It is generally supposed among us that it is only the very finest silver that admits of being laminated, and so converted into mirrors. Pure silver was formerly used for the purpose, but, at the present day, this too has been corrupted by the devices of fraud. But, really, it is a very marvellous property that this metal has, of reflecting objects; a property which, it is generally agreed, results from the repercussion of the air,1041 thrown back as it is from the metal upon the eyes. The same too is the action that takes place when we use a mirror. If, again, a thick plate of this metal is highly polished, and is rendered slightly concave,1042 the image or object reflected is enlarged to an immense extent; so vast is the difference between a surface receiving,1043 and throwing back the air. Even more than this—drinking-cups are now made in such a manner, as to be filled inside with numerous1044 concave facets, like so many mirrors; so that if but one person looks into the interior, he sees reflected a whole multitude of persons.

Mirrors, too, have been invented to reflect monstrous1045 forms; those, for instance, which have been consecrated in the Temple at Smyrna. This, however, all results from the configuration given to the metal; and it makes all the difference whether the surface has a concave form like the section of a drinking cup, or whether it is [convex] like a Thracian1046 buckler; whether it is depressed in the middle or elevated; whether the surface has a direction1047 transversely or obliquely; or whether it runs horizontally or vertically; the peculiar configuration of the surface which receives the shadows, causing them to undergo corresponding distortions: for, in fact, the image is nothing else but the shadow of the object collected upon the bright surface of the metal.

However, to finish our description of mirrors on the present1048 occasion—the best, in the times of our ancestors, were those of Brundisium,1049 composed of a mixture of1050 stannum and copper: at a later period, however, those made of silver were preferred, Pasiteles1051 being the first who made them, in the time1052 of Pompeius Magnus. More recently,1053 a notion has arisen that the object is reflected with greater distinctness, by the application to the back of the mirror of a layer of gold.1054