WEBSTER. — PHOPKKTTKS OK TIIK KTIIEH. 525 



As wo must not assiiiiif ordiiiai'v elasticity, so also we must not 

 assiinu' ordinary inertia of the rnndanifiiial j)articlrs. l-'or, alter all, 

 Xe\vton's laws of motion, that \ve ol)ser\<' for ordinary maltei-, ai)pear 

 to be only approximations to the laws that result from e(|iuition (11), 

 the more general law of motion. .Vnd furthermore, they ar(> hy no 

 means the only ones consistent with the relati\e nature of time and 

 space, nor is there any other a priori philosophical reason for assmning 

 that they are true, while there is good philosophical reason for assum- 

 ing that Hamilton's Principle, the uiathematical expression of the 

 perfect efficiency of the fundamental machinery of nature, is at least 

 plausible. Therefore, whatever motions of the parts of the ether it 

 may involve, and whether or not it is easy for us, with our Newtonian 

 mechanical training, to form a mental picture of the dynamics of 

 these motions, the fimdamental law of the dynamics of the ether, or 

 of any mental picture of it, must be Hamilton's Principle. . 



A Model of the Ether. — To get a mental picture of the actions 



of the ether, we must now make some arbitrary assumptions as to the 



nature of the two interlacing structures and the strains in them that 



+ — 



are represented by the vectors E and E. For simplicity we may think 



of them as nets with cubical meshes with each knot of either net in 



the centre of a mesh of the other, where\'er the electric vectors are 



+ 

 zero. The vector E may be a very minute displacement of one of 



these nets from this position, and the vector E the negative of a simi- 

 lar displacement of the other. If we now suppose the strings of these 

 nets to be hollow and rigid, and the knots to be hollow- boxes, so con- 

 structed that the displacements of the nets will be those of an incom- 

 pressible substance, we may suppose an electric charge to be a region 

 in which the pipes and boxes of one of the nets are filled with a Hcpiid 

 of high surface tension, that will expand the boxes into which it 

 flows, and cause a divergence of the displacement of the net. An 

 electron will then be a region of this sort, in the shape of a hollow sphere 

 when at rest, of which every flimension, including the thickness, is 

 very large compared with the meshes of the net. The pipes and boxes 

 of that net that lie inside this region may l)e filled with a fluid whose 

 only properties are adhesion with everything it touches and a constant 

 hydrostatic tension, independent of its volume. For the connections 

 between the nets we may assume anything we please. 



Equations (1) and (2) are satisfied by this model, which also gives 

 an interesting interpretation for (3) and (4). For in free ether the 



