a Pe eee Ce he ee ee eee 3 SA eee 
sk SER ee a IE Sion hal nea een om aera malts oe A Se 2h Cons, iy: 
poses 
ve Sen are 
umn are higher than in table 5; a corresponding result obt 
O. N. Rood on thermo-electric currents by percussion. - ¥7 
same metals soldered together were used; the form of these 
-plates remained nearly unaltered. 
Accordingly, to obtain the results given in 4 and 5, a 
pound plate of this kind was used; the breadth of the ski 
was 7 millimeters, length 150 millimeters thickness of iron and 
of German silver being about ‘2 of am 
The ia in table 4 was wound with four layers of heavy 
plain si 
Tasie 4, 
Distance fallen, lin. 2 in. 3 in. 4 in. Sin.“ 
1:6° 26° 38° 40° 49° 
First unreduced 7 es ie nf as 
exists 13 24 3:4 40 45 
1:3 2-2 3°65. 3°8 4:5 
Average, 1-38 2-3 3 37 46 
Table 5 gives results when 4 layers of waed silk were used 
with the same couple 
TaBLe 5 
Distance fallen, 1 in. 2 in. 3 in. 4in. 5in. 
15 3-1° 50° 64° 9° 
First unreduced hi 4 a be a 
deviations, 
, 15 2-9 4-2 56 83 
14 2-8 4°2 5 8-0 
Average, 15 294 846 6-04 8-4 
Reduced average, 1:07 21 3:28 43 6:0 
It will be observed that in tables 2, 3 and 5 the result is more 
or less perfectly indicated that the force of the current is pro- 
portional to the distance the ball falls through, or in other words 
to the square of its velocity at the moment of impact 
Effect of allowing the ball to remain in contact with insulated couple 
after the impact. 
The results given in table 6 were obtained directly after those 
given in table 5, everything remaining unaltered except that 
the ball was not raised out of contact with the couple. 
Tasie 6. 
Distance fallen, lin, 2 in. 3 in. 4in. 5 in. 
20° 2 5o 6° 4:99 oO 
First unreduced se 2°6 3-1 40 5-7 
deviation, 1-7 2-3 3-2 40 54 
as 2°3 3-0 36 51 
Average, 1s 2°42 3°22 3°95 55 
The extent to which the heat generated is thus conducted 
away from the couple is very noticeable in the last three ooh 
but it is a little remarkable tha Sie deviations in the first 
Am. Journ. 8c1.—Seconp SERIES, Vox. eon No. 124.—Juty, 1866, — 
3 
