444 THE POPULAR SCIENCE MONTHLY. 



Obscurity conies over the view when the physical sphere is ex- 

 changed for the ethical. It is easy, to admit that man is not free, but 

 acts as the tool of hidden causes, so long as his conduct is indifferent. 

 Whether Caesar in thought put on his right or his left caliga first was 

 all the same ; in either case, he went out with his boots on. Whether 

 he crossed the Rubicon or not, on that hung the world's history. So 

 little are we free in some unimportant matters, that one acquainted 

 with human nature can predict with surprising certainty which card 

 out of several laid down under certain conditions we will take up 

 first. But even the most decided monist could hardly adhere to the 

 earnest purposes of practical life in the face of the idea that all of 

 human existence is a fable convenue in which mechanical necessity 

 awards to Caius the part of a traitor, and to Sempronius that of a 

 judge ; and therefore Caius is taken to execution, while Sempronius 

 goes to his breakfast. We are not troubled that so many letters in 

 every hundred thousand miscarry because they are not directed ; but 

 it stirs our moral feelings to think that, according to Quetelet, so many 

 persons in every hundred thousand are to become thieves, murderers, 

 and incendiaries ; for it is painful to have to feel that we are not 

 criminals only because others, instead of ourselves, have drawn the 

 black lots that might have fallen to our share. 



Less known than the metaphysical efforts to reconcile free-will and 

 the moral law with the mechanical order of the world are the mathe- 

 matical essays directed to the same end that have lately been put 

 forth in France. They are related to the unsuccessful attempt of 

 Descartes to explain the working of the soul upon the body, of the 

 spiritual upon the material substance. While Descartes held that the 

 quantity of motion in the world was constant, and did not believe 

 that the soul could produce motion, he nevertheless thought that the 

 soul might determine the direction in which motion should take place. 

 Leibnitz showed that not the sum of motions but the sum of motive 

 forces is constant, and that also the sum of the directive forces, or of 

 the advance in the line of any axis projected in space, continues the 

 same. He, therefore, called the algebraic sum of all those axes par- 

 allel components of all mechanical movements. According to the last 

 point, which was overlooked by Descartes, the direction of motion can 

 not be determined or changed without a corresponding expenditure 

 of force. However small we may imagine this expenditure of force 

 to be, it forms a part of the mechanism of nature, and can not be 

 ascribed to the spiritual substance. 



The deceased mathematician, Cournot, M. de Sainte-Venant, and 

 Professor Boussinesq, of Lille, have undertaken to break the bands of 

 mechanical determinism by showing that motion can be produced, or 

 the direction of motion can be changed, without the expenditure of 

 force. Cournot and M. de Sainte-Venant have applied the idea of 

 release (. J uflosung, Fr. dccrochement), which has long been current in 



