the' Zeolite Family. ' S6d 



of oxygen ; and of these, alumina, peroxide of iron, &c. are 

 examples *. As these views respecting the constitution of the 

 latter class of oxides have not been adopted by the chemists 

 of this country, they appear also to have been slow to embrace 

 the theory of replacement in mineral substances which has been 

 considered as essentially connected with these views. 



The objections also, which have been urged against the parti> 

 cular instances brought forward by Mitscherlich in support of the 

 analogous, or, perhaps to a certain extent, identical theory of 

 Isomorphous substances, as first promulgated by him, have had 

 a similar effect on the chemists of this country. Yet still it is 

 perhaps worthy of attention, whether the doctrine of the replace- 

 ment of certain classes of ingredients in mineral substances, with- 

 out really changing the nature of these substances, is not wholly, 

 or to a considerable extent, borne out by facts, as appearing from 

 the actual analysis of various minerals; and whether this doctrine 

 may not therefore be regarded as a law either of universal appli- 

 cation in the Mineral Kingdom, or at least as holding good with 

 respect to certain species of mineral substances. If, after careful 

 observation, this should be held to be the case, it will then per- 

 haps be time enough to enquire, whether this law necessarily in- 

 volves the truth of the hypothesis, that certain oxides contain 

 one atom of oxygen only, whilst certain others contain three 

 atoms, or whether it may not be connected with some other pe- 

 culiarities, at present unknown, in the nature of these oxides. I 

 may at least, I think, suggest, without professing myself a con- 

 vert to the theory of replacements, that, in so far as its truth or 

 falsehood is capable of being established hy facts, it merits more 

 attention that it has hitherto received from the chemists of 

 Great Britain. Any one, I think, must be satisfied of this, who 

 attends to the well-known and remarkable illustration of the 

 doctrine, in the analysis of thirteen different varieties of garnet 

 by Wachtm.eister -f, where the replacement of the two classes of 

 ingredients was found to occur in a very singular manner ; or to 



• The original doctrine of Berzelius was, that the substances constituting 

 the fonner of these classes contained two atoms of oxygen, but he now holds 

 that they contain one only. 



t See au abstract of these analyses in the Anuais of Ptilosophy, No. v. 

 vol. ix. 



