a New Dynamico-Chemical Principle. 175 



2nd, Perfect solidity is accompanied with perfect elasticity. 



This proposition, although inserted in the form of a postu- 

 late from being dependent on the foregoing, is yet capable of 

 being demonstrated. If after collision two elastic bodies re- 

 cover their shape with a force equal to that by which they have 

 been compressed, they will recoil from each other without any 

 alteration being eifected in the sum of their motions. This 

 will likewise happen, however much we consider the extent of 

 compi'ession to be enlarged or diminished ; pei'fect elasticity 

 being always consequent to an equality existing betwixt the 

 force of the contracting and that of the dilating vibration. 

 This vibration may be therefore conceived to be infinitely re- 

 duced ; the body will then be perfectly solid, and this finally 

 becomes the limit of perfect resiliency. 



Exposition of a principle hy "johich it is proposed to explain 

 the marmer in 'which a mutual attraction may exist be- 

 tvoeen two particles of matter by the direct impulse of an 

 intermedium. 



I. Let there be an infinite number of particles of cylindric 

 form, the length of each being indefinitely greater than its 

 breadth ; and let them be extended through space at finite 

 equal distances from each other; and let an indefinite velocity 

 be then communicated to each, which may cause them to as- 

 sume a rectilineal motion in different directions. What will be 

 the after state of the medium so constituted? 



Each rigid line will pursue an undeviating course, until it 

 meets with another moving in a contrary direction, when a 

 collision will take place, and by 2nd postulate a perfect re- 

 flexion, without the sum of their motions being diminished, 

 although the whole momentum will then be stored up in the 

 particles in a different manner, a co7isiderable portion being 

 gradually abstracted to effect a rotatory movement, whilst the 

 rectilineal velocity becomes greatly diminished. Thus let the 

 line a b, having at first a motion in the direction c ?•, impinge 

 against another df having likewise a recti- 

 lineal motion in a contrary direction es. 

 Let p be the point of concourse : then by 



, • ir 1 /"'i^ 6-2832 J rtA^x 6-2832 



dynamical formula •— and — r- 



are the spaces which would be afterwards 

 described by e and c respectively during 

 one revohition of the lineyV/, ab; and the 

 ratio of the rotatory to tlie rectilineal momentum, will there- 

 fore be -vs-,-7T- and -TT^x^Tr if no elastic force is supposed 



■5230 (If 'biSodf * 



to 



