V. On the Developement of Electro- Magnetism 
by Heat. 
By tHe Rey. J. CUMMING, M.A. F.RS. M.GS. 
PROFESSOR OF CHEMISTRY 
IN THE UNIVERSITY OF CAMBRIDGE. 
{Read April 28, 1823.] 
Tue property which the Tourmaline and a few of the erys- 
tallized gems possess, of exhibiting the opposite electricities by 
_the action of heat alone, has hitherto been considered as peculiar 
to those bodies ; but a recent experiment by Dr. Seebeck of Berlin, 
has proved that this power, so far from being confined to non- 
conductors, as from analogy might have been suspected, is pos- 
sessed by one, at least, amongst a class of substances, which are, 
comparatively, perfect conductors both of heat and electricity. 
The experiment is described in these words: ‘‘'Take a bar 
‘‘of antimony about eight inches long and half an inch thick, 
“connect its extremities by twisting a piece of brass wire round 
‘them, so as to form a loop, each end of the bar having several 
“coils of the wire. If one of the extremities be heated a short 
“time by a spirit lamp, electro-magnetic phenomena may be ex- 
“hibited in every part of ES 
On repeating this experiment, it appeared to me highly pro- 
bable that other metals might possess the same property, and 
in prosecuting this enquiry, I have been led to some results, 
