VOL. XLll.] PHILOSOPHICAL TRANSACTIONS. t)81 



the same piece, and in the same cavity, it appears that the velocities of the 

 bullet, thence arising, are extremely near the subduplicate proportion of those 

 quantities of powder, and this independent of the length of the piece : whence 

 it is confirmed, that the elasticity of fired powder in various circumstances, is 

 nearly as its density ; and this does not only succeed in small quantities of 

 powder, and in small pieces, but in the largest likewise, under proper restric- 

 tions; at least there are experiments which could not be influenced by this 

 theory, where the quantities of powder were above 100 times greater than what 

 are used by this author, and in these trials this circumstance takes place to 

 sufficient exactness. 



It is presumed then, that by this theory a near estimate may be always made 

 of the velocities communicated to shells or bullets by given charges of powder; 

 at least these experiments evince how truly the velocities of small bullets are 

 hereby assigned ; and the author can show by the experiments of others, that 

 in a shell of 13 inches diameter, impelled by a full charge of powder, the same 

 principle nearly holds : it is true indeed, that when the charge is much smaller 

 than the usual allotment of powder, there are some irregularities, which are 

 particularly mentioned at the end of the Qth proposition ; but in the customary 

 charges, the velocities of bullets resulting from all the experiments hitherto 

 made, are really such as the theory laid down in the preceding part of this 

 treatise requires. And it appears, that these velocities are much greater than 

 what they have been hitherto accounted: and there are reasons from the theory 

 to believe, that in cannon-shot the velocities may still exceed the present com- 

 putation. 



With regard to the 2d chapter of this treatise, relating to the resistance of 

 the air, the author has in his preface mentioned his intention of annexing to it 

 a series of experiments, on the real track of bullets, as modulated by that re- 

 sistance : and therefore, as he proposes to complete those experiments* this 

 summer, unless unforeseen accidents prevent him, he chooses to postpone any 

 account of the subject of the 2d chapter till that time. 



Observations of a Comet, made at Vienna, in Feb. 1/43. By the Fa. Frantz. 



N" 470, p. 457. 

 This comet passed through the constellations Ursa Major, Draco, Leo, 

 Virgo, &c. 



* These experiments it neeins were never completed. 

 VOL. Vlll. 4 S 



