CRYSTALLIZ AT FOX THEORY.

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V particles of carbonate of lime. By artificial means weCari allow the particles of bodies the free play necessary totheir crystallization. Thus a solution of saltpetre exposedto slow evaporation produces crystals of saltpetre; alumCr ystals of great size and beauty may be obtained in aS1 milar manner; and in the formation of a bit of commons Ugar-candy there are agencies at play, the contemplationwhich, as mere objects of thought, is sufficient to make|he wisest philosopher bow down in wonder, and confesshimself a child.

-hhe particles of certain crystalline bodies are found toGrange themselves in layers, like courses of atomic ma-S 0 Qr y, and along these layers such crystals may be easilye Wen into the thinnest laminm. Some crystals possessVnt s Uch direction in which they may be cloven, some® e Yeral; some, on the other hand, may be split with dif-re ut facility in different directions. Bock salt may be^ °ven with equal facility in three directions at right anglese ach other; that is, it may be split into cubes; calcspar|! la y he cloven in three directions oblique to each other;. at is, into rhomboids. Heavy spar may also be cloven11 three directions, but one cleavage is much more perfect,jj. m ° re eminent as it is sometimes called, than the rest.

lca 18 a crystal which cleaves very readily in one di-jUction, and it is sufficiently tough to furnish films of ex-tri 1116 tenilit y : finally, any boy, with sufficient skill, whos a good crystal of sugar-candy in various directionsthe blade of his penknife, will find that it possessesUe dirootiofj i n particular, along which, if the blade of theplat 6 ' Je hhmed and struck, the crystal will split intoes possessing clean and shining surfaces of cleavage,thes ° 6SSOr ® e< %"'ick was intimately acquainted with allthe 86 / aC ^ S ’ an< ^ a great many more, when he investigatedUati ° eaVa h r( ' s l a te rocks; and seeing no other expla-open to him, he ascribed to slaty cleavage a crystal-

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