77 



s, resolved to prove the possibility of this ; 

 and having by means of a number of plain mirrors, 

 collected the sun's rays into one focus, he so aug- 

 mented the solar heat, that at last by increasing the 

 Dumber of mirrors, he could produce the most intense 

 degree of it. 



3. Tzetzes' description of the glass Archimedes 

 made use of, is indeed proper to raise such an idea 

 as Kircher entertained. That author says, Archi. 

 medes set fire to Alareel'ns' navy, by n cans of a burn, 

 ing glass composed of small square mirrors, moving 

 every way upon hinges; which when placed in the 

 sun's ray, directed them upon he Roman fleet, so as 

 to reduce it to ashes at the distance of a b >w~shot. 

 It is probable M de Btiti\.n avail, d himself of this 

 description, in cousin,; ' : n% his burning glass, com- 

 posed of l&s lsir!e plain mirrors, which produced 

 so considriabie a hi-ai, a* to set v* ood in flanu'S at 

 the ditcince o( two ium , t! ;v:d nine feet; melt 

 lead, at that of one liuuui-cti aui twenty, and silver, 

 at that of fifty. 



4. Another testimony occurs which leaves not the 

 least doubt in this case. Anthemius of Trahes in 

 Lydia, a celebrated architect, a >le sculptor, and 

 learned mathematician, who in the Emperor Justi- 

 nian's tirae built the church of St Sophia at Con- 

 stantinople, wrote a small treatise in Greek, winch 

 is extant only in manuscript, entitled Mechanical 

 Paradoxes, That work among other things, has a 

 chapter respecting burning glasses, where we meet 

 with the most complete description of the requisites 

 that Archimedes must have been possessed of ta 

 enable him to set fire to the Roman fleet. He begins 

 with this enquiry, u How in any given place, at a 

 bow shot's distance, a conflagration may be raised by 

 means of the sun's rays?" And immediately lays it 

 down as a first principle the situation of the place 

 must be suck that the rays of the sun may be 



