Dr. Draper on the Electro-motive Fcmer of Heat. 4*59 
These results explain the anomalies observed by some of 
those who investigated the course of thermo-electric currents 
by means of small metallic fragments. 
It would therefore seem, that when wires of the same 
metal are used as electromotors, the quantity of electricity 
evolved depends on the quantity of caloric that can be com- 
municated in a given time. Time, therefore, under these 
circumstances must enter as an element of thermo-electric 
action. In the case of a single metal, the maximum effect 
would be produced, when the hot element is a mass, and the 
cold one a point. 
And lastly, That the quantities of electricity evolved in a 
pile of pairs are directly proportional to the number of the 
elements.” 
In the first trials which I made, to determine the effect of 
increasing the number of pairs in a pile, the results obtained 
were contradictory ; by operating however in the following 
way, the proposition was at last satisfactorily determined. 
1st. The resistance to conduction was made nearly con- 
stant by uniting all the pairs intended to be worked with, at 
once. The current, therefore, whether generated by one, 
two, three, four, or more pairs, had always to run. through the 
same length of wire, and experienced in all cases an uniform 
resistance. 
2ndly. By making each individual element of considerable 
length, the liability of transmission from the hot to the cold 
extremity was diminished. 
Having, therefore, taken six pairs of copper and iron wires, 
y^^th of an inch thick and each element 38 inches long, I 
formed them, by soldering their alternate ends, into a con- 
tinuous battery. Then I successively immersed in boiling 
water one, two, three, &c. of the extremities, their length al- 
lowing freedom of motion, and the other extremities not dif- 
fering perceptibly from the temperature of the room. 
The following table exhibits one of this series of experiments. 
Table IV. 
No. of pairs. 
Calculated Deviations. 
Observed Deviations. 
1. 
55 
55 
2. 
no 
111 
3. 
165 
165 
4. 
220 
220 
5. 
275 
272 
6. 
330 
332 
