On the Transparency of the Ether. 



p —s = /? --^ + ju, — J ; 

 dt'- dy- ay- 



ox, since 



Zi! = — , 

 dt 



(3) 





6/- dy- d/Oy 



The left-hand side represents the force of acceleration per 

 unit of volume ; the first term of the right-hand side expresses 

 the force arising from the distortion of the surrounding ether, 

 and the second term the dissipative force arising from the 

 rate of distortion. A particular solution of this equation is 



$ = At^y-'^'. (4) 



Substituting in equation (3), we have 



-pp''=nli--iixp(i-. (5) 



Since we are dealing with simple periodic motions, / must 

 be real, and /3 must therefore be complex. 

 Let 



^ = -K + iy, (6) 



where y = -. Substituting in (5), and separating the real, 

 and the imaginary terms, we have 



o = pp- -\- tiK^ — n-/ — 2piiKy, 

 0^2 iiKy -\- pfjLK^ — py^y ? 



(7) 



whence 



■y — K 



a^+p^v" 



p\ 



(8) 



where v = -, is the kinematic coefficient of viscosity. Now 



P 

 Ky cannot be a large quantity, since the light of stars at a 



very great distance y reaches us ; hence k, and consequently 



7 



