HALL. — CONDUCTIVITY OP SOFT IRON. 129 



aud copper end-pieces has been dealt with more carefully and successfully 

 in recent experiments than in earlier ones, aud that in some cases the bars 

 have been placed in a glass tube instead of a woodeu one. The results 

 of these thermo-electric tests, subject to slight corrections for pecu- 

 liarities of the thermometers* used, are given below. The temperature 

 put down for each case, in the second column, is the mean of the ther- 

 mometer readings in the two copper blocks at the ends of the row of iron 

 bars. The third column, headed A, gives for each case the mean differ- 

 ence of temperature of the two thermometers. The fourth column, headed 

 E, gives for each case the thermo-electromotive force corresponding to a 

 difference of 1° between the two thermometers, each of which thermome- 

 ters is supposed to indicate with sufficient accuracy the temperature of 

 the copper-iron contact neighboring to it. 



Date T A B 



June 3, '99 2o°.8x 7°.04\ 1041 x IQ-S 



" 7, " '27°.7I 7°.52i 1017 



" 30, '' 25°. sl ^'-^HT-^n ^^^* 



July 3, " 2G°.5r'' '^ 8°.22r '^^ 1042 



" 4, " 26°. 41 6°.64\ 1031 



•' 6, " 27°.8j 6°.79j 1012 



June 6, " 40^5^ 7°. 44^ 979 



" 7, " 44°. T)/ 7°.23/ 964 



July 3, " 40°.6>4l°.3 7°.79>7°.19 982 " } 978 X 10-^ 



" 4, " 38°. si 6°.94\ 990 



" 6, " 42°. oj 6° .57; 976 



June 6, " 55°. 6^ 7°.03^ 926 



" 7, " 56°.5/ 6°.95/ 930 



July 3, " 52°.2>54°.5 7°.60>6°.89 941 " > 934 X IQ-^ 



" 4, " 53°. 8 1 6°. 64 1 938 " 



" 6, " 54°. ej 6°.25J 933 



26° .6 ,,„'^_,y°.30 _,.. ^^ )1028xl0-8 



volt 



a 



u 



a 



June 3, " 69°. 0\ 6°.07n 885 " 



" 7, " 74°.5) 6°. 24/ 850 " 



" 30, " 69°.4f 6°.18f 865 " v «7i ^ 10- 



July 3." 70°.6r^ -^ 7°.04r -^^ 874 " >«'1X1U 



" 4, " 71°. 3\ 6° .041 879 " 



" 6, " 71°. 9J 6°.66j 870 " 



clianged, and, fxcept during the moments of measurement of resistance, no electric 

 current flowing tlirougli the row of bars. 



* Baudin, Nos. 10,286 and 10,287, as in previous work. 

 VOL. xx.xvi. — 9 



