“In the following manner we may construct a mirror for seeing a multitude of objects on a plain surface. This kind of mirror, when constructed, is what is called _polyphaton_, that is to say, multiplying, for by opening and shutting, it shows twenty and more images of one single finger. If, therefore, you wish to prepare it, let two brazen or crystal rectangular mirrors be erected on the same base, and let the proportion of length be one and a half of the width, or any other proportion; and let each side for the whole of its length be so connected together that they may easily be shut and opened like a book, and that the angles may be varied, as they are usually constructed at Venice; for if you place _one object opposite to the face of each_, you will see _several figures_; and this in proportion as you shut it closer, and the angle shall be less. But, by opening, _the objects_ will be reduced in number, and the more obtuse the angle under which you see it, the _fewer objects_ will be seen. So if you exhibit your finger _as the object_, you will see nothing but fingers. The right fingers will be seen on the right side, and the left on the left side, which is contrary to the usual custom with looking-glasses; but this happens from the mutual reflexion and repulsion which produce a change of the images.” It is quite obvious, from the preceding passage, that the multiplying speculum described by Porta was not an invention of his own, but had been long made at Venice. In the very next chapter, indeed, where he describes a _speculum theatrale_ or _amphitheatrale_ (the _show-box_ of Harris and other modern authors), he expressly states, that a multiplying speculum was invented by the ancients.—“Speculum autem è planis compactum, cui si unum spectabile demonstrabitur, plura illius rei simulachra demonstrabit, _prudens invenit vetustas_; ut ex quibusdam Ptolemæi scriptis quæ circumferuntur percipitur;” that is, “a speculum consisting of plane ones, which, when one object is presented to it, will exhibit several images of it, was invented by skilful antiquity, as appears from some of the writings of Ptolemy.” This speculum, which consists of several mirrors arranged in a polygon, with the object within it, is characterized by Porta as puerile, and much less wonderful and agreeable than one of his own, which he proceeds to describe. This new speculum consists of ten mirrors, placed within a box, in a sort of polygonal form, with one of the sides of the polygon open. Architectural columns, pictures, gems, pearls, coloured birds, etc., are all placed within the box, and their images are seen heaped together in inextricable disorder, as a whole, but so as to astonish the spectator by their number, and by the arrangement of individual groups. Porta speaks of this effect as so beautiful, “_ut nil jucundius nil certe admirabilius oculis occurset nostris_,”—that nothing more agreeable, and certainly nothing more admirable, was ever presented to our eyes.