308 
SECOND REPORT- 1832 . 
deviations of a needle, in the thermo-electric circuit, is not in¬ 
variable, the deviations increasing slower than the temperature, 
the law of which deviation is unknown; hence a pyrometer 
constructed on thermo-electric principles gives inaccurate in¬ 
dications. 
The action of alloys is not intermediate between those of 
their constituents, and in some instances changes not only its 
quantity but its character at different temperatures. The ac¬ 
tion of iron with other metals is anomalous, being positive or 
negative with the same metal, according to the temperature. 
The thermo-electric order of conducting powers in metallic 
wires, is silver, copper, gold, zinc, brass, platina, and iron ; but 
compared with galvanic electricity, it is conducted with diffi¬ 
culty. 
Thermo-electric rotation may be produced by the action of 
an exterior magnet, but differs from electro-magnetic rotation 
n not being the result of a continuous action. The action of 
a magnet upon an indefinite thermo-electric conductor, varies 
inversely as the distance : hence the same laws seem applicable 
to hydro- and stereo-electric currents. 
The thermo-electric current appears to be incapable of 
passing through fluid non-metallic conductors, of heating wire 
placed in its circuit, or of either magnetizing steel, or forming 
a thermo-electric magnet; and therefore seems to have no as¬ 
signable tension. 
Hence it is somewhat beyond the limits of probability to sup¬ 
pose (as some have fancied,) that by these currents the metals 
themselves will be decomposed, and that the great revolution in 
chemistry, commenced by the pile of Volta, will be completed 
by that of Seebeck, 
Report on the recent Progress of Optics. By Sir David 
Brewster, LL.D. F.li.S. &c. 
There are few branches of science which have been so irregu¬ 
lar in their progress as that which treats of the nature and pro¬ 
perties of light. With the exception of some g-eneral notions 
respecting its rectilineal propagation, the equality of the angles 
of incidence and reflexion, and the refraction of light towards 
the perpendicular in passing from a rare to a dense, the ancient 
philosophers contributed little to the advancement of physical 
