a man may sit in the middle of the machine, turning an engine, by which
wings artificially disposed are made to beat the air after the manner of
a bird in flight. Also, an instrument, small in size, for raising and
depressing almost infinite weights, than which nothing on occasion is
more useful: for, with an instrument of three fingers in height, and of
the same width, and of smaller bulk, a man might deliver himself and his
companions from all danger of prison, and could rise or descend. Also,
an instrument might be easily made by which one man could draw to
himself a thousand men by force and against their will, and in like
manner draw other things. Instruments can be made for walking in the sea
or in rivers, even at the bottom, without bodily risk: for Alexander the
Great made use of this to see the secrets of the sea, as the Ethical
Astronomer relates. These things were made in ancient times, and are
made in our times, as is certain; except, perhaps, the machine for
flying, which I have not seen, nor have I known any one who had seen
it, but I know a wise man who thought to accomplish this device. And
almost an infinite number of such things can be made; as bridges across
rivers without piers or any supports, and machines and unheard-of
engines." Bacon goes on to speak of other wonders of Nature and Art, to
prove, that, to produce marvellous effects, it is not necessary to
aspire to the knowledge of magic, and ends this division of his subject
with words becoming a philosopher:--"Yet wise men are now ignorant of
many things which the common crowd of students [_vulgus studentium_]
will know in future times."[40]

It is much to be regretted that Roger Bacon does not appear to have
executed the second and more important part of his design, namely, "to
assign the causes and methods" of these wonderful works of Art and
Nature. Possibly he was unable to do so to his own satisfaction;
possibly he may upon further reflection have refrained from doing so,
deeming them mysteries not to be communicated to the vulgar;--"for he
who divulges mysteries diminishes the majesty of things; wherefore
Aristotle says that he should be the breaker of the heavenly seal, were
he to divulge the secret things of wisdom."[41] However this may have
been, we may safely doubt whether the inventions which he reports were
in fact the result of sound scientific knowledge, whether they had
indeed any real existence, or whether they were only the hal