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Depbiogijiicated Air. 22$

os air, all of which was fixed air, but Witha large residuum, about a third of thswhole, phlogisticated air.

As the common rust of iron contains agood deal of phlogiston, 1 did not expect:any better result from this experiment.But having, in some measure, purified itby this process, I put more oil of vitriolto what remained of the rust of iron, andthen I got from it only a little fixed air,and sixteen ounce measures of dephlogisti^cated air.

It is evident both from these experi-ments with the vitriolic acid, and thosecited in my second volume with spirit osnitre, that the earth of iron is easily con-verted into air ,• provided (which I thinkthe most probable) that any earth enters intothe composition of air. Should it be ofthis kind of earth that the bulk of atmo-spherical air in fact consists, it may perhapshelp to account for the magnetism of thewhole globe of the earth. This hint wassuggested to me by Mr. Michell.

a.

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