56 



It must be added, by way of explanation, that the bracket en- 

 closing the symbols of any two of the metallic specimens indicates 

 that they are neutral to one another at the corresponding temperature, 

 and the arrow-head below one of them shows the direction in which 

 it is changing its place with reference to the other, in the series, as 

 the temperature is raised. When there is any doubt as to a posi- 

 tion as shown in the Table, the symbol of the metal is a small letter 

 instead of a capital. 



The rapidity with which copper changes its place among some of 

 the other metals (the platinums and iron) is very remarkable. Brass 

 also changes its place in the same direction possibly no less rapidly 

 than copper ; and lead changes its place also in the same direction 

 but certainly less rapidly than brass, which after passing the thick 

 platinum wire (Pj) at 130 Cent, passes the lead at 140, the lead 

 itself having probably passed the thick platinum at some tempera- 

 ture a little below 130*. 



The conclusion as regards specific heats of electricity in the dif- 

 ferent metals, from the equation expressing thermo-electric force 

 given above, is that the specific heat of vitreous electricity is greater 

 in each metal passing another from left to right in the series as the 

 temperature rises than in the metal it passes : thus in particular, 



The specific heat of vitreous electricity is greater in copper than in 

 platinum or in iron ; greater in brass than in platinum or in lead ; and 

 greater in lead than in platinum. 



It is probable enough from the results regarding iron and copper 

 mentioned above, that the specific heat of vitreous electricity is 

 positive in brass ; very small positive, or else negative, in platinum, 

 perhaps of about the same value as in iron. It will not be difficult to 

 test these speculations either by direct experiment on the convective 

 effects of electric currents in the different metals, or by comparative 

 measurements of thermo-electric forces for various temperatures in 

 circuits of the metals, and I trust to be able to do so before long. 



III. On Thermo-electricity in crystalline metals, and in metals in a 

 state of mechanical strain. 



Having recently been occupied with an extension of the mechani- 



* I have since found that it does pass the thick platinum, at the temperature 

 119. [May 16, 1854.] 



