1 Q'^ 



Sept. n, l«ii!'-] [Lowrie. 



SOME SUGGESTIONS ON THE MAINTAINING FORCES OF 

 COSMICAL MOTION. 



By Walter H. Loweie. 



I desire to submit for consideration some suggestions tending to the 

 production of a true tlieory of the force by whicli the revolutions of tlie 

 planets are maintained against the tendency of attraction to draw all 

 bodies to a common centre, or a solution of what Sir John Herschel calls 

 "the theorem" of the conservation of the vis viva of cosmical motion. 



I know of none hitherto received except that composed of the postu- 

 late of an original impulse and the law of inertia : that a body set in 

 motion by a single impulse and out of relation with other bodies moves 

 forever with its initial velocity and direction. Such a proposition is 

 evidently not a product of induction, for no body was ever known to be in 

 such a case or to move thus; and therefore it defines no actual class of 

 motions whatever, as every physical law ought to do. Indeed philosoj^hy 

 never treats of things out of their relations. This is, therefore, a mere 

 metaphysical idea, meaning only this, that, in the investigation of mo- 

 tions so as to find their system, the mind demands a cause for every 

 change in their degree or direction. 



It very properly assumes an original propulsion; because motion ex- 

 ists, and its oi'igin could not possibly be a matter of human observation. 

 But the theory founded on this law goes beyond the law, and treats of 

 bodies that are in relation with each other, and then assumes, that, by 

 reason of this relation, that is, by the attraction of a primary body upon 

 its secondary, motion may be changed in direction Avithout being changed 

 in degree; and thus, according to it, the original propulsion is the true 

 motive power of all cosmical systems, while the only function of attrac- 

 tion is to deflect tangential into elliptical motion and hold it there. 



Now this theory is both logically and philosophically vicious; because 

 it takes our idea of absolute motion and uses it as a true expression or 

 law of relative motion; and because, while treating attraction as deflec- 

 tive of tangential motion, it overlooks the question, that it may also re- 

 tard and suppress it, and thus it treats this force as absolute in degree 

 while relative in direction. 



An idea or rule that is absolute in its character can tell us nothing 

 about actual things, though it may regulate our mode of thinking about 

 them. In this instance it bids us seek a cause which maintains cosmical 

 motion against tlie centralizing force of atti'action. We must seek it in 

 this cosmos, just as it is, with its countless bodies, all moving in harmony 

 and yet with countless forms and degrees of motion. 



It is impossible to And it in a single initial impulse given at the start 

 of the motion; because the force of attraction of each body on the others 

 would everywhere afl'ect the inotion thus given, deflecting, retarding, 

 accelerating, reversing and finally absorbing it, without its having any 

 capacity, as a vis viva, of recovering itself. The initial impulse once 



