The microscope and its revelations . may bewatched under the microscope with the gTeatest facility; all that is necessary beingto lay on a slip of glass,previously warmed, a sa-turated solution of thesalt, and to incline thestage in a slight degree,so that the drop shallbe thicker at its lowerthan at its upper crystallization willspeedily begin at theupper edge, where theproportion of liquid tosolid is most speedilyreduced by evaporation,and will gradually ex-tend downwards. If itshould go on tooslowly, or should ceasealtogether, whilst yet alarge proportion of theliquid remains, the
The microscope and its revelations . may bewatched under the microscope with the gTeatest facility; all that is necessary beingto lay on a slip of glass,previously warmed, a sa-turated solution of thesalt, and to incline thestage in a slight degree,so that the drop shallbe thicker at its lowerthan at its upper crystallization willspeedily begin at theupper edge, where theproportion of liquid tosolid is most speedilyreduced by evaporation,and will gradually ex-tend downwards. If itshould go on tooslowly, or should ceasealtogether, whilst yet alarge proportion of theliquid remains, the slide may be again warmed, and thepart already solidified may be redissolved; after whichthe process wiU recommence with increased rapidity.—Thisinteresting spectacle may be watched under any microscope;and the works of Adams and others among the older ob-servers, testify to the great interest which it had for becomes far more striking, however, when the crystals, asthey come into being, are made to stand-out bright upon a. ;jstiiUized Silver. CEYSTALLIZATION OF SALTS. 763 dark ground, by the use of the spotted lens, the paraboloid,or any other form of black-groimd illumination; still morebeautiful is the spectacle when the Polarizing apparatus isemployed, so as to invest the crystals with the most gorgeousvariety of hues. The following list specifies the salts andother mineral substances, whose crystalline forms are mostinteresting. When these are viewed with polarized light,some of them exhibit a beautiful variety of colours of theirown, whilst others require the interposition of the seleniteplate for the development of colour. Acetate of Copper of Manganese of Soda of Zinc Agate (transparent sections)Alum Arragonite (transparent sections)Arseniate of PotassBicarbonate of PotassBichromate of PotassBichloride of MercuryBoracic acidBorate of Ammonia of Soda (borax) Carbonate of Lime (from urine ofhorse) of Potass of Soda Chlorate of PotassChloride of Barium of Coba
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