A small rectangle or circle may be hung in a similar manner. When the circuit is closed, it tends to place itself with its axis in a N and S direction through the earth's influence. The supposition of an E and W horizontal earth current will explain this action.
To exemplify rotation of a vertical wire by a horizontal loop, Fig. 21 may be shown.
A circular copper vessel with a glass bottom (Fig. 21) has wound around its rim several turns of insulated wire. In the center of the vessel is a metallic upright upon the top of which is balanced in a mercury cup a light copper [inverted U] shaped strip. The ends of the inverted U dip into the dilute sulphuric acid contained in the circular vessel.
The current passes from, the battery, up the pillar, down the legs of the U to the liquid, thence through the insulated wire back to the battery.
Fig. 21.
This is the usual form of apparatus, modified in size for the vertical or horizontal lantern.
(To be continued.)
An expansion of two papers read before the A.A.A.S. at the Ann Arbor meeting.