Science for beginners . Fig. 245.—A modern city pumping station. Three-stage centrifugalpump, belt-driven by 150 , three-cylinder gas engine, with suctiongas producer. water is frequently not such as to warrant its use withoutpurification. Sometimes sufficient purification is secured bypumping the water into a settling tank where most of thesediment is removed and then passing it through sand filterswhere most of the finer suspended matter and bacteria areremoved. Sometimes it is found necessary to treat the waterchemically in addition to filtering it. This is most frequently 416 WATER SUP
Science for beginners . Fig. 245.—A modern city pumping station. Three-stage centrifugalpump, belt-driven by 150 , three-cylinder gas engine, with suctiongas producer. water is frequently not such as to warrant its use withoutpurification. Sometimes sufficient purification is secured bypumping the water into a settling tank where most of thesediment is removed and then passing it through sand filterswhere most of the finer suspended matter and bacteria areremoved. Sometimes it is found necessary to treat the waterchemically in addition to filtering it. This is most frequently 416 WATER SUPPLY AND SEWAGE DISPOSAL the case when a city gets its water supply from a river intowhich other cities nearer its source have emptied Fig. 246.—Central Square Water Works, 1800. From History ofSanitation, Cosgrove. 493. Development of City Water Systems.—The moderncity water system has been developed within the last shall see in Chap. XI, p. 502, that the steam engine was CITY WATER SYSTEMS 417 still a very crude machine at the beginning of the 19th cen-tury. City water systems were still less well was one of the first of American cities to con-struct a city water system. Fig. 246 is a section through theCentral Square water works of that city constructed in theyear 1800. Its crudeness is evident when compared with amodern city water plant. The boiler was constructed of plank with iron firebox and flues. The distributing pipeswere also of wood, being logs with the center bored system was never very satisfactory; the boiler leakedsteam and the pipes leaked water. In 1804, Philadelphia be-
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