from end to end. The conductors from each generator are led from the dynamo into this tunnel through earthenware pipes; they are then carried along the walls of the tunnel to the ground-floor panel of the switchboard, and are taken up this through the switches and instruments to the vertical bars of a three-way 'bus bar connector, by means of which any generator may be connected to either of three pairs of 'bus bars.

The generators are self exciting, and the pressure is regulated by means. of resistances inserted in series with the shunt winding of each generator, hung just beneath the switchboard gallery. The necessary regulating

FIG. 154.-General arrangement of L. T. generator and feeder 'bus bars at
the Glasgow lighting station.

switches are connected directly on to these resistances, and are controlled by a hand-wheel on the gallery, communicating with the regulating switch below by means of a spindle carried through the floor. A pointer shows the amount of resistance in circuit.

Some difficulty was experienced in designing a satisfactory method of signalling from the switchboard to the engine drivers, as no point of the station wall could be seen from all the engine stop-valves and governors. This difficulty has been got over by fixing on the top of the main board a large iron case containing several compartments. An opal glass in front of each compartment forms the front of the case. Behind each glass is

etc.

painted a number corresponding to each of the generators, boosters, Each compartment contains an incandescent lamp, which may be switched on and off by means of a switch attached to the regulating resistance standard of the generator to be signalled. Similar cases, also divided into compartments, are fixed near the stop-valves of the generators, etc.

These compartments are labelled with instructions such as,

FIG. 155.-Positive generator panel (Glasgow).

"Start," "Up," "Steady," "Down," "Stop." It is obvious that the figures and words on the opalescent glass will only be visible when the lamp is lighted behind it. A loud bell draws the driver's attention to the fact that the switchboard attendant wishes to communicate with him. By looking at the signalling case over the switchboard he sees which generator is signalled, and on going to the stop-valve he receives his instructions from the signal-box attached to the same.

Glasgow.

The arrangement of switchgear at the Glasgow lighting stations is widely different from that to be found in any other low-tension station. This was constructed to the design of Mr W. A. Chamen, the city electrical engineer. Fig. 154 illustrates the general scheme of connections.

Positive and negative generator panels A and B are placed on the ground floor directly opposite each generator. Connections are run from these to four sets of positive and negative 'bus bars CD supported beneath the feeder switchgear gallery. This gallery runs the entire length of the engine-room. The feeder panels E F are arranged in sections, each section dealing with eight feeders. The sections are arranged alternatively,

positive and negative. By this means the positive and negative connections are efficiently separated; at the same time the distance between the positive and negative connections to any one feeder does not exceed a few feet. The feeder panels are equipped with horizontal and vertical 'bus bars, by means of which any feeder may be plugged on to either of the four 'bus bars. These 'bus bars may, if desired, be maintained at different pressures, or may all be coupled in parallel.

Figs. 155 and 156 indicate the arrangement of apparatus on the

positive and negative generator panels. The lead from the positive terminal of the generator is connected to one terminal of the main circuit-breaker A. The other terminal of the circuit-breaker is connected to the top of a duplex fuse. This duplex fuse consists of two fuses in series, either one of which may be short-circuited by the switch B. After leaving the fuse the current is taken through one of the author's discriminating cutouts C (see fig. 99). This cutout is constructed to open the circuit only in the event of its generator failing and tending to short circuit the 'bus bars. The top of the cutout is connected to the centre contact of the four-way plug connector D. By means of this connector the generator may be plugged on to any of the four 'bus bars referred to above. The arrangement of the negative panel is somewhat similar, the chief difference being that a recording ammeter E is inserted in the circuit instead of the discriminating cutout. The details of the plug connector are shown in fig. 157.

FIG. 157.-Details of Glasgow plug switch.

This plug consists of a laminated S-shaped contact carried on a removable key. The projection at the end of this key fits in the slotted key-way mounted in the slate base. The plugs can only be withdrawn by turning them through 180 degrees from the position in which they were inserted, and they cannot be turned beyond this. Although these plugs are not intended for making or breaking the circuit, carbon sparking pieces