then remarks carefully the rate at 

 which the moisture dries away, and also whether the absorption takes 

 place in alternate bands or zones, and in one zone more rapidly than 

 in another. By this they judge of the beauty and value of the stone. 

 London Journal of Arts, Dec. 



ARTIFICIAL FORMATION OF MINERALS IN THE DRY WAY. 



M. DE SENARMONT has been successful in forming several minerals 

 by the humid way, which appear to throw much light on the pro- 

 cesses employed by nature in the formation of mineral veins, and 

 many of the earthy minerals found in the granitic rocks. He incloses 

 in a strong glass tube hermetically sealed the substances to act upon 

 each other, as, for instance, sulphate of iron and carbonate of soda, 

 in solution. The tube, being cautiously sealed, is placed in a gun-bar- 

 rel, half full of water, and this being also closed, the whole arrange- 

 ment is exposed to the action of heat. Double decomposition of course 

 follows the mixing of the above salts ; but under the increased pres- 

 sure and temperature, the carbonate of iron is redissolved, and event- 

 ually deposited in crystals of a grayish white character, which are not 

 altered by exposure to the air. The following is an account of eorne 

 of his results. 



He formed carbonate of magnesia from sulphate of magnesia and 

 carbonate of soda, temperature about 160 C. It was in the state of 

 white crystalline grains, hardly attacked by the acids. 



Carbonate of iron from sulphate of protoxide of iron and carbonate 

 of soda; temperature 150 C., and above. Also, from protochloride of 

 iron and carbonate of lime; temperature between 130 and 200 for 

 twelve, twenty-four, and thirty-six hours. 



Carbonate of manganese from chloride of manganese and carbonate 



