148 Prof. A. M c Aulay on Spontaneous Generation 



there are other constitutions to try, where the primary con- 

 ditions are also fulfilled. This fundamental assumption and 

 others that for simplicity have been tacitly made are to be 

 examined by aid of the equation of motion which flows 

 from (51). 



The equation of motion is at once written down by aid of 

 Th. 6 and Th. 7. Noting that x e = X € and that 



we obtain 



.... (52) 



With the upper sign, from the last term, we have a tension 

 along the lines of curl equal to — JV 2 y? ; with the lower a 

 pressure. \_A tension quite really implies a tendency of a 

 line of curl to shrink because it implies that shrinkage 

 causes decrease in potential energy.] We therefore assume 

 that the Maxwellian tension along the lines of electrostatic 

 induction determines that we must select the upper sign; we 

 henceforth drop the lower sign. In passing note that the 

 existence of this stress is yet another confirmation that we 

 are on the right lines. 



Our equations of motion now are 



iin/3A= -W(Hx)W^- JSW7.VV*?- VW3A, j 



the pressure term — Vp being necessitated as we have already 

 seen by the condition SV^ = in connexion with B (~Ldt = 0. 

 Putting 77 = we have the equation which must eventually 

 decide for or against the validity of our assumptions if the 

 provisional constitution is accepted. In this first plea for 

 an elastic solid aether we leave this apparently intractable 

 differential equation alone. Perhaps some mathematician 

 more familiar with differential equations than the present 

 writer may be persuaded to attempt its treatment. 



V. Second JEilier Hypothesis. 



The origin of the present investigation was by aid of 

 another tentative constitution ; this origin will now be briefly 

 described. 



I was aware that the term m = EFG in w produced no 

 effect on the bodily equation of motion. I was also acquainted 

 with the very remarkable medium, capable of strains of any 

 magnitude, which is given by 



tp/A=j2E»=--JTJTf=*' + 3. . . . (54) 



