233 
of Edinburgh, Session 1867-68. 
doubts having been suggested until comparatively recent times. 
The earliest authorities on the subject are Diodorus Siculus, Lucian, 
Galen, Dion Cassius, and Pappus. It is much to be regretted that 
a work by the last named author on the Siege of Syracuse is now 
lost ; but Zonares and Tzetzes, writers of the 12th century, in 
whose time it w r as extant, give quotations from it. That of the 
latter, translated pretty literally, runs thus £< When Marcellus 
had placed the ships a bow shot off, the old man (Archimedes) con- 
structed a sort of hexagonal mirror. He placed at proper distances 
from the mirror other smaller mirrors of the same kind, which were 
moved by means of their hinges and certain plates of metal. He 
placed it amid the rays of the sun at noon, both in summer and 
winter. The rays being reflected by this, a frightful fiery kindling 
was excited on the ships, and it reduced them to ashes, from the 
distance of a bow shot. Thus the old man baffled Marcellus, by 
means of his inventions.” 
At a later period, mirrors similar to that of Archimedes, appear 
to have engaged the attention of Baron Napier of Merchiston, and 
other mathematicians; but strange enough, the famous naturalist, 
Buffon, was the first to establish the practicability, and therefore 
the probability, of the achievement. He employed a combination of 
plane reflectors, consisting of ordinary looking-glasses, eight inches 
by six, attached to a single frame. With forty of these glasses he 
set on fire tarred beech at a distance of 66 feet. A plank smeared 
with tar and brimstone, was ignited at 126 feet, by 98 glasses. 
A combination of 128 glasses, with a clear sun, inflamed very sud- 
denly a plank of tarred fir at 150 feet. In addition to these expe- 
riments made at Paris, about the beginning of April, others were 
made in summer, by which wood was kindled at 200 and 210 feet, 
and silver and other metals were melted at distances varying from 
25 to 40 feet. 
So much for the positive side of the question, let us now briefly 
consider the negative side. 
Descartes and others treated the whole affair of the burning 
mirrors as a fiction, on the gratuitous assumption that the specula 
employed were single parabolic reflectors. A different and more 
valid reason for doubt has arisen from the circumstance, that 
2 H 
VOL. IV. 
