Figure 3 shows an iron loop (about 2-inch diameter) wrapped with a
silver wire helix which is quite stable in 53-55% acid and which
will easily support a circulating pattern of three impulses. For
demonstration, unilateral waves can be generated by first touching the
iron with a piece of zinc (which produces two oppositely travelling
waves) and then blocking one of them with a piece of platinum or a
small platinum screen attached to the end of a stick or wand. Carbon
blocks may also be used for this purpose.
The smallest regenerative or reverberatory loop which we are at present
able to devise is about 1 mm in diameter. Multiple waves, as expected,
produce stable patterns in which all impulses are equally spaced. This
phenomenon can be related to the slightly slower speed characteristic
of the relative refractory period as compared with a more fully
recovered zone.
[Illustration]
[Illustration: Figure 2—Conductivity control—mixed pellet-size
aggregates]
[Illustration: Figure 3—Regenerative or reverberatory loop]