470 



llErOUT- 



IH84. 



and n IJoliiicubergor or Hiuikol olcctroscopo ; lio makes mcasiiroments 

 of Volta i'orco fur nnraorons inohih, hut his special merit is llio deter- 

 rain.ntion of inntal-li«|uid contact forcos witliout introducinLf blotting 

 paper, glass, or fingers, as the earlier experinientera Lad done. 



l''i<!. ;'.— II;ml<cl'.s Arraivj-fnii'iil fur olixM-vinir ilu- '\'n\\:\ KtTort Ijclwccn ii Mital jinil 



a Lii|Miil. 



'I'lio !it|ni(l 1. N ill ii fimiu'l tiilic a ii. <• U n cnpiicr plato, nml m tlic niet:il iiiulcr ulisprvatinn. 

 l'ir>'t I' tiMicli'.'M » tor an iii>lant, tliuu r ii nii.'sed ;iiiil iiuuli' to tdiu'li v\ which U:uU U> ii 

 Iltmkel I'U'ctrdinutcr. 



'I'liis ^'ivcs ( u M + M I. 1,0. 



'I'iicn tho lic|iii(l is run i>nl ol'tlic I'uiiik'I, a (liate dl'thc uiutal m is iiliR'Cd ou its iiinutii. 

 Mill tin- f.\|)r> inu'iil rcpt'att'il. 



This ijivcs (11 M = l</J 



To I'liinin.iti' Ii siilistitiite a iilate of zinc I'or m, ami .^ct 



t'u,'/.\\-ky. 'riicii liiiiillv M L— Z^ I u /ti. 



y 



In all tlic.^i' oxprcssinns air cciiitiict rnrcos iiic iis usual iir.alictiil. I'lit it is vf-rv ti ni|itiiii; 

 tci try if hy iiicrciisinj; the iniinln'r of such t'r|UMlions oin' I'diiiiot calciilatc uoiiH' iiiclal ;iir 

 (iiiitact force-. Thus the s|icciiil ca-c win 11 .m is co|i]ier -ives one more e(|u«tion. W'f 

 can then tai e zinc instejul of m, ami can af-o make the cuMileiiser |)Into of zini' instead d' 

 <'o| ]ii'r, ami m. on ; but we f:ct no tcrwanler, fresh nnki'.owns iippcar as fust as .idili- 

 tionnl eiiiiatioiis, unci some of the e(|uations aro liahh' to (le;;cner«t(' into ideniities. 



So iar back as 1824 liocqucrel ' attempted the investigation of nietiil- 

 liquid contacts, and liufl- made some measurements in 184'J, hut his 

 results are scarcely likely to be reliable considering tho poor experimental 

 resources of that date. 



I'rofessor Clifton employed Kohlrauseh's method in 1877, using a 

 Thomson electrometer and a Clark cell as staudtird of K.M.F. Ifc hits 

 only published a pi-eliminary paper,'' in which lie overlooks minutiu' such 

 as change of contact force by time and adventitious circumstance?. 



A'/t/.isr — !?•{>] and 18t!o. See also I'd;/;/. Ann.cxv. p. .">", and cxxsi. pp. L'8(i and I4<l; 

 cxxxi. ]). r»07. 



(ierland : 'On tlio l'",.I\r.l'\ bolwecn Water and some Metals,' 7V//;/. Ann. cxxxiii. 

 ISd'i.p. ")i:i; exxxvii. I8(ii>, p. ">.")'i. In lii.s second papor, to iret over the air ellVtt, 

 (ierland joins two metals tliroujxli a oalvanomcter, ami then dippintr them into a 

 liquid observes the lirst swinp; of the needle. He also e(jmpensatcs the i;.M.F. by 

 Pogo:endorll'.s method. He thus deti'rmines the value of 



M,M'-u:M7Li.|uid+Li()uid Jl. 



' r.eequerel : Ann. dc Chimic, 1824. He put the liipiid in a copper raiisnle on tlie 

 plate of an idectrcseope, and connected it with the condenser plate by his liiiLicrs. 



'- r>ulf : lArbig, Ann. Chcm. it. Phariii. 1842. He made tho lower plate of his con- 

 denser the metal to be examined ; on it ho placed {i:lass, and then lilter paper 

 tioaked in the liquid, which he connected with the metal plate by a wire of the same 

 metal. 



» Clifton : P^oe. noyalSoc. xxvi. p. 299, 1877. 



