In the following pages (Intended as an APPENDIX to theirDictionary of Chemistry and Mineralogy ) the authors have endea-voured to give a perspicuous and sufficiently detailed account of the variousand highly important discoveries by which the science has been enrichedduring the few years that have elapsed since the publication of their formervolumes.

Considerable pains have been taken in verifying calculations ; incollecting valuable but diffused information into one focus; in stripping it of

the occasional acerbity of controversy; and in moulding the whole to that

.

form of practical utility, which may best secure it from being superceded byfuture discoveries.

We trust that the purchasers of the Dictionary will not find thepresent Supplement unworthy of their notice.