of Electro-Magnetism by Heat. 61 
by this means all the metals which can be procured in the form 
of wires may be compared in a few minutes. The others were 
connected with similar pieces of those metals which had been 
already examined. The series, Table IX. is so constructed, that 
every substance may be considered as positive to all below, and 
negative to all above, and therefore any metal in the upper part 
of the series will form a circuit with all below it, similar to, though 
less powerful than that of bismuth and antimony. Platina and 
iron form an arrangement of this description: equal wires of these 
metals of +, inch diameter gave, with the large compass, a deviation 
of 16° by the heat of a single spirit lamp*. As these metals admit 
of being welded together, and of sustaining an intense heat, I at 
first imagined, that an instrument might have been constructed 
on this principle, as a pyrometer; but, the slow increase of devi- 
ation at elevated temperatures, appears to present an insuperable 
objection. 
If either series, whether that formed by metallic bars with 
copper wires, or that made by the comparison of equal wires of 
different metals, be referred to the common galvanic series, to 
those of the conductors of electricity or heat, or to the order of 
specific gravities, it will be found that there is no correspondence 
between them: the electro-magnetic relations of the metals, as 
developed by heat, can be determined by experiment alonet. As 
this property cannot be previously inferred from any known dis- 
tinctions of the metals considered collectively, so it does not appear 
to be dependent upon any peculiarity, such as crystallization, in 
* Tf silver and iron wires be heated in connection, the deviation attains a maximum, 
diminishes on increasing the heat, and again attains the former maximum in cooling. 
+ The series is consistent with itself, that is, if on experiment, a metal be found to be 
positive to one, and negative to another substance in the series, it may be inferred, 
without further trial, that it is positive to all below the first, and negative to all above 
the second, 
