298 C. Barus — Compressibility of Colloids. 



may therefore act, as the case may be, either as a liquid or a 

 solid, just as, in the above experiments with gelatine, one and 

 the same originally continuous and homogeneous body mani- 

 fests itself in both roles, under the same conditions. 



If this be admitted, I think that one may form at least a 

 conception of a mechanism by which many ordinary dynamical 

 phenomena may be looked upon as ether manifestations ; and 

 elsewhere I may endeavor to give a few tentative examples 

 among many which I have entertained. 



If in rigid dynamics, a body or a molecule can only move 

 by breaking down the solid ether in front of it and leaving 

 triturated ether in its wake, force* is needed to start it or in 

 any way to change its state of motion. On the other hand, 

 the body if sustained in place would resist such breakdown. 

 Stress sufficient to break down the solid ether along given lines 

 of force need not do so when the obstacle of a fixed body 

 intervenes. In general, I hold the association of motion with 

 the actual flux of a stress conveying fluid after the manner set 

 forth in the present paper, not an unhappy conception, at least 

 from the point of view of the law of the conservation of 

 energy. 



Brown University, Providence, R. I. 



* During motion, stress in the continuous ether in front, and pressure in the 

 discontinuous ether behind the body or molecule, may in the first instance be 

 supposed to be in equilibrium. Note that fixity is an essential property of such 

 an ether. 



