full, and place in it about one-third of an ounce of quicksilver.

Next, place the platina plate between the two zinc plates, standing on their legs upon a table before you; and bring the top of the wooden bar (in a groove of which the platina is set) up flush with the top of the zinc plates. Let the brass post, standing on the top of this bar and soldered to the platina plate below, be toward the left-hand side. Then take the brass clamp and place it across the top of these metallic plates, a little to the right of the brass post, or about midway between the right and left sides, having its thumb-screw towards you, and with it screw the three plates firmly together. The platina is shorter than the zincs, to prevent its reaching the quicksilver in the bottom of the cell; and the wax balls on its sides are to insulate it from the zinc plates. This platina should never be allowed to touch the mercury or the zinc.

Let the plates, properly screwed together, be now placed in the cell with the Battery Fluid. Then, with the two copper connecting-wires, connect the post which stands on the wooden bar above the platina with the post stamped P on the helix-box, and the brass clamp N with the post N on the helix-box.

If, now, the screws regulating the vibrating armature be in perfect adjustment, the current will commence to run, with a buzzing sound; or it may be made to start by touching the hammer-like head of the flat steel spring. If not, the screws may be rightly adjusted in the following way: The top screw, which at its lower point is tipped with a small coil of platina wire, should be made to press delicately upon the center of the little iron plate on the upper side of the spring, so as to bear the latter down very slightly. Then raise or depress the screw-magnet, which turns up or down under the hammer, like the seat of a piano-stool, until the vibration of the spring commences. The rapidity of the vibrations, by which is secured the alternate closing and breaking of the electric circuit (or rather what, in practical effect, is equivalent to this—the direct and reverse action of the current in alternation) is increased by raising the screw-magnet and diminished by lowering it. When it is raised above what is required for ordinary use, the noise becomes too loud and harsh for many nervous patients to bear. It should then be depressed a little.

With respect to curative power, I have discovered but little perceptible difference, produced by the various degrees of rapidity in the vibrations, effected within the range of this magnet.

The force of the current is regulated by means of a tubular magnet, which slides over the helix, and is called the plunger. It is approached under a brass cap at the right-hand end of the machine. The plunger is withdrawn, more or less, to increase the force; pushed in to diminish it. If in any case the current can not be softened sufficiently with the plunger, the quantity of battery fluid in use must be made less.

After a time the current will become weak, and fail to run well. Then renew the battery fluid. When the quicksilver is all taken up by the zinc plates, the machine may be run for a while without adding more. But after it has considerably disappeared from the inside surface of the zinc plates, the latter will begin to show more rapid corrosion, while the current will be less. Then let a small quantity of quicksilver—one-fourth to one-third of an ounce—again be placed in the fluid.

When the machine is not in use, let the metals be removed from the fluid; and, if not to be soon again used, let them be rinsed with water, carefully avoiding to wet the wooden bar in which the platina is set.

The posts, with which the conducting-cords are to be connected, are arranged in a row near the front of the helix-box, and are marked A, B, C, D. Either two of these posts may be used to obtain a current; and since they admit of six varying combinations, six different currents are afforded by the machine, viz: the A B current, the A C current, the A D current, the B C current, the B D current, and the C D current. Whichever current is used, it may always be known which of the two posts employed is the positive and which the negative, by observing the letters stamped upon their tops. The one whose letter comes first in the order of the alphabet is positive; the other is negative. Also, the one standing towards the left hand is positive, and that at the right hand is negative. The qualities of the several currents are stated in a descriptive paper on the inside of the lid of the machine, which see. It will there be found that three of the currents—viz, the A B, the A C and the A D currents—are electrolytic: that is, dissolving by electric action. These electrolytic currents require to be used—one or another of them—whenever any chemical action is needed; as, in decomposing or neutralizing virus in the system, destroying cancers, reducing glands when chronically enlarged, removing tumors or other abnormal growths, and in treating old ulcers and chronic irritation of mucous membranes. The other three, being Faradaic or induction currents, and having no perceptibly chemical action, are used where only change of electro-vital polarization is required. These Faradaic currents differ from each other in respect to being concentrative or diffusive in their effects, and in their sensational force. B C is concentrative and delicately sensational. C D is also concentrative, though less so than B C, and is more strongly sensational. B D is diffusive, and the most energetically sensational of the three.

POLARIZATION.

It may be proper, in this place, to spend a few words upon electrical polarization in general.

Electrical polarity may be defined as a characteristic of the electric or magnetic fluid, by virtue of which its opposite qualities, as those of attraction and repulsion towards the same object, are manifested in opposite parts of the electric or magnetic body. These opposite parts are called the poles of the body, as the positive and negative poles. The difference between the positive and negative poles is believed to be that of plus and minus—plus being positive and minus negative. This is the Franklinian view, and, if I mistake not, is the one most in favor with men of science at the present day. This view supposes that the electricity or magnetism arranges itself in maximum quantity and intensity at the one extremity or pole of the magnetized body, and in minimum quantity and intensity at the opposite extremity or pole; and that, between these points—the maximum and the minimum—the fluid is distributed, in respect to quantity and intensity, upon a scale of regular graduation from the one to the other. The idea may be represented by a line, commencing in a point at the one end, and extending, with regularly increasing breadth, to the other end. The larger end would represent the positive pole, and the smaller, the negative pole. Or perhaps a better representation of the magnet would be a line of equal breadth from end to end, but having the one end white, or slightly tinted, say, with red, and the color gradually and regularly increasing in strength to the other end, where it becomes a deep scarlet. Let the coloring-matter represent the magnetism in the body charged, and we have the magnet illustrated in its polarization: the deep-red end is the positive pole, and the white or faintly-colored end is the negative pole.

It is a law of polarization that the positive poles of