. The street railway review . advantages, which, however, do not generally out-weigh ihe disadvantages. For instance, in power plants havinglong steam pipe runs between the boiler and prime mover the super-heater may be located near the prime mover, andmay thus supply superheat of the highest degree to the prime moverwithout the loss of heat in the pipe runs. It must be remembered that the location of the superheater nearthe prime movers foundation will generally mean difficulty inhandling coal and ashes. The independently-fired type will producea higher degree of superheat tha
. The street railway review . advantages, which, however, do not generally out-weigh ihe disadvantages. For instance, in power plants havinglong steam pipe runs between the boiler and prime mover the super-heater may be located near the prime mover, andmay thus supply superheat of the highest degree to the prime moverwithout the loss of heat in the pipe runs. It must be remembered that the location of the superheater nearthe prime movers foundation will generally mean difficulty inhandling coal and ashes. The independently-fired type will producea higher degree of superheat than the dcpendently-fired one, andthe degree of superheat may more easily be controlled by regulatingthe furnace. On the other hand, the temperature of superheat pro-duced by the dependently-tired type is usually considered sufficientlyhigh for ordinary practice. The first cost of the dependently-firedsuperheater is very much lower, no additional floor space is rc-(|uired, and it does away with special attendants, as it can be. tended by the boiler operator. To decide which of these two typesis to be chosen for a given power plant, many questions must beconsidered: the location of prime movers with respect to the boiler,the character and type of the boiler as well as the superheater towhich the latter should be attached, the length and size of steammains and other items. It may be of interest to give here some data as to which of thetwo types are most commonly employed, as reported by Herr Ernstbefore the Engineering Congress of the International Society ofBoiler Inspection at Zurich. Switzerland, 1902. Mr. Ernst states 860 STREET RAILWAY REVIEW [Vol. XV, No. 12. that, in the district of the Vienna Boiler Inspection and InsuranceSociety, which includes 599 power plants. 14 per cent are equippedwith the independcntly-fircd type; 86 per cent with the dependently-tired type, 10 per cent of the latter being located in the second andthird passes of the boiler furnace gases, while all
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