In view of the prime importance of electricity to a modern psychological laboratory, a rather elaborate system of wiring has been designed and built in. The unit of this system is a small delivery-board six inches wide by eight inches high, which carries the following five circuits: _a_, a time-circuit for running magnetic signals; _bb_, two low-tension circuits for chronoscope, bells, signals, etc.; _c_, a high-tension alternating current (110 v. and 60 phases) for alt. current motors, to be used where great constancy of speed is desired; _d_, a high-tension direct current (110 v.) for dir. current motors, where it is desired to vary the speed continuously (by the introduction of resistance). Two such delivery-boards have been set on opposite walls of all except the smallest rooms, which have but one board. Circuits _a_ and _b_ are represented on the board by binding-posts, while the high-tension currents, _c_ and _d_, appear as flush, protected sockets that take a double-pole plug. Circuit _a_ is a single circuit led from a time-pendulum permanently set in the battery-room, and carried once around the laboratory. It is connected with the _a_ binding-posts of the individual delivery-boards in parallel. It follows that the time-circuit is alike for all the rooms at any one time; but in different hours the pendulum can be adjusted to give various impulse-rates. If an investigation requires some special rate of impulse, the special time-apparatus is set up in the investigator's room and current for it taken from one of the _b_ pairs of posts. Each _b_ pair goes directly from the delivery-board to the battery-room and ends at a double-pole (telephone type) socket on a large switch-board. Thus every room has two or four direct and independent connections with the battery-room. The _c_ and _d_ circuits do not come from the battery-room, but from their respective generators that are stationed outside of the building. They are of course connected at the delivery-boards in parallel. The large switch-board in the battery-room consists of an upper and a lower part. The upper part bears the double-pole sockets from the _b_ posts in all the rooms; the lower part carries some fifty pairs of single-pole sockets that are connected with the batteries stationed near by. These pairs are labelled, and some give a current from cells of the Leclanché type, others of a gravity type. The student has merely to choose the kind and number of cells that he needs, from the lower part, and connect them with one of the double-pole sockets of the upper part which runs to a _b_ pair in his own room. By connecting two double-pole sockets with each other, the student can establish a circuit between any two rooms of the laboratory,--this for purposes of telephonic or other communication. Since every room has two, and most of the rooms have four of the _b_ circuits, the greatest variety and elasticity of service is attained.