5S Lord Napier's different Contrivances 



convinced most learned men that the renowned anticnt 

 rcaily performed the great exploit recorded of him. " The 

 discovery," says the excellent Maupcritus, " of the mirror 

 of Archimedes, which has been made by M. dc Buffon, 

 shows us that we might construct burning: towers or am- 

 phitheatres covered with mirrors, v.hich would produce a 

 fire whose violence would have no other limits, so to speak, 

 than those of the sun itself*." Fortune, leisure, and ge- 

 nius, are necessary to the success of all such experiments. 

 Lord Napier possessed these mdispcnsable requisites as well 

 as the count de Buftbn ; and when we consider wliat has 

 been actually done by the French philosopher, and invented 

 in far more arduous departments of science bv the Scottish 

 one, we have no right to doubt that he could actually have 

 Yerified the first proposal of his memoir. His expression 

 ** at any appointed distance," can only mean such a di- 

 stance as might be reasonably prescribed in a case of this 

 kind. 



II. Our Illustrious author's second proposal has the ap- 

 pearance of far greater difficulty than the first, and, as far 

 as I know, can derive little or no support from the colla- 

 teral evidence of other experiments antient or modern. 

 Paulian, in the article already cited, speaks, in general 

 terms, of kindling agaric, and gunpowder, by the rays of 

 burning charcoal, collected by one concave and reflected 

 from another; adding, that the experiment succeeds best 

 in the dark. Wolfius is more explicit. On the authority 

 of a philosopher of the name of Zahn, he tells us that this 

 experiment v^-as performed at Vienna, *' ope ditorum specn- 

 lorutii, &c., by means of two concaves of brass. The largest 

 was six feet, and the least three," (whether in diameter or 

 focal distance does not appear,) *' and they were set 20 and 

 24 feet asunder. In the focus of the largest were placed 

 pieces of burning charcoal, and in that of the least a can- 

 dle, whose wick was wrapt round with a thread dipt in 

 sulphur. The result was, that the reflected rays from 

 thercoals lighted the candle f." (The ingenious members 

 of 'the Askcsian Society have very lately fired gunpowder 

 by a similar apparatus.) And Regnault, in the place before 

 quoted, afHrms, that '^ the moderns have spherical con- 

 caves which kindle gunpowder with the ravs of charcoal, in 

 fhe foci of each other, at the distance of 50 French feet," 



* See Lfil. sur te Prcgres cles Sc:eit:es, in Les (Ewj. de Maupcrtuis^ 

 p. 349.. 

 t £/f.w, Malhes, Umv. torn- iji. p. lyi. 



above 



