the introductory letter, the writer observes on the resources of ancient
magic:--)

The secret use which was thus made of scientific discoveries and of
remarkable inventions, has no doubt prevented many of them from reaching
the present times; but though we are very ill informed respecting the
progress of the ancients in various departments of the physical
sciences, yet we have sufficient 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