_The Burning Glasses of Archimedes and Proclus._
LXI. The artifice, by which we are told Archimedes burnt the Roman ships,
which, under the command of Marcellus, were employed in the siege of
Syracuse, has been plausibly represented by historians; and has exercised
the ingenuity of not a few _mathematicians_, to find out how this could
have been effected. It is said, Archimedes did it by concentrating the
rays of the sun in the focus of a large burning glass, and reflecting
them on the ships. I judge, that this narration, although so much
vulgarized in authors, is fabulous; and my reason for being of this
opinion is, that none of the antients who treat of the siege of Syracuse
relate any such circumstance; nor does there appear the least mention of
the burning-glasses of Archimedes, either in Polybius, Livy, Plutarch,
Florus, Pliny, or Valerius Maximus: and it is very remarkable, that the
three first of these authors, treat very largely and particularly of the
machinations and contrivances which Archimedes made use of to destroy
the Roman ships. How then is it credible, that they should all have been
silent about the effect of the burning-glasses, if there had been any
such things used?
The first author in whom we meet with this information is Galen; to whose
testimony, besides his not being a historian by profession, and having
wrote four hundred years after the siege of Syracuse, may be made another
objection; which is, that he does not assert the thing positively, but
only speaks of it in the general terms of its being so said.
LXII. Thus much for the fact; but, with regard to the possibility of
executing the deed, the mathematicians who have disputed on the subject
are of various opinions, some denying the possibility, and others
affirming it. All the difficulty in the execution seems to depend upon
the distance of the ships from the walls, which some suppose to have
been so great, that it was next to impossible to make a burning-glass
of such a size that the focus of it would have been capable of reaching
them. It is proper to observe here, that the distance to which the
focus or burning point may be extended, bears a certain proportion to
the diameter of the glass. Some have fancied that they had found out a
contrivance, by which the burning-glass might be made to set fire to
a thing at any given distance; but the best mathematicians consider
as chimerical, the infinite extension of the line of the focus; which
being excluded, and the supposed distance the moderns allow to have
been between the ships and the walls established, which, according to
Father Kircher, who extends it the furthest, was thirty geometrical
paces; it will hardly be found possible to have made a glass that was
large enough to set the ships on fire. To obviate this difficulty, some
have imagined they had recourse to the invention of many concave or
parabolical glasses, which reflected the rays from one to the other. But
I can’t help remarking on the mathematicians, who have treated of this
matter, a great mistake, which they have been led into with regard to the
supposed distance: for Polybius, Livy, and Plutarch, place the ships so
near the walls, that the people on board them were capable of annoying
the besieged with darts and other missive weapons tipped with iron; and
Polybius goes so far as to say, that with ladders resting on the ships,
the Romans could pass from them to the walls; and if this was the fact,
there was no necessity to have recourse to a burning-glass of so large
a size, that it was next to impossible to have made, in order to set
fire to the ships. Thus it appears to me, that we may safely deny the
fact in opposition to the generality of the historians; and affirm the
possibility, in opposition to the common opinion of the mathematicians.
_Vid. Buffon._
LXIII. It is said of a celebrated mathematician named Proclus, who lived
in the reign of the emperor Anastasius, that he did the same with
Archimedes, that is, with burning glasses, set fire to the ships with
which count Vitalianus besieged Constantinople. The silence of all
the authors with respect to this matter, who were prior to Zonaras,
and who gave accounts of the war between Anastasius and Vitalianus,
is an argument against the probability of it; for neither Evagrius
the scholiast, who lived in the same century that war happened, which
was the sixth, nor count Marcelinus, who flourished in the seventh,
nor Cedrenus, who wrote in the eleventh, speak a word of Proclus or
his burning-glasses. Zonaras, who lived in the twelfth, is the first
who gives any relation of them, though he does not positively affirm
the truth of it, but only tells us the story with an _it is so said_,
or reported. I add to this, that count Marcelinus informs us count
Vitalianus did not raise the siege of Constantinople because his fleet
was destroyed, but because the emperor Anastasius solicited and procured
the raising the siege, by means of a large sum of money, and other
magnificent presents which he sent to count Vitalianus.
LXIV. I recollect also, that in a work called The Theatre of Human Life,
we find Evagrius, and Paul the Deacon, quoted in favour of the story of
the burning-glasses of Proclus; but neither in one or other of these
authors is there the least mention of such glasses; from whence we may
infer that these great compilations are exposed to great mistakes.