Evening star. [volume] (Washington, D.C.) 1854-1972, 1914-10-18
BURNING MIRRORS
TT is written that when the Roman ships

TT is written that when the Roman ships
besieged Syracuse, Archimedes burned
them to ashes by means of mirrors, and
Proclus is also said to have destroyed the
navy of Vitalian when those galleys besieged
Byzantium, by means of burning glasses.
And there is the wonderful story of Ptole-
my's mirror which, placed on the tower of
the Pharos, at Alexandria, represented ac-
curately everything that transpired in all
Egypt, on both land and water, with which
an enemy's feet could be seen one hundred
leagues away.
Descartes branded the story of Archi-
medes' mirrors as fabulous; but Kircher be-
lieved it to be true and made many expert
ments to prove his contention. He tried the
effect of a number of plane mirrors, and
with five of the same size, placed in frame,
contrived to throw the rays reflected from
them to the same spot at distance of more
than one hundred feet, and the degree of
heat obtained led him to conclude that by
increasing the number of mirrors he could
increase the heat to any desired degree. He
made voyage to Syracuse to inform him
self exactly of local conditions. From his
observations he was convinced that the
Roman galleys could not have been more
than thirty PAGES, or less than hundred
feet, from the place where Archlmedes
mounted his unique engine of destruction.
Button constructed machine consisting
of number of mirrors, and in his first exper
ment, using twenty-four mirrors, he set fire
to pitch and tow at distance of seventy
feet. Then, with a kind of polyhedron, con-
sisting of one hundred and sixty-eight pieces
of plain looking glass, each piece SIX inches
square, boards of beechwood were set on
fire at distance of one hundred and sixty
five feet. Next there were employed three
1,,,,, oh,
inches long and six broad, and with all the
mirrors in use wood could be ignited at a dis
lance of two hundred and twenty-five feet.
The last machine of this nature constructed
by Button contained four hundred mirrors,
each six inches square, and with the rays
from this he could melt lead and tin at dis
lance of one hundred and fifty feet.
THE most powerful burning mirror of mod
ern times was constructed by one Penn,
an English artisan. He succeeded in produc-
ing burning lens no less than three feet in
diameter, and this cost the man who was
financing the experiment upward of thirty
five hundred dollars. Its power was astonish-
ing, and the hardest and most solid sub
stances, such as iron, flint, and steel, melted
like wax when exposed to its immense focus,
only a few seconds being required. A diamond
weighing ten grains was exposed to the rays
for thirty minutes and was reduced to six
grains by the process. During the operation
the stone opened and foliated like the leaves
of flower and emitted whitish fumes; but
when it had closed again it still bore polish,
and was identical in shape, though four
grains lighter and proportionately smaller.
Ten cut garnets melted and ran together in
few seconds. In fact nothing was found
that could resist the terrible heat generated.
This remarkable machine was afterward
taken to China by an officer connected with
the British Embassy, and finally lost sight of.