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 arc, 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 extremitv 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- 



3 m2 



