472 



KEroitT — 1884. 



i 



(this is not to be confused with Volta's summation or scries law, which is 

 only applicable to metala), viz., that the total E.M.F. of a closed circnit 

 of any number of substances may be reckoned by adding up tlie Volta 

 forces observed electrostatically for every pair of substances in contact. 

 This law is, it scorns to nie, for reasons given later (7), very probable 

 theoretically, but still it was quite essential to have it experimentally 

 established, esjiecially as they point out that it is often called in question 



FUr. .-J.— Ihid view of Ayrluu ami J'eriy's A|iijuratus. 



without good ground. The establishment of this law is, I say, porlinps 

 their main work in this matter, besides the observation of the Volta ctTect 

 for various difficiilt substances, especially liquids and liquids, 



Clifton arrives at the same conclusion with regard to summation, ami 

 gives handy diagrams, reproduced in ' Jcnkin's Electricity,' of the contact. 

 force at the diilercnt junctions. ]\[y own opinion is that the intemlwl 

 and obvious signilicancc of those diagrams is theoretically wronsr, b'lt 

 they embody certain experirauntal results conveniently, and tlicy can 

 be interpreted ])roperly. 



Both Clifton and Ayrton and Perry appear to believe in tlic ^rtut 

 constancy of the value Zn/Cu. Clifton gives it as y'tlG VoU. ('Qiu'lK' 

 precision ! ' somewhat sarcastically ejaculates Pellat, who himself liiuls it 

 to vary between '03 and -92). Ayrton and Perry assert that it is mow 

 constant than a Daniel!. I believe that both Professor Clifton and I'ni- 

 fessors Ayrton and Perry have made several experiments besides tliosi' 

 recorded in their communications to the Itoyal Society, but as they liavu 

 not been published I can give no account of them. 



Among the Theses presented to the Faculty of Science! in Paris in 

 1881, we find an important memoir by Pellat,' which reviews the whole 



' Thi^'ses prusontoos u la Faciillc ilcs Science's (lf> Paris, iniir nlitcnir lo (liailo i''' 

 Doctcur-es-iSclenccs I'liysiques, {mr M. ]I. I'ellat, rrofestcur (]v l'li}>i(iuo au Luu' 



!i 



