Stones and Glasses. 269 



Oil stone. Dark greenish grey, from Turkey. 



Pierre a l*eau dur. Greenish, compact, scaly, paler than 

 lancet stone : all are used to sharpen cutlery. 



Muscovy glass, Isiiif/Iass, Talc, Talcum. From Russia, in 

 square lumps, separable into flakes of amazing thinness; used to 

 glaze ships' windows, as not liable to break when great guns are 

 fired ; also in microscopes to confine objects. 



Talc, Uhruc. Imported from the East Indies, in round pieces, 

 separable into scales ; used to silver paper. 



Irish slate, Alwn slate, Lapis Hibernicus. Sweetish, agglu- 

 tinant in bruises, fractures, a spoonful in beer. 



English talc, Asbestus. Fibrous; used to make wicks for 

 lamps, and cloth which is incombustible by a modern heat ; also 

 to absorb oil of vitriol and prevent its being accidentally spilled 

 from the bottles sold with chemical matches. 



LiME-STONE, Lapis calcarius ; Marble, Marmor. Both are 

 used in coarse powder to ascertain the strength of acids, to yield 

 carbonic acid gas while dissolving in them, 100 gr. yielding about 

 100 cub. in., or to make lime : marble powder. 



Stone lime. Oxide of calcium. Calx viva. Calx. From lime- 

 stone, or marble, by a red heat ; corrosive, antacid, depilatory : 

 used for cements, to make lime-water, and render the alkalies 

 caustic: composed of 2*5 calcium, and 1 oxygen ; equiv. 3*5. 



OsTEOcoLLA. Agglutinaut ; used in fractures, 3j, night and 

 morning. 



Gypsum, Sulphate of lime. Used as a cement ; also as a forc- 

 ing manure : composed of 3*5 lime, 5 acid, and 2*JiJ5th water. 



Raw PLASTER OF Paris. Differs from gypsum in contain- 

 ing carbonate of lime, which causes it to set firmer in moulding, 

 and also fits it for slowly absorbing the acid of wine ; it renders 

 cloudy white wines transparent. 



Boiled plaster of Paris, Burned Gypsum. Used as a 

 cement, and to make models of statues. 



Cawk, Heavy spar, Derbyshire ichite, Spathum ponderosum. 

 Sulphas bari/t(P. Found in mines ; used to mix with flake white, 

 to make muriate of barytcs, and lately sold for lapis calaminaris, 

 but it is not soluble in spirit of vitriol. 



Permanent white. Artificial sulphafr of hnrytrs. Precipi- 

 tate muriate of barytes by oil of vitriol, or a solution of Glauber's 

 ^alt ; used to mark jars in laboratories, as it is affected by a very 

 few substances. 



