VOL. XLVIII.] PHILOSOPHICAL TRANSACTIONS. 489 



matter himself; which led him to make innumerable experiments, to see whether 

 it were possible to be done or not, before he would give any opinion about it ; 

 and at length, when he had commended the parabolical speculum, which he and 

 others were inclined to think the most likely to succeed in such an enterprize ; 

 he was inclined to think that Archimedes made use of such a speculum. 



But soon afterwards he became dissatisfied with this notion, and beginning to 

 make new attempts, he fell upon one which lessened his former good opinion of 

 the parabolical speculum, and made him more sensible of the inconveniencies 

 attending it, or those of any other form, that had any great degree of concavity ; 

 and in short engaged him entirely in favour of his new thought, which was put 

 in execution in the following manner : 



He erected a frame, on which he placed 5 plane specula, of equal given di- 

 mensions, with such inclinations as made them all throw their reflected rays on 

 the same place, at more than 100 feet distance. When he had set the first spe- 

 culum, he went and laid his hand on the place where he caused the rays to fall, 

 and found it warm ; when he added those of the 2d, the heat was doubled ; the 

 3d increased the heat in the same proportion ; and the 4th being added, the heat 

 was scarcely to be borne ; but the 5th made it intolerable. Whence he con- 

 cludes, that, by multiplying those specula, the heat might be so increased, as 

 to set fire to combustible matter at greater distances, according to the number 

 applied. 



Schottus gives the same account of Kircher's experiment. He accompanied 

 him in all his trials, as well as in his journey to Syracuse, after he had brought 

 his plane mirrors to answer his purpose ; and, on viewing the place, they both 

 concluded, that the galleys of Marcellus could not be farther than 30 paces from 

 Archimedes. And yet Schottus declared, that if a concave speculum could be 

 constructed, as large as the rotunda, it could not have a sufficient focus to effect 

 what both Archimedes and Proclus are said to have done. 



Thus we see Kircher had scientifically established the problem, for the con- 

 struction of a burning machine, consisting of any number of plane specula ; 

 which was afterwards further confirmed by BufFon, as appears in 2 letters ; 

 printed in these Trans.* If so, we cannot suppose he could have seen what 

 either Kircher or Schottus had written about it. 



LXXXIII. On several Bones of an Elephant found at Leysdoivn in the Island 

 of Sheppey. By Mr. Jacob, Surgeon al Feversliain. p. 626. 



Three or 4 years before Mr. J. had sent the acetabulum of an elephant, which 



was discovered sticking in the clay, which was partly washed away from the clifti 



i 

 • See page 344 of the 9th vol. of these Abridgments, 



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