42 LECTURES AND ESSAYS [1869- 



&quot; schiefe Metaphysik &quot; to speak of the velocity at the end 

 of a part of time. &quot; This end must still be a part of time ; 

 if it were not, there would be rest, and no motion ; velocity 

 can be measured only by the space passed through in a 

 definite time &quot; (p. 352). An appeal to Attwood s machine 

 would probably be too empirical for our philosopher, 

 but the law of energy might surely convince Hegel of the 

 reality of a variable velocity dependent on potential 

 energy lost or gained. It is clear, at least, that Hegel 

 lacked the first elements of physical notions, and these 

 were not likely to be supplied by the method of Lagrange 

 to which he adheres, beginning with s=ft, and deducing 

 every other consideration by differentiation. 



The following criticism on a remark of Lagrange is 

 splendid : &quot;We find,&quot; says Lagrange, &quot;the motion repre 

 sented by s = at z in the actual fall of bodies. The next 

 simplest motion would be s = cf, but nature shows no such 

 motion, and we do not know what c could mean.&quot; (The 

 ground of this is, of course, to be found in the law of 

 the conservation of energy.) &quot; If so, we have at least 

 a motion whose equation is s B = at 2 , Kepler s law of 

 planetary motion ; and here the investigation of the first 



o /// 



derived function f-^, etc., the direct treatment of this 

 3 s 



equation by differentiation, the development of the laws 

 of that absolute movement from this starting-point, must 

 certainly be a most interesting task, in which analysis 

 would appear in the brightest splendour &quot; [!]. That 

 t and s in Kepler s law are not variables, but constants 

 determined for each planet ; that the equation has no 

 analogy whatsoever with the equation of motion ; that 

 its differentiation would be meaningless unless space were 

 filled with planets ; and that then it would have nothing 

 to do with &quot; the determinations of that absolute motion,&quot; 

 are considerations that never entered Hegel s head. 



It is rather hard that, from a metaphysical standpoint, 

 a man is still allowed to write about things he has not 



