1376.] 'J^'J [Chase. 



dreaminess and paradox ; pure physics, if such a tiling were possible, to 

 worldliness and shallowness. Metaphysics strives to learn too much ; 

 physics is satisfied with toD little. Science deals both with the physical 

 and with the metaphysical ; embracing all knowledge that bears, in any 

 way, upon the religious, the ethical, or the intellectual needs of man. An 

 exclusive regard to either phase of our triune nature leads almost of 

 necessity, to shortsightedness and narrowmindedness. In the modern science 

 of thermodynamics, the fertility of discovery, which has rewarded the 

 labors of European and American investigators, furnishes abundant evidence 

 of the usefulness of metaphysical anticipations as aids to physical re- 

 search. 



Newton looked to aethereal oscillation as a probable source of gravitation, 

 finding it easier to imagine the approach of inert bodies through the in- 

 fluence of elastic thrusts, than to conceive of any practicable form of pull; 

 Le Sage, adopting Newton's view, developed it with considerable detail, 

 and later French Academicians have shown, in various ways, and to 

 various extents, the likelihood of the hypothesis ;* Anderssohn has given 

 an experimental demonstration of its sufficiency ; Norton and Challis have 

 engaged in similar speculations, which they have extended so as to embrace 

 all known forms of force ; Weber, Kohlrausch, and Clerk Maxwell have 

 confirmed Faraday's partial identification of light and electricity by actual 

 measurement if Faraday's cautious suggestion of "lines of force, " pro- 

 posed to treat all ftjrces mathematically and independently of any hypothe- 

 ses as to their nature, a proposal which has been largely and wisely followed 

 by many recent investigators. As a further contribution towards such treat- 

 ment I submit the following propositions, to which I have been led in the 

 progress of my own researches, and which may be serviceable in other in- 

 vestigations.:]: 



Let / = velocity communicable, at distance r in time t, by any central force 

 varying inversely as r^. 

 /' = velocity communicated by a single impulse or in a single instant, 

 /j- =(/"' = " " by i equal impulses, or in i instants if the dis- 

 tance remains constant. Then 

 I. If the pressure resulting from /is constant, it must either be exactly 



* For some of the most important of these papers, see references of W. 13. 

 Taylor, in Journal of the F'ranklin Institute. cii,71. 



tThe 9th postulate may, perhaps, be made still more general by this measure- 

 ment. That we know no instance of absolutely static force, is indisputable ; 

 the communication of momentum or vis viva by any physical agency which 

 has no momentum nor vis viva is, to me, inconceivable; the consideration of 

 electrostatic force as force static relatively to the Karth, and of electrodyna- 

 mic force as force moving with the velocity of light, furnishes almost de- 

 monstrative evidenceof a universally oscillating sethereal medium which may 

 be the secondary or physical source of all physical motion and all physical 

 force. 



t Most of the propositions of Newton's Principia are applicable to all cen- 

 tral forces. 



