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ALKALI, a mineral salt, found on the shores of severallakes in Lower Egypt , the Borith of scripture, aud known tothe ancients under the name of Natron or Nitre. Alkali, by usdistinguished into Potash and Soda, was also procured by theArabian chemists, from the ashes after the combustion ofvegetables and minerals, and was termed by the RomansLixiviary Ashes, and used by them for the purpose ofscouring cloth, and with oil for ointments ; but the vola-tile salt or alkali procured by the distillation of vege-table, and especially animal matter, is first noticed bymodern chemists about the middle of the last century. Thepurest in which it is known to us is that of a gas, whichreadily unites with water, but unless combined with someother substance, this Alkali has never been procured in a solidstate ; when made to unite with oils, it forms auimoniacalsoaps. Eau de Luce, which is the union of oil of amber withammonia, is first noticed by Dusie, in his “ElaboratoryLaid Open," published in 1758.

ALLEGORY. The practice of Allegorical interpretationwas a favorite mode of delivering instruction in ancient times ;for what we call fables, or parables, are no other than Alle-gories. This method originated among the Egyptians, andwas adopted by the Greek philosophers for the purpose ofgiving a rationale of their faith, and preventing the peoplefrom being shocked at those absurdities which the poets hadintroduced into their religion. The Jews also made use ofAllegories to interpret the sacred writings, in which they werefollowed by the primitive writers on Christianity .

ALLOY. The coins of Philip, the father of Alexander, arethe earliest noticed as having Alloy in them.

ALLUM. This salt, which is of such extensive utility inmany of the Arts and Manufactures, was unknown to the