Bridge tramways similar to those in use on the ore-unloading docks are employed in the furnace yards to convey the ore from the railroad cars to stock piles, and a patent furnace hoist automatically conveys the ore together with the coke and limestone to the top of the blast furnace and performs the operation of 'charging.' The automatic hoist consists of an inclined iron-trussed bridge reaching from the floor of the stock house to the top of the furnace shell and from thence over the top opening of the furnace. On this bridge is laid a track of T rails on which travels a skip or ear, containing the charge of one to three tons as may be desired. The track is so arranged at the top that the contents of the car are automatically dumped into the hopper on the arrival of the car at the top. The skip car is hoisted or hauled to the top by a double engine with a friction clutch drum.
The exigencies of handling great quantities of coal for shipment have been quite as productive of ingenious mechanical devices as have the requirements of the iron industry. Bridge tramways have been employed extensively for both loading and unloading of fuel, and in the case of anthracite coal clam-shell buckets and bucket shovels which scoop up the coal have been introduced in connection with the bridge tramway instead of the ordinary bucket. However, preeminent among all the varied forms of coal-handling apparatus stands the car-dumper, a class of machine, each step in the evolution of which has been marked