Thermoelectricity of Molten Metals. 497 
peratures to a very high point by a method presenting many 
advantages over measurements made with an air-thermo- 
meter (smaller space of constant temperature, independence 
of expansion and changes in form of the vessel). We should 
further, and probably for the first time, obtain numbers 
which are entirely dependent upon the chemical nature of 
the substance, and free from uncertainties as to how hard or 
soft the body is. They would offer us a more ready con- 
clusion as to the internal processes by which thermoelectric 
forces are excited. In fact, it appears very remarkable how, 
under similar external conditions (where any desired quanti- 
ties of heat are available), large quantities of heat are trans- 
formed into the form of energy of mechanical work, at the 
points of contact of many metals, and with others very small 
quantities *. | 
Since, further, each molten metal in thermoelectric rela- 
tionship must be characterized by a single constant (which 
no doubt may vary with the pressure), this must stand in 
some relationship to other constants, characterizing the par- 
ticular metal, and independent of the temperature ; but of 
such there is only the atomic weight available. 
3. These considerations induced me to measure the thermo- 
electric forces of molten metals against each other between as 
wide limits of temperature as possible. A linear dependence 
upon the temperature appeared to me @ priori so probable, 
that I directed my attention from the first to the utmost 
possible chemical purity of materials, and, moreover, chose 
only elements. Alloys were investigated only in the second 
lace. 
In the following I give the combinations which were 
measured, as well as the range of temperature employed ; ¢ 
denotes the temperature of the colder point of contact, T the 
highest reached at the warmer point of contact. 
eon ST Soce ies f= 202% or! 100% 5 :T370?. 
Bee. 8 ei) en ¢=220°; T= 580°. 
MOE. 3. \ oheenpd—20?-or 100 s| P—b20". 
nee) Ga) 2 Wel t= 200s) T= 460°. 
* That we may regard the Peltierian heat as the equivalent of the 
work which the electricity does in passing to a lower potential-level at 
the points of contact, requires no justification. The work lost at the 
one contact-point can be restored by the equal amount gained at the 
other, just as the quantities of work in the portions of the two arms of a 
siphon at equal heights compensate each other. We cannot conclude 
anything, as Maxwell has done, as to the difference of potential produced, 
as a result of contact-electricity, from the Peltierian heat at the point of 
contact of two conductors. 
