PERPETUAL LAMPS AND ARCHIMEDES.
Stability is not the characteristic of man or his works. The discovery of
perpetual motion has long been the object of our ambition; the sole
approach to which appears to be our futile perseverance in the pursuit.
Let us be content, therefore, with aspiring to duration, a sufficient
triumph for perishable man; and be it noted that this quality, though
impressed by human art upon inert matter, such as the Pyramids of Egypt,
is incompatible with the mutability of our social institutions.
The word perpetual has been too often and too easily applied. The
marvellous is too often substituted for the true, just as great vices are
more widely apparent than great virtues. Who has not heard, for instance,
of perpetual lamps, miraculous as the Wonderful Lamp of the Arabian Tales!
The Pagan priesthood originated these fabulous sepulchral lights; and
those of our own faith who had the weakness to adopt their deception,
endangered our confidence by recourse to unworthy trickeries. Pausanias
mentions a lamp of massive gold, consecrated by Callimachus, and endowed
with such properties as to endure a year without deterioration. Another is
said to have existed in a temple in England. Pope Gelasius affirms, in the
acts of St. Sylvester, that in the Baptistery of Rome, there was a lamp
which had burned without intermission since the reign of Constantine,
viz., half a century. That the dark ages should have admitted such marvels
is not surprising. But one of the illuminati of the sixteenth century,
Fortunio Liceti, composed a treaty concerning the existence of such lamps,
asserting that, upon opening the tomb of the giant Pallas, a lamp was
found which had been burning since the times of the pious Æneas. Another
was stated to have been found in the tomb of Tullia, during the
Pontificate of Paulinus, about fifteen centuries and a half after its
construction. In the reign of Justinian, a portrait of our Saviour was
discovered at Edessa with a lamp unrenovated from the period of the
Christian era, that is, during a period of five centuries. Fortunio cites
a vast number of similar examples; from which he infers that the Romans
possessed the secret of making inextinguishable lamps. His conviction
upon the subject is such, that he attempts to explain the possibility by
a theory that the combustion of the smoke produced fresh oil for the
nourishment of the lamp. This must surely have been the far-famed oil of
the Phoenix.
It is scarcely worth while to controvert such absurdities; the fable of
perpetual lamps having faded before the dawning light of reason. Is it,
however, to be credited, that the genius of Descartes did not secure him
against this vulgar error? The views of that great man on the subject
deserve to be quoted as a proof of the aberrations to which superior minds
are subject. "After considering the fire produced by gunpowder," says
Descartes, "which is the most transitory in existence, let us inquire
whether there can exist a flame, enduring without the aid of fresh matter
for its support, like those found in the tombs of the ancients shut up for
centuries. I will not vouch for the truth of their existence; but think it
possible that in a vault so close that the air could never be disturbed,
the parts of the oil transformed into smoke, and from smoke into soot,
might, by sub-formation, arch themselves over the flame so as to protect
it from the air, and render it so weak as to lose the power of consuming
either oil or wick, so long as there should remain a shred unburnt by
which means the primary element existent in the flame and identified with
the little self-formed vault, might revolve therein like a little star.
It necessarily follows that the second element became expelled on all
sides, while trying to penetrate the pores still remaining in the little
dome; and the flame which remained feeble while the place was closed,
brightened the moment it was opened, and the external air admitted. The
surrounding smoke dispersed, the flame recovers its vigour for a moment,
and then expires. Such lamps, in fact, become perpetual, only from having
exhausted their oil."
This statement is extracted from the Fourth Book of the Principles of
Philosophy of Descartes. In spite of the respect due to his name, we see
in it only a tissue of verbosity exhibiting science at a nonplus, and
advocating a groundless theory. But such a chimera on the part of so
eminent a man, ought to afford consolation to second-rate capacities, as a
proof that no one is exempt from delusions.
From Descartes, let us turn to Archimedes, who conferred ten-fold power
upon the arm of man by arming it with the lever; and with becoming
deference avow our want of faith in the mirror by the burning reflections
of which he managed to destroy the Roman galleys!
"Combustible bodies," observes Descartes, "cannot be ignited by means of
mirrors unless comprehended in the necessary focus. Geometry shows us that
the distance of a focus of a concave mirror is equal to the half of its
sphere; that is, if the mirror have been set from a sphere of a radius of
one foot, the distance of the focus will be of six inches. A sphere having
a radius of one foot, gives, therefore, but a focus of six inches, so that
to establish a focus at two hundred feet, would require a sphere with a
radius of four hundred feet, or eight hundred in diameter! Besides, how
could Archimedes procure such a mirror, when the art of casting mirrors
was unknown, and the manufacture of glass in its infancy? That it was a
metallic mirror is difficult to conceive. Such were the solutions
attempted of an insoluble problem. Doubtful anecdotes are so often and so
boldly adopted by the authors of antiquity, that we may regard as
unsubstantiated all facts upon which they are silent. Neither Livy,
Diodorus, nor Polybius mention the mirror of Archimedes; so that the
invention is probably modern, and most likely a fable of the sixteenth
century, prolific in inventions and amplifications. The press, then in its
infancy, delighted in the propagation of marvels and fallacies attributed
by their imbecile authors to the ancients, so as to assign them some
semblance of truth. Among such inventions was the mirror of Archimedes.
Gallienus, indeed, mentions the burning of the fleet by Archimedes; but is
mute on the subject of the mirror, which he could scarcely have omitted,
had the fact been genuine. Tzetzes and Zoronas are the first who mention
it; the former in the following words:
"When the Roman galleys were within arrow-shot, Archimedes caused an
hexagonal mirror to be made, and other smaller ones, each having
twenty-four angles, which were placed at a proportionate distance, and
could be worked by their hinges and certain metallic blades; their
position being such that the rays of the sun reflected upon their surface,
produced a fire which destroyed the Roman galleys, though at the distance
of a bow-shot."
The author does not condescend to give his authority; relying for the
evidence of his authenticity upon his confederate, Zoronas, who relates
that, at the Siege of Constantinople, under the reign of Anastasius,
Probus burnt the enemy's fleet by means of brazen mirrors. He states that
the invention was not new, but belonged to Archimedes, who, as testified
by Dion, used them at the Siege of Syracuse by Marcellus.
The mutual confederacy of a couple of mountebanks is as easily understood
as it would be susceptible of annihilation; did not such men as Kirchen
and Buffon become sureties, not for what Archimedes has done, but for what
he was capable of effecting. Previous to Descartes, the former had
asserted the possibility of igniting combustible matter at a great
distance by means of small plane mirrors, which could be managed so that
the rays might be directed upon any given object. This was simply a
theory; but Buffon decided upon making the experiment, the result of which
is well known. He caused to be constructed one hundred and sixty-eight
little mirrors six inches by eight, and directing their rays towards a
point, succeeded in igniting a body at a considerable distance. By this he
discovered a new principle, viz: that the action of the solar rays
reflected is in direct ratio of the diameter of the focus; proving,
moreover, that by multiplying the mirrors, an indefinite line of
combustion might be established.
Can we infer, however, from these experiments of Buffon, that Archimedes
actually destroyed the Roman galleys? We think not; considering the
silence of the Roman writers on the subject, and the progress of science
in the time of Buffon, with reference to its discoveries in the time of
the Siege of Syracuse by Marcellus. Whether this mirror existed or not,
however, Archimedes must be admitted to be one of the greatest geniuses
the World of Science ever produced.