I

According to what was said of such cases by one better than we are:

the precious stone,

The emerald, accounted of much worth,

Is shamed by artful mimicry in glass,

whenever he is not by, who hath power to prove it, and

Detect the craft so cunningly devised.

Again, when

alloy of brass

Is mixed with silver, who that simple is

Shall easily be able to assay?

IRENÆUS Heresies, preface to Bk. i.