to make trial with three or four Emralds, whoſe being true was not doubted, and found them all ſomewhat, though not equally, endow'd with Electricity, which I found to be yet more conſiderable in an Emrald of my own, whoſe colour was ſo excellent, that by skilful perſons 'twas look'd on as a rarity. And though, by this ſucceſs of my inquiry, I perceived I could not, as elſe I might have done, ſhew the Curious a new way of judging of true and falſe Emralds, yet the like way may be, though not always certain, yet oftentimes of uſe, in the eſtimating whether Diamonds be true or counterfeit, eſpecially, if, being ſet in Rings, the ſureft way of trying them cannot conveniently be employed. For whereas Glaſs, though it have ſome Electricity, ſeems, as far as I have obſerved, to have but a faint one, there are often found Diamonds that have a very vigorous one. And I do not remember I met with any Electrick of the ſame bulk, that was more vigorous than a rough Diamond I have, which is the ſame that I formerly mentioned to have moved a Needle above three minutes after I had ceaſed to chafe it. And this brings into my mind, that it has been obſerved, that Diamonds draw better whilſt rough, than they do after they are cut and
poliſh'd,
