680 Prof. L. T. More on Dielectric 



where a is the inverse of Young's modulus and Kj the varia- 

 tion of the dielectric constant with mechanical pressure, 

 represented by 8K/8f. It is then Maxwell's equation with the 

 addition of a second constant. This variation of the dielectric 

 constant must be an exceedingly small quantity, for of the few 

 who have investigated it, some have obtained a positive value, 

 some a negative, and others a null effect. So that the 

 pressure p may be increased, diminished, or unaffected by this 

 quantity. 



If one is willing to grant the fundamental assumption made 

 for these theories, there is little doubt that the conclusions are 

 correct. It is easy to see that the assumption made for each 

 of them is essentially the same ; namely, that a stress in the 

 aether is communicated to matter immersed in it, or, in other 

 words, the granting of the vital point of the discussion. 

 Those who develope the polarization theory suppose material 

 particles to be immersed in a fluid aether, as may be illus- 

 trated by fragments of silk thread in pure turpentine. If 

 charged electrodes are placed in the turpentine, the silk threads 

 are observed to form chains extending approximately along 

 the Faraday lines of force. We may readily imagine the 

 ends of each fibre to be polarized by induction which by 

 their mutual attractions and repulsions form lines of stress 

 tending to shorten along the lines of force and to repel each 

 other perpendicularly to them. In the first place, it is rather 

 doubtful to consider this phenomenon as due to a static 

 system of forces which the Faraday lines demand. But the 

 real error lies deeper, — to assume that particles of matter 

 in the aether act like particles of silk in turpentine is to grant 

 the whole question. We know that a stress in one kind of 

 matter is transmitted undiminished to any other kind of 

 matter, as in this case from turpentine to silk. But we not 

 only have no confirmation, but in fact many reasons for 

 believing that static stresses in the aether are not communicated 

 to matter. Lorentz indeed goes so far as to say that it is 

 absurd to imagine a strain in the aether itself and so impossible 

 to conceive of a strain imparted to matter. One of the chief 

 reasons for the abandonment of the elastic solid theory of 

 light in favour of the electro-magnetic theory is to obviate the 

 absurdities introduced when the aether was supposed to be an 

 elastic solid. As to the theories viewed from a thermodynamic 

 standpoint, the assumption is just as glaring as it is in fact 

 the same. Sacerdote and the other writers on electrostriction 

 from this standpoint claim that the connecting link between 

 the aether and matter is expressed by the coefficient 

 Kj= BK/Sfj that is by the variation of the inductive capacity 



