446 Messrs. Trowbridge and Penrose on 



When the system had reached a condition of thermal equi- 

 librium, the current from the battery was passed, and the 

 observations were made. The vessels of mercury and the cor- 

 responding pencils are denoted by " a " and '"!>" The cur- 

 rent entered alternately in " a " and ,: &," the deflections of the 

 galvanometer being taken, in each case, every half minute. 

 The deflections showed that the pencil " a " was warmer than 

 " &;" but the difference of temperatures was greater in one case 

 than in the other. 



The following table represents the results of two sets of ex- 

 periments. The small numbers at top show which column of 

 each pair was taken first. 



First experiment. 



Se 



cond experiment. 



Current 

 enters 



at -a." 



Current 

 enters 

 at " b." 



j Difference, 

 proportional 

 ; to 47 E. 



Current 

 enters 

 at "a." 



Current 

 enters 

 at "6" 



Difference, 



proportional 



to 47 E. 



'21-0 



34-5 



20-8 

 324 



0-2 



21 



20-8 

 347 



2 



202 

 328 



0-6 

 1-9 



2 



21-2 

 34-5 



310 



33-0 



02 

 1-5 



195 

 310 

 370 



2 



18-2 

 293 

 342 



1-3 



1-7 

 2-8 



2 



21-4 



34-3 



20-6 

 32-8 



0-8 

 lo 



19-8 ' 



31-8 



37-3 



2 



180 

 29-2 

 340 



1-8 

 2-6 

 3-3 



2 



21-7 

 360 

 42-4 



21-6 

 343 

 400 



0-1 

 1-7 

 2-4 



20-0 

 326 



38-7 



2 



18-8 

 304 



357 



1-2 

 2-2 

 3-0 



2 



230 

 38-2 

 45-5 



i 

 21-7 

 350 

 41-2 



13 

 32 

 43 



21-0 

 338 

 398 



2 



19-8 

 313 

 363 



1-2 

 2-5 

 35 



2 



235 

 39-0 

 45-8 



23-0 ' 

 37-0 



43-8 



05 

 20 



200 

 32-2 

 37-4 



2 



190 

 29-8 

 343 



1-0 

 24 

 31 



From this table it appears that the Thomson Effect in ordi- 

 nary graphite is negative ; that is, heat is apparently evolved 

 when the current passes from cold to hot, or the negative cur- 

 rent carries heat with it. The difference in the last columns 

 are obviously proportional to four times the Thomson Effect, 



