ON PERCUSSION. Si 



A s coal therefore appears to be the ultimate eifect pro- 

 duced by sulphuric acid upon the resinous bodies, so does 

 the first variety of the tanning substance seem to be the ter- 

 minating product afforded by the same when acted upon 

 by nitric acid. This eifect of nitric acid has been already 

 amply discussed, neither does it appear necessary that I 

 should here repeat the remarks which have been made on 

 some of the simultaneous products, such as the vegetable 

 acids ; but amongst the elfects produced by sulphuric 

 acid, the coal which is formed seems to merit some atten- 

 tion. 



[The remainder in our n€:£t.] 



-1 ■ . ' , ■ 



IV. 



On the Force of Percussion, By William Hyde Wol- 

 L ASTON, M.D. Sec. R.S. Being the Balcerian Lecture 

 zshich was read before the Roi/al Societi/ in the month 

 of November last*. 



HEN different bodies move with the same velocity. Concise state- 

 it is universally agreed that the forces, which they can ex- nient of the 

 crt against any obstacle opposed to them, are in propor- *^^*PV^^ th***^" 

 tiont6 the quantities of master contained in the bodies forces of bodici 

 respectively. But, when equal bodies move with unequal ^" niotio^ 

 velocities, the estimation of their forces has been a sub- 

 ject of dispute between different classes of philosophers. 

 Leibnitz and his followers have maintained that the forces 

 of bodies are as the masses multiplied into the squat^es of 

 their velocities, (a multiple to which I shall for concise- 

 ness give the name of impetus); while those, who are con- 

 sidered as Newtonians, conceive that the forces are in 

 the simple ratio of the velocities, and consequently as the 

 momentum OT qnatititas rnotus^ a name given by Newton 

 to the multiple of the velocity of a body simply taken 

 into its quantity of matter. 



It cannot be expected that at this time any new expe- 

 riment should be thought of, by which the controversy 

 can be decided, since the most simple experiments that ' 



♦ From the PhH, Tram, for xSofi. 



hare 



