18 ~ O. N. Rood on thermo-electric currents by percussion. 
with a narrow couple is given below in table 8. To ascertain 
that the plate had not been altered, experiments were made: 
with it afterward, the ball being lifted. 
To find out whether any peculiar influence was exercised by 
the mass of the couple within small limits, the above mentioned 
plate was now cut down, till its breadth was 3 millimeters. It 
was covered with waxed silk and the following results obtained: 
TABLE si 
Distance falien; lin. Qin. 3 in. 4 in. 
0° 328° 480° 646° 7-20° 
‘ 1°35 2-42 477 6°10 710 
ie 1-20 2°42 3°50 490 6°38 
Reduced deviations, 114 2:07 3-00 5:00 7-00 
1:07 201 3:00 4:90 6-46 
1-14 1:90 3°20 " 6:20 
Average, 1:23 235. - . 871 539 672 
To compare the temperature here developed with what was 
produced in the broad plate before it was cut down, I give below 
the reduced deviation of the broad plate taken from table 5: 
: lin, 2in. 3in. din. 
Reduced deviation of narrow plate, 1°23 2°35 | 371 5°39 
” = “ broad AG 10 21 3°28 4:30 
Difference, 16 25 “43 1-09 
The narrow plate used in table 7 being employed and arranged 
exactly as before, the ball was allowed after its fall to remain in 
contact with the insulated couple. 
TaBLE 8. 
Distance fallen, 1 in. 2 in, 3 in. 4in. 5 in. 
2-49 30° or 59° 56° 
Sea 2°5 31 3°8 39 59 
Unreduced deviations, 25 3-0 34 35 52 
26 31 37 39 59 
Average, 25 6 : 
Rated average, 1°79 2°17 2°57 27 
Hifect of the first twenty, &c. falls on the newly prepared plate. 
When the couple is wound with plain or with waxed silk, 
and subjected to the action of the falling body, the first 15-20 
eviations of the needle are much larger than any above given 
with the successive falls as the silk becomes compac the 
deviations decrease in size, reach a minimum, and remain about 
as constant as shown in the tables. The results so far given 
then, except, of course, in case of table 1, were obtained after 
this point had been approxiisaayy reached. I give below, as a 
sample, the first set of deviations obtained directly after winding 
with waxed silk the couple used in table 7. The ball was lifted 
in the usual way. 
