Second Series— Thermo-Multiplier. 353 
tension, such as that of the thermal pile. I have even found (as 
already stated) that this peculiar electro-magnetic arrangement is ~ 
not destroyed by producing a brisk action in the opposite direction. 
Now, in relation to the statical or dynamical effects, we cannot be 
. surprised if the galvanometer coil be brought into action after a 
short interval of repose, and in the same direction as before, that 
this molecular arrangement, of whatever kind it be, not being 
completely destroyed or undone (which it requires many minutes 
completely to effect), the electricity finds a more ready passage 
through the wire than if it had not previously been transmit- 
ting electricity ; consequently, the whole electro-magnetic effect 
is more nearly instantaneously developed, and the extent of the 
first impulsive arc bears a greater proportion to the total effect, 
which, after an unlimited time, the electric current is capable of 
producing (indicated by the statical deviation), than if the wire 
had been in a perfectly neutral state when the action commenced. 
This view is suggested by my experiments, which shewed the 
relation between the dynamical and statical effects to depend 
materially upon the position of zero, upon the time allowed to 
elapse between the experiments, and upon the degree of previous 
excitement. It also shews why the difference of the two effects 
diminishes, relatively to the are, as the arc increases. The time 
of performing the first sweep is nearly (I apprehend not exactly) 
the same for large and small arcs. The time for the production 
of the effect is, therefore, not greater in the one case than in the 
other. But the intensity of the force being greater in one case, 
and acting for as long a time, the coercive force or inertia of the 
conducting material is already nearly overcome by the time that 
the needle has reached the extremity of its oscillation.. The 
effect, therefore, will (as observed) approach more nearly to the 
permanent effect. 
13. The tabular numbers (art. 8) refer to the experiments 
made with the conical reflector (art. 6) applied to the pile. 
They are derived from several distinct series of experiments se- 
3M 2 
