MR JOHN SCOTT ON THE BURNING MIRRORS OF ARCHIMEDES. 125 



into the field of actual warfare a novel piece of ordnance without subjecting it to 

 a previous trial. Though on this hypothesis the element of success as an engine 

 of war is questionable, the invention of the mirror as a fact in the history of 

 science remains entire. Neither should it be forgotten, as perhaps a reason for 

 the silence of Polybius, Livy, and Plutarch, that with the fall of Syracuse and 

 the death of the illustrous inventor, all definite information relating to the scien- 

 tific principles of the mirror seems to have perished — a result not improbable, 

 when we consider that its application to the art of war would induce the original 

 possessors to retain its construction, as far as possible, a secret in their own 

 hands. Finally, it is an admitted axiom in estimating historical evidence, that 

 the silence of one author respecting an event is never considered sufficient to in- 

 validate a plain and consistent statement of that event made by another. That 

 our conclusions should be formed in strict accordance with the principle enunci- 

 ated, may be made apparent by striking and well-ascertained facts, some of which 

 have been inaccurately recorded, and others altogether omitted by the most 

 reliable contemporary historians. As an instance of the former, modern authori- 

 ties maintain that the account given by Livy of the route by which Hannibal 

 conducted his army across the Alps cannot be reconciled with that by Polybius, 

 and an extract from Sir Charles L yell's " Principles of Geology " will show an 

 historical omission equally inexplicable. Speaking of the first eruption of 

 Vesuvius, he says, " The younger Pliny, although giving a substantial detail of 

 so many physical facts, and describing the eruption and earthquake and the 

 shower of ashes which fell at Stabise, makes no allusion to the sudden overwhelm- 

 ing of two large and populous cities, Herculaneum and Pompeii. In explanation 

 of this omission, it has been suggested that his chief object was simply to give 

 Tacitus a full account of the particulars of his uncle's death. It is worthy of re- 

 mark, however, that had the buried cities never been discovered, the accounts 

 transmitted to us of their tragical end might well have been discredited by the 

 majority, so vague and general are the narratives, or so long subsequent to the 

 event. Tacitus, the friend and contemporary of Pliny, when adverting in 

 general terms to the convulsions, says merely cities were consumed or buried. 

 . . . . Suetonius, although he alludes to the eruption incidentally, is silent 

 as to the cities. They are mentioned by Martial in an epigram as buried in 

 cinders ; but the first historian who alludes to them by name is Dion Cassius, 

 who flourished about a century and a half after Pliny." 



Returning to Buffon's combination of reflectors — when the focus had to be 

 changed, a numerous staff of assistants required about half an hour to re-adjust 

 the mirrors. After all, the superposition of the reflected light would be imperfect, 

 each operator being liable to mistake the deviation of the image reflected by some 

 other glass for that of which he had charge. Peyrard has appended to his trans- 

 lation of the works of Archimedes a memoir of his own, in which he calls atten- 



