The Works Of Messrs. Schneider And Co.

ELECTRIC TRAMWAYS. 119 insure a perfect centreing of the armature. Carbon brushes are used ; they do not spark on the commutator. Their positions are regulated by means of a screw adjustment, which acts on a movable brush-holder disc, and which turns on the commutator bearing block. The dynamo, fixed on slides, rests on porcelain insulators, embedded in the foundations, and which protect it against atmospheric dis- turbances. These dynamos, owing to the range in their power of working, are very suitable for tramway central stations ; they can be driven several hours at an éxeess of 25 per cent, without any dangerous overheating, and for short periods at an excess of 30 per cent. A repairing and main- tenance shop is built near the central station ; the dynamo which works the transmission shafting is a 2 horse-power Thury machine, supplied direct with current from the central station. The car dépôt is also near thé central the switchboard, works through a feeder ; it serves to cut off automatically the current supply of a line in which a short circuit is produced, which would damage the dynamos. The apparatus for protection against atmospheric disturb- ances is the usual notehed lightning arrester, working in conjunction with reaction coils and condensera. All the devices are placed on the front of the switchboard, the connections are in the rear, and the rhéostat résistances are placed in a cupboard underneath. In order to facilitate access in case of repairs and accidents, a passage is pro- vided between the rear of the switchboard and the wall. This passage is closed by a door. The tramway consista of two diverging branches ; one is 12| kilometres in total length, and the other 5 kilo- metres, with a maximum gradient of 6 per cent, over a length of 300 metres. Two uninsulated cables start from the switchboard, and supply current to the trolley wires. Fig. 340. Electric Tramway. station. The switchboard consiste of two marble slabs on an oak mounting, and is fitted with all the grouping, starting, safety apparatus, &c., belonging to the generating dynamos. These apparatus consist of field rhéostats with automatic regulator, ammeters, voltmeters, make-and- breaks, disconnectors, releasing apparatus for current intensity, and lightning arresters. The automatic regulator acts in relation with the compound winding, in order to maintain constant the potential difference at the terminals of the generating dynamos. It consists of an arrangement that governs the direction in which the field rhéostat handles are moved, these being worked by a small direct- current electric motor. This regulator acts perfeetly as regards rapidity and précision. The automatic disconnector with which each generating dynamo is provided, serves to cut out the circuit of the dynamo, when it cannot usefully supply current to the system, owing to the fall of its voltage. The releasing arrangement for current intensity, fitted to For one of the branches the cable has a section of 180 square millimétrés (.279 square inch) for one-half the length of the line, and a section of 50 square millimétrés (.078 square inch) foi- the other half. For the other braneh, the feeder has a section of 110 square millimétrés (.171 square inch) for part of its length, the section at the other end being 50 square milli- métrés (.078 square inch). The feeder and contact wires are United every 800 metres. In the interior of the town, the trolley and bracket pôles are formed of iron tubes socketed in each other, and securecl at the sockets by means of ornamented rings. Their lower end is let in a concrète foundation to a depth of 2 metres. In the streets, where the track is alongside the pavement, the pôles are provided at the top with tubular arms, to which are fixed the trolley-line insulators. Where the line is in the centre of the streets, steel wire stretched between iron pôles, or fixed in the walls of opposite bouses,