conveniently be divided as follows, viz.

• a. The tub;
• b. The electrodes and connections;
• c. The water;
• d. Chemicals;
• e. The batteries.

(a) The Tub. This must be made of a non-conducting material. Of substances that will answer, I will mention: wood, porcelain, soapstone, vulcanized rubber, or glass. In choosing one of these materials, regard should be had to the facility of attaching the electrodes. In this respect wood deserves the preference over all the others mentioned. Where economy is to be studied, it has a further item in its favor.

The tubs, which I have now in use for nearly three years are made of wood, and I find them to answer very well. It must not be forgotten, however, that a wooden tub requires to be well painted on the inside, in order to prevent its becoming water-soaked, because in that event it would become a conductor of electricity, and interfere to some extent, with the administration of the electric current in the bath.

The shape and size of the tub may be the same as those of an ordinary bath tub. To suit individual cases however, its length may be made to vary. The only peculiarity in its construction is at the head. Here, instead of slanting, it is made square, and the slightly concave (from side to side) board against which the back of the bather is to rest, is fitted in afterwards. This is necessary, because it is very difficult to make a wooden tub with a slanting back water-tight. If the length of the tub from outside to outside is made to measure about five feet ten inches, the back-rest fitted in at a proper slant will bring the inside of the tub to about the right length for an average male adult. All around the upper edge of the tub runs a wooden coping, which must not be fastened down however until all the attachments for conducting the current are in situ. Along that portion of the top of the tub where required—and this will depend on the situation of the binding posts presently to be mentioned—and underneath the coping, runs a groove for the reception of the wires that are to connect the carbon electrodes on the inside of the tub with the binding posts on the outside. This groove is continued vertically along the inside of the back-rest and foot of the tub respectively, to communicate at either end with the bed for the reception of the carbon plates. These vertical grooves should at their lower end be a little over ¼ inch deep, in order to admit of the wires being introduced beneath the carbons.

The face of the foot of the tub and that of the back-rest, should have in their centres (from side to side) and commencing at about five inches from the bottom of the tub, a bed for the reception of the carbons. The dimensions of these receptacles must of course correspond to those of the carbon plates to be employed as electrodes. Those which I use measure 12×8″ at the head, 8×6″ at the foot of the tub. They are ¼″ thick. They are placed so as to have their long diameter correspond to the height of the tub. The bed which is to receive the carbon at the head of the tub must be deeper than ¼″ on account of the concavity of the back-rest.

In order to adapt a tub to individuals of different lengths, it will be found advantageous to have two small vertical cleats on each side of the tub, near the foot and bottom, for the reception of a foot-board, which will practically shorten the tub and adapt it to persons of different lengths. This board may conveniently be six inches wide, and should have a number of perforations about an inch in diameter, for the transmission of the current to the feet. 1¼″ pine plank is the most suitable wood to use in the construction of the tub. This is preferable to any of the hard woods, because of the greater facility of fitting in the electrodes etc. It is also the most economical.

(b) The electrodes and connections. These consist of two carbon plates, two brass binding posts, and insulated wires to connect the carbons with the binding posts, and these with the battery. The carbons are such as are ordinarily employed in the construction of galvanic batteries, and can, as well as the wire and binding posts, be procured from any house that deals in telegraph material. Their size is to some extent optional; the dimensions I have given above however answer very well.

The inside of the tub having received one or preferably two coats of paint, the carbons are now fitted in the receptacles provided for them. The next step is the attaching of the binding posts. These should be of the kind known as “single” binding posts with “wood screws.” The most convenient location for them will be found on the coping covering the horizontal portion at the head of the tub. Here the coping, as it has to cover not only the upper edge of the head of the tub, but that of the back-rest also, is of necessity much wider than at any other portion, and thus affords most room for the binding posts.

Having marked out then a site for the binding posts, say in the centre of the coping at the head of the tub—which should now be placed in position—and about two inches apart, the posts are laid aside to be put in place when the wires are all in situ, and the coping fastened down.

In order to facilitate the description of the placing of the wires by means of which communication is to be established between the electrodes and the binding posts, I shall term the end of the wire that is to be attached to the electrodes the distal, that which is attached to the binding posts the proximal end. A gimlet hole sufficiently large to admit of the passage of one wire should be made half an inch outwards from the centre of the site of each binding post. The best wire to use is about No. 16 copper wire, coated with gutta percha or rubber. The site of the posts being as above suggested, it will be found that the wire which is to connect the head electrode with one post requires to be about 18 inches long, that which runs from the other post to the foot-electrode, between eight and nine feet. The distal ends of the wires should be stripped of their coating for a length of about three inches, the proximal ends for about two inches. The denuded portion of the distal ends should be rolled up in the form of a spiral coil; this will insure their constant impinging on the carbons more certainly than could be expected from a simple straight end of wire.

The carbons having now been fitted in their beds, the distal end (coil) of the head wire is placed beneath the carbon, and the wire itself continued up along the vertical groove to either one of the gimlet holes. Through this, from within outward, the proximal end of the wire is now drawn and left for the present. The distal end of the second wire having now been placed beneath the carbon at the foot of the tub, this wire is continued up through the vertical groove, along the upper edge of the foot of the tub to the side nearest the binding post to which the wire is to be attached, along the groove on the upper edge of this side to the head of the tub, and thence to the respective gimlet hole, and through this, from within outward. The wires being now all in position, all the coping is next screwed or nailed down firmly, care being taken that the screws or nails used for this purpose do not injure any of the wires. The coping fastened down, the binding posts are now screwed down in the sites previously marked out for them. Before they are screwed entirely down, the denuded portion of the proximal end of each wire is securely wound around the screw of the respective binding post, and the posts are then