§44 PHILOSOPHICAL TRANSACTIONS. [aNNO 1747. 



lie towards mathematics and astronomy; for were not this the case, must it not 

 be surprising, that having, as they say, so long a series of observations in the 

 one science, and of professors in the other, they should never have been able to 

 get beyond the first elements of either? 



It is not his design, he says, to enter into any controversy with the learned 

 fathers of the Society of Jesus; the world has been frequently indebted to thenv 

 for their philosophical labours; and will be so again, when they shall have con- 

 sidered the Chinese history with proper accuracy, and told us in what manner 

 they have been able to preserve accounts and observations of so ancient a date. 

 Public libraries, it is allowed, they have none; nor does it appear they ever had. 

 Where then could things so useless, as the generality must have thought astro- 

 nomical observations, be reposited ? When intrusted to private hands, they must 

 have run great risk of being destroyed by wars, by fires, and in popular commo- 

 tions; which must frequently have happened in so long a course of years. 



Of a new Mirror, which Burns at 66 Feet Distance, invented by M, de Buffon, 

 F. R S. and Member of the Royal Academy of Sciences at Paris. By Mr. 

 Turberville Needham. N° 483, p. 493. 



This instrument may be considered as Archimedes revived; and the credit of 

 antiquity, in this point, is in some measure re-established. This machine con- 

 sists of 140 small plain mirrors, each of about 4 by 3 inches square; they are 

 fixed at about a quarter of an inch distance from each other, on a large wooden 

 frame about 6 feet square, strengthened with many cross bars of wood for 

 mounting the mirrors. Each of them has 3 moveable screws, which the ope- 

 rator commands from behind, so contrived, that the mirror can be inclined to 

 any angle in any direction that meets the sun ; and by this means the solar image 

 of each mirror is made to coincide with all the rest. 



They tried the experiment one morning with 24 only; for no more were then 

 ready for the purpose: the effect was, that in very few seconds of time, a com- 

 bustible matter prepared with pitch and tow, and daubed on a deal-board, was 

 set on fire, and burned vigorously at the distance of Q6 French feet. Judge 

 now of the effect 140 will produce; and whether the invention may not be im- 

 proved to the height of all that has been advanced of Archimedes by the ancients. 

 The only difficulty they found was, to make the solar images of the mirrors coin- 

 cide; but this is owing to the yet imperfection of their method of mounting, 

 which may be easily improved. 



On the same Mirror Burning at 1 50 Feet distance. By the Marquis Nicolini, 



F. R. S. N" 483, p. 495. 



The affair of Archimedes setting the Roman fleet on fire by means of burning 



