304 
SECOND REPORT— 1832 . 
cording to their position with respect to each other and the 
exterior surface, the heat is conducted away with more or less 
rapidity ;—each portion, so far as the heat extends, acting both 
as a thermo-electric element and as a conductor of heat, but be¬ 
yond that space acting simply as a conductor. The effects of 
crystalline structure in modifying thermo-electric action Mr. 
Sturgeon considers as arising from the laminae of each crystal 
being only injuxtaposition, and that therefore the heat passes more 
readily through the parts of each than from one to another. This 
hypothesis it is obvious is inapplicable to metals devoid of crystal¬ 
line structure, as wires of copper or silver, and still more so to 
metals in a liquid state: but by conceiving each wire to be divided 
into an indefinite number of circular laminae, we may suppose each 
of these to act as a layer of cold particles upon the laminae on 
one side and of hot upon those on the other, and the total effect 
of the whole to depend on their aggregate action; each bar or 
wire acting as an assemblage of an indefinite number of small 
plates, as the common magnet may be conceived to be com¬ 
posed of an indefinite number of atomic magnets. Still, ad¬ 
mitting this mutual action of the metallic particles, the original 
induction of electricity by heat and its subsequent propagation 
remain to be explained. This Becquerel conceives maybe ac¬ 
counted for on the hypothesis that, whenever a particle of a 
metal is heated, part of the neutral electric fluid which is 
attached to it is decomposed, the vitreous fluid being retained, 
and the resinous driven off and passing into the adjoining par¬ 
ticles. In proportion as the heat extends by communication 
from particle to particle, similar effects take place in each of 
those that are acquiring heat, and the contrary in those that 
are losing it. Thus the first effect is only to produce an oscil¬ 
latory movement of the electric fluid between the adjacent par¬ 
ticles ; but if the source of heat be permanent, the retrograde 
movements are prevented, and a continued current takes place. 
I can only observe as to this theory, that the hypothesis appears 
to assume the very point that was to be established. I am not 
aware of any experiments to prove such a decomposition of the 
electricities of an uninsulated particle of metal. 
The next class of experiments to be mentioned are those 
which relate to the transmission and augmentation of thermo- 
electricity. 
Reverting to the original experiment of Seebeck, the brass 
wire connecting the extremities of the bar of antimony might act 
simply as a conductor, or might modify at the same time that 
it transmitted the electricity, according as the susceptibility to 
this species of electric excitation was confined to antimony, or 
