338 ■ REPORT— 1887. 



static electric stress is possible in the interior of a mass of fluid ? The 

 question is but the paraphrase of another. Why do we believe liquids to 

 obey quite accurately Ohm's law for very minute forces ? On this head 

 we have direct experimental evidence by Professor Fitzgerald and Mr. 

 Trouton, and less direct but equally conclusive evidence from von Helm- 

 holtz. Whether the evidence is perfect and thorough is doubtless a 



Electrolj'te. Dielectric. 



The two vertical lines are electrodes, the slant or broken line represents the kind of 

 slope of potential in the two cases respectively. 



debatable point, but this much is not debatable : it is out of the question 

 to assert that liquids obey Ohm's law and at the same time to assert the 

 existence of a finite electrostatic stress in the interior of a fluid. In other 

 words, however chemists are able to explain the fact of unresisting atomic 

 processions through the liquid — whether by actual procession of individuals 

 or by continual directed interchange — they will be rigorously driven to 

 some form of such doctrine as soon as they accept the evidence for the 

 accuracy of Ohm's law in electrolytic conduction. 



We all know that this doctrine of non-resistance is in some shape or 

 another the old Williamson-Clausius hypothesis,' which was based on then 

 newly known facts concerning dissociation. 



It would appear, however, that some chemists demur to the existence 

 of a constant average of dissociation among the molecules of a liquid ; and 

 it behoves us of Section A to receive their scruples with great respect, 

 being, we naay suppose, based upon intimate familiarity with all manner 

 of circumstances and reactions of which we physicists are only superficially 

 cognisant. 



But there are ways of picturing all that is necessary to free atomic 

 interchange without postulating actual and constant dissociation. A 

 potential dissociation will be granted, suflicient for all purposes, provided 

 chemists admit the probability of a frequent interchange of atoms among 



' Since the Eeport was read, Professor Clausius has favoured the Committee with 

 a note objecting to this designation as based on an erroneous view of scientific 

 history. The Committee have not yet expressed their opinion on the point so raised, 

 and meanwhile the joint names are used merely for convenience of quotation, with- 

 out prejudice to an altered nomenclature hereafter. 



