14 Wilde, Evolution of the Mental Faculties. 



parts cannot lose their motion otherwise than by 

 communicating it to other parts, or by its accruing to 

 the whole body; so that there is no just reason for 

 supposing that any motion or force is lost in flattening 

 or hollowing of soft bodies, in their collision; and this new 

 tenet is invented merely to serve a particular purpose."* 



Smeaton, with his accustomed ingenuity, devised an 

 elegant method of reproducing the effects of the collision 

 of inelastic bodies and measuring exactly, by means of 

 springs, the force spent in producing change of figure.f 

 Although his demonstrations were published more than a 

 century ago, they are still ignored and controverted by 

 many writers upon natural science. The modern editions 

 of Hutton's valuable treatise on pure and applied mathe- 

 matics are still disfigured by the same formula for the 

 collision of inelastic bodies as for those which are elastic. 

 Young also, in his classical lectures on natural philosophy,! 

 repeats the same error when dealing with the collision of 

 inelastic bodies, and affirms that the sum of the momenta 

 is the same after collision as it was before collision. It is 

 hardly necessary for me to point out to members of this 

 Society that the loss of force referred to by the term 

 *' change of figure " is the transformation of the molar 

 motion of bodies into the molecular motion of heat. 



Among the more recent professors of natural philo- 

 sophy who have given their support to the Cartesian 

 measure of moving force are Dr. Lardner (185 1), Clerk 

 Maxwell (i876),§ and P. G. Tait (i899).|| The following 

 paragraphs, 195, 251, 252, from a widely-known hand- 

 book of natural science by Dr. Lardner, who was 



* Maclaurin's Account of Netuton'sPhilosophical Discoveries^ 1748. p. 118. 



t Phil. Trans., Vol. LXXII., 1782. 



X Lecture VIII. 



% Matter and Motion. 



II Newton's Laws of Motion. 



