cient evidence that almost every branch of
knowledge had contributed its wonders to the magician's budget, and we
may even obtain some insight into the scientific acquirements of former
ages, by a diligent study of their fables and their miracles.

(In the second letter, upon Ocular Illusions, is the following beautiful
passage on the Eye:--)

This wonderful organ may be considered as the sentinel which guards the
pass between the worlds of matter and of spirit, and through which all
their communications are interchanged. The optic nerve is the channel by
which the mind peruses the hand-writing of Nature on the retina, and
through which it transfers to that material tablet its decisions and its
creations. The eye is consequently the principal seat of the
supernatural. When the indications of the marvellous are addressed to us
through the ear, the mind may be startled without being deceived, and
reason may succeed in suggesting some probable source of the illusion by
which we have been alarmed. But when the eye in solitude sees before it
the forms of life, fresh in their colours and vivid in their outline;
when distant or departed friends are suddenly presented to its view;
when visible bodies disappear and reappear without any intelligible
cause; and when it beholds objects, whether real or imaginary, for whose
presence no cause can be assigned, the conviction of supernatural agency
becomes under ordinary circumstances unavoidable. Hence it is not only
an amusing but an useful occupation to acquire a knowledge of those
causes which are capable of producing so strange a belief, whether it
arises from the delusions which the mind practises upon itself, or from
the dexterity and science of others.

(The Optical phenomena, as might be expected, are most abundant, as they
include the subject of spectral illusions and apparitions, and natural
phenomena marked with the marvellous. The properties of Sound are next
in interest; among them we find explained the wonder of singers breaking
glasses with their great power of voice; the automaton flute-player,
talking engines, echoes, &c. The Mechanical causes are less numerous:
among them we are glad to see _noticed_ the feat of lifting heavy
persons, which we ourselves have often seen accomplished; but Sir David
Brewster does not supply the cause. As the matter may be new to many
readers, we quote the two relating pages.)

One of the most remarkable and inexplicable experiments r