On the site of the ancient city of the Aurunci, and on the volcanic phenomena which it exhibits / [Charles Daubeny].

  • Charles Daubeny
Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: On the site of the ancient city of the Aurunci, and on the volcanic phenomena which it exhibits / [Charles Daubeny]. Source: Wellcome Collection.

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    subject of what be has called Isomorphism, we were stopped at the very threshold of Berzelius’ theory, by finding the same mineral to contain, sometimes one base, sometimes another, without any other aj^])arent limitation, except that the proportions they severally bore to each other should be as their a- tomic weights. Thus garnet might contain alumina, peroxide of iron, lime, magnesia, protoxide of iron, severally combined with silica, or any one or more of these bases might be absent, provided only there was one base with three atoms of oxygen combined with two of the negative element, and another with one atom of oxygen united with one of the latter, j)resent in the compound. The difficulty which this occasioned was however removed, when Mitscherlich had shewn, that several bases admitted of being substituted one for the other without destroying the essential character of the crystallization, or producing any further change in it than a slight difference in the angle; the only necessary condition being, that each of the bases so replacing each other should contain an equal number of atoms of oxygen. Thus potass, soda, lime, magnesia, protoxide of iron, &c. may replace each other, as containing each an atom of oxygen, to an atom of the radical present; as likewise may alumina, peroxide of iron, and ])eroxide of man¬ ganese, since they each contain three, to two of base, so that the same mineral admits of a consider¬ able diversity of composition, whilst still retaining its own peculiar crystalline form P Rammelsberg, a disciple of Rose, has proposed a chemical classification of siliceous minerals founded on this principle, which
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