Page:Theophrastus - History of Stones - Hill (1774).djvu/199

 -powder is the great Thing in Ue with us on thee Occaions, and next to it Emery; and Emery was alo known to the Antients, and ued by them on the ame Occaions. Diocorides. Heychius.

Cardanus imagines, but erroneouly, that the Porus of the Antients was our Emery; or ele, that our Emery was unknown to them; which is no les an Error: For it is evident, they were well acquainted with its Ues. And as to what he adds, of their working on Gems with the Porus, and Fragments of the Lapis Obdianus, Salmaius, who had certainly read more than mot Men, affirms, he never could find any Account of it among them. Pliny relates, indeed, that Fragments of the harder Kind of the Otracites were ued for this Purpoe; lib. 37. c. 10. Otracia eu Otracites et tetacea durior: altera Achatæ imilis nii quòd Achates politura pinguecit; duriori tanta inet vis ut aliæ gemmæ calpantur fragmentis ejus. And that a Sand prepared from the Porus, was ued for polihing Marble, but not Gems; ''Craior enim harena laxioribus egmentis terit, & plus erodit marmoris, majuque opus cabritie polituræ relinguit. Rurus Thebeicia polituris accommodatur, & quæ fit e poro lapide aut e pumice. For poro lapide, many of the Copies have toro lapide, and duro lapide''; but the concurrent Accounts of other of the Antients determine it to be this particular Stone that is meant. And the ame Author expresly ays, LXXVI. Iron, however, being harder in its Texture than Stone, will cut uch as are both harder and more olid than thee.

LXXVII. There eems, however, yet an Aburdity in this, ince the Whettone has Power upon, and takes off a Part of the Iron Intruments which are harpened on it, and the Intrument may be made to cut and work upon the Whettone; but notwithtanding,