30 6 
SECOND REPORT— 1832 . 
heat, or of inducing magnetism. In the magneto-electric cur¬ 
rents discovered by Mr. Faraday, which resemble the ther¬ 
mo-electric in the difficulty with which they are transmitted 
through even metallic conductors, tension has been manifested, 
accompanied with the faculty of inducing magnetism in steel by 
the helix ; and I cannot but suspect that it will be found capable 
of heating small wires introduced into its circuit. On the other 
hand, no such effects have been obtained from the thermo-electric 
current; as I have repeatedly failed (and I believe others have not 
been more successful,) in magnetizing a needle by a thermo¬ 
electric current, of greater deviating power than that from a 
pair of galvanic elements, which succeeded without difficulty. 
Similarly, in regard to their heating power, by passing a wire 
through the axis of Briguet’s thermometer, I have detected an 
increase of temperature in it when connected w T ith a minute 
voltaic series, but none with the thermo-electric. I cannot 
therefore but think this a subject w r orthy of further inquiry. 
Having noticed the thermo-electric experiments that have 
been made on a single mass of metal, and on two metals partly 
in contact, it only remains for me to call your attention to 
some very interesting researches on the thermo-electric action 
of two metals symmetrically united throughout. This part of 
the subject was first considered by Dr. Trail in 1824; who 
ascertained that if two plates of different metals w r ere applied 
together throughout, (which in fact resolves itself into the case 
of two very short bars connected in the usual manner,) these 
would form a thermo-electric arrangement. This experiment 
was varied, and very important consequences deduced from it, 
by Mr. Christie in 1827. Acting upon a suggestion in the 
Cambridge Transactions , that as the diurnal variation of the 
compass needle seemed in some measure dependent on the 
position of the sun, it might possibly have a thermo-electric ori¬ 
gin, he has shown in a paper in the Philosophical Transactions 
for 1827,—to which I cannot too strongly call your attention,— 
that these natural phenomena, so far as they can be imitated 
experimentally, accord w r ith the supposition that the earth and 
its atmosphere may form a thermo-electric combination put into 
action by the sun. Imitating this arrangement by a circular 
ring of copper surrounding a plate of bismuth, and applying 
heat to a point in the ring, he found that the characters and 
extents of the deviations were such as would arise from the 
polarizing the plate in lines nearly at right angles to the axis 
of heat,—contrary poles being opposite to each other in the tw T o 
surfaces; and applying this to represent the state of the 
equatorial regions of the earth, we should have two magnetic 
