296 C. Cx. KNOTT. 



meta] fixed ii])oii was ralladiiiin. a snhstnnce convenient in every 

 way. Its (liauTani line is strai^'lit u]) to liii^ii tein])eratnres ; aiul its 

 character does not perceptil)ly clumge even after severe heating-s. Un- 

 forlunatclv, however, the necessity of nsin,o- ])ismnth ]iniit('(I tlie 

 investigation t(^ moderate temperatnres. 



The l)isninth was l)roken np into small pieces, which were packed 

 tightly into the l)ore of a si]>hon sliaped glass tube. Gentle heating 

 in 11 Ihmsen flame sufficed to melt the metal, which ran together and 

 solidified (^n cooling into a fiirly unifnan rod. The junction wires 

 were fused into the ends of the hisnmth rod. 



As tinallv set up, the a])paratus consisted of a triple Cohalt- 

 Bismuth-Palh'.dium junrtion dippirig in oil. This formed the "hot 

 junction." liesi;4ari<'e boxes were included in the p:dla(ham and 

 bisnuith bi-andies. because of the magnitude of the thermoelectro- 

 motive i\mv:' between these three metals and cojiper, great prec:nition 

 was necessary in keeping tlie various cold junctions at the same tem- 

 perature. 



The palladium branch always contained 100 ohms resistance. 

 The resistarir-c of the l)i:anuth Irninch varied from infinity to 200, 

 lower values c:u"rvirig the intermedia.te line too fu" below the coltalt 

 line. For each of tlie seven selected ratios of resistances, a, careful 

 series of thermoelectric observations was made. A delicate high 

 resistance galvanometer was used ; and the temperatures were mea- 

 sured bv a mei-(au'ial thermometer. The electromotive forces between 

 the cobalt and eadi intca'inediate "equivalent metal" were in this 

 way measured directlv. From these the thermoelectric powers at 

 chosen ttanpci'aiures could be calcul-ated. lîut one of tliese " e(pii- 

 valent metals" was ])alladiiim itself, when tlie re:;istance in the bisnuith 

 branch ^vas made intiiiite. Siil)tracting 'dl llie oilier tluaanoeleetric 

 powers from this one, we obtained the thermoelectric powers lietween 



