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INFERENCES.

sion either by itself or with the black oxid of manganese, lime,and other such matters. Why it retains the nature of crude ironwhen fused under charcoal dust. Why by successive ignitionsit becomes progressively more ductile and more difficultly fusi-ble. Why it yields ductile iron if melted with oxid of iron.Why ductile iron when fused with and under a stratum of pow-dered charcoal may be converted either into crude iron or intosteel. Why ductile iron becomes steel by cementation withcharcoal. Why ductile iron is never changed into steel by mereigniting and forging; and finally, why ductile iron may in somemanner assume the nature of steel, if it be smelted with blacklead under a cover of powdered charcoal.

The habitudes of the different varieties of iron that have tillnow occupied our attention are not confined within narrowlimits ; and for this reason there are innumerable gradations tobe met with, beginning from the black crude iron, to the mostpure and ductile bar iron.

The knowledge, treatment, and modifications of iron in itsdifferent states have great influence on die happiness and powerof nations. The perfection of iron-works follows the degree ofthe civilization of man. Under the form of cast-iron, it servesto construct numbers of machines and utensils. In bar-iron itserves for innumerable purposes: it unites force and resistanceto flexibility and spring. In steel it is fitted not only for thegrossest purposes of mechanical machinery, but also for thosewhich are the nicest and most delicate, as we see in the instru-ments of anatomists, engravers, See. for which uses the odiermetals, on account of their inferior hardness, cannot be employ-ed. The capability of acquiring the still inexplicable property,called the magnetic power, has given birth to an important in-strument, which has opened inexhaustible sources of industryand wealth to nations—the mariners compass; yet in its non-me-tallic state its uses are many and incalculable. For instance it iscapable of yielding the most beautiful colours, Prussian blue,black dyes, See. In medicine it renders services equally nume-rous and important.