This excerpt is from The Papers of Joseph Henry, which document Henry’s pioneering work in electromagnetism and experimental apparatuses.
Exp. 4th. *To shew the revolution of a large Ampere’s cylinder by means of the coil.*⁹
Fig 4th.
The coil remains in its horizontal position and a large Ampere’s cylinder or bucket b is placed in the centre. When the bucket is charged with a strong solution of acid (Nitric) and the current transmitted through the coil, the moveable part of the apparatus begins to revolve with considerable velocity; when the direction of the current is reversed, the motion stops and then recommences in an opposite direction. The motion will be a little more rapid, if the bucket be supported as shewn in the figure, on the end of the iron cylynder described in the last exp, this becoming magnetic reacts on the revolving apparatus and increases the effect. The experiment however is more pleasant without the use of the iron, although the motion is less rapid.
This is a highly interesting experiment when the motion is properly produced. The bucket I have used is nearly 6 inches in external diameter. The space between (a & b Fig 7)* the internal and external cylynder for the reception of the acid and the moveable zinc cylynder is about ¾ of an inch wide and about an inch deep. The two metalic arches e, f are made of thin sheet copper nearly ¼ of an inch wide and painted white so that their motion may be distinctly seen at a distance. The whole height of the apparatus is between 8 and 9 inches. Every part should be made as light as possible, the bucket of very thin copper and the zinc cylinder of thin zinc plate which can be easily renewed. The one employed by me is so light that it makes several revolutions when strong acid is first poured in by the action of the magnetism of the earth, alone.
Exp. 5th. To exhibit the revolutions of mercury with the coil¹⁰
Fig. 5th.
Place a plate of mercury in the centre of the coil on the top of the iron cylyender mentioned in Exp. 3d. Also, place an end of the coil in the mercury at the side of the plate at e; the other end of the coil being in connection with one pole of the battery and the current completed by means of the wire d, which also dips into the plate of mercury on the oposite side at f. When the battery is put in action the mercury begins to revolve in a whirlpool around the point of its surface which is immediately above the end of the iron cylyender on which the plate rests. When the current is reversed, the motion of the mercury is changed. The revolutions may be shown at a distance by throwing on the surface of the metal some pieces of light substance which will partake of its motion and render it more perceptible.
Exp. 6th. To exhibit powerful magnetic induction with the coil.
Fig. 6th.
Represents the coil placed vertically with a large piece of iron a (the lifter of my large magnet weighs 27 lbs.) in the centre. b, c represents a piece of bar iron about 3½ feet long bent into the form of a horse shoe and placed over the sides of the coil so as to support the weight in the centre by the magnetism developed when a current is transmitted through the coil. The face of the horse shoe and the iron should be ground to each other. The great power may be shown by suspending weights to the lifter from below.
NB The results will be more energetic with a large battery than a small one. I have ex[ecuted] these experiments with a battery of a single element exposing about 50 feet of zinc surface to the action of the acid.